MP18 Environmental Fate of Mercury|
Monday, 14 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall
P225 (OWN-1117-662595) Spatial Distribution of Mercury in an East Texas Coal Seam.
Start time: 8:00 AM
Paul, J1, Ownby, D1, 1 Stephen F. Austin State University, Nacogdoches, TX, USA
With new mercury release regulations a possibility, it is imperative for power companies to manage Hg content in incoming coal. Therefore, understanding Hg distribution throughout a coal seam is important for coal burning electrical utilities in order to evaluate Hg emission reduction programs. One potential option would be to selectively mine low Hg coal from within a seam. This research measured Hg concentrations in three detailed (0.1 ft sections) and 28 regular cores (sectioned on visual mineral/maceral content changes) from an East Texas coal seam. Prior to analysis of lignite coal for Hg, ASTM Method 6414-01 was optimized for our Perkin Elmer AAnalyst FIAS system using NIST SRM 2682b (subbituminous), EPRI ES-5 (lignite), and CANSPEX 2003-1 (lignite) standard materials. Perkin Elmer's recommended conditions for flow injection systems (1.1% SnCl2 in 3% HCl) were used for analysis; resulting in improved sensitivity. An additional modification of digestion acid concentrations was evaluated by altering ASTM's recommended 6 mL HCl: 2 mL HNO3 stepwise to 1.5 ml HCl: 5 mL HNO3 to optimize sensitivity. Upon altering ASTM 6414-01, average recoveries of 97%, 108%, 100% were achieved for the standard materials listed above. Upon analysis of the lignite seam, there was no correlation of Hg concentration with depth. In detailed cores, differences of over 100 ug Hg/kg were commonly observed in adjacent sections. A 3-D geospatial model of Hg distribution within the coal seam further illustrates heterogeneity found throughout the mining area. The effect of ash content, total organic carbon, and pyritic sulfur on Hg concentrations will also be discussed.
P226 (JOH-1117-819915) The Inventory of Mercury in an Inter-tidal Mudflat.
Start time: 8:00 AM
Johnson, B1, Walter, L1, Hunt, J1, 1 Department of Civil & Environmental Engineering, UC Berkeley, Berkeley, Ca, USA
Tomales Bay is renowned for its rich fishery, oyster beds and the habitat it provides for thousands of migratory waterfowl. Once thought of as a pristine analog to nearby San Francisco Bay, a mercury mine located within the Walker Creek watershed has provide a point source of mercury mining waste that is detected in the creek and its delta in Tomales Bay. The Gambonini mine upstream of the delta was active between 1964 and 1970 where over 300,000 m3 of mine waste rich in cinnabar was dumped on the slopes of the adjacent ravine. In 1982 a dam built to reduce the flow of mine waste into Walker Creek broke, releasing the mercury laden sediment. Twenty five sediment cores 1-2 meters in length where recently collected at the inter-tidal mudflat that makes up the delta having an area of 2 km2. All cores where deep enough to establish pre-mining Hg concentrations in the sediment. Samples were passed through a 63 m mesh sieve to compare the depth profiles of total Hg within the fine fraction of sediment to that of the courser fraction of sediment. Elevated concentrations are found within the fine fraction and were as high as 10 mg/kg near the surface. The sediment cores provide, through statistical interpolation, a three dimensional distribution of mercury within the delta and an estimate of the total inventory. The preservation of Hg depth profiles indicates that mercury laden sediment, once deposited, is stable within the mudflat. These data are used to assess the impact of mercury mine waste on the Walker Creek watershed and we estimate less than 5% of the Hg from the mine tailings are accounted for by Mercury in the mudflat. The remaining 95% is likely upland within the 30 km long creek that connects the mine site to the mudflat and may be transported into the delta in the future.
P227 (DEL-1117-728048) Mercury deposition and diffusion in sediments of the St. Lawrence River area near Cornwall, Ontario.
Start time: 8:00 AM
Delongchamp, T1, Blais, J1, Ridal, J2, Lean, D1, 1 University of Ottawa, Ottawa, ON, Canada2 St. Lawrence River Institute of Environmental Sciences, Cornwall, ON, Canada
The St. Lawrence River near Cornwall, Ontario was designated an Area of Concern by the International Joint Commission in 1985. Mercury (Hg) contaminated sediments are the major environmental issue of concern in the area. Industrial inputs of Hg have been reduced as a result of plant closures and the implementation of controls. However, contaminated sediments remain a potential source of mercury to the system. Currently, the Ministry of the Environment has recommended consumption restrictions for large walleye in the area. There is concern that elevated levels of Hg in sediments in the area are contributing to the elevated levels in walleye. This study focused on mercury processes occurring within the sediments and at the sediment-water interface, to assess whether contaminated sediments act as a source or a sink of mercury. Cores were collected from three contaminated zones along the Cornwall waterfront. These sites were chosen based on their proximity to current and historical industrial point sources of mercury. In sediments from these sites, total mercury ranged from 0.7 to 60 ug/g and methylmercury (MeHg) ranged from 0.02 to 0.7 ug/g. The 210Pb dated cores showed that historical (1970) mercury accumulation rates at these sites were up to 70 times higher than current rates. Also, MeHg levels in sediment pore-water were higher than MeHg levels in surface water. Calculated diffusion rates of MeHg from sediments to the river water ranged from 12 to 740 ug m-2 yr-1. These results indicate that sediments are a major source of methylmercury to the water column in the St. Lawrence River.
P228 (YEE-1117-854355) Methylmercury in San Francisco Bay Surface Sediments.
Start time: 8:00 AM
Yee, D1, Lowe, S1, Ross, J1, Conaway, C2, Scelfo, G, 1 San Francisco Estuary Institute, Oakland, CA, USA2 University of California Santa Cruz, Santa Cruz, CA, USA
Surface sediment samples were collected for the San Francisco Estuary Regional Monitoring Program for Trace Substances (RMP) from sites distributed throughout the estuary in the summers of 2002 to 2004. Trace pollutants including mercury, methylmercury, and a suite of ancillary sediment parameters (TOC, TN, grain size, porewater pH, redox potential) were measured in the field or in the laboratory. Reports in the literature have shown correlations of MeHg to total mercury, TOC, and grain size (%fines) in sediments, relationships examined in samples collected for the RMP. Of the measured ancillary parameters, sediment total nitrogen and surficial redox potential (Eh) were found to be among those most strongly correlated to MeHg concentrations. The activity of sulfate reducing bacteria under anaerobic conditions is expected to produce the majority of MeHg found in estuarine sediments, and the correlation of these parameters with sediment MeHg support this expectation. Implications for future sampling and monitoring and options for ecosystem management will be discussed.