Transcript Axler-Wetland Biogeochem-Major+N-9-27-2011

Wetland Biogeochemistry: Major ions, nutrients = N
Biology 5870 Sep 24, 2015
Rich Axler, NRRI-UMD
Senior Research Associate
Grad Faculty: Water Resources Science
Grad Faculty: Integrated Biosystems
[email protected] 218-788-2716
Developed by: R.Axler and C. Hagley
Draft Updated: January 13, 2004
U1-m2/3Part 5-s1
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)
•WETLAND/LAKE PHOSPHORUS
PHOSPHORUS BUDGET
BUDGET
•WETLAND/LAKE
 What goes on inside the box determines how it functions
Developed by: R.Axler and C. Hagley
Draft Updated: January 13, 2004
U1-m2/3Part 5-s2
Source, Sink, or Transformer?
Rates (mass/area/time, mass/volume/time,
Aerobic
Anaerobic
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-s3
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-s4
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-s5
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-s6
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-s7
Short-term variability- Hypereutrophic Halsteds
Bay, L. Minnetonka, MN
Temp Red = warm
O2 Black = anoxic
Productive Bay
Developed by: R.Axler and C. Hagley
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?
Draft Updated: January 13, 2004
U1-m2/3Part 5-s8
Seasonal DO variability (Apr-Oct) SKIP
or depth into sediments in cms
Black = anoxia Green = high DO
Developed by: R.Axler and C. Hagley
Draft Updated: January 13, 2004
U1-m2/3Part 5-s9
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
- Stoneflies = high DO
- Tubificids = low DO
Developed by: R.Axler and C. Hagley
• Types of plants
- cattails, bulrushes, reeds, rice
vs alders, cedars, and upland
plants
Draft Updated: January 13, 2004
U1-m2/3Part 5-s10
Major sources of O2
 Sources
 Photosynthesis (phytoplankton, periphyton,
macrophytes)
 Air from wind mixing
 Inflows
 tributaries may have higher or lower DO
 groundwater 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-s11
Emergent plant adaptations
Cattail roots from subsurface flow gravel bed
constructed wetland – 3 ys old (domestic
septic tank effluent [NERCC Cell 1])
Other adaptations
to low O2 ??
Even dead, cattails pass
O2 the wet substrate directly, and by venturiinduced (wind) convection.
Developed by: R.Axler and C. Hagley
Draft Updated: January 13, 2004
U1-m2/3Part 5-s12
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-s13
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-s14
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-s15
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
Concentration @
Concentration @
(at 10oC)
1 atm (mg/L)
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-s16
Water chemistry – Major ions
Ion balance for typical fresh water
Anions
Percent
Cations
Percent
HCO3322-
74
Ca22+
63
SO4422-
16
Mg22+
17
Cl-
10
Na+
15
K+
4
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-s17
Major ion concentrations – freshwater SKIP
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)
Developed by: R.Axler and C. Hagley
Draft Updated: January 13, 2004
U1-m2/3Part 5-s18
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-s19
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-s20
Microbial metabolism
RESPIRATION
What’s reduced?- O2 ,NO3-, Mn4+ ,Fe2+ ,S42-, 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)
Developed by: R.Axler and C. Hagley
Draft Updated: January 13, 2004
U1-m2/3Part 5-s21
II. Nitrogen – basic properties
 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
Developed by: R.Axler and C. Hagley
Draft Updated: January 13, 2004
U1-m2/3Part 5-s22
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-s23
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-s24
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-s25
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-s26
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-s27
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-s28
Nitrogen – bacterial transformations
NH4+-N
Organic-N
Decomposition
NH4+-N
NO3- -N
Involves oxygen (oxic). Autotrophic
and chemosynthetic ("burn” NH4+-N
to fix CO2).
N2 (gas)
Anoxic process. Heterotrophic.
("burn" organic matter and respire
NO3-, not O2). Also creates N2O
•Nitrification
NO3- -N
Denitrification
N2 (gas)
Heterotrophic ammonification or
mineralization. Associated with oxic
or anoxic respiration.
Organic-N
Nitrogen fixation
Some blue green algae are able to
do this.
Developed by: R.Axler and C. Hagley
Draft Updated: January 13, 2004
U1-m2/3Part 5-s29
Nutrients
– nitrogen
NutrientsThecycle
Nitrogen Cycle
•modified from Horne and Goldman. 1994. Limnology. McGraw Hill.
Developed by: R.Axler and C. Hagley
Draft Updated: January 13, 2004
U1-m2/3Part 5-s30
Chemical forms of nitrogen in aquatic systems
organism-N + detrital-N
+ dissolved organic-N
Org–N
Ammonium:
basic unit for
biosynthesis
NO3- -
NO3
Nitrate: major
runoff fraction
Dissolved
Fixed or
inorganic-N
available-N
(DIN)
NH4 + +
NH4
NO2- -
NO2
N2 = largest reservoir
but cannot be used by
most organisms
N2
N2O
NO2
0
+1
+2
Nitrite:
usually
transient
•gases
Oxidation state
-3
-2
-1
Developed by: R.Axler and C. Hagley
Draft Updated: January 13, 2004
+3
+4
+5
U1-m2/3Part 5-s31
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-s32
Main N-cycle transformations
Assimilation
Assimilation
Denitrification
Mineralization
(algae + bacteria)
Org-N
NO2-
Assimilation
NH4+
NO3-
Nitrification 2
Nitrification 1
(oxic bacteria)
Ammonification
Anammox
N2 - Fixation
Denitrification
(anoxic bacteria)
- Soil bacteria
- Cyanobacteria
- Industrial activity
- Sulfur bacteria
(anoxic bacteria)
N2
N2O
NO2
0
+1
+2
•gases
Oxidation state
-3
-2
-1
Developed by: R.Axler and C. Hagley
+3
Draft Updated: January 13, 2004
+4
+5
U1-m2/3Part 5-s33
Whole lake/wetland N-budget
N2
Tribs, GW, Precip
DON, PON, NO3-, NH4+
N2-fixation
Assimilation
NH4
Nitrification
DIN
PON
DON
Mineralization
Mixing
oxic
anoxic
NO3Nitrification
Mineralization
Outflow
Algae/Plants
+
NH4+
Sedimentation
Sedimentation
NO3
-
Ammonia
volatilization
NO2-, N2O
NO
diffusion
Burial
Surficial Sediments
Burial
Deep Sediments
Developed by: R.Axler and C. Hagley
Draft Updated: January 13, 2004
U1-m2/3Part 5-s34
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 - ??)
Developed by: R.Axler and C. Hagley
Draft Updated: January 13, 2004
U1-m2/3Part 5-s35