University of California Water Resources Center

Copper is so ubiquitous in urban streams that it has been labeled a priority pollutant by the Nationwide Urban Runoff Program. Regulations and monitoring programs that have been developed in response to this problem concentrate on only total or total and dissolved copper concentrations. Our research has focused on measuring the partitioning of copper into its labile and non-labile fractions in urban storm water from the San Francisco Bay Area and its implications to toxicity. We found dissolved copper levels in runoff varied from 5 to 40 ug/L, but labile copper comprised only 10% to 25 % of the total dissolved copper levels. In experiments with runoff spiked with additional copper, we found that labile copper concentrations predicted toxicity better than dissolved copper concentration.