[M-IS14] Biogeochemistry

[MIS14-P05] Chloride fluxes in bulk precipitation and throughfall in six sites throughout the Japanese archipelago

*Yoshiyuki Inagaki¹, Naohiro Imamura¹ (1.Forestry and Forest Products Research Institute)

Keywords:chloride, bulk precipitation, throughfall, sea salt, anthropogenic

In forest ecosystems, chloride ions are supplied by bulk precipitation and throughfall. Generally, it is known that most of chloride ions are derived from sea salt. However, information about the contribution of sea salt and non-sea-salt chloride inputs in Japanese forest ecosystems is still limited. In this study, we compared chloride and sulfate input by bulk precipitation and throughfall in six areas throughout the Japanese archipelago. Data was derived from the database as Forest Atmospheric depositions and Stream water Chemistry Database by Forestry and Forest Products Research Institute. Chemistry of bulk precipitation and throughfall was measured in 13 forest ecosystems including 5 deciduous and 8 evergreen forests. Non-sea-salt fraction of chloride and sulfate were calculated using the sodium concentration. Mean values of percentage of non-sea-salt sulfate and chloride in the bulk precipitation were 86%, and -5%, respectively, whereas those in throughfall were 87%, and 27% respectively. The results suggest that substantial amount of chloride in the throughfall is derived from non-sea-salt source although most of chloride in the bulk precipitation is derived from sea salt. The percentage of non-sea salt chloride was positively correlated with that of sulfate, indicating that non-sea salt chloride was greater at sites where the anthropogenic sulfate input was greater. Moreover, the percentage of non-sea salt chloride was greater in the inland areas where sodium input by throughfall was low and did not differ between deciduous and evergreen forests. In conclusion, the results suggest that anthropogenic chloride input by throughfall is substantial and its contribution is greater in inland areas.