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 L(-1) and were highest when events originated west of the ELA. THg concentrations in precipitation ranged from 0.95 to 9.31 ng L(-1) 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.