EVALUATION OF TIME-INTEGRATING SEDIMENT SAMPLERS FOR ASSESSMENT OF OCCURRENCE AND CONCENTRATIONS OF HYDROPHOBIC ORGANIC CONTAMINANTS IN SMALL STREAMS

Hydrophobic organic contaminants are primarily associated with sediments in streams. Transport of suspended sediments is episodic and related to storm runoff, so obtaining representative suspended sediment samples for organic contaminant analysis can be problematic . It is difficult to schedule sampling to coincide with episodic storms and the mass of sediment in typical 1-liter samples is too small for determination of environmental concentrations of contaminants. Bed sediments are commonly used in sampling programs, but they might include older sediment unrelated to recent storm runoff. We have evaluated time-integrating suspended-sediment samplers previously developed for use in geochemical source studies for their application to hydrophobic and ionic organic contaminants. The samplers were installed in small, wadeable streams during June through September 2007 at nine locations in predominantly urban areas in Seattle, Washington to study pyrethroid pesticides, and at four locations in agricultural areas in Iowa and Mississippi to study glyphosate. The samplers were installed in the streams for time periods ranging from 27 to 70 days. Sufficient sediment mass (median 1.8 g sediment; range 0.5 to 40.1 g) was collected for determination of organic contaminants and other parameters. At sites where the samplers were installed for more than one event, more sediment was collected during runoff. In general, the mean particle size and sorting of sediment collected by the samplers was generally similar to that in discrete samples obtained concurrently at the different sites using equal-width increment methods. The evaluation of physical parameters of the sediments suggests that these time-integrating samplers can provide a simple technique for obtaining a representative suspended sediment sample for determination of organic contaminants, including pesticides (pyrethroids and glyphosate) and polycyclic aromatic hydrocarbons in the sediment collected by the samplers.