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Salinity of Lakes, Rivers, and Reservoirs

Salinity of Lakes, Rivers, and Reservoirs. Saline vs. Marine. Marine water mainly sodium chloride 35% o Saline waters vary in dominant ions Surface waters range from almost pure water to several times the ionic strength of sea water. Saline lake Classification. Some Saline Inland Waters.

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Salinity of Lakes, Rivers, and Reservoirs

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  1. Salinity of Lakes, Rivers, and Reservoirs

  2. Saline vs. Marine • Marine water mainly sodium chloride 35%o • Saline waters vary in dominant ions • Surface waters range from almost pure water to several times the ionic strength of sea water

  3. Saline lake Classification

  4. Some Saline Inland Waters

  5. Don Juan Pond (~400‰) • Lake Vanda –deep meromictic lake

  6. Lake Assal -Djibouti • Crater lake 155m below sea level. • Salinity 348 ‰

  7. Dead Sea 337‰ and 378m below sea level

  8. Great Salt Lake

  9. Mono Lake

  10. Major Cations of Surface Waters Hard Water Soft Water Calcium Sodium Magnesium Potassium • Calcium • Magnesium • Sodium • Potassium

  11. Major Anions of Surface Waterscomment on Tables 10-1, 10-3, & 10-4 Hard Water Soft Water Chloride Sulfate Carbonate • Bicarbonate • Carbonate • Sulfate • Chloride

  12. Salinity due to: • Substrate (soil, geology) • Total precipitation • Ratio of precipitation to evaporation Comment on Table 10-2

  13. Aral Sea

  14. Saline lakes form when • Outflow is restricted • Evaporation rate exceeds inflow or outflow • Inflow equals evaporation plus outflow

  15. Saline Lakes are different from hard water lakes • Mainly sodium chloride

  16. Conductivity • Specific conductance

  17. Sources of ions • Direct weathering of rock (e.g. sodium chloride) • ReDox reactions involving iron, manganese, sulfur, nitrogen, phosphorus, and carbon • H+ from carbonic acid, acid rain, humic acids • Influence of groundwater

  18. Precipitation as a source of ions • Wind-borne salt • Dust • Acid rain

  19. Calcium • Essential element for most living things • Soft-water: low Ca • Hard-water: high Ca • Photosynthesis causes decline of Ca • Metabolism causes increase of Ca Interpret Figures 10-3, 10-4, & 10-5

  20. Ca & conductivity in Lawrence Lake

  21. Ca in Wintergreen Lake

  22. Magnesium • Necessary for chlorophyll • Unlike Ca, very soluble and does not easily precipitate Interpret Figure 10-6 and compare with Figure 10-3

  23. Magnesium in Lawrence Lake

  24. Sodium, potassium and other minor cations also very soluble

  25. Sodium concentrations

  26. Monovalent: Divalent Cation Ratios • M:D < 1.5 favors diatoms • M:D > 1.5 favors desmids

  27. Anions, especially halides in surface waters • Examine Figure 10-8, chloride concentrations in Little Crooked Lake

  28. Chloride in Little Crooked Lake

  29. Origins of freshwater biota • Bacteria: homiosmotic • Protists: variable, most from marine forms • Plants: from terrestrial groups, few saline plants (e.g. Spartina). Some like Nymphaea primitive freshwater aquatic forms • Animals: Many from marine environments; however, insects from terrestrial groups

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