Restoration of E&P Sites
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Transcript of Restoration of E&P Sites
Of Earthworms and Nematodes In Restoration of E&P Sites
Kerry Sublette, Eleanor JenningsCenter for Applied Biogeosicences
University of Tulsa
Kathleen DuncanUniversity of Oklahoma
Greg Thoma, Duane WolfUniversity of Arkansas
Josh BrokawWashington State University
Mac A. CallahanUSDA Forest Service
Tim ToddKansas State University
Project Objective:Accelerated Restoration of Oil- and
Brine-impacted Sites• Both the original spill and the remediation process
disrupt soil ecology– Disruptions in N and P cycling– Reduced diversity of soil microbes and
invertebrates– Loss of vegetation
• All levels of ecosystem affected– Producers– Consumers– Decomposers
Project Summary• This project began as an effort to determine the
efficacy of the introduction of non-indigenous earthworms to remediated oil and brine spill sites in order to accelerate the restoration of these sites in terms of soil quality and health.
• Original treatments to be investigated included all combinations of the following plus no treatment:– inoculation with E. fetida– fertilizer addition – hay cover
• Treatments were applied in enclosures designed to retain E. fetida and exclude other macrofauna.
Project Summary• Within 60 days earthworms indigenous to the area
were detected in significant numbers both outside and inside of the enclosures and very few E. fetidacould be found.
• This observation led to the recognition that all enclosures were accessible to indigenous earthworms and in reality there were only four treatments: – hay + fertilizer (HF)– hay only (H) – fertilizer only (F) – no treatment (N)
• We were left with the assumption that earthworm activity correlates with the availability of food (surface hay)
Project Timeline
• Ripped and tilled sites• Installed earthworm enclosures and added
amendments (fertilizer and/or hay)• After 30 days inoculated with Eisenia fetida
– 5 worms per enclosure per worm treatment• Initial conditions:
– 350-600 mg/kg Na+ in brine site– 9,500-16,000 mg/kg total extractable hydrocarbons in
hydrocarbon site• Sampling:
– August 2005– October 2005– June 2006– September 2006
Metrics Used to Evaluate Treatments
• Soil nutrients• Microbial biomass as PLFA
– PLFA = phospholipid fatty acid analysis• N-cycling bacteria• Nematode numbers and community structure• Plant biomass• No acceptable metric for earthworm numbers was
identified– Earthworms were observed but were not confined to the
enclosures; therefore, direct counts were unreliable– Earthworm castings were damaged when the layer of damp
decomposing hay was removed to expose the surface in HF and H treatments
Block 1 Block 2 Block 3 Block 4
Original Experimental Design – Brine Site
(Similar layout at Hydrocarbon Site)
Worms + Hay + Fertilizer
Worms + Hay
Worms + Fertilizer
Hay + Fertilizer
Worms
Hay
Fertilizer
No Treatment
Filling enclosure with homogenized soil at hydrocarbon site
Filling earthworm enclosure with homogenized soil
Hay
Earthworm enclosures installed and amendments added at hydrocarbon site
Pantyhose cover added after 30 days
Entire site covered with hay for moisture and temperature control
Earthworm Observations
• At the first sampling, earthworms were found in the top 15 cm of most enclosures– A. trapezoides– Diplocardia sp.– Very few E. fetida
• Average worms/enclosure: 1.74 with surface hay and 0.63 without surface hay-supports positive correlation of worms with surface hay
TreatmentBrine Site
August 2005 October 2005 June 2006
HF 26.0 ± 2.1 23.3 ± 2.8 29.4 ± 3.3H 25.7 ± 3.3 24.2 ± 3.4 29.2 ± 2.9F 26.1 ± 1.6 22.5 ± 3.0 25.9 ± 4.0N 25.7 ± 1.6 21.9 ± 2.5 29.6 ± 3.3
NativePrairie
13.7 ± 1.5(n=4)
TreatmentHydrocarbon
Site
August 2005 October 2005 June 2006
HF 22.0 ± 3.8 18.9 ± 3.9 23.1 ± 6.4H 21.7 ± 4.5 18.2 ± 4.6 23.2 ± 8.4F 20.7 ± 4.3 19.3 ± 4.8 28.4 ± 13.3N 18.2 ± 4.9 19.4 ± 4.1 21.3 ± 6.5
NativePrairie
13.5 ± 1.7(n=4)
Soil Moisture
Mean ± std. dev. with n=8 or 9 unless otherwise indicated
Earthworms and Soil Health
• Earthworm castings – contain higher concentrations of SOM and bioavailable
nutrients than the surrounding bulk soil– exhibit greater microbial activity and higher rates of
respiration than bulk soil – lead to the formation of stable soil aggregates which
increase the permeability of the soil to air and water• Earthworm burrows create pathways for root growth, water
movement, and nutrient transport • Earthworm-related effects stimulate the uptake of nutrients by
plants which results in increased growth rates of plants and greater levels of biomass
Sample Date
TreatmentBrine Site
NO3-Nmg/kg
NH4-Nmg/kg
P(mg/kg)
%N %C
August 2005
HF 1.65 ± 0.74 a 7.7 ± 4.8 a 25.7 ± 19.6 ab 0.28 ± 0.53 a 1.51 ± 0.31 a
H 1.74 ± 0.69 a 14.6 ± 9.0 b 11.7 ± 8.1 a 0.11 ± 0.03 a 1.69 ± 0.38 aF 1.50 ± 0.55 a 6.5 ± 2.5 a 34.5 ± 24.4 b 0.10 ± 0.008 a 1.51 ± 0.25 aN 1.85 ± 1.04 a 12.5 ± 8.1 ab 15.7 ± 17.6 ab 0.38 ± 0.72 a 1.45 ± 0.24 a
October 2005
HF 3.42 ± 1.37 a 2.78 ± 1.00 a 24.0 ± 12.5 a 0.12 ± 0.02 a 1.67 ± 0.25 a
H 4.21 ± 3.29 a 2.05 ± 0.97 a 6.4 ± 1.7 b 0.12 ± 0.008 a 1.57 ± 0.28 aF 2.85 ± 0.67 a 2.52 ± 1.08 a 22.5 ± 10.7 a 0.11 ± 0.006 a 1.61 ± 0.30 aN 4.95 ± 3.74 a 1.99 ± 1.14 a 6.8 ± 1.3 b 0.12 ± 0.007 a 1.54 ± 0.23 a
Brine Site Nutrients1,2
1 All values are mean ± std. dev. with n=8 or 92 Different letters following values for a given sample data indicate significant differences at p<0.05
Sample Date
TreatmentHydrocarbon
Site
NO3-N(mg/kg)
NH4-N(mg/kg)
P(mg/kg)
%N %C
August 2005
HF 12.1 ± 6.2 a 3.25 ± 0.57 a 89.2 ± 51.9 a 0.20 ± 0.01 a 3.63 ± 0.30 a
H 10.1 ± 6.0 a 3.20 ± 0.82 a 27.3 ± 7.1 b 0.19 ± 0.01 a 3.66 ± 0.30 a
F 18.7 ± 24.4 a 3.00 ± 0.33 a 69.2 ± 30.2 a 0.18 ± 0.008 a 3.51 ± 0.30 aN 8.7 ± 7.2 a 2.72 ± 0.41 a 27.7 ± 11.5 b 0.19 ± 0.009 a 3.53 ± 0.25 a
October 2005
HF 6.6 ± 0.9 a 1.29 ± 0.24 a 66.4 ± 18.3 a 0.20 ± 0.01 a 3.68 ± 0.22 a
H 7.5 ± 4.4 a 1.41 ± 0.15 ab 22.9 ± 7.2 b 0.19 ± 0.01 a 3.62 ± 0.34 a
F 8.0 ± 3.9 a 1.62 ± 0.40 b 55.0 ± 13.7 a 0.20 ± 0.01 a 3.76 ± 0.33 aN 5.4 ± 0.8 a 1.50 ± 0.34 ab 25.5 ± 9.5 b 0.19 ± 0.02 a 3.69 ± 0.20 a
Hydrocarbon Site Nutrients1,2
1All values are mean ± std. dev. with n=8 or 92Different letters following values for a given sample data indicate significant differences at p<0.05
Earthworms and Soil Health
• Earthworm castings – contain higher concentrations of SOM and bioavailable
nutrients than the surrounding bulk soil– exhibit greater microbial activity and higher rates of
respiration than bulk soil – lead to the formation of stable soil aggregates which
increase the permeability of the soil to air and water• Earthworm burrows create pathways for root growth, water
movement, and nutrient transport • Earthworm-related effects stimulate the uptake of nutrients by
plants which results in increased growth rates of plants and greater levels of biomass
Soil Viable Biomass in Terms of Concentration of Phospholipids (pmoles/g)1
TreatmentBrine Site
August 20052 October 20052 June 20063
HF 8,315 ± 3,464 a 11,497 ± 3936 a 7,168
H 9,917 ± 4,863 a 12,843 ± 3790 a 5,686F 7,126 ± 3,099 a 11,033 ± 4089 a 6,700N 6,893 ± 1,483 a 11,038 ± 3111 a 7,827
NativePrairie
10,333
TreatmentHydrocarbon
Site
August 20052 October 20052 June 20063
HF 7,623 ± 1,356 a 9,301 ± 3082 a 10,270
H 8,489 ± 2,975 a 8,146 ± 1970 a 6,974
F 6,872 ± 2,339 a 7,577 ± 2751 a 6,929
N 7,270 ± 1,944 a 8,248 ± 3870 a 8,874
NativePrairie
23,718
2mean ±std.dev with n=8 or 9
3Eight-fold composite
1Concentration of phospholipids proportional to concentration of viable microbial biomass
Ecological Indicators - Nematodes
• Nematodes are the numerous multicellular animals on earth; most are microscopic round worms
• In soil environments they are classified as mesofauna – confined to and move about in thin films of moisture coating soil particles
• Nematodes may be classified as to their mode of feeding based on morphology (particularly mouth structure):– Microbivores feed on bacteria– Fungivores feed on fungi– Herbivores feed on plant material
(including roots)– Omnivores feed on all of the above– Predators feed on other nematodes
• Nematode analyses obtained at reasonable cost through university ag extension services
Earthworms and Soil Health
• Earthworm castings – contain higher concentrations of SOM and bioavailable
nutrients than the surrounding bulk soil– exhibit greater microbial activity and higher rates of
respiration than bulk soil – lead to the formation of stable soil aggregates which
increase the permeability of the soil to air and water• Earthworm burrows create pathways for root growth, water
movement, and nutrient transport • Earthworm-related effects stimulate the uptake of nutrients by
plants which results in increased growth rates of plants and greater levels of biomass
Brine SiteAugust 2005
HF H F N
Treatment
0
100
200
300
400
500
600
700
800
900
Nem
atod
es (#
/100
g)
Total Herbivores Total Microbivores Total Fungivores Total O/P
Brine SiteOctober 2005
HF H F N
Treatment
0
100
200
300
400
500
600
700
800
900
Nem
atod
es (#
/100
g)
Total Herbivores Total Microbivores Total Fungivores Total O/P
Brine SiteJune 2006
HF H F N
Treatment
0
100
200
300
400
500
600
700
800
900
Nem
atod
es (#
/100
g)
Total Herbivores Total Microbivores Total Fungivores Total O/P
Lots of microbivoreswith hay All numbers
low; community structure shifting from microbivores to fungivores?
Fungivoresdominate
Very few herbivores
Hydrocarbon SiteAugust 2005
HF H F N
Treatment
0
200
400
600
800
1000
1200
1400
Nem
atod
es (#
/100
g)
Total Herbivores Total Microbivores Total Fungivores Total O/P
Hydrocarbon SiteOctober 2005
HF H F N
Treatment
0
200
400
600
800
1000
1200
1400
Nem
atod
es (#
/100
g)
Total Herbivores Total Microbivores Total Fungivores Total O/P
Hydrocarbon SiteJune 2006
HF H F N
Treatment
0
200
400
600
800
1000
1200
1400
Nem
atod
es (#
/100
g)
Total Herbivores Total Microbivores Total Fungivores Total O/P
Lots of microbivoreswith hay
Herbivores increasing; microbivoresstill dominant with hay
Preliminary Conclusions• If the native soil surrounding a remediated oil or brine spill contains
earthworms – build it and they will come!– Organic matter and moisture– Look for burrows and castings
• Nutrient cycling stimulated by surface organic matter and presumably earthworm activity
• Nematode numbers and community structure are sensitive metrics of soil ecosystem status in these types of remediated spills
Understanding the status of a soil ecosystem can be really tricky when you look too close
We get a better picture when we step back and take an integrative approach
Acknowledgement
This work was funded by
the Integrated Petroleum Environmental Consortium (IPEC)