Ionic concentrations and loads of rainwater on forested land in a suburban area in the KANTO region, Japan - the measurement results of rainwater at FFPRI in Tsukuba -

摘要

Several characters of rainwater chemistry were investigated on forested land in a suburban area in the KANTO region, Japan. Rainwater was collected at FFPRI in Tsukuba, Ibaraki prefecture from 1995 to 2000. The concentrations of bulk precipitation were generally in the order: NH_4~+>Na~+>Ca~(2+)>Mg~(2+), K~+ and Cl~->NO_3~- > SO_4~(2-). So, the mean concentrations of No_3~- and SO_4~(2-) in this area were comparable with those of affected areas by atmospheric pollution. Estimated annual deposition ofNH_4~+, No_3~- and SO_4~(2-) was 43.3, 32.4 and 25.6mmol m~(-2)yr~(-1), respectively. High N deposition by precipitation was also observed in this area. At the same time, the annual mean of inorganic nitrogen input (NH_4-N+NO_3-N) was 10.6kg N ha~(-1)yr~(-1). NH_4-N composed 58 percent of inorganic nitrogen input and as such, NH_4-N plays a large role in N input at this study site.