1. PROBLEM: N DEPOSITION INCREASES

3. Historical and future trends in N deposition

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

8. N CYCLE OVERVIEW

10. 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

11. NITROGEN: OXIDATION STATES  Minimum oxidation number is –3  Maximum oxidation number is +5

12. Oxidation States NH 3 ammonia-3 NH 4 - ammonium-3 N 2 H 4 hydrazine-2 NH 2 0HHydroxylamine-1 N 2 Dinitrogen 0 N 2 ONitrogen (I) oxide+1 (nitrous oxide) NONitrogen (II) oxide+2 (nitric oxide) HNO 2 Nitrous Acid+3 NO 2 - Nitrite+3 NO 2 Nitrogen (IV) oxide+4 (nitrogen dioxide) HNO 3 Nitric Acid+5 NO 3 - Nitrate+5

13. Assimilation (algae + bacteria) Assimilation -3+5+4+3+2+1 0 -2 Oxidation state Assimilation Denitrification NO 2 N2ON2O N2N2 NH 4 + NO 2 - Mineralization Org-N Main N-cycle transformations N 2 - Fixation - Soil bacteria - Cyanobacteria - Industrial activity - Sulfur bacteria Denitrification (anoxic bacteria) Nitrification 1 (oxic bacteria) Nitrification 2NO 3 - Ammonification gases

14. Important N Species NH 3 ammoniagas, volitization NH 4 - ammoniumatmospheric form of NH3, nutrient N 2 H 4 hydrazinecarcinogenic, rocket fuel NH 2 0HHydroxylamineamines, opiotes N 2 dinitrogen atmospheric N N 2 Onitrous oxidebrown cloud, greenhouse gas, denitrification NOnitric oxidetailpipe emissions, smog HNO 3 nitric Acidenergy emissions NO 3 - nitratenutrient, acidification

21. AMMONIUM FATE  Assimilated by plants and microbes  Adsorbed on CEC  Occluded  Quinone-NH 2  Volatilized as NH 3  Nitrified

23. Problems With NH 3 Volatilization  Acid Atmospheric Deposition raises pH of rainwater, more SO 2 dissolves ammonium sulfate forms - oxidizes soil releases sulfuric & nitric acid  Eutrophication water and land  Loss of N to farmers  Lowers N:P

24. Sources of NH 3 on Livestock Farms  Manure Application  Animal Housing  Manure Storage  Grazing  Fertilizer Application  Crops Descending Order of Importance Bussink & Oenema, 1998

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

30. Nitrification: another look 2NH 4 + + 3O 2 --> 2NO 2 - + 2H 2 O + 4H + Nitrosomanous 2NO 2 - + O 2 --> 2NO 3 - + energy Nitrobacter

31. NITRIFICATION  C:N ratio less than 20  Ammonium oxidation  Nitrite oxidation

32. NITRATE FATE  Assimilation  Dentrification  Leaching  Erosion

34. Denitrification  Conversion of NO 3 to N 2 O or N 2 by facultative anaerobic heterotrophs  2NO 3 + H 2 O  N 2 O + 2O 2 + 2OH +

35. Greenhouse Gas

36. 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 CO 2

44. 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.

46. Excess NH4; pushes system to net nitrification

48. Heavily N-limited; usually no NO3 produced

49. 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

50. ABER SPAGHETTI DIAGRAM

51. NITRATE LOSSES  Increasing N deposition increases net nitrification  Nitrate mobile  Nitrate export to surface waters increases as N deposition increases