Chemical characteristics of rainwater at Motooka, Fukuoka

Rainwater was collected with bulk samplers for two years from September 1998 to June 2000 at Motooka, Fukuoka, where a new campus of Kyushu University is under construction. Two rainwater samplers of open-air type for bulk sampling were set in the area. The rainwater stored in the tank was collected and chemically analyzed at an interval of two weeks during this monitoring period. Lowest pH of 4.0 was observed once, and relatively low PH, lower than the average pH of rainwater in Japan (pH 4.7), were measured 17 times out of 45 times in total. Concentrations of NO₃^- and non-sea salt (nss) SO₄^2- showed seasonal variations such that higher values during wintertime compared with other three seasons. Deposited amounts of these ions were calculated to be relatively constant for NO₃^- when precipitation for one observation period, two weeks, exceeded 40 to 50 mm, but varied in a wide range for SO₄^2- regardless of precipitation.