Statistical Analysis of Ionic Components in Rain Water

Abstract

During the period from Nov. 1, 1982 to Oct. 31, 1983, rain water samples were collected in Nara city by volumetric fractional sampling of two groups, the early rain water (1-5 mm rainfall amount) and the succeeding rain water (6 mm-rainfall amount). And with respect to ten dissolved ions (H⁺, SO₄^2-, NO₃^-, Cl^-, F^-, NH₄⁺, Na⁺, K⁺, Ca²⁺, Mg²⁺) in rain waters, the principal component analysis [PCA] and the multiple regression analysis [MRA] were carried out with two rain groups that were the early and succeeding rain waters.
As a result of PCA, the ionic components in the early and succeeding rain waters were able to characterize with two principal components (Z₁, Z₂). The first principal component Z₁ was considered to be a factor indicating the degree of synthetic pollution of rain waters and the second principal component Z_2- was a factor indicating the contribution of origins of ionic components in rain waters. The degree of synthetic pollution of rain waters and the contribution of origins of ionic components in rain waters of seasonal and volumetric fractional distinction were possible to evaluated by the use of these two principal components of Z₁ and Z₂. Each ionic component in the early rain water was roughly divided into two main groups of pcllutants originated from human work and/or formed from secondary products of atmospheric chemical reactions and pollutants originated from natural generation. On the other hand, each ionic component in the succeeding rain water was also roughly divided into three main groups of pollutants possessed intermediate property of two groups described above, in addition to these two groups. These matter was described by the use of structural model of rainfall that the early rain water was mainly brought about the washout and the succeeding rain water was rainout.
As a result of MRA, the ionic components affecting to H⁺ concentration in rain waters were estimated to be four ions i.e. SO₄^2- NO₃^-, NH₄⁺ and Ca²⁺. It has become apparent that the ionic components acting to increase the H+ concentration were the order of NO₃^->SO₄^2- in the early rain water and SO₄^2->NO₃^-in the succeeding rain water. While the ionic components acting to decrease the H+ concentration were the order of Ca²⁺>NH₄⁺in the early rain water and NH₄⁺>Ca²⁺ in the succeeding rain water.