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PROBLEM: N DEPOSITION INCREASES

PROBLEM: N DEPOSITION INCREASES. Historical and future trends in N deposition. Cheasepeake Bay N runoff. Greater the N dep; greater amount of N that goes into the ocean, causing pollution. N CYCLE OVERVIEW. NITROGEN ATOM ISOTOPES. N-13; 10 minutes N-14; Stable N-15; Stable

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PROBLEM: N DEPOSITION INCREASES

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  1. PROBLEM:N DEPOSITION INCREASES

  2. Historical and future trends in N deposition

  3. Cheasepeake Bay N runoff Greater the N dep; greater amount of N that goes into the ocean, causing pollution.

  4. N CYCLE OVERVIEW

  5. 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

  6. NITROGEN: OXIDATION STATES • Minimum oxidation number is –3 • Maximum oxidation number is +5

  7. Oxidation States NH3 ammonia -3 NH4- ammonium -3 N2H4 hydrazine -2 NH20H Hydroxylamine -1 N2 Dinitrogen 0 N2O Nitrogen (I) oxide +1 (nitrous oxide) NO Nitrogen (II) oxide +2 (nitric oxide) HNO2 Nitrous Acid +3 NO2- Nitrite +3 NO2 Nitrogen (IV) oxide +4 (nitrogen dioxide) HNO3 Nitric Acid +5 NO3- Nitrate +5

  8. Main N-cycle transformations Assimilation Org-N NO2- NO3- NH4+ Nitrification 1 (oxic bacteria) Nitrification 2 Ammonification N2 N2O NO2 • gases Oxidation state -3 -2 -1 +1 +2 +3 +4 +5 0 Assimilation (algae + bacteria) Assimilation Denitrification Mineralization Denitrification (anoxic bacteria) N2 - Fixation - Soil bacteria - Cyanobacteria - Industrial activity - Sulfur bacteria

  9. Important N Species NH3 ammonia gas, volitization NH4- ammonium atmospheric form of NH3, nutrient N2H4 hydrazine carcinogenic, rocket fuel NH20H Hydroxylamine amines, opiotes N2 dinitrogen atmospheric N N2O nitrous oxide brown cloud, greenhouse gas, denitrification NO nitric oxide tailpipe emissions, smog HNO3 nitric Acid energy emissions NO3- nitrate nutrient, acidification

  10. AMMONIUM FATE • Assimilated by plants and microbes • Adsorbed on CEC • Occluded • Quinone-NH2 • Volatilized as NH3 • Nitrified

  11. 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

  12. Sources of NH3 on Livestock Farms • Manure Application • Animal Housing • Manure Storage • Grazing • Fertilizer Application • Crops Descending Order of Importance Bussink & Oenema, 1998

  13. CO(NH2)2 + H2O + urease 2NH3 +CO2

  14. Nitrification: another look 2NH4+ + 3O2 --> 2NO2 - + 2H2O + 4H+ Nitrosomanous • 2NO2 - + O2 --> 2NO3 - + energy Nitrobacter

  15. NITRIFICATION • C:N ratio less than 20 • Ammonium oxidation • Nitrite oxidation

  16. NITRATE FATE • Assimilation • Dentrification • Leaching • Erosion

  17. Denitrification • Conversion of NO3 to N2O or N2 by facultative anaerobic heterotrophs • 2NO3 + H2O N2O + 2O2 + 2OH+

  18. Greenhouse Gas

  19. 300x more active than CO2 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

  20. 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.

  21. Excess NH4; pushes system to net nitrification

  22. Heavily N-limited; usually no NO3 produced

  23. 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

  24. ABER SPAGHETTI DIAGRAM

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