Seasonal and temporal changes in the fluxes of major inorganic ions via wet and dry depositions, observed in Matsumoto, central Japan

Abstract

Wet and dry deposits were collected using an automatic fractionation precipitation collector for three and a half years in Matsumoto city, central Japan. Because of the imperfect collection of some inorganic ions, the fraction collected as dry deposit is named "dry dish sample" in this study. The collected samples were analyzed for major cations and anions using ion chromatography. Based on the elemental ratios, Na + , Cl -, and Mg 2+ in the precipitation are considered to be of sea salt origin. However, the Cl -found in the dry dish samples was deficient with respect to Na + , possibly resulting from chlorine loss from aerosols, and the Mg 2+ content of dry dish samples is thought to be derived from the soil. Abnormally high concentrations of Ca 2+ and SO 4 2-were observed in both the precipitation and dry dish samples for a few days after the eruption of Miyakejima volcano. The Na + and Cl -concentrations in precipitation showed high values in winter, and the yellow sand carried from China in the spring affected the concentrations of Ca 2+ and Mg 2+ in the precipitation, as well as those in the dry dish sample. High time-resolution sampling of the precipitation disclosed short variations in its composition, which would have otherwise escaped our attention. When continuous precipitation from stratiform clouds occurred due to a warm front, the concentration of chemical constituents in the precipitation was high in the first fraction of precipitation, but was subsequently markedly reduced. On the other hand, when intermittent precipitation was produced from cumuliform clouds due to a cold front, it became more complex: in such cases, there was no predictable pattern for the subsequent concentration fluctuations, i.e., the concentrations of the chemical constituents fluctuated within a day.

Long-range transportation and deposition of chemical substances over the Northern Japan Alps mountainous area

“…observations of wet deposited chemical components between 1997 and 2000 in Matsumoto City was 1.0-2.0 with an average of 1.6 (Suzuki and Shirohada, 2006). These values correspond to the S/N ratios detected at Sites 4 and 5, which are close to Matsumoto.…”