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Water Quality

Water Quality. ESI. Stream Water. soluble. insoluble. Suspended solids or sediment. Total Dissolved Solids (TDS) Mostly salts - ions. Particles settle out. Evaporate water after filtering, determine mass of residue. Mass after collecting by filtration.

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Water Quality

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  1. Water Quality ESI

  2. Stream Water soluble insoluble Suspended solids or sediment Total Dissolved Solids (TDS) Mostly salts - ions Particles settle out Evaporate water after filtering, determine mass of residue Mass after collecting by filtration TDS by conductivity since common solids are ions Cause of turbidity or cloudiness of stream water

  3. Suspended Sediment Does suspended sediment vary with stream discharge? mean Data from http://va.water.usgs.gov/chesbay/RIMP/conc.html Mean discharge 60,000 cfs based on 34 years of data

  4. How can we control suspended sediment? • Use of silt fence at construction sites • Settling ponds for stormwater runoff • Riparian Forest buffers along streams and rivers • No till/contour plowing agriculture

  5. Suspended Sediment Wades in until his feet disappear! Late 1980’s Late 1990’s The GOAL Source: www.mdp.state.md.us/info/patux.htm

  6. Turbidity and Light Penetration What is the biological importance of light penetration to submerged aquatic vegetation (SAV)? As turbidity increases, light penetration decreases. SAV

  7. How has the area of SAV’s in the Bay region varied? Recovery of bay grasses has occurred! http://www.dnr.state.md.us/bay/sav/past_present.html

  8. The importance of bay grasses Disperse wave energy, decrease turbidity and erosion Provide food and shelter for many organisms Produce O2 by photosynthesis Absorb nutrients from the water http://www.dnr.state.md.us/bay/sav/importance.html

  9. Total Dissolved Solids (TDS) • Mostly dissolved mineral salts as ions (cause of conductivity) Na+ Cl- Ca++ SO4-2 • Organic compounds Examples: rain <10 mg/L drinking water <500 mg/L rivers 100 – 2000 mg/L seawater 35,000 mg/L

  10. Water Temperature How does temperature vary over a year? 2000 2001 2002 http://www.dnr.state.md.us/bay/conditions/le11.html

  11. Dissolved oxygen (DO) anoxic mg O2/L water 0 1 2 3 4 5 6 7 8 9 10 hypoxic oxic Severely stressful or lethal Stressful Healthy Required by higher organisms!

  12. What is the source of dissolved oxygen in stream water? • Oxygen, O2, from air (79%N2/20%O2) dissolves in water – added by turbulence in stream flow • Produced by photosynthesis by organisms such as algae CO2 + H2O  (CH2O)x + O2

  13. Solubility, mg/L Temperature, oC Solubility of oxygen gas (O2) How does the solubility change when temperature increases? Is this your prediction?

  14. Now consider both the dissolved oxygen and temperature data over an annual cycle. How does the solubility change when temperature increases? Mean values from http://www.dnr.state.md.us/bay/conditions/pot1830.html

  15. How does the solubility change when temperature increases? DO is an indirect function of temperature.

  16. Dissolved Oxygen in the Chesapeake Bay • Monthly for 1998 • August levels for 1984 to 1998 mg O2/L Images from http://noaa.chesapeakebay.net/data/interp1.htm

  17. Oxygen Demand • Substances that use oxygen in reactions: organic compounds + O2 products • STELLA dissolved oxygen model • Lower the dissolved oxygen of streams. • Once reaction is over, DO levels can recover.

  18. acid rain (NOx, SOx) pH of 4.2 - 4.4 in Washington DC area pH 0-14 scale for the chemists 2 3 4 5 6 7 8 9 10 11 12 acidic (H+) > (OH-) neutral @ 25oC (H+) = (OH-) distilled water basic or alkaline (H+) < (OH-) normal rain (CO2) pH = 5.3 – 5.7 fish populations drop off pH < 6 and to zero pH < 5 natural waters pH = 6.5 - 8.5

  19. Nutrients • nitrate (NO3-) – very soluble • phosphate (PO4-3) – soluble at low levels • part of TDS • cause excessive biological growth, which consumes DO

  20. Nutrient Sources in the Environment Banned in Bay watershed fertilizers detergents acid rain animal feedlots phosphate rock wastewater Not found in Bay watershed sources of both nutrients

  21. high medium low Judging Water Quality Using Macroinvertebrate Organisms in Bottom Sediments POOR FAIR GOOD Wide-range tolerance Organism Tolerance to Environmental Stress Intermediate tolerance Clean water only Water quality Increasing species diversity

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