PROBLEM: N DEPOSITION INCREASES
Dec 16, 2015
Cheasepeake Bay N runoff
Greater the N dep; greater amount of N that goes into the ocean, causing pollution.
NITROGEN ATOM ISOTOPES
N-13; 10 minutes N-14; Stable N-15; Stable N-16; seconds N-14 is 272 times
more abundant than N-15
Atomic wt is 14.0067
Oxidation StatesNH3 ammonia -3NH4
- ammonium -3N2H4 hydrazine -2NH20HHydroxylamine -1N2 Dinitrogen 0N2O Nitrogen (I) oxide +1
(nitrous oxide)NO Nitrogen (II) oxide +2
(nitric oxide)HNO2 Nitrous Acid +3NO2
- Nitrite +3NO2 Nitrogen (IV) oxide +4
(nitrogen dioxide)HNO3 Nitric Acid +5NO3
- Nitrate +5
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
Important N Species
NH3 ammonia gas, volitizationNH4
- ammonium atmospheric form of NH3, nutrientN2H4 hydrazine carcinogenic, rocket fuelNH20HHydroxylamine amines, opiotesN2 dinitrogen atmospheric NN2O nitrous oxide brown cloud, greenhouse gas, denitrificationNO nitric oxide tailpipe emissions, smogHNO3 nitric Acid energy emissionsNO3
- nitrate nutrient, acidification
AMMONIUM FATE
Assimilated by plants and microbes
Adsorbed on CEC Occluded Quinone-NH2
Volatilized as NH3
Nitrified
Problems With NH3 Volatilization
Acid Atmospheric Deposition raises pH of rainwater, more SO2 dissolves ammonium sulfate forms - oxidizes soil releases sulfuric & nitric acid
Eutrophication water and land
Loss of N to farmers Lowers N:P
Sources of NH3 on Livestock Farms
Manure Application Animal Housing Manure Storage Grazing Fertilizer Application Crops
DescendingOrder ofImportance
Bussink & Oenema, 1998
Nitrification: another look
2NH4+ + 3O2 --> 2NO2 - + 2H2O + 4H+ Nitrosomanous
2NO2 - + O2 --> 2NO3 - + energy
Nitrobacter
Denitrification
Conversion of NO3 to N2O or N2 by facultative anaerobic heterotrophs
2NO3 + H2O N2O + 2O2 + 2OH+
Relative to carbon dioxide the other greenhouse gases together comprise about 27.63% of the greenhouse effect (ignoring water vapor) but only about 0.56% of total greenhouse gas concentrations. Put another way, as a group methane, nitrous oxide (N2O), and CFC's and other miscellaneous gases are about 50 times more potent than CO2
300x more active than CO2
Immobilization/Assimilation
Incorporation of inorganic N to organic N Plants/microbes can use only inorganic N
(NH4 and N O3) to produce organic matter However, new evidence suggests “tasty”
organic N (primarily amino acids) can be utilized by plants/microbes.
LEAKY FAUCET HYPOTHESIS
Persistent “leak” of DON from catchments
DON is decoupled from microbial demand for N.
DON export coupled to soil standing stock of C, N
Lag between N inputs and DON export
NITRATE LOSSES
Increasing N deposition increases net nitrification
Nitrate mobile Nitrate export to
surface waters increases as N deposition increases