Removal of low levels of Cu from ongoing sources in the presence of other elements - Implications for remediated contaminated sediments.

Mesocosms were used to investigate the effects of Cu influx, alone and in the presence of other elements, on sediments remediated by active caps, passive caps, and in situ treatment. Competitive interactions between Cu and other elements were investigated because contaminants often co-occur. Elements in surface water remained at significantly lower concentrations in mesocosms with apatite and mixed amendment caps than in mesocosms with passive sand caps or uncapped sediment. Element concentrations in Lumbriculus variegatus were significantly higher in untreated sediment than in active caps and significantly related to element concentrations in sediment measured by DGT probes. The cumulative toxicity of Cu mixed with other elements was greater than the toxicity of Cu alone in treatments without active caps, but the ability of active caps to control Cu was not affected by the presence of other elements. Active caps can protect remediated sediments by reducing bioavailable elements in ongoing contamination.