HR: 0800h
AN: B11B-0401    [Abstracts]
TI: Measurement of Mercury Concentrations in Marsh Drainages Over a Tidal Cycle
AU: * Henry, B
EM: henryb@exponent.com
AF: Exponent, 1086 Morningside Ave., Schenectady, NY 12309, United States
AU: Bigham, G N
EM: bighamg@exponent.com
AF: Exponent, 15375 SE 30th Place, Ste. 250, Bellevue, WA 98007, United States
AB: This study was undertaken to characterize short-term temporal patterns in total mercury and methylmercury concentrations that would indicate transport patterns and to determine if drainages (marsh sediment and channels) in a mercury-contaminated marsh were sources or sinks for total mercury and methylmercury. Measurements of total mercury, methylmercury, and total suspended solids were made over a tidal cycle on two separate sampling events (January and June) at three locations in the contaminated marsh and two reference locations. During the first event, samples were collected by hand from a small boat every 30 minutes from approximately two hours before to two hours after high tide, using ultra-clean techniques. During the second event, water samples were obtained with automated ISCO sampling devices programmed to collect samples every 45 minutes during a one-half (12-hour) tidal cycle. Unfiltered total mercury and methylmercury concentrations were significantly higher at the location closest to the former chlor-alkali facility (up to 4,000 ng/l and 20 ng/L, respectively) compared to the location in a separate drainage (up to 180 ng/l and 5 ng/L, respectively) but in the same marsh. Concentrations at the reference stations (up to 28 ng/L and 0.7 ng/L, respectively) were considerably lower. Total mercury and methylmercury concentrations were generally lowest at high tide while concentrations during flood and ebb were comparable. Unfiltered total mercury and methylmercury concentrations tended to correlate with suspended solids concentrations. The percent of total mercury and methylmercury in the dissolved form decreased as unfiltered concentrations increased. There was no clear evidence that the mass of total mercury or methylmercury was higher during ebb than flood, suggesting that these locations are not a definitive source of either to downstream locations. If mercury is methylated in marsh sediment during the tidal cycle, the additional mass was small compared to the mass carried by the flood and ebb.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0442 Estuarine and nearshore processes (4235)
DE: 0461 Metals
DE: 0497 Wetlands (1890)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting