Post on 29-Dec-2015
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s1
Rich Axler, NRRI-UMDSenior Research Associate
Grad Faculty: Water Resources Science Grad Faculty: Integrated Biosystems
raxler@d.umn.edu 218-788-2716
Wetland Biogeochemistry: Major ions, nutrients = NBiology 5870 Sep 24, 2015
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s2
I. Wetland biogeochemistry (mostly about nutrients (N,P)
Biogeochem is about the transport and transformations of chemicals
Can talk about input-output mass balances the wetland is a box (sources & sinks)
What goes on inside the box determines how it functions
•WETLAND/LAKE PHOSPHORUS BUDGET•WETLAND/LAKE PHOSPHORUS BUDGET
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s3
Anaerobic
Aerobic
Source, Sink, or Transformer?
Rates (mass/area/time, mass/volume/time, or mass/time) = Dynamic
versus
Pools (mass, or concentration [mass/volume or mass/area) = Static
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s4
Water chemistry (biogeochemistry): Gases, major ions & nutrients
Gases
Oxygen (O2)
Carbon dioxide (CO2) – dissolves in water to form carbonic
acid H2CO3 , then fractionates to HCO3- + CO3
-2 + CO2
according to pH of the water
Nitrogen (N2)
Hydrogen sulfide (H2S)
Major ions: anions HCO3- , SO4
-2, Cl- ; cations Ca+2, Mg+2, Na+, K+
Nutrients (nitrogen and phosphorus)
Trace (micronutrient) metals, vitamins, etc
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s5
Additional nomenclature
Dissolved (soluble) versus particulate
What type of filter, net, or screen to use
And organic versus inorganic
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s6
Gas solubility
Maximum amount of gas that can be dissolved in water (“~” 100% saturation) determined by temperature, dissolved ion concentration, and elevation
solubility decreases with temperature
“warm beer goes flat” solubility decreases with higher dissolved ion content
(TDS, EC25, salinity) “DO saturation is lower in saltwater than freshwater (for the same temperature, solids “drive out” gases)
Why does elevation affect the concentration of dissolved gases?
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s7
O2 variability
Diel (24 hr) variation due to ____________?
Seasonal variation due to _____________ ?
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s8
Short-term variability- Hypereutrophic Halsteds Bay, L. Minnetonka, MN
Productive Bay
Temp Red = warm O2 Black = anoxic
This is a month of 6hr data from an 8m deep bay. Similar patterns have been found in algal mats (millimeters), shallow wetlands and ponds (centimeters), tidal flats, etc.
What factors control the DO depth and time pattern?
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s9
Seasonal DO variability (Apr-Oct) SKIP
Black = anoxia Green = high DO
or depth into sediments in cmsor depth into sediments in cms
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s10
Water chemistry: O2
~ 21% of air Very soluble (DO) Highly reactive and concentration is dynamic Involved in metabolic energy transfers (PPr & Rn) Major regulator of metabolism (oxic-anoxic)
Aerobes (fish) vs anaerobes (no-fish, no zoops) Types of fish
- Salmonids = high DO (also coldwater because of DO)- Sunfish, carp, catfish = low DO (also warmwater)
Types of invertebrates • Types of plants- Stoneflies = high DO - cattails, bulrushes, reeds, rice- Tubificids = low DO vs alders, cedars, and upland
plants
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s11
Major sources of O2
Sources Photosynthesis (phytoplankton, periphyton,
macrophytes) Air from wind mixing Inflows
tributaries may have higher or lower DOgroundwater may have higher or lower DO
Diffusion between layers (surface to bottom and vice versa)
Diffusion from plant roots (and stems?)
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s12
Emergent plant adaptations
Cattail roots from subsurface flow gravel bed constructed wetland – 3 ys old (domestic septic tank effluent [NERCC Cell 1])
Even dead, cattails passO2 the wet substrate -directly, and by venturi- induced (wind) convection.
Other adaptations to low O2 ??
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s13
Major sinks of O2
Sinks Respiration
bacteria, plants, animals; water and sediments Diffusion to sediment (respiration deeper) Outflow (tributary or groundwater) Chemical oxidation (abiotic)
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s14
O2: Human significance SKIP for lecture
Not a direct threat to humans Directly affects fish physiology and habitat Indirectly affects fish and other organisms via toxicants
associated with anoxia: H2S NH4
+ (converts to NH4OH and NH3 above ~pH 9)
Indirectly affects domestic water supply H2S (taste and odor) Solubilizes Fe (staining)
Indirectly affects reservoir turbines Via H2S corrosion and pitting (even stainless steel) Via regulation of P-release from sediments (mediated via
Fe(OH)3 adsorption)
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s15
Gases: N2
~ 78% of air Concentrations in water usually saturated because it is
nearly inert Supersaturation (>100 %) can occur in reservoir
tailwaters from high turbulence May be toxic to fish (they get “the bends)
N2 -fixing bacteria and cyanobacteria (blue-green “algae”) convert it to bio-available NH4
+
Denitrifying heterotrophic bacteria convert NO3- to N2
and/or N2O under anoxic conditions
neither N2 fixation nor denitrification typically affects overall N2 levels
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s16
Gases: CO2 SKIP Only about 0.035% of air (~ 350 ppm) Concentration in H2O higher than expected based on low
atmospheric partial pressure because of its high solubility
Gas(at 10oC)
Concentration @ 1 atm (mg/L)
Concentration @ normal pressure (mg/L)
N2 23.3 18.2
O2 55.0 11.3
CO2 2319 0.81
How long does your soda pop fizz after shaking it?
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s17
Water chemistry – Major ions
SiO2 < 1
Note: plant nutrients such as nitrate, ammonium and phosphate that can cause algae and weed overgrowth usually occur at 10’s or 100’s of parts-per-billion and along with other essential micronutrients usually are <1% of the actual amount of cations or anions present in the water which are at levels of 10’s of thousands of parts-per-billion
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s18
Anions mg/L Cations mg/L
HCO3- 58.4 Ca+2 15.0
SO4-2 11.2 Mg+2 4.1
Cl- 7.8 Na+ 6.3
SiO2 13 K+ 2.3
NO3- <1.0 Fe+3 ~0.7
Total = ~91.4 anions + ~28.4 cations = ~ 120 mg/L (TDS)
Major ion concentrations – freshwater SKIP
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s19
Why the focus on N and P?Limiting nutrients – demand versus supply
Nitrogen and phosphorus are typically in extremely short supply in water relative to plant demand
The “Redfield ratio” is the average composition of elements in phytoplankton algae
Ratio – 100DW:40C:7N:1P
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s20
Electron Acceptors in Oxidation of Organic Carbon
Everyone understands this – right ??
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s21
RESPIRATION
What’s reduced?- O2 ,NO3-, Mn4+ ,Fe2+ ,S4
2-, and CO2
[aerobic respiration; anaerobic denitrification, sulfate
reduction, methanogenisis etc.] What’s oxidized? Organic carbon (“food”)
Who does it? Auto- & Heterotrophs (plants, animals, bacteria)
Why? To get energy for cellular metabolism
Other important biotic energy producing redox reactions
What’s oxidized?- NH4+, S2- oxidation, Fe3+ , …
[nitrification, sulfide and iron oxidization, …)Who does it?- Chemoautotrophs (chemosynthesizers) Why? To get energy for CO2 fixation (to make organic-C)
Microbial metabolism
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s22
Nitrogen is relatively scarce in some watersheds and therefore can be a limiting nutrient in aquatic systems
Essential nutrient (e.g., amino acids, nucleic acids, proteins, chlorophyll)
Key differences from phosphorus Not geological in origin Unlike phosphorus, there are many oxidation
states
II. Nitrogen – basic properties
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s23
Nitrogen – biologically available forms
N2 (gas)– major source, but usable by only a few species Blue green algae (cyanobacteria) and certain
anaerobic bacteria Nitrate (NO3
-) and ammonium (NH4+) – major
forms of “combined” nitrogen for plant uptake Also called dissolved inorganic nitrogen (DIN)
Total nitrogen (TN) – includes: DIN + dissolved organic nitrogen (DON) +
particulate nitrogen (PON ~ PN)
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s24
Nitrogen – general properties
Essential for plant growth (amino acids/proteins; nucleic
acids, chlorophyll, …)
Always important to plant growth and can be “limiting”: phosphorus enriched lakes, ponds, wetlands
Pristine, unproductive lakes, streams and wetlands located in
watersheds with nitrogen-poor soils (Know places like this?)
Estuaries, open ocean (major cause of Gulf “hypoxia” +HABS)
Wetlands with high rates of N-loss relative to inputs
Lots of input from the atmosphere in many regions
Combustion NOx , fertilizer dust, fertilizer aerosols (NH3)
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s25
Nitrogen – general properties
Mobile – in the form of nitrate (soluble), it goes wherever water flows Ammonium (NH4
+) tends to adsorb to soil particles (usually electronegative but be careful here)
Blue green algae can fix nitrogen (N2 ) from the atmosphere
Nitrogen has many redox states and is involved in many bacterial transformations
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s26
Nitrogen – sources
Atmospheric deposition Wet and dry deposition (NO3
- and NH4+)
Combustion gases (power plants, vehicle exhaust, acid rain), dust, fertilizers
Streams and groundwater (“mostly” NO3-)
Sewage and feedlots (NO3- and NH4
+) Agricultural runoff (NO3
- and NH4+)
Regeneration from aquatic sediments and bottom water (NH4
+)
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s27
Nitrogen - toxicity
Methemoglobinemia – “blue baby” syndrome > 10 mg/L NO3
--N or > 1 mg/L NO2--N in well
water Usually related to agricultural contamination of
groundwater NO3
- – possible cause of stomach/colon cancer Un-ionized NH4
+ can be toxic to coldwater fish NH4OH and NH3 at higher pHs ( > ~ 9)
N2O and NOx – contribute to smog, haze, ozone layer depletion, acid rain, climate change, global dimming
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s28
Nitrogen – many oxidation states
Unlike P there are many oxidation states Organisms have evolved to make use of these
oxidation-reduction states for energy metabolism and biosynthesis
-3 0 + 1 + 2 + 3 + 5
NH4+ N2 N2O NO2 NO2
- NO3-
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s29
Nitrogen – bacterial transformations
Organic-N NH4+-N Heterotrophic ammonification or
mineralization. Associated with oxic or anoxic respiration.
NH4+-N NO3
- -N Involves oxygen (oxic). Autotrophic and chemosynthetic ("burn” NH4
+-N to fix CO2).
NO3- -N N2 (gas) Anoxic process. Heterotrophic.
("burn" organic matter and respire NO3
-, not O2). Also creates N2O
N2 (gas) Organic-N Some blue green algae are able to do this.
Decomposition
•Nitrification
Denitrification
Nitrogen fixation
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s30
Nutrients- The Nitrogen Cycle
•modified from Horne and Goldman. 1994. Limnology. McGraw Hill.
Nutrients – nitrogen cycle
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s31
Org–N
N2 = largest reservoir
but cannot be used by most organisms
Fixed or available-N
organism-N + detrital-N+ dissolved organic-N
NH4 +
NO2-
NO3-
-3 +5+4+3+2+10-1-2Oxidation state
NO2N2ON2•gases
Chemical forms of nitrogen in aquatic systems
NH4 +
NO2-
NO3-
Dissolved inorganic-N (DIN)Ammonium:
basic unit for biosynthesis
Nitrite: usually
transient
Nitrate: major runoff fraction
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s32
Functionally in the lab using filters…
Total-N = particulate organic-N + dissolved organic-N
+ particulate inorganic-N + dissolved inorganic-N
TN = PN + DON + DIN
Dissolved inorganic-N = [Nitrate + Nitrite]-N + ammonium-N
DIN = NO3-N + NO2-N + NH4-N
Notes:
• Nitrate+nitrite are usually measured together.
• Nitrite is usually negligible.
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s33
Assimilation
(algae + bacteria)
Assimilation
-3 +5+4+3+2+10-1-2Oxidation state
AssimilationDenitrification
NO2N2ON2
NH4+
NO2-
Mineralization
Org-N
Main N-cycle transformations
N2 - Fixation- Soil bacteria- Cyanobacteria - Industrial activity- Sulfur bacteria
Denitrification(anoxic bacteria)
Nitrification 1(oxic bacteria)
Nitrification 2
NO3-
Ammonification
•gases
Anammox (anoxic bacteria)
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s34
Surficial Sediments
N2
Algae/PlantsAlgae/Plants
oxic anoxic
NO3- NH4
+
Nitrification
Assimilation
Mineralization
NH4+
NitrificationNO2
-, N2ONO
Den
itri
fica
tio
n
Sed
imen
tati
on
DIN PON
DON
Sed
imen
tati
on
Deep SedimentsBurialBurial
Ammoniavolatilization
Tribs, GW, PrecipDON, PON, NO3
-, NH4+
NO3-
Outflow
diffusion
N2-fixation
Whole lake/wetland N-budget
Mixing
Mineralization
Developed by: R.Axler and C. Hagley Draft Updated: January 13, 2004 U1-m2/3Part 5-s35
Wetland plants: importance to N- cycling
• Supply O2 to root rhizosphere
• Aerobic vs anaerobic interface• Enhanced nitrification (with O2)
• Enhanced denitrification • (without O2 via nitrate production)
• Assimilate nitrate and ammonium (temporary storage)• Source of DOC to microbial communities in root zone
• Enhanced O2 depletion and bacterial activity in general• Stabilize sediments (reduce N-loss via flushing and erosion)
• Plants and plant litter may affect temperature ( + or - ??)