Measurement of integrated pollutant levels in streams

Grab Samples from streams may miss episodic events of PAH release and seldom measure time-integrated pollutant abundance. Time weighted averaging and automsamplers are expensive and cumbersome. We tested a sampler made of XAD resins confined in a nylon bag and staked in a stream to estimate the average levels of PAHs over time. The resin was extracted and analyzed by HPLC with a UV diode array spectral analyzer and a fluorescence detector. We studied four streams in the Anacostia and Patuxent River watersheds. At each site we measured biological impairment and chose one stream for more detailed subsampling. We were able to localize sources of individual PAHs to within watersheds of first and second order streams. Our measurements more closely estimate average flux (moles/cm$\sp2$/day) than either concentration (moles/L) or pollutant load (moles/day). We contend that average flux is a better measure of biological exposure than either concentration or load.