MP6 Mercury in Stream Ecosystems
202 Oregon Ballroom
1:20 PM - 4:40 PM, Monday
() The release of mercury and methylmercury from river sediment as a result of resuspension.
Heyes, A1, Reardon, M1, Mack, E2, Stahl, R2, 1 Chesapeake Biological Laboratory, Solomons, MD, USA2 E.I. du Pont de Nemours and Company, Wilmington, DE, USA
ABSTRACT- The presentation will report the results of a study designed to assess the importance of river sediment resuspension and the inundation of bank soils during storm events in the release of inorganic mercury (Hg) and methylmercury (MeHg) into the water column. In addition, the study was designed to examine if such events stimulate the methylation of inorganic Hg by the resident microbial community. Thus, the project goals were to examine the relative mobility and bioavailability of Hg in surficial sediments at depositional sites in the river channel, and in river bank soil of high and low mercury concentrations. The potential for Hg methylation within these sediments/soils after resuspension/disturbance was monitored over a period of days, as was the dissolved and total Hg and MeHg concentrations, and the suspended solids and other ancillary parameters. The experiments were conducted in microcosms with varying lengths of resuspension and with and without added dissolved organic carbon (DOC), added to stimulate microbial activity. The sediments and soils ranged in Hg and MeHg concentration, but overall the higher Hg containing sediments had a lower relative MeHg concentration. The results showed that, not surprisingly, the degree of sediment resuspension for a particular applied shear differed for different sediment types. The fate and release of Hg and MeHg upon resuspension was different for the various treatments. The overall results of this study will be presented, and the results contrasted to those obtained in other aqueous environments in other studies.
Key words: mercury, methymercury, resuspension, methylation