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Water Chemistry…… What does it all mean?

Water Chemistry…… What does it all mean?. Eric Starkey Upper Columbia Basin Network, Moscow ID. Overview. Basic Parameters What do they show? How do they vary over time? Why are these parameters important? Calibration Why is frequent calibration necessary? What is the process?

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Water Chemistry…… What does it all mean?

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  1. Water Chemistry……What does it all mean? Eric Starkey Upper Columbia Basin Network, Moscow ID

  2. Overview • Basic Parameters • What do they show? • How do they vary over time? • Why are these parameters important? • Calibration • Why is frequent calibration necessary? • What is the process? • How is it done?

  3. Overview • Water chemistry sampling equipment • Grab sample/test kit • Multi-parameter handheld unit (YSI 556) • Multi-parameter sonde (HACH Hydrolab) • Methods of sampling water (temporal and spatial) • Point sample • Continuous • Transect • Vertical profile

  4. Basic Parameters • Temperature • Effects many other parameters • Increased temperature = decreased D.O. = bad news for aquatic organisms! • Upper lethal for trout 77-78 °F (25-25.5 °C) • pH differs slightly according to temperature • Indicates along with other parameters • Degree of stream shading • Input of ground water/dewatering • Thermal pollution • Habitat suitability for aquatic organisms

  5. Basic Parameters • Temperature Variability • 24hour, Seasonal (Example from Nez Perce National Historical Park – Lapwai Creek)

  6. Basic Parameters • Dissolved Oxygen (mg/L) • Likely the most important parameter to consider relative to aquatic life! • Responds to temperature, barometric pressure, salinity, productivity, decomposition, pollutants • Indicates along with other parameters • Levels of eutrophication, productivity, decomposition • Excessively high water temperature Ideal D.O. ≥5 mg/L

  7. Basic Parameters • Dissolved Oxygen Variability • 24hour, Seasonal (Example from Nez Perce National Historical Park – Lapwai Creek) Midnight Noon Why does DO increase each afternoon?

  8. Basic Parameters • Specific Conductance (µS/cm) • Measure of the electrical conductance of water, translates to the amount of dissolved constituents • Increased Sp. Cond. = increased salinity • Decreased Sp. Cond. = decreased salinity • Many natural processes can change Sp. Cond. • Temperature - Geology - Name Another? • Might also be an indication of • Industrial Pollutants Typical for this area 150-300 µS/cm

  9. Basic Parameters • Specific Conductance Variability • 24hour, Seasonal (Example from Nez Perce National Historical Park – Lapwai Creek) Noon Noon Why the increase each night?

  10. Basic Parameters • pH (Units) • Measure of the acidity or basicity of a solution • activity of dissolved hydrogen ions (H+) • Responds to productivity, as CO2 ↑ pH ↓ • Influences • The effects of pollutants on aquatic organisms • Efficiency of gills • Indicates along with other parameters • Eutrophication • Other forms of pollution Ideal pH 6.0 – 9.5

  11. Basic Parameters • pH Variability • 24hour, Seasonal (Example from Nez Perce National Historical Park – Lapwai Creek) Midnight Noon Why does pH increase each afternoon?

  12. Upland Drivers of Water Chemistry • Temperature: stream shading/upland vegetation (sagebrush vs. forested), surface flow (parking lots vs grassland) • Dissolved Oxygen: fertilizer input, stream shading, organic input (leaves, etc.)/decomposition • Specific Conductance: geology, rainfall • pH: stream shading, temperature, geology

  13. Quality Control • Always use the sensor guard • The cleaner the better! • Rinse sensors with distilled water after use • Make sure not to damage the D.O. membrane or pH sensor when cleaning • Never store the sensors in lake water or distilled water • Store with ¼ inch of pH 4 standard solution • CALIBRATE prior to use! (especially if the instrument has not been used for several days)

  14. Units • Best units for data collection • Temperature: °C • Specific Conductance: µS/cm • pH: Units • Dissolved Oxygen: mg/L • Also % Saturation • Why? • Comparability • Consistency

  15. Calibration

  16. Calibration • Why? • Calibration Drift – electronic or sensor drift • Fouling – biological growth or sediment on sensors • Quality Control • How often? • Prior to use if the instrument has been unused for more than a few days • Every week if used consistently

  17. Calibration • YSI 556 handheld meter • Temperature, Specific Conductance, pH, Dissolved Oxygen • Section 6. pg. 37-55 of user manual • Calibration materials • Distilled water • Calibration cup • Paper towels • Calibration standards • pH 7 and pH10 • 1412 µS/cm • Distilled water

  18. Temperature • No Calibration  • Double check with thermometer (should be within 0.5 °C)

  19. Conductivity • Rinse with D.I. water • Dry with paper towel (be careful not to damage the pH bulb and D.O. membrane) • Rinse with standard solution • Discard standard solution • Go to the calibration screen for Specific Conductance • Fill calibration cup with enough solution to cover sensor • Enter the standard value • Calibrate

  20. Dissolved Oxygen • As oxygen crosses the membrane, it is consumed in a chemical reaction which generates a small electrical current between the electrodes • The current measured is directly proportional to the amount of oxygen in the water sample • Must be kept moving in order to get a correct reading • Determine barometric pressure • Local weather station (mbar, corrected to sea level) • Convert to mmHg • Convert from barometric pressure at seal level to pressure at altitude BP’= BP-2.5(Aft/100)

  21. Dissolved Oxygen • Rinse with D.I. water • Dry with paper towel (be careful not to damage the pH bulb and D.O. membrane) • Add 1/8th inch of water to calibration cup • Place cap on cup but do not tighten • Wait 10-15 minutes for air in cup to saturate with water • Enter barometric pressure • Calibrate

  22. pH • Measures hydrogen ion concentration • Requires a 2-point calibration at pH 7 and 10 • Rinse with D.I. water • Dry with paper towel (be careful not to damage the pH bulb and D.O. membrane) • Rinse with pH 7 / discard • Add pH 7 standard • Enter temperature corrected pH value • Calibrate • Repeat steps 3-6 with pH 10

  23. Storage • Short Term Storage (< 1month) • Add ¼ inch of pH 4 standard to calibration cup • Disconnect sensor cable from unit • Remove all sand etc. from case and cable • Long term storage (>1 month) • Store as above and remove batteries • Replace D.O. cap/electrolyte when used again

  24. Questions?

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