IMPORTANCE OF NITROGEN IN THE ENVIRONMENT

1. IMPORTANCE OF NITROGEN IN THE ENVIRONMENT • N2 comprises 80% of the atmosphere • N2 can not be used by most organisms • N2 is not a problem until its in a reactive form like NH3 or NO3 and is out of balance in nature • N is the major component of proteins and nucleic acids • Often the most limiting nutrient for plant growth • When out of balance, N can have both direct and indirect negative impacts on the environment

2. THE NITROGEN CYCLE

3. N CYCLE • N enters the cycle through: • N fixation • Fertilization • N fixation • Non-biological Lightning Burning fossil fuels N2 + O2 2 NO 2NO + O2 2 N O2 2 N O2 + H2O HNO3 + HNO2 HNO3 H+ + NO3- (Nitrate; Readily used by plants) • Biological N fixation Microorganisms Nitrogenase N2 + 6 e- + 8H+ 2NH3 (Ammonia)+ H2 Fe, Mo

4. Biological N fixation • Symbiotic N fixers • Responsible 70% of all N fixation • Microorganisms • Rhizobium bacteria • Infect roots of legume plants • Frankia bacteria • Infect the roots of certain trees • Process • Bacteria reduce N2 to NH3 • Plants take up NH3 and combine it with Carbon skeletons to produce amino acids • Other plants only have access to this fixed N by the plant dying and becoming part of the soil organic matter-N pool • High levels of N will reduce biological N fixation • Free living N fixers • Responsible for 30% of world N fixation • Microrganisms • Cyanobacteria • Found in rice paddies • Azospirrilium, Azobacter, and Clostridium bacteria • Found in soil • Generate NH3 for their own use.

5. N fertilizer • Produced by the Haber-Bosch process • Developed in 1913 • Process High pressure High temperature N2 + 3H2 NH3 Fe catalyst • Primarily responsible for the green revolution, but also responsible to large increase of reactive N in our environment

6. Ammonification (Mineralization) • N in plant protein may become part of the soil’s OM nitrogen pool by microbial degradation of: • Dead plant litter • Undigested protein in animal feces • OM-nitrogen converted to ammonia by soil bacteria • Process R-NH2 NH3 + R • Done by both aerobic and anerobic bacteria • Increased by: • Increased soil OM-N pool • Increased soil temperatures • Soil pH > 7 • High soil moisture • NH3 rapidly converted to NH4+ at pH < 7.5 • NH4+ is relatively stable • N is digested by animals is excreted as urea (mammals) or uric acid (poultry)

7. O Urease H2N – C – NH2 2NH3 + CO2 Urea O H C N 5 steps w/ H N C Urease C O 4NH3 + 5CO2 O C C N N H H Uric acid

8. FATE OF AMMONIA RELEASED BY MINERALIZATION • Use by plants • Immobilization • Bacteria incorporate N into their own cells and contribute to soil OM-N pool • Occurs in soils containing high C:N ratios • Leaching • Occurs in sandy soils • Have a low capacity for binding NH4+ • Ammonium cations may leach into ground water as precipitation infiltrates soils • Soils that are high in clay or organic matter can bind NH4+ which can only be lost with erosion

9. Nitrification • Highest proportion of NH4+ is converted to NO3 by aerobic bacteria Nitrosomas Nitrobacter O2 4H O2 NH4 NO2 NO3 • Rapid under conditions of: • Warm temperatures • Well aerated soils • Neutral pH • Moist soils • High fertility • Slow under conditions of: • Cold temperatures • Saturated soils • Low pH • During nitrification, soil pH may decrease as NH4 is converted to NO3

10. Volatilization • NH4+ is not volatile • In soils with high pH (> 7.0), NH4+ is converted to NH3 which can volatize into the atmosphere as a gas • NH3 is also released when the urea (in mammals) or uric acid (in poultry) excreted in urine mixes with the urease or uricase enzymes produced by the bacteria in the feces in in manure in barns, outdoor lots, manure storage structures, and in fields after application • Amounts of NH3 volatilized • 20 to 70% of the N in manure • Ammonia losses from animal agriculture represents 75% of all NH3 emitted in the U.S. • Rate of NH3 volatilization is increased by: • Soil pH > 7.0 • Soil temperatures > 50 F • Greater air movement

11. FATE OF NO3 PRODUCED DURING NITRIFICATION • Use by plants • Leaching into groundwater • NO3 is highly soluble in water and does not bind to soil particles • During periods of excessive precipitation, NO3 transported to ground water as water infiltrates the soil • Carries Ca, Mg, and K cations out of the soil reducing fertility while leaving Al which is toxic to plants • NO3 may be transported to surface waters via tile drainage • Factors that lead to increased leaching in spring • Build up on NH4+ in soil during winter • Increased NO3 in soil as nitrification increases with increased soil temperatures • Low utilization of NO3 by immature plants • High soil moisture

12. Denitrification • Conversion of NO3 to N2 in anerobic conditions in soil or manure storage areas • Process C6H12O6 + 4 NO3 6CO2 + 6H2O + 2N2 + NOx NOx = NO, NO2 or N2O • N2 and NOx are gases released into the environment • N2 is inert in the environment • NOx has numerous adverse effects on the environment • Denitrification is increased by: • High soil N levels • Anerobic soils • Flooded soil • Compacted soil • Warm temperatures • High OM in soil

13. POSITIVE EFFECTS OF INCREASING THE AMOUNTS OF REACTIVE N IN THE ENVIRONMENT • Increased yields and nutritional value of feeds • Increased wealth of the human population • Increased productivity of N-limited crops and ecosystems • Increased yields per acre • Could reduce cultivation of marginal and forested lands • Increased carbon sequestration

14. ADVERSE EFFECTS OF NITROGEN IN THE ENVIRONMENT

15. ADVERSE EFFECTS OF NITRATE (NO3) IN THE ENVIRONMENT • Enters drinking water supplies • Hazard (Blue Baby Syndrome) • Formation of methemoglobin that prevents hemoglobin in red blood cells from carrying oxygen to peripheral tissues Normal: O2 Hemoglobin in Oxygenated hemoglobin red blood cells Peripheral tissue (Uses O2) Nitrate toxicity: Gut bacteria NO3 NO2 O2 Hemoglobin in Methemoglobin red blood cells Peripheral tissue • Hazardous level: 10 ppm in water

16. ADVERSE EFFECTS ON AMMONIA IN THE ENVIRONMENT • Hazards • Odor • Direct toxin • Physiological effects and amounts • Livestock (<100 ppm, usually found in livestock facilities) • Eye irritation • Respiratory tract irritation • Reduced disease resistance • Humans (OSHA limit is 50 ppm) • 9 ppm Eye, nose and throat irritation • 50 – 150 ppm Severe cough and mucous production Nasal irritation • > 150 ppm Scarring of the upper and lower respiratory tract Pulmonary edema Chemical burns of eyes • 500 ppm Acute death

17. Problem for workers and animals in confinement • Limited threat to the community • Recommended limits (One-hour average exposure) Measurement Concentration Dilution Neighboring residence < 150 ppb 1:7 Property line < 70 ppb 1:15 • Toxicity in aquatic environments (Manure spills) • Most natural water sources • NH4-N at 2 ppm is toxic to fish • In alkaline waters at high temperatures • NH4-N at 0.1 ppm is toxic to fish • Particulate matter less than 2.5 um (PM2.5) • Formed when atmospheric NH3 reacts with SO2, NOx, and volatile organic compounds (VOCs) • Produce (NH4)2SO4, NH4NO3, and NH4HSO4 • Forms in rain clouds and fog • Dispersed to ground as rainfall and snow (Wet deposition) • Released in air as aerosols (Dry deposition)

18. Sources of components of PM2.5 • Agriculture • Burning fossil fuels • Hazards of PM2.5 • Human health • Penetrate into lungs • Increased hospital emissions • Increased respiratory diseases • Decreased lung function • Alteration in lung tissue and respiratory defense mechanisms • Chronic bronchitis • Increased risk of myocardiac infarctions • N deposition in the environment • Acidifying lakes and streams • Algae bloom in water sources • Depletion of minerals in soils • Decreased biodiversity of ecosystem • Health-based standard for PM2.5 • Annual average – 15 ug/m3 • 24 hr standard – 65 ug/m3 • Monitored at 1100 sites across the US

19. Acidify soil • Process • During nitrification, H+ are released that lower pH of soil • NH4 NO3 4H+ • Reduces ability of plants to uptake nutrients Total Ammonia Emissions by County for 1995

20. ADVERSE EFFECTS ON NOx IN THE ENVIRONMENT • Major sources • Combustion of fossil fuels • Agriculture • Hazards • Component of PM2.5; NO2 • Acid rain; NO2 • NOx + H HNOx • Effects • Damages lung tissue • Increases acid in waters • Harms fish population • Increases acid in soil • Harms trees • Damages buildings and statues

21. Formation of ground level ozone; NO2 • Formed when volatile organic compounds (VOCs) react with NOx in the presence of heat and sunlight • Effects • Health • Respiratory infections and diseases • Premature aging of lungs • Ecosystems • Reduced agricultural and forest yields • Reduced survivability of tree seedlings • Increased susceptibility of plants to stress and disease • Damage to foliage of plants • Forms smog with PM reducing visibility • Destruction of stratospheric ozone; N2O • In upper atmosphere, N2O triggers reactions that deplete the stratospheric ozone layer which protects the earth from ultraviolet radiation • Human skin cancer • Damages plant foliage • Greenhouse gas; N2O • N2O has 310 x the greenhouse gas effect of CO2 • Contributes to global warming

22. ADVERSE EFFECTS OF NH3, NO3, AND NOx IN AQUATIC AND TERRESTRIAL ENVIRONMENTS • In aquatic environments Mobile aquatic Hypoxic communities move zone (Gulf of Increased N Algae bloom Decay of dying Mexico) in marine algae reduce environment dissolved O2 in Fish kills water Pfisteria Produce toxins Fish lesions (Red tides) Fish and shellfish kills Memory loss, confusion, gastro- intestinal problems (Humans)

23. In terrestrial environment • Increased soil N favors growth of plants with high N needs • Alterations of soil chemistry • Loss of Ca, Mg and K • Build up of Al

24. National Atmospheric Deposition Program 1999 Annual Summary