The input and output flux data of total Hg (THg) and methylmercury (Me
Hg) from three catchments located in different geographical regions in
Sweden and one catchment in southern Finland were compared to elucida
te the role of current atmospheric Hg/MeHg deposition with regard to w
aterborne Hg/MeHg output. There was a negative co-variaton between the
open field THg inputs and the ratio of THg output to open field input
. The highest ratio (and lowest input) occurring in N. Sweden and S. F
inland, while the lowest output ratio (and highest inputs) occurred in
southwest Sweden. A much larger variation was found in the ratio of o
utput to open field input for MeHg (14 to 160%). Examinations of MeHg
input/output data in relation to catchment charateristics suggest that
riparian peat, mires and wet organic soil contributed to the large Me
Hg output from certain catchments, probably due to in situ production
of MeHg. This finding is consistent with other studies which have foun
d that catchment characteristics such as wetland area, flow pathways,
seasonal temperature and water flow are important in controlling the o
utput of MeHg. These catchment characteristics govern the fate of the
contemporary input of Hg and MeHg as well as the mobilization of the s
oil pools.