John W. M. Rudd

Wet deposition of methyl mercury in northwestern Ontario compared to other geographic locations

Concentrations of methyl mercury (MeHg) and total mercury (THg) in precipitation were measured at the Experimental Lakes Area (ELA), a remote field station in northwestern Ontario. We found that precipitation was a source of both MeHg and THg to boreal ecosystems, but at lower rates than in industrialized regions of North America and Scandinavia. MeHg concentrations in precipitation ranged from 0.010 to 0.179 ng L1 and were highest when events originated west of the ELA. THg concentrations in precipitation ranged from 0.95 to 9.31 ng L1 and were highest when the events came from the southeast. There was no relationship between THg and MeHg over time in precipitation. Inputs of both MeHg and THg to ecosystems were highest during summer months.

Turning attention to reservoir surfaces, a neglected area in greenhouse studies

Carol A. Kelly, Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2; John W. M. Rudd, Freshwater Institute, Department of Fisheries and Oceans, Winnipeg, MB R3T 2N6; Vincent L. St. Louis, Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2; Tim Moore, Department of Geography, McGill University, Montreal, Quebec H3A 2K6 n nWith reservoir construction increasing worldwide since the 1950s, the volume of water retained in these structures today is so great that if they didnt exist, sea level would be 3 cm higher. Despite the 500,000 km2 global area reservoirs comprise—about twice the area of the Laurentian Great Lakes—almost nothing is known about reservoir surfaces as sources or sinks of the “greenhouse” gases carbon dioxide (CO2) and methane (CH4).