nitrogen2008
9 Pages

nitrogen2008

Course Number: ERS 765, Fall 2009

College/University: Nevada

Word Count: 805

Rating:

Document Preview

Outline N in the environment Forms Necessary for life Contrast with P Nutrient availability-Chadwick paper Pools General forms and processes Atmosphere Terrestrial systems Schimel paper Aquatic systems Marine environment Human impact Regional cycles Global cycles Climate change Nitrogen at # 7, 1s2, 2p2, 2p3 Valence state +5 +4 +3 0 3Important form NO3-, HNO3 NO2 NO2N2 NH3, NH4+, R-NH2 Important...

Unformatted Document Excerpt
Coursehero >> Nevada >> Nevada >> ERS 765

Course Hero has millions of student submitted documents similar to the one
below including study guides, practice problems, reference materials, practice exams, textbook help and tutor support.

Course Hero has millions of student submitted documents similar to the one below including study guides, practice problems, reference materials, practice exams, textbook help and tutor support.

N Outline in the environment Forms Necessary for life Contrast with P Nutrient availability-Chadwick paper Pools General forms and processes Atmosphere Terrestrial systems Schimel paper Aquatic systems Marine environment Human impact Regional cycles Global cycles Climate change Nitrogen at # 7, 1s2, 2p2, 2p3 Valence state +5 +4 +3 0 3Important form NO3-, HNO3 NO2 NO2N2 NH3, NH4+, R-NH2 Important for life on earth Essential element Required in DNA, RNA, amino acids and proteins Component of hemoglobin and acetylcholine Essential for plants Need fertilizer to feed the world Nitrogen release through volcanic erruptions and hydrothermal systems 1 The availability of N and P controls many aspects of local ecosystem function and global biogeochemistry Contrasts with P P has no significant gaseous component Typically only found as PO43 Soil is major pool and rock weathering is important for controlling availability Adsorption by mineral fractions controls availability In most ecosystems availability controlled by degradation of organic forms Major form of reactive P not provided by microbes-root exudates and mycorrhizae increase availability Sources of nutrients to ecosystems Atmosphere Rock weatheringRecycling Human fertilizer production Nitrogen often limiting factor for ecosystem productivity N in soils is usually unavailable needs to be transformed by microbial processes Particulate bound important transport in aquatic systems Chadwick paper N Pools 6 * 10 ^6 Tg in the atmosphere, biosphere and sediments Air has 80% Sedimentary rock 19% ~ 1% in oceans, terrestrial vegetation and soils 2 Conclusions Chadwick paper General forms N2-dominant form-least reactive, triple bond takes a lot of energy to break bond Nr- reactive forms, odd nitrogen, nitrogen that can be used by microbes and plants and photochemically and radiatively active Inorganic reduced forms Inorganic oxidized forms Organic forms 3 Atmosphere forms N2 Inorganic reduced forms- ammonia Inorganic oxidized forms NOy N2O Terrestrial and aquatic systems Forms and Processes Fixation Nitrification Assimilation Mineralization Ammonification Denitrification Reduced organic N Oxidized organic N Couple d with C fixation Figure 1 Chpt 8.12 Terrestrial Nitrogen Cycling Getting from the atmosphere to ecosystems Fixation BNF-biological 140 x 10^12 g/y (range 30 to 200) Natural ecosystems (100-290 range) asymbiotic 44 x 10^12 g/y Symbiotic ~100 x 10^12 g/y N2 fixation N fixation only supplies 12% of the nitrogen assimilated by plants each year estimated at 1200 Tg thus recycling in ecosystems is important N2, N2O Plant N Denitrification Assimilatory nitrate reduction NH4+ Organic N NO3- Agriculture 40 x 10^12 g/y Nitrification NO-lightning 3 to 10 x 10^12 g/y Haber Bosch process >80x 10^12 g/y Fossil fuel combustion Leaching Forms in the soil are ammonia, nitrate and organic forms 4 Ecosystem processesNitrification of Oxidation ammonia and ammonium First to nitrite Nitrosomonas Then to nitrate-Nitrobacter .Uptake by organisms rapid Discuss Schimel paper Coupled with carbon, nitrate highly water soluble, form transported in aquatic systems Nitrogen Cycling Nitrogen assimilation Plant N N2, N2O NH4 versus NO3 Assimilatory reduction- uptake of nitrate and reduction to ammonia and organic Mineralization ammonification NH4+ Organic N immobilization NO3- 5 Terrestrial cycling NH3 volatilizaton N2, N2O Plant N Dentrification Reduction of nitrate to any gaseous species N2 and N2O Anaerobic conditions N2 fixation Litterfall Root turnover Denitrification Uptake Mineralization NH4+ Organic N immobilization Nitrification NO3- Leaching Schlesinger Chpt 6 Oceans Table 6 uncertainty Same processes as terrestrial systems BNF 87 to 156 Atmospheric deposition 30 Denitrification 147 to 454 Distribution of oxygen and temperature in the N Pacfic Ocean (Craig and Hayward, 1987) 25 Rivers 4060 Tg/yr Removal to marine sediments 6 Human impact Land use change Decrease in BNF with land use change 128 to 107 Tg/y Agricultural inputs Legumes 40 Fertilizer 80 Agricutural outputs Ammonia volatilization 30 Fossil fuels Combustion 40 Population increase direct link with increase N in the environment N 1% by weight of coal Eutrophication N2O climate and ozone Acid deposition or global fertilization Humans fix 160 Tg/y- land fixation 110 oceans 140 Tg Figure 2 Chapter 8.12 Green is fertilizer, Blue is legumes, rice, sugar cane, Red fossil fuel Model-estimated anthropogenic (19902000 minus preindustrial) atmospheric deposition fluxes for carbon, nitrogen, and sulfur (molm2y1); alkalinity; and potential alkalinity, assuming complete nitrification of NH4+ + NH3 (eqm2y1). NOTE Regional pollution issues because of rapid deposition of atmospheric forms Spatial patterns of total inorganic nitrogen deposition in (a) 1860, (b) early 1990s, and (c) 2050, mg N/m2/y (Source: Galloway et al., 2004). Figure 4 Chapter 8.12 7 National Deposition Ag BNF 40 Fertilizer >80 Fossil fuels 40 Agriculture Global cycle Fossil fuel Ammonia 40 From Schlesinger 1997 x 10^12 g Major processes that transform molecular nitrogen into reactive nitrogen, and back, are shown. Also shown is the tight coupling between the nitrogen cycles on land and in the ocean with those of carbon and phosphorus. Blue fluxes denote 'natural' (unperturbed) fluxes; orange fluxes denote anthropogenic perturbation. The numbers (in Tg N per year) are values for the 1990s (refs 13, 21). Few of these flux estimates are known to better than 20%, and many have uncertainties of 50% and larger13, 21. 8 Climate change-Science Gruber and Galloway How will the available nitrogen impact the carbon cycle and the ability of ecosystems to take up carbon? Nitrogen fertilization-increased uptake of carbon? Figure 8.12 Mississippi River Basin Eutrophication 9

Textbooks related to the document above:

MOST POPULAR MATERIALS FROM ERS 765
MOST POPULAR MATERIALS FROM ERS
MOST POPULAR MATERIALS FROM Nevada