Bioavailability of mercury and dioxins in the sediments of a brackish lake in SE Norway and effects of activated carbon amendment

Summary

Bioavailability of mercury and dioxins in the sediments of a brackish lake, Gunneklevfjorden in SE Norway, has been investigated by ex situ measurements in box-core samples transferred from the fjord to a nearby mesocosm laboratory. Here, the samples were maintained for 7 months by continuous exchange of the brackish water (5-10 PSU) overlying the sediments in each box-core. Bioavailability was measured as fluxes of TotHg, MeHg, dioxin and furan toxicity equivalents (PCDD/F TE), hexacholorbenzene (HCB) and octachlorostyren (OCS) from sediment to water and uptake in polychaetes added to the sediment in phase two of the experiment. Triplicate samples were collected from three stations in the open areas of the fjord and one station in a shallow seagrass location in the southern part of the fjord. Electrode measurements (O2, H2S and pH) showed rather extreme environmental conditions (7