CALL FOR PROPOSALS:

ORGANIZERS

  • Harvey Thorleifson, Chair
    Minnesota Geological Survey
  • Carrie Jennings, Vice Chair
    Minnesota Geological Survey
  • David Bush, Technical Program Chair
    University of West Georgia
  • Jim Miller, Field Trip Chair
    University of Minnesota Duluth
  • Curtis M. Hudak, Sponsorship Chair
    Foth Infrastructure & Environment, LLC

 

Paper No. 1
Presentation Time: 1:35 PM

THE INCREASING IMPACT OF ROAD SALT: WIDESPREAD AQUATIC TOXICITY AND WATER QUALITY IMPACTS ON LOCAL, REGIONAL, AND NATIONAL SCALES


CORSI, Steven1, GRACZYK, David1, GEIS, Steven2, BOOTH, Nathaniel3, RICHARDS, Kevin1 and HIRSCH, Robert M.4, (1)U.S. Geological Survey, 8505 Research Way, Middleton, WI 53562, (2)Wisconsin State Laboratory of Hygiene, 2601 Agriculture Drive, Madison, WI 53718, (3)Wisconsin Water Science Center, U.S. Geological Survey, 8505 Research Way, Middleton, WI 53562, (4)U.S. Geol Survey, 409 National Center, USGS, Reston, VA 20192, srcorsi@usgs.gov

While road salt influence on water quality has been documented for at least forty years, a new perspective on the severity of aquatic toxicity impact was gained by a focused seasonal analysis. Dramatic impacts were observed on local, regional, and national scales. Locally, samples from 7 of 13 Milwaukee area streams during two road salt runoff events exhibited toxicity in Ceriodaphnia dubia and Pimephales promelas bioassays with chloride concentrations as high as 6,470 mg/L, far exceeding the U.S. Environmental Protection Agency (USEPA) acute and chronic water quality criteria of 860mg/L and 230 mg/L, respectively. Twelve years of testing at Wilson Park Creek in Milwaukee resulted in chloride concentrations as high as 7,730 mg/L in 37 samples. Toxicity was observed in 72% of these samples in chronic bioassays and 43% in acute bioassays. Analysis of long-term chloride data from the Milwaukee River using weighted regressions on time, discharge, and season indicates substantial increasing concentration from 1973 to 2005. Concentrations were greatest during winter low-flow periods, but even during warm-weather months and during high-flow periods, notable increasing trends were present. Regionally in eastern and southern Wisconsin, continuous specific conductance was monitored as a chloride surrogate in 11 watersheds with urban land use from 6% to 100%. Elevated specific conductance was present during cold-weather months at all sites with effects during warm-weather months at the most urban sites. Specific conductance increased with urban land use and was measured as high as 30,800 µS/cm (Cl = 11,200 mg/L). Estimated chloride concentrations exceeded USEPA acute water quality criteria at 55% and chronic water quality criteria at 100% of these sites. Nationally, U.S. Geological Survey historical chloride data was examined for 13 northern and 4 southern metropolitan areas. Chloride concentrations exceeded USEPA water quality criteria at 25% (acute) and 55% (chronic) of the 168 northern monitoring locations during cold-weather months. Only 1% (acute) and 16% (chronic) of sites exceeded criteria during warm-weather months. At southern sites, 2% and 4% of sites had samples that exceeded chronic water quality criteria during cold- and warm-weather months, respectively; no samples exceeded acute criteria.
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