Module 4 Stream Ecology Laboratory

1. Module 4 Stream Ecology Laboratory SolidsTSS and Turbidity

2. Total Suspended Solids Sediment plume off the south shore of Lake Superior

3. Total Suspended Solids SAMPLING CONCERNS: • collect from undisturbed water • when standing in a stream, reach upstream into the current for the sample In lakes, boat propeller action also may disrupt sediments in shallow areas avoid sampling from temporarily disrupted area

4. Total Suspended Solids TSS, as well as turbidity and any other parameter dominated by the particulate fraction, can be very patchy - it may be wise to composite from a number of spots within the site’s area

5. Total Suspended Solids Figure 1 - filter a known amount of water through a pre-washed, pre-dried at 103-105 oC, pre-weighed (~ + 0.5 mg) filter - rinse, dry and reweigh to calculate TSS in mg/L  - possibly save the filters for other analyses such as volatile suspended solids (VSS) that estimates organic matter

8. Total Suspended Solids Analytical balance Drying oven Filter and petri dish

9. TSS – Methodology Calculate TSS by using the equation below TSS (mg/L) = ([A-B]*1000)/C where A = final dried weight of the filter (in milligrams = mg) B = Initial weight of the filter (in milligrams = mg) C = Volume of water filtered (in Liters)

10. How does Turbidity relate to TSS ? A general rule of thumb: 1 mgTSS/L ~ 1.0 - 1.5 NTU’s of turbidity BUT – Turbidity scattering depends on particle size so this is only a rough approximation

11. Turbidity-Transparency Tube (for streams, ponds, wetlands, some coastal zones) May have stopper and valve

12. Turbidity-Transparency Tube • Analogous to secchi depth in lakes: a measure of the dissolved and particulate material in the water • Useful for shallow water bodies where a secchi would still be visible on the bottom or fast moving streams • Best for clearwater bodies of water (not stained with dissolved organic compounds from bogs) but not tooclear water • It is a good measure of turbidity and suspended sediment (TSS) • Used in many volunteer stream monitoring programs Image: http://www.watermonitoringequip.com/

13. How does Turbidity relate to TSS ? A general rule of thumb: 1 mgTSS/L ~ 1.0 - 1.5 NTU’s of turbidity BUT – Turbidity scattering depends on particle size so this is only a rough approximation

14. Even small amounts of wave action can erode exposed lakeshore sediments, in this case a minepit lake from northeastern Minnesota. Guess the mineral mined here. Field Profiles-Turbidity • Turbidity measures the scattering effect suspended particles have on light • inorganics like clay and silt • organic material, both fine and colored • plankton and other microscopic organisms • Field turbidity measurements are made with • turbidimeters (bench meter for discrete samples) • Submersible turbidity sensors (Note - USGS currently considers this a qualitative method) • Transparency or turbidity tubes

15. http://www.bradwoods.org/eagles/turbidity.htm Turbidimeters -Nephelometric optics Principle: • nephelometric turbidity estimated by the scattering effect suspended particles have on light • detector is at 90o from the light source Units: • Nephelometric Turbidity Units (NTU) • standards are formazin or other certified material • JTU’s are from an “older” technology in which a candle flame was viewed through a tube of water • 1 NTU = 1 JTU (Jackson Turbidity Unit)

16. 1. Portable Bench vs Submersible Turbidimeters Discrete depth - collect water sample and analyze water in Lab vs Continuous profile using submersible sensor YSI 6820 with unwiped turbidity YSI wiping turbidity Hydrolab

17. Field profiles-turbidity Sensor calibration • Turbidity free water = zero (0 NTU) standard • USGS recommends filtering either sample water or deionized water through a 0.2 um or smaller filter to remove particles • WOW uses deionized water that is degassed by sparging (bubbling) with helium to minimize air bubbles that give false turbidity readings • Standards range depends on anticipated sample values • lakes - typically 0-20 NTU • streams and wetlands - 0-20, 0-50 or 0-100 NTU • 2 non-zero standards typically adequate (response is linear) • formazin particles (either from a “recipe” or purchase a certified, concentrated stock solution (usually 4000 NTU) • other commercially available materials - polystyrene • need to worry about storage limits - Primary stock of 400 NTU’s lasts < 1 month when refrigerated. Dilute working standards from intermediate stock solution daily.

18. Source Concentrations Suggested holding times Hach Company 2 to 20 NTU Prepare daily 20 to 40 NTU Prepare monthly Standard Methods All dilutions Prepare daily EPA Region 5 All dilutions Prepare weekly Field profiles-turbidity - calibration standards prep

19. Field Probes-turbidity • Comparability of different methods: • With the proliferation of automated in situ turbidity sensors there is concern about the comparability of measurements taken using very different optical geometries, light sources and light sensors. • The US Geological Survey and US Environmental Protection Agency are currently (August 2002) developing testing procedures for a field comparison of a number of instruments produced by different manufacturers. We will include these results when they become available. • Standard Methods refers to : APHA.1998. Standard methods for the examination of water and wastewater. American Public Health Association, Washington, D.C.