Detecting copper residues in sediments from aquatic copper-based pesticide applications

Copper-based algaecides and herbicides are commonly used to mitigate risks of problematic algae and weeds, however there are concerns regarding copper accumulation from treatments. Modeling and laboratory experiments can be used to predict copper accumulation and measurement in sediments, as well as benthic invertebrate responses following treatments. Modeling was used to estimate copper residual concentrations in sediments from algaecide and herbicide treatments. Reported and measured method detection limits (MDLs; minimum concentration of an analyte of interest that can be measured with 99 percent confidence in a specific matrix using an analytical method) were compared to model estimated copper residual concentrations in sediments to determine measurement of copper accumulation from treatments. Laboratory toxicity experiments were used to measure the bioavailability of copper in sediments. Comparisons of results from modeling and laboratory experiments to field measurements were used to determine the accuracy of site specific predictions. Site specific predictions of copper accumulation and responses of benthic invertebrates following treatments can be used to guide decisions regarding risk mitigation of algae and aquatic weeds with copper-based algaecides and herbicides.