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