土壌からの水銀発生量とその変動要因

抄録

To investigate soil-air surface exchange of mercury, we observed mercury emission fluxes from soil surfaces at two open-field sites and a forest site using a flux chamber method. In addition, we carried out laboratory experiments in which factors affecting mercury fluxes were controlled. The field observations showed that the mercury fluxes increased with increasing soil surface temperatures and solar radiation. From the laboratory experiments, it was clear that soil moisture content affects the variations in mercury fluxes, which are dependent on soil types. Also, it was inferred that organic carbon content of soil affects the mercury fluxes from soils. Based on the field and laboratory experiments, we found the mercury fluxes at the forest site can be estimated approximately from the single parameter of soil surface temperature. The estimated annual mercury emission flux (40 μg m^-2) at the study forest site has been comparable to the current mercury deposition fluxes (10-26 μg m^-2) in Japan. This suggests that soil-air surface exchange of mercury is an important process governing the dynamics of atmospheric mercury in Japan.