Patterns of accumulation of heavy metals in the sediment of roadside streams

Abstract

The purpose of this study was to evaluate the reliability of monitoring stream sediment to assess chronic highway-generated metals contamination. Concentrations of cadmium, lead, and zinc in the sediments of six small softwater streams were measured for a period of two years following the opening of a new highway. Metals concentrations at highway sites (H) averaged two (Zn) to five (Cd) times greater than at upstream reference sites (U) or downstream sites located ⩾ 200 m downstream (D). However, three of the six streams did not consistently demonstrate the H > U=D pattern. Metals concentrations were generally low at all sites on these streams; interstream variation at highway sites was more strongly related to distance of the stream from the road surface, stream velocity, and organic content of the sediment, than to traffic volume. Temporally, H/U ratios of metals concentrations peaked after one year and declined in the second year, concurrent with an increase in precipitation. These findings indicate that interstream, intrastrearn, and temporal variations of metals concentrations in sediments are high, but also suggest sampling designs to effectively assess metals contamination from highways by monitoring this component of the aquatic ecosystem.