Study of pollutants in precipitation (rain and snow) transported long distance to west coasts of Japan Islands using oblique rotational factor analysis with partially non-negative constraint

In recent years, acidic precipitation (rain and snow) is receiving global interest, especially in East Asia where a rapid industrialization and an economic growth have been observed. In Japan, heavy acidification of precipitation in winter has been observed at areas close to west coasts of the Japan Islands and is related to the long distance transportation of the acidic pollutants across the Sea of Japan. In order to characterize transportation process of the pollutants and the seasonal and regional variations of the transportation, the precipitation samples were collected at nine areas from north to south of Japan in the period from July 2000 to June 2001 and the compositions of the precipitation samples were analyzed by a chemometrical method developed by our group “Oblique Rotational Factor Analysis with Partially Non-Negative Constraint (ORFA-PNNC)”. It consists of the Principal Component Analysis and the oblique rotation of the composition matrix based on the non-negative constraint. Our method has a very distinctive feature that the non-negative constraint is exempted from the hydrogen ion so as to take the neutralization reactions among the acidic pollutants and alkaline pollutants into account. Furthermore, in this study, the normalization of the concentration data of the samples was incorporated into the analysis to extract the feature of ions with small concentration such as potassium ion and nitrous ion.