Seasonal changes in the concentrations and depositions of dissolved substances in precipitation observed in a forest region located in an inland Tohoku district

摘要

We observed seasonal changes in the concentrations of dissolved substances in precipitation at an open area in a forest region in an inland Tohoku district. The amount of deposition brought by precipitation except NO_3 was smaller to national averages. The amount of Na and Cl was small in particular. We consider that the experimental site is located in a clean area, however the concentration of NH_4 and NO_3 was higher than other clean areas. The concentration of Na and Cl originating in seasalt carried by strong seasonal winds was high from December to January, while the concentration of nss-Ca was high from March to April. It appears that the high concentration of nss-Ca was caused by eolian dust (Kosa) from mainland China. These findings indicate that substances carried from the Sea of Japan or mainland China had reached the experimental site. Concentrations of nss-SO_4 and NO_3 were also high during the same period for the nss-Ca. This suggests that the acidic loads such as S0_4 and NO_3 werelong-range loads that had been transported from mainland China and had extended to the experimental site in the inland Tohoku district.