MP13 Aquatic Ecotoxicology
Monday, 14 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall
(BUH-1117-841712) Toxicity of ash from burned areas along the Rio Grande to endangered Rio Grande silvery minnow.
Buhl, K1, 1 U.S. Geological Survey, CERC-Yankton Field Research Station, Yankton, South Dakota, USA
ABSTRACT- Extensive fires in the Bosque along the middle Rio Grande in and around Albuquerque, NM during the summer of 2003 have created the potential for large quantities of ash to enter river by surface runoff and wind erosion. This has raised concerns about the potential impacts of the ash and associated contaminants on the endangered Rio Grande silvery minnow (Hybognathus amarus). The objective of this study was to determine the acute toxicity to young silvery minnow and chemical characteristics of ash collected from burned areas along the Rio Grande. Silvery minnow (mean weight, 59-97 mg) were exposed to a geometric series of ash solutions, control water, and one soil solution (equal to the highest ash concentration) for 96 h under static conditions. Samples of ash, soil, and the test solutions were analyzed for a number chemical parameters to assess the likely toxic components. Of the 35 semivolatile compounds measured in the ash, only phenol was present a quantifiable concentration (1,000 
g/kg). Concentrations of priority metal pollutants in ash, soil, and test solutions were below published probable effect concentrations for freshwater sediments and waterborne toxic concentrations for fish. In both tests, all mortality occurred during the first 24 h of exposure and the concentration-response was identical, producing a 24-h and 96-h LC50 of 20.74 (95% CI, 17.00-26.84) g ash/L. Comparisons of water quality data to published toxicity values indicated that the most likely toxic components in the ash solutions were un-ionized ammonia, potassium, and possibly sulfate. Other parameters that may have contributed to the toxicity were elevated pH, bicarbonate-carbonate, and the ash particles. The ash solutions had high biological and chemical oxygen demands and dissolved oxygen concentrations in these solutions decreased precipitously after 24 h. Entry of large amounts of ash into the Rio Grande has the potential to degrade the water quality and adversely affect the silvery minnow.
Key words: Hybognathus amarus, endangered, ash, toxicity