TA1 Developing Suspended and Bedded Sediments Criteria
256 Portland Ballroom
8:00 AM - 12:00 PM, Tuesday
() Total Suspended Solids and Turbidity - Aquatic Risks During Storm Events and Long-Term.
Volosin, J.1, Cardwell, R.2, 1 Parametrix, Inc., Orchard Park, New York, U.S.A.2 Parametrix, Inc., Corvallis, Oregon, U.S.A.
ABSTRACT- This study quantified potential risks to aquatic plants, invertebrates and fish exposed to suspended solids (SS) and turbidity during rainstorm events and long-term (30 days). Turbidity and SS may affect aquatic life via a variety of ways, including impaired feeding and abrasion, respectively. Acute and chronic no effect concentrations (PNECs) reported in the literature for all exposure durations were used. Adverse effect metrics (sublethal, lethal and population level) reported for various exposure durations were identified. Fish in general and salmonids specifically were more sensitive to turbidity than plants and invertebrates, and 20% of the effect endpoint metrics were exceeded at turbidities ≤10 NTU and ≤50 mg/L SS. Data came from continuous governmental monitoring of turbidity or SS, and were either measured or estimated using site-specific regressions of turbidity and SS. All SS risks reflected the duration required to elicit the effect and effect magnitude. Turbidity risks reflected only effect magnitudes, because of no clear relationship between effect magnitude and exposure duration. Storm event durations, measured by an increase in turbidity above the median, generally ranged from 15 to 30 hours. Turbidity posed greater risks than SS in the four rivers evaluated (Kansas, Minnesota, Oregon, South Dakota). During storm events, turbidity risks averaged (±S.E.) 33% (±11%) compared to 11% (±7%) for SS. Long-term turbidity risks averaged 23% (±11%) compared to 11% (±4%) for SS. Thus, apparent risks during storm events are predicted to be greater due to turbidity. However, turbidity and SS risks are not equivalent, because they reflect reliance on different endpoints derived from toxicity studies of different durations. Risks will also be compared based on effects normalized to the exposure durations observed in-situ.
Key words: Turbidity, Suspended solids, Aquatic risk