Research Article Short-Term Effects of Biogas Digestates and Pig...

Research ArticleShort-Term Effects of Biogas Digestates and Pig SlurryApplication on Soil Microbial Activity

J Abubaker12 K Risberg1 E Joumlnsson1 A S Dahlin3 H Cederlund1 and M Pell1

1Department of Microbiology Swedish University of Agricultural Sciences (SLU) PO Box 7025 750 07 Uppsala Sweden2Department of Soil and Water Faculty of Agriculture Sabha University PO Box 19332 Sabha Libya3Department of Soil and Environment Swedish University of Agricultural Sciences (SLU) PO Box 7014 750 07 Uppsala Sweden

Correspondence should be addressed to M Pell mikaelpellsluse

Received 9 October 2014 Accepted 27 November 2014

Academic Editor Rafael Clemente

Copyright copy 2015 J Abubaker et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

The effect of four biogas digestates (BD-A BD-B BD-C and BD-D) and pig slurry (PS) on soil microbial functions was assessed atapplication rates corresponding to 0ndash1120 kgNH

4

+-Nhaminus1 At dose corresponding to 140 kgNH4

+-Nhaminus1 309ndash325of the carbonapplied in BD-A BD-C and PS was utilized during 12 days while for BD-B and BD-D corresponding utilization was 190 and 169respectively All BDs resulted in net nitrogen assimilation at low rates (175ndash140 kg NH

4

+-N haminus1) but net mineralization dominatedat higher rates PS resulted in net mineralization at all application rates All residues inhibited potential ammonium oxidation(PAO) with EC

50-values ranging between 45 and 302 kg NH

4

+-N haminus1 Low rates of BDs appeared to weakly stimulate potentialdenitrification activity (PDA) while higher rates resulted in logarithmic decrease The EC

50-values for PDA were between 238 and

347 kg NH4

+-N haminus1 No inhibition of PDA was observed after amendment with PS In conclusion biogas digestates inhibitedammonia oxidation and denitrification which could be an early warning of potential hazardous substances in the digestatesHowever this effect can also be regarded as positive since it may reduce nitrogen losses

1 Introduction

In recent years the production of biogas from differentorganic substrates has increased dramatically [1] resultingin an increase in the amount of biogas digestates generated[2] The potential of biogas digestates as fertilizers has gainedgreat attention due to their beneficial plant nutrient profilesand content of organicmaterial [3] and hence their potentialto reduce the use ofmineral fertilizers However the chemicalproperties of the biogas digestates vary due to the widerange of raw materials used as substrates in the biogasprocess Common substrates are animal manure slaughter-house waste source-separated municipal household-wasterestaurant waste waste from the food industry sludge fromwastewater treatment crop residues and residues from thebioenergy sector [4 5] Therefore the biogas digestatesgenerated may also contain potentially toxic substances forexample heavy metals [6] and organic toxicants [7 8] whichmight affect the soil ecosystem negatively Due to insufficientconfidence in its quality and safety as well as unfamiliarity

with the product the use of these residues is still limited Inorder to close the knowledge gaps biogas digestates should beevaluated for their short- and long-term effects before large-scale application to arable land

Short-term soil effects could be very different from effectsin the long run The short-term effect reflects the situationat the time of fertilization when high amount of fertilizeris added in relation to the short-term need by the soil andplant system This imbalanced input is common practice inagriculture but induces stress to the microbial ecosystem andmay affect critical soil functions such as those within thecarbon and nitrogen cycle Soilmicrobial processes in generalhave been shown to be sensitive indicators of short- andlong-term changes of soil properties following applicationof organic residues [9 10] Microorganisms are in directcontact with roots soil particles and chemicals and theirproduction of enzymes responds quickly to changes in thesoil environment [11] Hence the soil microbial communitycan be used as a ldquotest-organismrdquo in order to detect inhibitoryor toxic compounds in an organic fertilizer that could

Hindawi Publishing CorporationApplied and Environmental Soil ScienceVolume 2015 Article ID 658542 15 pageshttpdxdoiorg1011552015658542

2 Applied and Environmental Soil Science

otherwise be very expensive or even impossible to analyzeIf negative effects are detected this could motivate a morethorough chemical investigation

Several microbial soil tests related to carbon cycling havebeen used to assess andmonitor soil quality [12] For instancesoil respiration provides information on the heterotrophicactivity of the microbial biomass [13] and estimates of totalsoil microbial biomass are commonly used as indicators ofsoil quality [14] Tests of microbial functions related to thenitrogen cycle may be particularly useful when assessing soilmicrobial health and determining plant nitrogen availability[15] All main microbial processes in the nitrogen cyclemineralization immobilization or assimilation nitrificationdenitrification and nitrogen fixation have been used forstudying treatment effects on soil [9 16] Denitrification andnitrification are sensitive to disturbances and hence theseprocesses are ideal for detecting the presence of contaminantssuch as heavy metals pesticides and organic toxicants [917] In general nitrification that is ammonia oxidation andnitrite oxidation is performed by only a small number ofspecialist species within bacteria but also within Archaeawhich makes monitoring nitrification a suitable tool forpredicting toxicity [18] By contrast nitrogen mineralizationis performed by a multitude of species with the ability toreplace each other if any group is negatively affected and maybemore suitable for detecting general impacts and changes insoil fertility and nitrogen availability [19]

The overall aim of the present study was to evaluate thesuitability of using biogas digestates as fertilizers in arablecropping In dose-response tests we studied the short-termeffect on soil microbial respiration nitrogen mineralizationcapacity ammonium oxidation and denitrification potentialin order to detect any negative effects on these criticalsoil functions The effects induced by the digestates werecompared to those induced by pig slurry a well-knownfertilizer used in agriculture

2 Material and Methods

21 Soil Sampling and Characteristics Clay soil was collectedfrom the top 0ndash20 cm layer of an arable field located in centralSweden (N 59∘369851015840 E 16∘396741015840 (WGS84 lat lon) Thesoil is classified as an Eutric Cambisol (FAO 1998) and hassince 1998 annually been fertilized with 100 kg N (50 NH

4-

N and 50 NO3-N) No farmyard manure has been applied

since 1975 From 1998 a simple crop rotation has been appliedwith spring barley and oats grown in alternate years thecrop residue is removed as straw After sampling the soilwas briefly stored at +2∘C before it was sieved (Oslash lt 4mm)thoroughlymixed and then portioned into polyethylene bagsand stored at minus20∘C until use [20] Total soil carbon (Tot-C)total nitrogen (Tot-N) and total sulphur (Tot-S) were deter-mined after combustion at 1250∘C with a carbon nitrogenand sulphur analyzer (CNS-2000 LECO Equipment CorpSt Joseph MI USA) Tot-C was corrected for carbonate togive organic carbon (Org-C) Available phosphorus (P-AL)and potassium (K-AL) were extracted with the ammoniumlactate method (AL) and analyzed as described by Egneret al [21] The pH was determined in 001M CaCl

2with

Table 1 Chemical physical and microbiological characteristics ofthe soil used in the experiment [10]

Parameter ValueChemical analysespH 56Org-C () 13Tot-C () 13Tot-N () 01Tot-P (mg kgminus1 ds) 700Tot-S (mg kgminus1 ds) 200P AL (mg kgminus1 ds) 48K AL (mg kgminus1 ds) 185Cu (mg kgminus1 ds) 26Zn (mg kgminus1 ds) 91Cd (mg kgminus1 ds) 03Ni (mg kgminus1 ds) 24Pb (mg kgminus1 ds) 20Cr (mg kgminus1 ds) 36Physical analysesDM () 853Sand () 14ndash20Silt () 36ndash44Clay () 37ndash49WHC (g gminus1 ds) 051Microbial analysesNMC (120583g N gminus1ds 10 dminus1) 212PAO (ng NO2-N gminus1 dsminminus1) 48PDA (ng N2O-N gminus1 dsminminus1) 78B-resp (120583g CO2 g

minus1 ds hminus1) 078SIR (120583g CO2-C gminus1 ds hminus1) 135

the volvol ratio 1 2 (pHCaCl2) Pseudo-total phosphorus(Tot-P) cadmium (Cd) chromium (Cr) copper (Cu) nickel(Ni) lead (Pb) and zinc (Zn) were analyzed by ICPMS(Perkin-Elmer ICP Optima 3000 Waltham MA USA)according to SS 02 83 11 [22] Dry matter (DM) was assessedby the method described by McLaren and Cameron [23]The particle size distribution was determined by the pipettemethod according to Jung [24] The analyses of biologicalproperties of the soil are described below (see Section 24Microbiological Assays) The chemical physical and biolog-ical characteristics of the soil are presented in Table 1

22 Organic Residues Biogas digestates were collected fromfour large-scale biogas plants (BD-A BD-B BD-C and BD-D) in Sweden The digestates were chosen to represent bothmesophilic and thermophilic processes fed with a wide rangeof organic residues from municipality and agriculture Alldigestates fulfilled the SPCR 120 certification rules for asafe fertilizing agent (httpwwwavfallsverigesein-english211114) These certification rules are based on documentssuch as the European Union health rules regarding ani-mal by-products and derived products not intended forconsumption (EC number 10692009 httpeur-lexeuropaeu 251114) Furthermore all values for metals except for

Applied and Environmental Soil Science 3

Table 2 Operating parameters of the biogas plant reactors (ie temperature retention time and substrate) from which the four biogasdigestates (BD-A BD-B BD-C and BD-D) were obtained

Operation parameters Type BD-A BD-B BD-C BD-DTemperature Mesophilic1 Thermophilic2 Thermophilic1 Mesophilic2

Retention time (days) 40ndash50 40ndash50 40ndash50 20

Substrate type3 IndashVII ()

I 40 mdash 33 mdashII 60 mdash 24 66III mdash mdash 43 mdashIV mdash 97 mdash mdashV mdash 3 mdash mdashVI mdash mdash mdash 24VII mdash mdash mdash 10

1Mesophilic 20ndash45∘C2Thermophilic gt40∘C3Substrate types slaughterhouse waste (I) source-separated organic household waste (II) food processing waste (III) distillerrsquos waste from ethanol production(IV) cereals (V) silage (VI) and sludge from grease traps (VIII)

Cu and Zn are conforming to the guideline for soilimprovers according to the ldquoEU Ecolabelrdquo (httpeceuropaeuenvironmentecolabel 211114) The values for Cu andZn are the same as for wastewater sludge which allowed fordispersion on arable land according to the Swedish StatuteBook SFS 1998944 (httpwww riksdagenseen 211114)Approximately 10 L digestate was collected from each biogasplant according to the SPCR 120 rules for collecting samplesfor analysis and transported refrigerated At arrival to thelaboratory the digestate was thoroughly mixed before beingportioned into small bottles and stored at minus20∘C until useThe compositions of the main feedstock to each of the fourbiogas plant reactors process temperatures and retentiontimes are presented in Table 2 Pig slurry (PS) was collectedfrom a fattener pig farm with well-mixed slurry storage Thechemical and physical characteristics of the residues are givenin Table 3 The pH was measured with a pH meter directlyafter agitating and without dilution (PHM 93 Reference pHMeter Radiometer Medical Broslashnshoslashy Copenhagen Den-mark) Dry matter (DM) was determined according to SS-EN 12880 [25] Tot-C according to ISO 10694 [26] and Tot-N and organic N (Org-N) according to ISO 13878 [27] Totalphosphorus (Tot-P) total sulphur (Tot-S) and total amountsof the metals calcium (Ca) potassium (K) magnesium (Mg)manganese (Mn) mercury (Hg) Cd Cr Cu Ni Pd and Znwere all analyzed according to SS 28311 [28]

23 Experimental Setup The soil was amended with eachresidue at a range of doses 0027 0054 0108 0216 0432086 and 17mg NH

4

+-N gminus1 dry soil (ds) after whichthe microbial activity was measured directly These dosescorresponded to field application rates of 175 35 70 140280 560 and 1120 kg NH

4

+-N haminus1 assuming a field bulkdensity of 131 g cmminus3 and a distribution depth of 5 cm Toreach the desired soil moisture level in the assay or to allowthe desired N rate to be provided the residues were in somecases blended with appropriate amounts of deionized water

Table 3 Chemical and physical characteristics of the four differentbiogas digestates (BD-A BD-B BD-C and BD-D) and pig slurry(PS) used in the experiments

Parameter BD-A BD-B BD-C BD-D PSpH 79 79 8 87 66Dry matter DM () 61 37 17 59 91Tot-C (g kgminus1 ww) 19 9 7 24 40Tot-N (g kgminus1 ww) 79 59 26 53 53Org-N (g kgminus1 ww) 26 22 06 20 29NH4+-N (g kgminus1 ww) 53 37 203 33 24

CN 71 42 110 121 136Tot-P (g kgminus1 ww) 09 07 02 04 14K (g kgminus1 ww) 16 28 11 37 25S (g kgminus1 ww) 060 122 012 026 047Mg (g kgminus1 ww) 02 01 01 03 06Ca (g kgminus1 ww) 06 01 03 13 17Cr (mg kgminus1 ww) 130 149 111 195 107Mn (mg kgminus1 ww) 201 266 918 286 426Ni (mg kgminus1 ww) 388 355 17 17 396Cu (mg kgminus1 ww) 697 694 398 974 218Zn (mg kgminus1 ww) 474 465 299 395 801Cd (mg kgminus1 ww) 03 03 12 03 03Pb (mg kgminus1 ww) 01 07 46 34 01Hg (mg kgminus1 ww) lt01 lt01 lt01 lt01 lt01ww = wet weight

prior to application to the soil In addition each microbialsoil test contained a control without residue amendment

24 Microbiological Assays

241 Soil Respiration For determination of soil respirationportions of thawed soil corresponding to 20 g ds wereweighed into 250mL airtight plastic jars and preincubated fortwo weeks at 20∘C to allow the soil respiration to stabilizeThe four BDs and the PS were subsequently added at rates


corresponding to 175 35 70 and 140 kg NH4

+-N haminus1 Thetarget moisture content of the soil after amendment was 65of its water holding capacity (WHC) The high water contentof the residues prevented amendment of the highest dosescorresponding to 280ndash1120 kg NH

4

+-N haminus1 The treatmentscorresponding to 175 and 35 kg NH

4

+-N haminus1 were replicatedthree times except for PS at 35 kg NH

4

+-N haminus1 which wasreplicated four times due to uncertainties in adding thisheterogeneous residue The treatments 70 and 140 kg NH

4

+-N haminus1 were replicated four times and the nonamendedcontrol six times In the soil respiration assay the digestateswere spread evenly onto the surface of the soil sample by useof a 10mL automate pipette After addition the respiration jarswere gently tapped against the table to allow gas exchangeto further distribute the digestate in the soil volume and toachieve a more homogenous soil aggregate distribution Therespiration rate was monitored every 30 minutes for five daysbefore amendment with residue to obtain basal respirationrates and then for 12 days after amendment Evolutionof CO

2collected in 03M KOH solution was determined

with a Respicond III instrument (Nordgren Innovations ABUmea Sweden) [29] Basal respiration was determined bylinear regression of the accumulated respiration data fromthe 5 days of incubation prior to the residue additionsThe basal respiration rate was subtracted from the primaryrespiration rate recorded after residue amendment to give theresidue-induced respiration rates Characteristic data werethen extracted from the residue-induced respiration curvesobtained according to the ISO standard for evaluation ofrespiration curves [30] Due to the differences between theISO standard (which uses glucose as substrate) and thepresent experiment not all the characteristic values givenin the ISO standard could be obtained The values actuallyobtained were (1) the time for the maximum respirationactivity (main peak time 119905peakmax) and (2) the microbialspecific growth rate (120583) derived from data transformed tothe natural logarithmic scale In addition (3) the maximumrespiration activity (main peak height ℎpeakmax) and (4) thetotal utilization rate ( of added C converted to CO

2) over

the 12-day incubation were assessed

242 Nitrogen Mineralization Capacity (NMC) The NMCassay was performed according to Waring and Bremner [31]asmodified by Stenberg et al [20] In the assay aliquots of 10 gww thawed soil were placed in five 250mL Duran flasks foreach treatment Different amounts of residue (representing175ndash1120 kg NH

4

+-N haminus1) were added to each set of fivereplicate flasks The dose of digestate was distributed evenlyonto the soil surface After waiting 10 minutes to allowthe digestate to absorb each flask received deionized waterto achieve a total addition of 25mL water (including thewater in the digestate but not in the soil) The flasks weremade anaerobic by evacuating and flushing them with purenitrogen (N

2) five times to inhibit nitrification The slurries

were then incubated for 10 days at 37∘C At the starttwo flasks were sampled and after 10 days the remainingthree flasks were sampled At sampling 25mL 4M KClwas added to the slurries and the flasks were placed on

a shaker for 2 h (175 rpm) after which samples of 75mL werewithdrawn into test tubes All the tubes were centrifugedfor 3min (4500 rpm) and the content filtered through afilter paper (Munktell size 00A Munktell Filter AB FalunSweden) The filtrate was then analyzed for NH

4

+ by flowinjection analysis (FIAstar 5000 Analyzer FOSS AnalyticalHileroslashd Denmark)The accumulation of ammonium during10 days (NMC)was calculated as the difference betweenmeanamounts at the start and after 10 days A supplementaryNMC test was performed by also adding glucose yieldingfinal substrate concentrations of 0 05 and 1 (ie 0 05and 1mg glucose mLminus1 resp) to soil amended with doses of(NH4)2SO4or BD-D corresponding to 1120 kg NH

4

+-N haminus1

243 Potential AmmoniumOxidation Rates (PAO) ThePAOassay was performed according to Pell et al [9] and ISO15685 [32] and effects of amendment rates corresponding to175ndash1120 kg NH

4

+-N haminus1 were tested In the assay for eachrate to be tested 3 times 25 g ww thawed soil was weighed into250mL Duran flasks After distributing the dose of digestateevenly onto the soil and then waiting for 10 minutes forthe digestate to be absorbed substrate-potassium phosphatebuffer and deionizedwaterwere added to reach a final volumeof 100mL (including the water in the digestate but not inthe soil) The final substrate in the assay contained 100mMphosphate buffer (pH 72) 04mM (NH4)

2SO4 and 15mM

NaClO3 Chlorate was used to inhibit the further conversion

of nitrite to nitrate The soil slurry was incubated on a rotaryshaker (175 rpm) at +25∘C for 6 hours Slurry samples of2mL were withdrawn after 2 hours and then once everyhour resulted in a total of five samples The samples wereplaced into test tubes prefilled with 2mL of 4M KCl tostop ammonium oxidation After each sampling occasionthe samples were centrifuged at 4500 rpm for 3min andthe supernatant filtered through a filter paper (Munktellsize 00A) The filtrate was then analyzed for NO

2

minus by flowinjection analysis (FIAstar 5000 Analyzer) The ammoniumoxidation rate (PAO)was calculated as themean value (119899 = 3)from linear regression of accumulated nitrite in each flaskover time

244 Potential Denitrification Activity (PDA) PDA wasassayed in amended soil according to the modified short-incubation C

2H2-inhibition method described by Pell et al

[33] and effects of amendment rates corresponding to 175ndash1120 kgNH

4

+-N haminus1 were tested In the assay for each rate tobe tested 3 times 25 g ww thawed soil was weighed into 250mLDuran flasks The dose of digestate was distributed evenlyonto the soil surface After waiting 10 minutes to allow thedigestate to absorb each flask was supplied with deionizedwater and substrate solution to achieve a total addition of25mL water (including the water in the digestate but not inthe soil)The substrate solution contained glucose andKNO

3

and the final concentration of these in the 25mL slurrysolution was 1mM Each residue was assayed in separateexperimental sessions with a control treatment replicatedthree times includedwhere only autoclaved water (equivalentto that in the residue) and substrate solution were added


to the soil After addition of the substrate solution theflasks were sealed and then evacuated and flushed with N

2

five times Then 25mL of acetylene was injected to inhibitthe reduction of N

2O to N

2 after which the flasks were

placed on a shaker at 175 rpm at a constant temperatureof +25∘C During the assay seven 05mL gas samples werecollected from the flask head space and injected into gastight20mL glass vials The first sample was withdrawn 15 minutesafter acetylene injection and then every 30 minutes Allsamples were analyzed by a gas chromatograph equippedwith an electron capture detector (Perkin Elmer Clarus 500Waltham MA USA) The rate of N

2O formation increased

with time and the data were fitted by nonlinear regression toa product-formation equation that takes exponential growthinto consideration [34] to yield the initial product formationrate (PDA mean value 119899 = 3)

In order to further explain the results of the PDAexperiment and to validate the PDA method a follow-upexperiment was performed This experiment included (1)a control treatment identical to the original PDA assayas described above (2) a control treatment supplied with625mL of a trace element solution according to Cohen-Bazire et al [35] and (3) a control treatment with doubleconcentration of glucose (2mM) The trace element solutionconsisted of 025mg Lminus1 Na

2MoO4sdot2H2O 1095mg Lminus1

ZnSO4sdot7H2O 500mg Lminus1 FeSO

4sdot7H2O 154mg Lminus1

MnSO4sdotH2O 039mg Lminus1 CuSO


CoCl2sdot6H2O and 017mg Lminus1 Na

2B4O7sdot10H2O All three

treatments were replicated three times In addition anonreplicated treatment (4) was performed where PS washeat-treated at 80∘C for 15 minutes to denature enzymesand kill any bacteria present before addition to the soil anda standard PDA assay was performed The PS amendmentcorresponded to 1120 kg NH

4

+-N haminus1

25 Data Treatment and Statistical Analyses Soil respirationdata were analyzed by analysis of variance using JMP version900 (SAS Institute Inc Cary NC USA) where residue typeresidue rates and residue type times residue rate interactionwere considered as fixed factors The Tukey (HSD) multiplecomparison test was used for repeated testing of paireddifferences between treatments Nitrogenmineralization data(NMC) are reported as mean values at different doses withstandard deviation The PAO and PDA responses to theincreasing doses of the residues were plotted using SigmaPlotversion 80 (Systat Software Inc San Jose CA USA) andfitted with a four parameter logistic model

119860 = 119860min +119860max minus 119860min

1 + (119888EC50)minus119867 (1)

where119860 is themeasured activity119860max is themaximum activ-ity (with no residue addition) 119860min is the lowest theoreticalactivity (at infinite residue addition) 119888 is the amendment rateEC50is the amendment rate that gives 50 activity and119867 is

the Hill coefficient The effect concentrations lowering PAOand PDAby 10 (EC

10) and 90 (EC

90) were calculated from

the values obtained in the nonlinear regression High 1198772-values of the regression indicated a good fit and are presented

Table 4 Amount of dry matter (DM) heavy metals and nutrientsadded at an amendment rate corresponding to 70 kg NH4

+-N haminus1with the four types of biogas digestates (BD-A BD-B BD-C andBD-D) and pig slurry (PS)

Parameter BD-A BD-B BD-C BD-D PSDM (kg haminus1) 854 632 425 1180 2650Tot-C (kg haminus1) 266 154 175 480 1170Tot-N (kg haminus1) 106 109 85 110 155Org-N (kg haminus1) 36 38 15 40 85NH4+-N (kg haminus1) 70 70 70 70 70

Cr (g haminus1) 182 254 2775 390 312Mn (g haminus1) 2810 4540 2300 5730 12400Ni (g haminus1) 543 606 425 34 1160Cu (g haminus1) 976 1190 995 1950 6360Zn (g haminus1) 6640 7940 7480 7910 23400Cd (g haminus1) 42 51 30 60 88Pb (g haminus1) 14 120 115 68 29Hg (g haminus1) 14 17 25 20 29

together with the EC-values in Table 6 In the PDA follow-up experiment Studentrsquos 119905-test was performed to reveal anysignificant differences Differences between treatments in allstatistical analyses were deemed statistically significant at119875 lt005 unless otherwise stated

3 Results

31 Chemical Properties of the Organic Residues Applied toSoil Overall the content of Tot-C and Org-N was lowerin the BDs than in PS (Table 3) However all BDs exceptfor BD-C had a higher concentration of NH

4

+-N thanthe PS The amounts of dry matter plant nutrients andheavy metals added with each residue at rates correspondingto 70 kg NH

4

+-N haminus1 are shown in Table 4 As nutrientaddition with the amendments was calculated on the basisof their NH

4

+-N level the PS treatments generally receivedmore Tot-C than the BD treatments The dry matter addedwith the 70 kg NH

4

+-N haminus1 dose varied between 425 and1180 kg haminus1 for the BDs while it was 2650 kg haminus1 for PSThecorresponding amounts of Tot-C and Org-N were 154ndash480and 15ndash40 kg haminus1 respectively in the different BDs and 1170and 85 kg haminus1 in PS The amounts of Mn Ni Cu Zn andHg added were higher with the PS than the BDs whereas theapplication of BD-C and BD-D resulted in the highest dosesof Cd Pb and Cr respectively

32 Soil Respiration The varying C concentrations in theresidues in combination with the increasing doses led todifferent amounts of C being respired (Table 5) At the lowestdose corresponding to 175 kg NH

4

+-N haminus1 the amounts ofC respired were very low for some of the residues and thebackground ldquonoiserdquo of the respirometer prevented extractionof some of the characteristic respiration values Howeverthe two highest amendment rates (ie corresponding to 70and 140 kg NH

4

+-N haminus1) provided clear and reliable signals


Table 5 Calculated parameters from soil respiration curves after amendment with four types of biogas digestates (BD-A BD-B BD-C andBD-D) and pig slurry (PS) 119905peakmax is the time of maximum respiration activity after amendment and the maximum peak height (ℎpeakmax) isthe respiration rate at that time Specific growth rate (120583) was calculated according to ISODIS 17155 (ie on a log10 basis)TheC utilization rateis the cumulative respired C during the 12 days of incubation Values not sharing the same letters (andashe) are statistical significantly different(119875 lt 005)

Residue type Amendment rate(kg NH4

+-N haminus1) 119905peakmax (h) ℎpeakmax (mg CO2 hminus1) Specific growth rate (120583)

Utilization rate ofC

( of added C)

BD-A

175 550c 0046e 0013d 398a

35 574b 0078de 0017d 285abc

70 621b 0141de 0017d 309ab

140 662a 0287d 0019d 325ab

BD-B

175 mdash mdash mdash mdash2

35 le851 ge00681 mdash 218bcd

70 184f 0117de 0018d 166d

140 196f 0259de 0022d 190cd

BD-C


35 le851 ge01751 mdash 137d

70 146g 0249de 0067bc 194cd

140 181f 0668c 0057bc 309ab

BD-D

175 le851 ge00371 mdash 137d

35 le851 ge00881 mdash 157cd

70 le851 ge02021 mdash 150d

140 le851 ge04051 mdash 169d

PS

175 126g 0232de 0090a 322ab

35 208f 0519c 0053c 278abc

70 292e 1111b 0060bc 311ab

140 365d 2233a 0074ab 314ab1Maximum respiration occurred before or at time of stabilization of the respirometer readings Average values from the first reliable reading (at 85 h) arereported but were not used in the statistical tests2Data points in the respiration measurements were frequently below the detection limitmdash Data not obtainable

Table 6 Effect concentrations lowering potential ammonia oxidation rate (PAO) and potential denitrification activity (PDA) in the soil by10 50 and 90 (EC10 EC50 and EC90) in response to addition of four types of biogas digestates (BD-A BD-B BD-C and BD-D) and pigslurry (PS)

Test Effect parameter Residue typeBD-A BD-B BD-C BD-D PS

PAO

EC10 (kg NH4+-N haminus1) 136 30 98 271 20

EC50 (kg NH4+-N haminus1) 140 45 156 291 50

EC90 (kg NH4+-N haminus1) 144 68 250 312 128

1198772 of nonlinear regression 099 098 099 093 100

PDA

EC10 (kg NH4+-N haminus1) 141 120 87 55 na



1198772 of nonlinear regression 098 098 097 098 na

na = values not obtainable (no inhibitory effect)

(Figure 1) Nevertheless for BD-D 119905peakmax and ℎpeakmax couldonly be approximated because of a very early maximumrespiration activity in this treatment

Increasing rates of amendment generally yielded signif-icantly later peak times (119905peakmax) and taller peaks (ℎpeakmax)

(Table 5) At 70 and 140 kg NH4

+-N haminus1 addition of BD-A resulted in the highest 119905peakmax followed by PS Thedifferences in 119905peakmax between BD-A BD-B BD-C and PSwere statistically significant except between BD-B and BD-Cat 140 kg NH

4

+-N haminus1 For BD-D 119905peakmax occurred before


the start of the readings and thus was not considered inthe statistical analysis The ℎpeakmax was considerably tallerfor PS than for any BD However the maximum respirationrate expressed as percentage of applied C was highest forBD-C (Figure 1) The specific growth rate (120583) and the Cutilization rate were generally not affected by the amendmentrate (Table 5) The highest 120583 was observed for PS and BD-C and the lowest for BD-A and BD-B but again it couldnot be determined accurately for BD-D as the respirationpeak seemed to have occurred already before the stabilizationof the respirometer readings at the start of the experiment(Figure 1)The utilization rate of C over the 12 dayswas higherfor BD-A andPS with values ranging between 278 and 398and lower for BD-D with values ranging between 137 and169

33 Nitrogen Mineralization Capacity Overall two trendsin NMC were observed after amendment with increasingamounts of residue (Figure 2) Up to a certain applicationrate increasing rates of BD resulted in decreasing NMCNegative values were observed with all BDs at doses cor-responding to 70 kg NH

4

+-N haminus1 However at applicationrates above 70ndash280 kg NH

4

+-N haminus1 a pronounced trend ofincreasing NMC with increasing dose was observed Soilamended with PS showed positive NMC at all rates and atthe highest rate PS displayed the highest NMC of all residuestested (1254120583g NH

4

+-N gminus1 ds 10 dminus1) Adding glucose alongwith the highest dose of BD-D and (NH

4)2SO4resulted in a

transition from positive to negative NMC (data not shown)

34 Potential Ammonium Oxidation Rates PAO was nega-tively correlated with the amendment rate for all residuesstarting at rates corresponding to 175ndash140 kg NH

4

+-N haminus1depending on the residue type (Figure 3) The negativeresponses were dose-dependent with BD-B and PS display-ing the strongest negative responses EC

10 EC50 and EC

90

for all tested residues ranged between 30ndash271 45ndash291 and68ndash312 kg Nhaminus1 respectively (Table 6) Digestates BD-Aand BD-D that originated from mesophilic biogas processeshad higher EC

10values than BD-B and BD-C generated in

thermophilic processes and PS

35 Potential Denitrification Activity All the residuesinduced a slight positive response in PDA at low doseswhich means that the activity of the denitrifying enzymeswas higher at these doses than in the control (Figure 4)Higher doses than 70 kg NH

4

+-N haminus1 of the four BDsresulted in a logarithmic decrease in the PDA The EC

10

EC50 and EC

90for each residue are shown in Table 6

The EC10

values of BD-D but also BD-C were lower thanthe corresponding values of the other two BDs The PSinduced a different response pattern in comparison withthe BD in that PDA increased proportionally with the PSamendment rate In the PDA follow-up experiment neithertrace element addition nor extra glucose in the assay solutionled to higher PDA compared with the control without anyaddition (119905-test 119875 lt 005) Amendment with heat-treatedPS at rates corresponding to 1120 kg NH

4

+-N haminus1 resulted

in a considerably lower PDA than amendment with non-heat-treated PS (4 versus 12 ng N

2O-N gminus1 ds minminus1

resp)

4 Discussion

In arable cropping systems organic fertilizers are generallyapplied according to their content of easily available NTherefore using the mineral N content as the basis forcalculating the application rate should be a realistic approachfor evaluating and comparing the quality of organic residuesand their impact on the soil microbial ecosystem With suchan approach the amounts of C added will vary depending onthe C content of the residue which must be considered whenevaluating the data

41 Soil Respiration All treatments displayed increasingmain peak heights (ℎpeakmax) and main peak times (119905peakmax)with increasing amounts of residue added Peak heights were10ndash30 higher after amendment with pig slurry comparedwith the BD treatments which wasmost likely an effect of the23ndash67 times higher Tot-C addition However ℎpeakmax didnot seem to reflect the total C content among the differentbiogas digestates in any apparent way The BD-D treatmentwhich resulted in the highest addition of C displayed arelatively small ℎpeakmax reflecting its small maximum respi-ration rate as a percentage of applied C The BD-A and BD-C treatments which provided roughly the same amount ofC gave distinctly different respiration patterns Generallyhigher amendment rates did not seem to have any effectson soil respiratory efficiency as indicated by the similarspecific growth and utilization rates recorded (Table 5) Oneexception to this was the utilization rate of BD-C that wasdoubled at the highest amendment rate

As would be expected from the wide variety of substratesthat were used to feed the biogas plant reactors differencesin biodegradability between the different amendments wereapparent from a number of the respiratory characteristic val-ues measured For example early respiration peaks seemedto occur in the BD-A and BD-D treatments even before thestabilization of the respirometer readings at the start of theexperiment It is likely that such early peaks were due to ahigh fraction of microbiologically accessible soluble organicC in these treatments leading to a flush in CO

2production

immediately after addition as reported by Alburquerque et al[36] and Marstorp [37] In fact these digestates both origi-nated frombiogas plant reactors operating at low temperature(mesophilic) and BD-D from a plant with a short retentiontime that is conditions less favorable for degradation oforganic components [38]

The overall utilization rate that is the degree of mineral-ization of the organic C added with the BDs and PS during12 days ranged between 150 and 325 for the two highestdoses This fell within the range found in the literature for aperiod of 12ndash14 days after application of digested materials tosoil Kirchmann and Lundvall [39] thus reported utilizationranging between 20 and 30 of the C in digested animalmanures while De Neve et al [40] and de la Fuente et al


00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-A

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(a)

00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-B

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(b)

00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-C

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(c)

00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-DRe

spira

tion

rate

( o

f add

ed C

hminus1)

(d)

00

02

04

06

08

10

12

0 100 200 300Time (h)

PS

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(e)

Figure 1 Soil respiration rate after amendment with four types of biogas residues (BD-A BD-B BD-C and BD-D) and pig slurry (PS) atrates corresponding to 140 kg NH

4

+-N haminus1 (mean 119899 = 4)


BD-A

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)

Amendment rate (kg N haminus1)

(a)

BD-B

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(b)

BD-C

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(c)

BD-D

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(d)

PS

0 200 400 600 800 1000 12000

200

400

600

800

1000

1200

1400

1600

NM

C(120583

g N

gminus1

ds10

dminus1)


(e)

Figure 2 Dose-response test of nitrogen mineralization capacity (NMC) in the soil after amendment with different types of biogas residues(BD-A BD-B BD-C and BD-D) and pig slurry (PS) Error bars represent mean values plusmn standard deviation (119899 = 3) Note the difference inthe 119910-axis scaling of PS


BD-A

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-

Amendment rate (kg NH4+ haminus1)-N

(a)

BD-B

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2minus

gminus1

dsm

inminus1)

-N


(b)

BD-C

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(c)

BD-D

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(d)

PS

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(e)

Figure 3 Potential ammonium oxidation (PAO) in the soil at seven amendment rates of four types of biogas residues (BD-A BD-B BD-Cand BD-D) and pig slurry (PS)

[41] observed that ca 12 and 15ndash33 of biogas digestateC were utilized respectively Interestingly in the presentstudy the utilization rate at the highest dose of BD-A andBD-C both originating from slaughterhouse and food wastefed processes was approximately equal to that of PS (325

and 309 versus 314 resp) The low C utilization rateof BD-B could be explained by the fact that distillerrsquos wasteconstituted 97 of the feedstock in this biogas processDistillerrsquos waste originates from a fermentation processoptimized for converting C into high yields of ethanol giving


BD-A

0 200 400 600 800 1000 12000

2

4

6

8

10

12

Amendment rate (kg NH4+-N haminus1)

PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(a)

BD-B

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(b)

0 200 400 600 800 1000 12000

2

4

6

8

10

12 BD-C


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(c)

BD-D

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(d)

PS

0 200 400 600 800 1000 12000

5

10

15

20

25


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(e)

Figure 4 Potential denitrification activity (PDA) in the soil at seven amendment rates of four types of biogas residues (BD-A BD-B BD-Cand BD-D) and pig slurry (PS)


a digestate dominated by compounds recalcitrant to furtherdecomposition The apparent low C utilization rate of BD-Dis probably an effect of the main respiration peak occurringbefore the first respirometer readings in the experiment

42 Nitrogen Mineralization Capacity Normally the CNratio of the degraded material regulates if nitrogen isassimilated or mineralized when organic amendments withCN ratios below 20 are added to soils net mineralizationdominates while at higher CN ratio net assimilation is thedominant process [42 43] In the present study the CNratio of the organic matter in the BDs ranged between 42and 12 while it was 13 in the PS theoretically this shouldhave stimulated mineralization resulting in a net release ofN This held true for the highest doses of BDs where itseemed that available C in the soil and residues was limitingand could not sustain the ability of the microorganisms toassimilate the ammonium released The observations madein the supplementary glucose experiment confirmed that Climited N assimilation in these cases Adding glucose to thesoil amended with a high dose of (NH

4

+)2SO4resulted in

net assimilation while glucose addition to the soil amendedwith BD-D caused a transition from net mineralization tonet assimilation and the balance was further shifted byincreasing glucose concentration (data not shown) confirm-ing observations by Azam et al [44] A correlation betweenthe content of easily available C in the organic residue and theamounts of nitrogen immobilized was also demonstrated byfor example Kirchmann and Lundvall [39] who concludedthat fatty acids acted as an easily decomposable C source formicroorganisms causing assimilation of N upon applicationto soil

At lower doses additions of BDs induced a small butsignificant net assimilation rather than release of N indi-cating that the CN ratio of the added digestate alone didnot determine which process dominated However this Nassimilation is likely to be a transient process since addition ofthe same digestates at application rates between 35 and 140 kgNH4

+-N haminus1 was found to stimulate N mineralization after77 days of incubation in a pot experiment with spring wheat[45] An initial period of immobilization of ammoniumafter application of anaerobically digested material to thesoil has been reported before in several studies [36 46]Alburquerque et al [36] attributed this assimilation to aconcomitant high microbial activitycarbon mineralization

The CN ratio of the residues used in the present studycould not explain the variability in Nmineralization capacitybetween the amendment types specific compounds in theBDsmay therefore bemore critical for short-termN turnoverthan the total contents of C and N These observations agreewell with those of for example Qafoku et al [47] who foundthat potential N mineralization was strongly correlated withwater-soluble organic N but poorly correlated with the CNratioThis confirms that discussing short-termNmineraliza-tion in terms of the available fractions of C and N ratherthan the total amounts is more informative The pattern ofrespiration rates following application of organic materials tothe soil may indicate which compounds and amounts that are

decomposed [48 49] For example the 119905peakmax of BD-A and asecond hump on the respiration curve of PS both at 70ndash80 hcoincided in timewith respiration peaks seen after addition ofsole proteins (ie albumin casein and rubisco) under similarexperimental conditions by Gunnarsson and Marstorp [50]and Gunnarsson (unpublished) This could indicate thatproteins contained in BD-A and PS were decomposed atthis time leading to the observed net mineralization of Nand lending support to the notion that differences in Nmineralizing capacity of the amendments may be sought intheir easily available organic fractions

43 Ammonia Oxidation and Denitrification Activity Alltested residues inhibited PAO and PDA at amendment ratesthat could be considered realistic field rates and some-times even at lower rates with the exception of PS thatstimulated PDA at all rates One possible explanation forthis inhibitory effect could be pollutants contained in theseresidues and hence the results should be considered anearly warning of potential contamination It has been shownthat ammonia oxidation is sensitive to pollutants that arecommonly found in PS and BDs for example phenols [51]Furthermore anaerobically digested residue contains variousorganic compounds such as fatty acid esters [52 53] whichaffect ammonia oxidation negatively [54 55] It has alsobeen shown that anaerobically digested residues originatingfrom source-separated organic waste and industrial foodwaste can contain high concentrations of organic pollutantssuch as polycyclic aromatic hydrocarbons (PAH) and diethyl-hexyl phthalate (DEHP) as well as high concentrations offungicides such as imazalil and thiabendazole [56] whichmight affect soil microorganisms negatively Residues gener-ated from anaerobic digestion at thermophilic temperaturesaffect ammonia oxidation more negatively than mesophilicdigestates [57] since the degradation of organic pollutants ismore efficient under lower temperatures [8 51] This couldalso be the explanation for the higher EC

10values observed

for PAO in the present study upon addition of BD-A andBD-D compared with the other two BDs as the formerdigestates originated from mesophilic processes Moreoverat doses corresponding to between 70 and 1120 kg NH

4

+-N haminus1 concentrations of Cu and Zn ranged between 14-50mg and 10ndash252mg kgminus1 of soil respectively The higherconcentrations of Cu and Zn in these cases fell within therange that is toxic for denitrification as Holtan-Hartwig et al[58] observed that adding 032 and 120mg kgminus1 soil of Cu andZn respectively to the soil can inhibit denitrification activityHowever the inhibitory effects observed on PAO and PDAmay last for just a very short period as shown by Abubaker[59] when he measured the activity 24 h 11 and 24 daysafter addition of the same biogas digestates Such transientnegative effects on ammonia oxidation bacteria have alsobeen observed by Nyberg et al [57] in soil amended with PS

In contrast no inhibition effect of PDA was detectedin the soil amended with PS instead a stimulatory effectwas observed which was positively correlated with increasingdoses of PS The higher supply of C with PS addition couldhave been a possible explanation for the higher PDA since


denitrifying bacteria use C as energy source [60] Howeverdoubling the amount of glucose or adding a trace elementsolution did not increase the PDA in comparison with thecontrol (data not shown) Instead the low PDA of heat-treated PS indicated that the PS itself contained denitrifiersor heat-sensitive enzymes with denitrifying abilities

5 Conclusions

Application of four different biogas digestates and pig slurryto soil resulted in both stimulatory and inhibitory short-term effects onmicrobial functions Soil respiration displayedvarying patterns reflecting the differences in both the quan-tity and quality of the organic carbon in the residues butno negative effects were observed Based on the nitrogenmineralization capacity results it can be concluded thatadding biogas digestates to the soil system could limit thenitrogen availability to plant roots in the short-term at ratesranging between 70 and 280 kg NH

4

+-N haminus1 The resultsalso showed that fertilization with pig slurry resulted in moreavailable mineral N in the soil compared with addition ofbiogas digestates This is probably the explanation of theresults reported about the same residues by Abubaker etal [45] where PS gave high wheat yield compared to BDsAdding biogas digestates to the soil had a strong negativeeffect on both ammonia oxidation and denitrification whichis a concern in terms of soil health and should be an earlywarning of potential hazardous substances in the residuesHowever retarded nitrification and denitrification directlyafter application of a residue can also be regarded as positiveas losses of nitrogen by leaching or gaseous emissions couldthereby be decreased

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors gratefully acknowledge the MicroDrivE pro-gram (httpmicrodrivephosdevse) funded by the SwedishUniversity of Agricultural Sciences (SLU) for financiallysupporting and encouraging this work

References

[1] P Borjesson and B Mattiasson ldquoBiogas as a resource-efficientvehicle fuelrdquo Trends in Biotechnology vol 26 no 1 pp 7ndash132008

[2] S Fouda S von Tucher F Lichti and U Schmidhalter ldquoNitro-gen availability of various biogas residues applied to ryegrassrdquoJournal of Plant Nutrition and Soil Science vol 176 no 4 pp572ndash584 2013

[3] A Herrmann K Sieling B Wienforth F Taube and HKage ldquoShort-term effects of biogas residue application on yieldperformance and N balance parameters of maize in differentcropping systemsrdquo Journal of Agricultural Science vol 151 no4 pp 449ndash462 2013

[4] M Kvasauskas and P Baltrenas ldquoAnaerobic recycling of organicwaste and recovery of biogasrdquo Ekologija vol 54 no 1 pp 57ndash632008

[5] M H Gerardi The Microbiology of Anaerobic Digesters JohnWiley amp Sons Hoboken NJ USA 2003

[6] T Kupper D Burge H J Bachmann S Gusewell and J MayerldquoHeavy metals in source-separated compost and digestatesrdquoWaste Management vol 34 no 5 pp 867ndash874 2014

[7] M Engwall and A Schnurer ldquoFate of Ah-receptor agonistsin organic household waste during anaerobic degradationmdashestimation of levels using EROD induction in organ cultures ofchick embryo liversrdquo Science of the Total Environment vol 297no 1ndash3 pp 105ndash108 2002

[8] L Leven and A Schnurer ldquoEffects of temperature on biolog-ical degradation of phenols benzoates and phthalates undermethanogenic conditionsrdquo International Biodeterioration ampBiodegradation vol 55 no 2 pp 153ndash160 2005

[9] M Pell B Stenberg and L Torstensson ldquoPotential denitrifica-tion and nitrification tests for evaluation of pesticide effects insoilrdquo Ambio vol 27 no 1 pp 24ndash28 1998

[10] M Odlare M Pell and K Svensson ldquoChanges in soil chemicaland microbiological properties during 4 years of application ofvarious organic residuesrdquoWaste Management vol 28 no 7 pp1246ndash1253 2008

[11] A K Bandick and R P Dick ldquoField management effects on soilenzyme activitiesrdquo Soil Biology and Biochemistry vol 31 no 11pp 1471ndash1479 1999

[12] L A Biederman and S G Whisenant ldquoAmendment placementdirects soil carbon and nitrogen cycling in severely disturbedsoilsrdquo Restoration Ecology vol 19 no 3 pp 360ndash370 2011

[13] A Michelsen M Andersson M Jensen A Kjoslashller and MGashew ldquoCarbon stocks soil respiration andmicrobial biomassin fire-prone tropical grassland woodland and forest ecosys-temsrdquo Soil Biology andBiochemistry vol 36 no 11 pp 1707ndash17172004

[14] R C Dalal ldquoSoil microbial biomassmdashwhat do the numbersreally meanrdquo Australian Journal of Experimental Agriculturevol 38 no 7 pp 649ndash665 1998

[15] R Nieder E Neugebauer A Willenbockel K C Kersebaumand J Richter ldquoNitrogen transformation in arable soils ofNorth-West Germany during the cereal growing seasonrdquo Biol-ogy and Fertility of Soils vol 22 no 1-2 pp 179ndash183 1996

[16] T Rosswall ldquoMicrobiological regulation of the biogeochemicalnitrogen cyclerdquo Plant and Soil vol 67 no 1-3 pp 15ndash34 1982

[17] M Odlare and M Pell ldquoEffect of wood fly ash and composton nitrification and denitrification in agricultural soilrdquo AppliedEnergy vol 86 no 1 pp 74ndash80 2009

[18] A N Harvey I Snape and S D Siciliano ldquoValidating potentialtoxicity assays to assess petroleumhydrocarbon toxicity in polarsoilrdquo Environmental Toxicology and Chemistry vol 31 no 2 pp402ndash407 2012

[19] P van Beelen and P Doelman ldquoSignificance and applicationof microbial toxicity tests in assessing ecotoxicological risks ofcontaminants in soil and sedimentrdquo Chemosphere vol 34 no3 pp 455ndash499 1997

[20] B StenbergM JohanssonM Pell K Sjodahl-Svensson J Sten-strom and L Torstensson ldquoMicrobial biomass and activitiesin soil as affected by frozen and cold storagerdquo Soil Biology ampBiochemistry vol 30 no 3 pp 393ndash402 1998

[21] H Egner H Riehm and W R Domingo ldquoInvestigations onchemical soil analysis as the basis for estimating soil fertility


II Chemical extractionmethods for phosphorus and potassiumdeterminationrdquo Kunliga Lantbruksogskolans Annaler vol 26pp 199ndash215 1960

[22] Swedish Institute for Standards (SIS) ldquoSoil analysismdashdetermination of trace elements in soilmdashextraction withnitric acidsrdquo Tech Rep SS028311 Swedish Institute forStandards (SIS) Stockholm Sweden 1997

[23] R G McLaren and K C Cameron Soil Science SustainableProduction and Environmental Protection 2nd Ed OxfordUniversity Press Oxford UK 1996

[24] G Jung ldquoMekanisk analysmdashbeskrivning av en rationell metodfor jordartsbestamning (mechanical analysismdasha description ofa rational method for determination of soil type)rdquo Report872 Department of Soil Science The Swedish University forAgricultural Sciences 1987

[25] SIS (Swedish Standards Institute) ldquoCharacterization of sludgesdetermination of dry residue and water contentrdquo Tech Rep SS-EN Standard 12880 SIS (Swedish Standards Institute) Stock-holm Sweden 2000 (Swedish)

[26] International Organization for Standardization ldquoSoil qualitymdashdetermination of organic and total carbon after dry combustion(elementar analysis)rdquo ISO 10694 ISO Geneva Switzerland1995

[27] ISO (International Organization for Standardization) ldquoSoilquality-determination of total nitrogen content by dry combus-tion (elemental analysis)rdquo ISO 13878 ISO Geneva Switzerland1998

[28] SIS (Swedish Standards Institute) Soil AnalysismdashDeteremination of Trace Elements in SoilsmdashExtraction withNitric Acids SS28311 Stockholm Sweden 1997 (Swedish)

[29] A Nordgren ldquoApparatus for the continuous long-term moni-toring of soil respiration rate in large numbers of samplesrdquo SoilBiology amp Biochemistry vol 20 no 6 pp 955ndash957 1988

[30] ISO (International Organization for Standardization) ldquoSoilquality-determination of abundance and activity of soilmicroflora using respiration curvesrdquo ISO 17155 ISO GenevaSwitzerland 2001

[31] S A Waring and J M Bremner ldquoAmmonium productionin soil under waterlogged conditions as an index of nitrogenavailabilityrdquo Nature vol 201 pp 951ndash952 1964

[32] International Organization for Standardization ldquoSoil qualitymdashdetermination of potential nitrificationmdashrapid test by ammo-nium oxidationrdquo ISO 15685 ISO Geneva Switzerland 2004

[33] M Pell B Stenberg J Stenstrom and L Torstensson ldquoPotentialdenitrification activity assay in soilmdashwith or without chloram-phenicolrdquo Soil Biology and Biochemistry vol 28 no 3 pp 393ndash398 1996

[34] J Stenstrom A Hansen and B Svensson ldquoKinetics of micro-bial growth associated product formationrdquo Swedish Journal ofAgricultural Research vol 21 no 2 pp 55ndash62 1991

[35] G Cohen-Bazire W R Sistrom and R Y Stanier ldquoKineticstudies of pigment synthesis by non-sulfur purple bacteriardquoJournal of Cellular and Comparative Physiology vol 49 no 1pp 25ndash68 1957

[36] J A Alburquerque C de la Fuente andM P Bernal ldquoChemicalproperties of anaerobic digestates affecting C and N dynamicsin amended soilsrdquo Agriculture Ecosystems amp Environment vol160 pp 15ndash22 2012

[37] H Marstorp ldquoInfluence of soluble carbohydrates free aminoacids and protein content on the decomposition of Loliummultiflorum shootsrdquo Biology and Fertility of Soils vol 21 no 4pp 257ndash263 1996

[38] C Gallert and J Winter ldquoMesophilic and thermophilic anaero-bic digestion of source-sorted organic wastes effect of ammoniaon glucose degradation and methane productionrdquo AppliedMicrobiology and Biotechnology vol 48 no 3 pp 405ndash410 1997

[39] H Kirchmann and A Lundvall ldquoRelationship between Nimmobilization and volatile fatty acids in soil after applicationof pig and cattle slurryrdquo Biology and Fertility of Soils vol 15 no3 pp 161ndash164 1993

[40] S De Neve S Sleutel and G Hofman ldquoCarbon mineralizationfromcomposts and food industrywastes added to soilrdquoNutrientCycling in Agroecosystems vol 67 no 1 pp 13ndash20 2003

[41] C de la Fuente J A Alburquerque R Clemente and M PBernal ldquoSoil C and N mineralisation and agricultural valueof the products of an anaerobic digestion systemrdquo Biology andFertility of Soils vol 49 no 3 pp 313ndash322 2013

[42] D D Myrold ldquoTransformations of nitrogenrdquo in Principles andApplications of Soil Microbiology D M Sylvia J J FuhrmannP G Hartel and D A Zuberer Eds chapter 12 pp 259ndash294Prentice Hall Upper Saddle River NJ USA 1st edition 999

[43] M S Luce J K Whalen N Ziadi and B J Zebarth ldquoNitrogendynamics and indices to predict soil nitrogen supply in humidtemperate soilsrdquo Advances in Agronomy vol 112 pp 55ndash1022011

[44] F Azam F W Simmons and R L Mulvaney ldquoImmobilizationof ammonium and nitrate and their interaction with native Nin three Illinois Mollisolsrdquo Biology and Fertility of Soils vol 15no 1 pp 50ndash54 1993

[45] J Abubaker K Risberg and M Pell ldquoBiogas residues asfertilisersmdasheffects on wheat growth and soil microbial activi-tiesrdquo Applied Energy vol 99 pp 126ndash134 2012

[46] M Grigatti G Di Girolamo R Chincarini C Ciavatta and LBarbanti ldquoPotential nitrogen mineralization plant utilizationefficiency and soil CO

2emissions following the addition of

anaerobic digested slurriesrdquo Biomass and Bioenergy vol 35 no11 pp 4619ndash4629 2011

[47] O S Qafoku M L Cabrera W R Windham and N SHill ldquoRapid methods to determine potentially mineralizablenitrogen in broiler litterrdquo Journal of Environmental Quality vol30 no 1 pp 217ndash221 2001

[48] S Gunnarsson Optimisation of N ReleasemdashInfluence Of PlantMaterial Chemical Composition on C and N Mineralisation[Doctoral Thesis] vol 381 of Acta Universitatis agriculturaeSuecia Swedish University of Agricultural Sciences 2003

[49] S Gunnarsson HMarstorp A S Dahlin and EWitter ldquoInflu-ence of non-cellulose structural carbohydrate composition onplant material decomposition in soilrdquo Biology and Fertility ofSoils vol 45 no 1 pp 27ndash36 2008

[50] S Gunnarsson andHMarstorp ldquoCarbohydrate composition ofplant materials determines N mineralisationrdquo Nutrient Cyclingin Agroecosystems vol 62 no 2 pp 175ndash183 2002

[51] L Leven K Nyberg L Korkea-aho and A Schnurer ldquoPhenolsin anaerobic digestion processes and inhibition of ammoniaoxidising bacteria (AOB) in soilrdquo Science of the Total Environ-ment vol 364 no 1ndash3 pp 229ndash238 2006

[52] M-L Nilsson H Kylin and P Sundin ldquoMajor extractableorganic compounds in the biologically degradable fraction offresh composted and anaerobically digested household wasterdquoActa Agriculturae Scandinavica Section B Soil and Plant Sciencevol 50 no 2 pp 57ndash65 2000

[53] R R Singhania A K Patel G Christophe P Fontanille andC Larroche ldquoBiological upgrading of volatile fatty acids key


intermediates for the valorization of biowaste through darkanaerobic fermentationrdquo Bioresource Technology vol 145 pp166ndash174 2013

[54] M R Hockenbury and C P L Grady Jr ldquoInhibition ofnitrification effects of selected organic compoundsrdquo Journal ofthe Water Pollution Control Federation vol 49 no 5 pp 768ndash777 1977

[55] G V Subbarao K L Sahrawat K Nakahara et al ldquoA paradigmshift towards low-nitrifying production systems the role ofbiological nitrification inhibition (BNI)rdquo Annals of Botany vol112 no 2 pp 297ndash316 2013

[56] E Govasmark J Stab B Holen D Hoornstra T Nesbakk andM Salkinoja-Salonen ldquoChemical and microbiological hazardsassociatedwith recycling of anaerobic digested residue intendedfor agricultural userdquo Waste Management vol 31 no 12 pp2577ndash2583 2011

[57] K Nyberg A Schnurer I Sundh A Jarvis and S HallinldquoAmmonia-oxidizing communities in agricultural soil incu-bated with organic waste residuesrdquo Biology and Fertility of Soilsvol 42 no 4 pp 315ndash323 2006

[58] L Holtan-Hartwig M Bechmann T R Hoslashyas R Linjordetand L R Bakken ldquoHeavy metals tolerance of soil denitrifyingcommunities N

2O dynamicsrdquo Soil Biology and Biochemistry

vol 34 no 8 pp 1181ndash1190 2002[59] J Abubaker Effects of fertilisation with biogas residues on crop

yield soil microbiology and greenhouse gas emissions [PhDthesis] Acta Universitatis Agriculturae Suecia 2012

[60] L Philippot S Hallin andM Schloter ldquoEcology of denitrifyingprokaryotes in agricultural soilrdquoAdvances in Agronomy vol 96pp 249ndash305 2007

Submit your manuscripts athttpwwwhindawicom

Forestry ResearchInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Environmental and Public Health

Journal of



EcosystemsJournal of


MeteorologyAdvances in

EcologyInternational Journal of


Marine BiologyJournal of


Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

Advances in


Environmental Chemistry

Atmospheric SciencesInternational Journal of



Waste ManagementJournal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal of

Geophysics


Geological ResearchJournal of

EarthquakesJournal of


BiodiversityInternational Journal of


ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

OceanographyInternational Journal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014


ClimatologyJournal of


otherwise be very expensive or even impossible to analyzeIf negative effects are detected this could motivate a morethorough chemical investigation

Several microbial soil tests related to carbon cycling havebeen used to assess andmonitor soil quality [12] For instancesoil respiration provides information on the heterotrophicactivity of the microbial biomass [13] and estimates of totalsoil microbial biomass are commonly used as indicators ofsoil quality [14] Tests of microbial functions related to thenitrogen cycle may be particularly useful when assessing soilmicrobial health and determining plant nitrogen availability[15] All main microbial processes in the nitrogen cyclemineralization immobilization or assimilation nitrificationdenitrification and nitrogen fixation have been used forstudying treatment effects on soil [9 16] Denitrification andnitrification are sensitive to disturbances and hence theseprocesses are ideal for detecting the presence of contaminantssuch as heavy metals pesticides and organic toxicants [917] In general nitrification that is ammonia oxidation andnitrite oxidation is performed by only a small number ofspecialist species within bacteria but also within Archaeawhich makes monitoring nitrification a suitable tool forpredicting toxicity [18] By contrast nitrogen mineralizationis performed by a multitude of species with the ability toreplace each other if any group is negatively affected and maybemore suitable for detecting general impacts and changes insoil fertility and nitrogen availability [19]

The overall aim of the present study was to evaluate thesuitability of using biogas digestates as fertilizers in arablecropping In dose-response tests we studied the short-termeffect on soil microbial respiration nitrogen mineralizationcapacity ammonium oxidation and denitrification potentialin order to detect any negative effects on these criticalsoil functions The effects induced by the digestates werecompared to those induced by pig slurry a well-knownfertilizer used in agriculture

2 Material and Methods

21 Soil Sampling and Characteristics Clay soil was collectedfrom the top 0ndash20 cm layer of an arable field located in centralSweden (N 59∘369851015840 E 16∘396741015840 (WGS84 lat lon) Thesoil is classified as an Eutric Cambisol (FAO 1998) and hassince 1998 annually been fertilized with 100 kg N (50 NH

4-

N and 50 NO3-N) No farmyard manure has been applied

since 1975 From 1998 a simple crop rotation has been appliedwith spring barley and oats grown in alternate years thecrop residue is removed as straw After sampling the soilwas briefly stored at +2∘C before it was sieved (Oslash lt 4mm)thoroughlymixed and then portioned into polyethylene bagsand stored at minus20∘C until use [20] Total soil carbon (Tot-C)total nitrogen (Tot-N) and total sulphur (Tot-S) were deter-mined after combustion at 1250∘C with a carbon nitrogenand sulphur analyzer (CNS-2000 LECO Equipment CorpSt Joseph MI USA) Tot-C was corrected for carbonate togive organic carbon (Org-C) Available phosphorus (P-AL)and potassium (K-AL) were extracted with the ammoniumlactate method (AL) and analyzed as described by Egneret al [21] The pH was determined in 001M CaCl

2with

Table 1 Chemical physical and microbiological characteristics ofthe soil used in the experiment [10]

Parameter ValueChemical analysespH 56Org-C () 13Tot-C () 13Tot-N () 01Tot-P (mg kgminus1 ds) 700Tot-S (mg kgminus1 ds) 200P AL (mg kgminus1 ds) 48K AL (mg kgminus1 ds) 185Cu (mg kgminus1 ds) 26Zn (mg kgminus1 ds) 91Cd (mg kgminus1 ds) 03Ni (mg kgminus1 ds) 24Pb (mg kgminus1 ds) 20Cr (mg kgminus1 ds) 36Physical analysesDM () 853Sand () 14ndash20Silt () 36ndash44Clay () 37ndash49WHC (g gminus1 ds) 051Microbial analysesNMC (120583g N gminus1ds 10 dminus1) 212PAO (ng NO2-N gminus1 dsminminus1) 48PDA (ng N2O-N gminus1 dsminminus1) 78B-resp (120583g CO2 g

minus1 ds hminus1) 078SIR (120583g CO2-C gminus1 ds hminus1) 135

the volvol ratio 1 2 (pHCaCl2) Pseudo-total phosphorus(Tot-P) cadmium (Cd) chromium (Cr) copper (Cu) nickel(Ni) lead (Pb) and zinc (Zn) were analyzed by ICPMS(Perkin-Elmer ICP Optima 3000 Waltham MA USA)according to SS 02 83 11 [22] Dry matter (DM) was assessedby the method described by McLaren and Cameron [23]The particle size distribution was determined by the pipettemethod according to Jung [24] The analyses of biologicalproperties of the soil are described below (see Section 24Microbiological Assays) The chemical physical and biolog-ical characteristics of the soil are presented in Table 1

22 Organic Residues Biogas digestates were collected fromfour large-scale biogas plants (BD-A BD-B BD-C and BD-D) in Sweden The digestates were chosen to represent bothmesophilic and thermophilic processes fed with a wide rangeof organic residues from municipality and agriculture Alldigestates fulfilled the SPCR 120 certification rules for asafe fertilizing agent (httpwwwavfallsverigesein-english211114) These certification rules are based on documentssuch as the European Union health rules regarding ani-mal by-products and derived products not intended forconsumption (EC number 10692009 httpeur-lexeuropaeu 251114) Furthermore all values for metals except for










4


4











4


4


4


4




2) over



4





4


4

+-N haminus1


4


2SO4 and 15mM



2





4


3




2


2O to N














4

+-N haminus1


119860 = 119860min +119860max minus 119860min

1 + (119888EC50)minus119867 (1)



10) and 90 (EC








3 Results


4


4


4


4



4


4







( of added C)

BD-A

175 550c 0046e 0013d 398a

35 574b 0078de 0017d 285abc

70 621b 0141de 0017d 309ab

140 662a 0287d 0019d 325ab

BD-B



70 184f 0117de 0018d 166d

140 196f 0259de 0022d 190cd

BD-C


35 le851 ge01751 mdash 137d

70 146g 0249de 0067bc 194cd

140 181f 0668c 0057bc 309ab

BD-D

175 le851 ge00371 mdash 137d

35 le851 ge00881 mdash 157cd

70 le851 ge02021 mdash 150d

140 le851 ge04051 mdash 169d

PS

175 126g 0232de 0090a 322ab

35 208f 0519c 0053c 278abc

70 292e 1111b 0060bc 311ab




PAO

EC10 (kg NH4+-N haminus1) 136 30 98 271 20

EC50 (kg NH4+-N haminus1) 140 45 156 291 50

EC90 (kg NH4+-N haminus1) 144 68 250 312 128


PDA










4





4


4


4


4)2SO4resulted in a



4


10 EC50 and EC

90





4


10

EC50 and EC


The EC10


4




resp)

4 Discussion




2production




00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-A

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(a)

00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-B

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(b)

00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-C

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(c)

00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-DRe

spira

tion

rate

( o

f add

ed C

hminus1)

(d)

00

02

04

06

08

10

12

0 100 200 300Time (h)

PS

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(e)


4



BD-A

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(a)

BD-B

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(b)

BD-C

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(c)

BD-D

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(d)

PS

0 200 400 600 800 1000 12000

200

400

600

800

1000

1200

1400

1600

NM

C(120583

g N

gminus1

ds10

dminus1)


(e)



BD-A

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(a)

BD-B

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2minus

gminus1

dsm

inminus1)

-N


(b)

BD-C

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(c)

BD-D

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(d)

PS

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(e)





BD-A

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(a)

BD-B

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(b)

0 200 400 600 800 1000 12000

2

4

6

8

10

12 BD-C


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(c)

BD-D

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(d)

PS

0 200 400 600 800 1000 12000

5

10

15

20

25


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(e)





4

+)2SO4resulted in







10values observed


4





5 Conclusions


4




Acknowledgments


References









































































Journal of












Volume 2014

Advances in









Geophysics























4


4











4


4


4


4




2) over



4





4


4

+-N haminus1


4


2SO4 and 15mM



2





4


3




2


2O to N














4

+-N haminus1


119860 = 119860min +119860max minus 119860min

1 + (119888EC50)minus119867 (1)



10) and 90 (EC








3 Results


4


4


4


4



4


4







( of added C)

BD-A

175 550c 0046e 0013d 398a

35 574b 0078de 0017d 285abc

70 621b 0141de 0017d 309ab

140 662a 0287d 0019d 325ab

BD-B



70 184f 0117de 0018d 166d

140 196f 0259de 0022d 190cd

BD-C


35 le851 ge01751 mdash 137d

70 146g 0249de 0067bc 194cd

140 181f 0668c 0057bc 309ab

BD-D

175 le851 ge00371 mdash 137d

35 le851 ge00881 mdash 157cd

70 le851 ge02021 mdash 150d

140 le851 ge04051 mdash 169d

PS

175 126g 0232de 0090a 322ab

35 208f 0519c 0053c 278abc

70 292e 1111b 0060bc 311ab




PAO

EC10 (kg NH4+-N haminus1) 136 30 98 271 20

EC50 (kg NH4+-N haminus1) 140 45 156 291 50

EC90 (kg NH4+-N haminus1) 144 68 250 312 128


PDA










4





4


4


4


4)2SO4resulted in a



4


10 EC50 and EC

90





4


10

EC50 and EC


The EC10


4




resp)

4 Discussion




2production




00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-A

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(a)

00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-B

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(b)

00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-C

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(c)

00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-DRe

spira

tion

rate

( o

f add

ed C

hminus1)

(d)

00

02

04

06

08

10

12

0 100 200 300Time (h)

PS

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(e)


4



BD-A

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(a)

BD-B

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(b)

BD-C

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(c)

BD-D

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(d)

PS

0 200 400 600 800 1000 12000

200

400

600

800

1000

1200

1400

1600

NM

C(120583

g N

gminus1

ds10

dminus1)


(e)



BD-A

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(a)

BD-B

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2minus

gminus1

dsm

inminus1)

-N


(b)

BD-C

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(c)

BD-D

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(d)

PS

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(e)





BD-A

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(a)

BD-B

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(b)

0 200 400 600 800 1000 12000

2

4

6

8

10

12 BD-C


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(c)

BD-D

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(d)

PS

0 200 400 600 800 1000 12000

5

10

15

20

25


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(e)





4

+)2SO4resulted in







10values observed


4





5 Conclusions


4




Acknowledgments


References









































































Journal of












Volume 2014

Advances in









Geophysics

















4


4


4


4




2) over



4





4


4

+-N haminus1


4


2SO4 and 15mM



2





4


3




2


2O to N














4

+-N haminus1


119860 = 119860min +119860max minus 119860min

1 + (119888EC50)minus119867 (1)



10) and 90 (EC








3 Results


4


4


4


4



4


4







( of added C)

BD-A

175 550c 0046e 0013d 398a

35 574b 0078de 0017d 285abc

70 621b 0141de 0017d 309ab

140 662a 0287d 0019d 325ab

BD-B



70 184f 0117de 0018d 166d

140 196f 0259de 0022d 190cd

BD-C


35 le851 ge01751 mdash 137d

70 146g 0249de 0067bc 194cd

140 181f 0668c 0057bc 309ab

BD-D

175 le851 ge00371 mdash 137d

35 le851 ge00881 mdash 157cd

70 le851 ge02021 mdash 150d

140 le851 ge04051 mdash 169d

PS

175 126g 0232de 0090a 322ab

35 208f 0519c 0053c 278abc

70 292e 1111b 0060bc 311ab




PAO

EC10 (kg NH4+-N haminus1) 136 30 98 271 20

EC50 (kg NH4+-N haminus1) 140 45 156 291 50

EC90 (kg NH4+-N haminus1) 144 68 250 312 128


PDA










4





4


4


4


4)2SO4resulted in a



4


10 EC50 and EC

90





4


10

EC50 and EC


The EC10


4




resp)

4 Discussion




2production




00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-A

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(a)

00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-B

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(b)

00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-C

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(c)

00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-DRe

spira

tion

rate

( o

f add

ed C

hminus1)

(d)

00

02

04

06

08

10

12

0 100 200 300Time (h)

PS

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(e)


4



BD-A

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(a)

BD-B

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(b)

BD-C

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(c)

BD-D

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(d)

PS

0 200 400 600 800 1000 12000

200

400

600

800

1000

1200

1400

1600

NM

C(120583

g N

gminus1

ds10

dminus1)


(e)



BD-A

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(a)

BD-B

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2minus

gminus1

dsm

inminus1)

-N


(b)

BD-C

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(c)

BD-D

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(d)

PS

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(e)





BD-A

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(a)

BD-B

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(b)

0 200 400 600 800 1000 12000

2

4

6

8

10

12 BD-C


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(c)

BD-D

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(d)

PS

0 200 400 600 800 1000 12000

5

10

15

20

25


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(e)





4

+)2SO4resulted in







10values observed


4





5 Conclusions


4




Acknowledgments


References









































































Journal of












Volume 2014

Advances in









Geophysics
















2


2O to N














4

+-N haminus1


119860 = 119860min +119860max minus 119860min

1 + (119888EC50)minus119867 (1)



10) and 90 (EC








3 Results


4


4


4


4



4


4







( of added C)

BD-A

175 550c 0046e 0013d 398a

35 574b 0078de 0017d 285abc

70 621b 0141de 0017d 309ab

140 662a 0287d 0019d 325ab

BD-B



70 184f 0117de 0018d 166d

140 196f 0259de 0022d 190cd

BD-C


35 le851 ge01751 mdash 137d

70 146g 0249de 0067bc 194cd

140 181f 0668c 0057bc 309ab

BD-D

175 le851 ge00371 mdash 137d

35 le851 ge00881 mdash 157cd

70 le851 ge02021 mdash 150d

140 le851 ge04051 mdash 169d

PS

175 126g 0232de 0090a 322ab

35 208f 0519c 0053c 278abc

70 292e 1111b 0060bc 311ab




PAO

EC10 (kg NH4+-N haminus1) 136 30 98 271 20

EC50 (kg NH4+-N haminus1) 140 45 156 291 50

EC90 (kg NH4+-N haminus1) 144 68 250 312 128


PDA










4





4


4


4


4)2SO4resulted in a



4


10 EC50 and EC

90





4


10

EC50 and EC


The EC10


4




resp)

4 Discussion




2production




00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-A

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(a)

00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-B

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(b)

00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-C

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(c)

00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-DRe

spira

tion

rate

( o

f add

ed C

hminus1)

(d)

00

02

04

06

08

10

12

0 100 200 300Time (h)

PS

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(e)


4



BD-A

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(a)

BD-B

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(b)

BD-C

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(c)

BD-D

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(d)

PS

0 200 400 600 800 1000 12000

200

400

600

800

1000

1200

1400

1600

NM

C(120583

g N

gminus1

ds10

dminus1)


(e)



BD-A

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(a)

BD-B

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2minus

gminus1

dsm

inminus1)

-N


(b)

BD-C

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(c)

BD-D

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(d)

PS

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(e)





BD-A

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(a)

BD-B

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(b)

0 200 400 600 800 1000 12000

2

4

6

8

10

12 BD-C


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(c)

BD-D

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(d)

PS

0 200 400 600 800 1000 12000

5

10

15

20

25


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(e)





4

+)2SO4resulted in







10values observed


4





5 Conclusions


4




Acknowledgments


References









































































Journal of












Volume 2014

Advances in









Geophysics



















( of added C)

BD-A

175 550c 0046e 0013d 398a

35 574b 0078de 0017d 285abc

70 621b 0141de 0017d 309ab

140 662a 0287d 0019d 325ab

BD-B



70 184f 0117de 0018d 166d

140 196f 0259de 0022d 190cd

BD-C


35 le851 ge01751 mdash 137d

70 146g 0249de 0067bc 194cd

140 181f 0668c 0057bc 309ab

BD-D

175 le851 ge00371 mdash 137d

35 le851 ge00881 mdash 157cd

70 le851 ge02021 mdash 150d

140 le851 ge04051 mdash 169d

PS

175 126g 0232de 0090a 322ab

35 208f 0519c 0053c 278abc

70 292e 1111b 0060bc 311ab




PAO

EC10 (kg NH4+-N haminus1) 136 30 98 271 20

EC50 (kg NH4+-N haminus1) 140 45 156 291 50

EC90 (kg NH4+-N haminus1) 144 68 250 312 128


PDA










4





4


4


4


4)2SO4resulted in a



4


10 EC50 and EC

90





4


10

EC50 and EC


The EC10


4




resp)

4 Discussion




2production




00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-A

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(a)

00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-B

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(b)

00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-C

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(c)

00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-DRe

spira

tion

rate

( o

f add

ed C

hminus1)

(d)

00

02

04

06

08

10

12

0 100 200 300Time (h)

PS

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(e)


4



BD-A

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(a)

BD-B

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(b)

BD-C

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(c)

BD-D

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(d)

PS

0 200 400 600 800 1000 12000

200

400

600

800

1000

1200

1400

1600

NM

C(120583

g N

gminus1

ds10

dminus1)


(e)



BD-A

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(a)

BD-B

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2minus

gminus1

dsm

inminus1)

-N


(b)

BD-C

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(c)

BD-D

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(d)

PS

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(e)





BD-A

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(a)

BD-B

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(b)

0 200 400 600 800 1000 12000

2

4

6

8

10

12 BD-C


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(c)

BD-D

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(d)

PS

0 200 400 600 800 1000 12000

5

10

15

20

25


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(e)





4

+)2SO4resulted in







10values observed


4





5 Conclusions


4




Acknowledgments


References









































































Journal of












Volume 2014

Advances in









Geophysics

















4


4


4


4)2SO4resulted in a



4


10 EC50 and EC

90





4


10

EC50 and EC


The EC10


4




resp)

4 Discussion




2production




00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-A

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(a)

00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-B

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(b)

00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-C

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(c)

00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-DRe

spira

tion

rate

( o

f add

ed C

hminus1)

(d)

00

02

04

06

08

10

12

0 100 200 300Time (h)

PS

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(e)


4



BD-A

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(a)

BD-B

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(b)

BD-C

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(c)

BD-D

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(d)

PS

0 200 400 600 800 1000 12000

200

400

600

800

1000

1200

1400

1600

NM

C(120583

g N

gminus1

ds10

dminus1)


(e)



BD-A

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(a)

BD-B

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2minus

gminus1

dsm

inminus1)

-N


(b)

BD-C

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(c)

BD-D

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(d)

PS

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(e)





BD-A

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(a)

BD-B

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(b)

0 200 400 600 800 1000 12000

2

4

6

8

10

12 BD-C


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(c)

BD-D

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(d)

PS

0 200 400 600 800 1000 12000

5

10

15

20

25


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(e)





4

+)2SO4resulted in







10values observed


4





5 Conclusions


4




Acknowledgments


References









































































Journal of












Volume 2014

Advances in









Geophysics















00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-A

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(a)

00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-B

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(b)

00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-C

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(c)

00

02

04

06

08

10

12

0 100 200 300Time (h)

BD-DRe

spira

tion

rate

( o

f add

ed C

hminus1)

(d)

00

02

04

06

08

10

12

0 100 200 300Time (h)

PS

Resp

iratio

n ra

te(

of a

dded

C hminus1)

(e)


4



BD-A

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(a)

BD-B

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(b)

BD-C

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(c)

BD-D

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(d)

PS

0 200 400 600 800 1000 12000

200

400

600

800

1000

1200

1400

1600

NM

C(120583

g N

gminus1

ds10

dminus1)


(e)



BD-A

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(a)

BD-B

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2minus

gminus1

dsm

inminus1)

-N


(b)

BD-C

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(c)

BD-D

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(d)

PS

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(e)





BD-A

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(a)

BD-B

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(b)

0 200 400 600 800 1000 12000

2

4

6

8

10

12 BD-C


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(c)

BD-D

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(d)

PS

0 200 400 600 800 1000 12000

5

10

15

20

25


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(e)





4

+)2SO4resulted in







10values observed


4





5 Conclusions


4




Acknowledgments


References









































































Journal of












Volume 2014

Advances in









Geophysics















BD-A

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(a)

BD-B

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(b)

BD-C

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(c)

BD-D

0 200 400 600 800 1000 1200

0

100

200

300

400

500

600

minus100

NM

C(120583

g N

gminus1

ds10

dminus1)


(d)

PS

0 200 400 600 800 1000 12000

200

400

600

800

1000

1200

1400

1600

NM

C(120583

g N

gminus1

ds10

dminus1)


(e)



BD-A

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(a)

BD-B

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2minus

gminus1

dsm

inminus1)

-N


(b)

BD-C

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(c)

BD-D

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(d)

PS

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(e)





BD-A

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(a)

BD-B

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(b)

0 200 400 600 800 1000 12000

2

4

6

8

10

12 BD-C


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(c)

BD-D

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(d)

PS

0 200 400 600 800 1000 12000

5

10

15

20

25


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(e)





4

+)2SO4resulted in







10values observed


4





5 Conclusions


4




Acknowledgments


References









































































Journal of












Volume 2014

Advances in









Geophysics















BD-A

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(a)

BD-B

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2minus

gminus1

dsm

inminus1)

-N


(b)

BD-C

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(c)

BD-D

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(d)

PS

0 200 400 600 800 1000 12000

1

2

3

PAO

(ng

NO

2N

gminus1

dsm

inminus1)

minus-


(e)





BD-A

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(a)

BD-B

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(b)

0 200 400 600 800 1000 12000

2

4

6

8

10

12 BD-C


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(c)

BD-D

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(d)

PS

0 200 400 600 800 1000 12000

5

10

15

20

25


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(e)





4

+)2SO4resulted in







10values observed


4





5 Conclusions


4




Acknowledgments


References









































































Journal of












Volume 2014

Advances in









Geophysics















BD-A

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(a)

BD-B

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(b)

0 200 400 600 800 1000 12000

2

4

6

8

10

12 BD-C


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(c)

BD-D

0 200 400 600 800 1000 12000

2

4

6

8

10

12


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(d)

PS

0 200 400 600 800 1000 12000

5

10

15

20

25


PDA

(ng

N2O

-Ngminus

1ds

min

minus1)

(e)





4

+)2SO4resulted in







10values observed


4





5 Conclusions


4




Acknowledgments


References









































































Journal of












Volume 2014

Advances in









Geophysics

















4

+)2SO4resulted in







10values observed


4





5 Conclusions


4




Acknowledgments


References









































































Journal of












Volume 2014

Advances in









Geophysics
















5 Conclusions


4




Acknowledgments


References









































































Journal of












Volume 2014

Advances in









Geophysics

































































Journal of












Volume 2014

Advances in









Geophysics














Research Article Short-Term Effects of Biogas Digestates and Pig...

Documents

Transcript of Research Article Short-Term Effects of Biogas Digestates and Pig...