Characteristic analysis on the anions and pH profiles of rainwater of Zhoushan archipelago

Rainwater samples were collected at Zhoushan Archipelago in 2002-2003, 4 main anion concentrations (F^-, Cl^-, NO₃^-, SO₄^2-) and pH value of rainwater sample were determined. The concentration variation range and character were depicted. Principal component analysis (PCA) and factor analysis (FA) were used to acquire a further knowledge on the characteristics of anions and pH value. Distribution character of samples was clearly depicted in the new PC1-PC2 ordinate generated by orthogonal projection and the reasons that caused the outliers in samples were discussed. In order to get the latent variables which most distinguishably effect the sample distribution, data profiles were investigated by factor analysis: two latent variables were responsible for the sample distribution within sufficient analysis accuracy, SO₄^2--NO₃^- factor (FA1), called as anthropogenic factor, and Cl^- (FA2), called as marine factor, which corresponding to PC1 and PC2 in orthogonal projection respectively. Results from factor analysis were more practical than from orthogonal projection, that is, the reasons attributed the outlier sample distribution at Zhoushan Archipelago were ascribed into two latent variables: anthropogenic factor (SO₄^2--NO₃^- ) and marine factor (Cl^-).