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Bed sediment is collected as part of the NAWQA program in order to monitor and assess contaminant distribution in streams. There are three main reasons for analyzing bed sediment for contaminants.

First, bed sediment is composed of fine-grained particles and organic matter, which are natural accumulators of trace elements and hydrophobic organic contaminants in streams.

Secondly, bed sediment provides a time-integrated sample of particulate matter transported by a stream, which may lead to better detection of contaminants than from a single or periodic water sample.

Thirdly, when combined with biological tissue analysis, bed-sediment concentrations provide a useful measure of the potential bioaccumulation of trace elements and hydrophobic organic contaminants at a particular site.

The surficial 2 to 3 centimeters of bed sediment within each depositional zone at a sampling site is subsampled several times in in proportion to the relative size of each zone- the larger the area of a zone, the larger the number of subsamples collected. Then the subsamples from each depositional zone are composited. Confidence in the estimate of the mean concentration of contaminants in a composite sample increases as the number of subsamples in the composite increases.

For the LIRB, mostly wadeable streams were sampled. Bed sediment was sampled by using a Teflon tube and disk. The Teflon tube was inserted into the bed sediment, and the disk was slipped underneath to collect the sample.