Study on the acidification and pollution of precipitation based on a data set collected on a 0.5-mm precipitation basis

A precipitation data set collected on a 0.5-mm precipitation basis was studied. This made it possible to discern the temporal variation of component concentration in the precipitation event in detail. The parameters analyzed in this study were pH (i.e., H+ concentration), electric conductivity (EC), and SO42− and NO3− concentrations. The H+ concentration was significantly correlated with NO3− concentration, rather than SO42− concentration. On the other hand, the EC was more correlated with SO42− concentration than NO3− concentration. Furthermore, the temporal variation of precipitation SO42− and NO3− concentration in the longest precipitation event in one year corresponds more to that of suspended particulate matter concentration, than to SO2 and NOx (=NO + NO2) concentrations in the atmosphere. These findings strongly indicate that the acidification of precipitation was deeply related to acidic NO3−-bearing compounds while the precipitation pollution was profoundly related to SO42−-bearing compounds, including sea salt particles which produce sea salt (ss-) SO42−.