T. Ozeki et al., EVALUATION OF SOURCES OF ACIDITY IN RAINWATER USING A CONSTRAINED OBLIQUE ROTATIONAL FACTOR-ANALYSIS, Environmental science & technology, 29(6), 1995, pp. 1638-1645
Acidity (or basicity) of sources of rainwater pollutants, whether they
work as acids, bases, or neutral substances, is not easily evaluated
by using conventional multivariate analysis such as the principal comp
onent analysis (PCA) or that with the Varimax rotation. We examined th
e application of an oblique rotational factor analysis in this work ba
sed on the nonnegative constraint as to the ion concentrations except
hydrogen ion and to the contributions of pollutant sources in rainwate
r. The method is as follows: (1) the PCA, (2) the Varimax rotation, an
d (3) the oblique rotation with partially nonnegative constraint. The
method and its validity are demonstrated by using analytical data for
391 rainwater samples collected at Hyogo prefecture in Japan during 19
91-1992. As a result, four predominant pollutant sources were extracte
d; they were a source with sea salt origin, a source acidifying rainwa
ter, a source basifying rainwater, and a source specific to potassium
ion. At most, six pollutant sources were extracted and were reasonably
interpreted from the chemical, biological, geographical, and meteorol
ogical points of view.