Characteristics of pH, EC values and ionic components in rain and snow for 7 years at Mt. Ontake, Central Japan

Abstract

pH, EC and ion concentration in rain and snow were measured at Mt. Ontake (2,120m above sea level), Nagano Prefecture. The average of pH, EC for 7 years were 5.04, 5.7μS/cm. Ion concentrations were low level in comparison with that in other mountain areas. EC value in snow period (Dec.-Mar.) was higher than that in rain period (Jun.-Oct.) because the concentration of all ions was high in December and January. The concentrations of Na^+, K^+, Ca^<2+>, Mg^<2+>, Cl^- and ss-SO_4^<2->, which most are the sea salt origin, were clearly high. On the other hand, the concentrations of NH_4^+, NO_3^-, nss-SO_4^<2-> in snow period, which are the non-sea salt origin, were high tendency compared with that in rain period. Therefore, it was estimated that increase of ion concentration in snow period was caused by two (or more) compound factors. Ion concentrations of Na^+, K^+, Ca^<2+>, Mg^<2+>, Cl^-, ss-SO_4^<2-> were high tendency at the five comparison observation sites (Wajima, Happou-one, Tateyama, Inuyama, Nagoya), too. However, the concentration ratio of snow period ageinst rain period about Na^+, K^+, Ca^<2+>, Mg^<2+>, Cl^-, ss-SO_4^<2-> in Ontake was not so high as that in Wajima, Happou-one and Tateyama in the Japan Sea side, was almost the same as that in Inuyama and Nagoya in the Paciffic Ocean side. On the other hand, the concentration ratio of snow period against rain period about NH_4^+, NO_3^-, nss-SO_4^<2-> were high in Ontake, the similar tendency was seen in Wajima and Happou-one in the Japan Sea side. This phenomenon that was observed in Ontake was similar to the phenomenon observed by Fujita et al. that the ion concentrations of nss-Ca^<2+>, NH_4^+, NO_3^- and nss-SO_4^<2-> were high in the periods from Oct. to Mar. from 1987 to 1996 in west Japan areas.