Evaluation of metals in marine and freshwater surficial sediments from the environmental monitoring and assessment program relative to proposed sediment quality criteria for metals

Abstract

AbstractSurficial sediments collected from Lake Michigan (N = 46) and the Virginian Province of the east coast of the U.S. (N = 131) by the Environmental Monitoring and Assessment Program (EMAP) of the U.S. Environmental Protection Agency (EPA) were evaluated relative to a proposed approach to sediment quality criteria (SQC) for five metals (copper, cadmium, zinc, nickel, and lead). Concentrations of acid‒volatile sulfide (AVS), simultaneously extracted metals (SEM) from the AVS extraction, total metals, and total organic carbon were measured in the sediments. Interstitial pore‒water concentrations of the five metals also were measured in the freshwater sediment samples. Overall, 91% of 131 surficial marine sediments and 50% of 46 surficial freshwater sediments contained detectable AVS. In 93 of the marine sediments the concentrations of AVS were greater than total SEM (molar sum of copper, cadmium, zinc, nickel, and lead) indicating a low probability of bioavailable metal. In contrast, 91% of the surficial freshwater samples contained greater concentrations of total SEM than AVS. However, pore‒water concentrations of the five metals in the freshwater samples were uniformly low and never exceeded 0.3 toxic units based on an additive toxicity model that utilized final chronic values from EPA water quality criteria documents for the five metals. These predictions of minimal metal bioavailability in the EMAP samples were consistent with a general lack of toxicity in laboratory assays with the sediments and with the fact that they had been collected predominantly from ostensibly uncontaminated sites.