OUTPUT OF METHYLMERCURY FROM A CATCHMENT IN NORTHERN SWEDEN

The runoff output of methylmercury (MeHg) from the 50 ha Svartberget C atchment in northern Sweden was studied during 1993. These outputs are compared to those from the Gardsjon Catchment in the southwestern par t of Sweden, Although the wet deposition of MeHg is several times high er in southern Sweden the output of MeHg per unit area from the two ca tchments was comparable (0.12 g/km(2)yr). Furthermore, the concentrat ion of MeHg (0.4 ng/L) in the Svartberget Catchment was more than twic e that from the Gardsjon Catchment. These results suggest that the con temporary wet deposition of MeHg in itself is not a good indicator of runoff concentration or output per unit area. DOC transport and catchm ent characteristics such as wetland area, or possibly other forms of c ontemporary atmospheric deposition may all be more important for expla ining MeHg output from the terrestrial ecosystem.