nitrogen inorganic nitrogen: nh 4 (ammonia) no 2 (nitrite) no 3 (nitrate)
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Nitrogen
inorganic nitrogen:
NH4 (ammonia)
NO2 (nitrite)
NO3 (nitrate)
Organic Nitrogen
amino acids & proteins
humic compounds
sources of nitrogen
1. sedimentation
2. nitrogen fixation
3. surface & ground water
4. anthropogenic sources: agricultural fertilizers, sewage, & industrial
Nitrogen Losses
• outflow from the watershed basin
• bacterial denitrification- reduction
C6H12O6 + NO3 -----> NO2 + CO2 + H2O
In an anaerobic environment nitrite is used as source of oxygen.
C6H12O6 + NO2 -----> N2 + CO2 + CO3 + H2O
Nitrogen Cycle
Nitrogen Cycle
Phosphorus• important macronutrient; may limit
biological productivity
• relatively scarce in the hydrosphere (ave. concentrations 10-50 ug/L); low solubility
cellular constituents: e.g. DNA & RNAmineralsdissolved phosphorus
Phosphorus• anthropogenic sources: fertilizers &
detergents
• rapidly assimilated by the biota
• exchange across sediment-water interface depends upon redox potential at the interface zone; under anaerobic conditions phosphorus is released from the sediment where during periods of mixing phosphorus leaves the hypolimnion
Phosphorus Cycle
Ionic Composition of Surface Waters
• major cations: Ca2+,Mg2+, Na+, K+
• major anions: CO32-, HCO3
-, SO42-,
Cl-
• relative abundance
Ca>Mg>Na>K>CO3>SO4>Cl
Total Dissolved Solids (TDS)
derived from rocks, soil, & atmosphere
conductivity- an index of TDS
hard -vs- soft water
• hardness is a measure of divalent cations, mostly Ca2+ & Mg2+
• hard water has a higher buffer capacity
• water tends to resist change in pH under these equilibrium conditions (buffer capacity)
Inorganic Carbon• atmospheric CO2 ~ 0.033 %
• very soluble in water
• CO2 + H2O -----> H2CO3 (carbonic acid)
• H2CO3 -----> H+ + HCO3- (bicarbonate)
• HCO3- -----> H+ + CO3
2- (carbonate)
Inorganic Carbon and pH
Euryhaline vs. Stenohaline
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