IMPORTANCE OF NITROGEN IN THE ENVIRONMENT

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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

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THE NITROGEN CYCLE
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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

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• 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

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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

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Ammonification (Mineralization)

• N in plant protein may become part of the soils
  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 gt 7
• High soil moisture
• NH3 rapidly converted to NH4 at pH lt 7.5
• NH4 is relatively stable
• N is digested by animals is excreted as urea
  (mammals) or uric acid (poultry)

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• 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

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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 CN 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

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• 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

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• Volatilization
• NH4 is not volatile
• In soils with high pH (gt 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 gt 7.0
• Soil temperatures gt 50 F
• Greater air movement

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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

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• 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

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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

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ADVERSE EFFECTS OF NITROGEN IN THE ENVIRONMENT
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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

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ADVERSE EFFECTS ON AMMONIA IN THE ENVIRONMENT

• Hazards
• Odor
• Direct toxin
• Physiological effects and amounts
• Livestock (lt100 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
• gt 150 ppm
• Scarring of the upper and lower
  respiratory tract
• Pulmonary edema
• Chemical burns of eyes
• 500 ppm

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• Problem for workers and animals in confinement
• Limited threat to the community
• Recommended limits (One-hour average exposure)
• Measurement
  Concentration Dilution
• Neighboring residence
  lt 150 ppb 17
• Property line
  lt 70 ppb 115
• 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)

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• 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

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• 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
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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

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• 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

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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

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• 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

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National Atmospheric Deposition Program 1999
Annual Summary