1. Nitrogen inorganic nitrogen: NH 4 (ammonia) NO 2 (nitrite) NO 3 (nitrate)

2. Organic Nitrogen amino acids & proteins humic compounds

3. sources of nitrogen 1. sedimentation 2. nitrogen fixation 3. surface & ground water 4. anthropogenic sources: agricultural fertilizers, sewage, & industrial

4. Nitrogen Losses outflow from the watershed basin bacterial denitrification- reduction C 6 H 12 O 6 + NO 3 -----> NO 2 + CO 2 + H 2 O

5. In an anaerobic environment nitrite is used as source of oxygen. C 6 H 12 O 6 + NO 2 -----> N 2 + CO 2 + CO 3 + H 2 O

6. Nitrogen Cycle

8. 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 & RNA minerals dissolved phosphorus

9. 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

10. Phosphorus Cycle

11. Ionic Composition of Surface Waters major cations: Ca 2+,Mg 2+, Na +, K + major anions: CO 3 2-, HCO 3 -, SO 4 2-, Cl - relative abundance Ca>Mg>Na>K>CO 3 >SO 4 >Cl

12. Total Dissolved Solids (TDS) derived from rocks, soil, & atmosphere conductivity- an index of TDS

13. hard -vs- soft water hardness is a measure of divalent cations, mostly Ca 2+ & Mg 2+ hard water has a higher buffer capacity water tends to resist change in pH under these equilibrium conditions (buffer capacity)

14. Inorganic Carbon atmospheric CO 2 ~ 0.033 % very soluble in water CO 2 + H 2 O -----> H 2 CO 3 (carbonic acid) H 2 CO 3 -----> H + + HCO 3 - (bicarbonate) HCO 3 - -----> H + + CO 3 2- (carbonate)

15. Inorganic Carbon and pH

16. Euryhaline vs. Stenohaline