逐步多元线性回归模型解释近年上海市降水pH降低原因

Explain the Cause of pH Value Decreasing These Years in Precipitation of Shanghai City with Stepwise Linear Multi-variation Regression Mode

分析2002年-2007年上海市降水化学组成变化特征可得,近年来,上海市降水的pH下降迅速,硫酸根离子与硝酸根离子的比值以及钙铵离子的比值整体上都呈下降趋势。根据上海市降水中的各离子浓度建立了氢离子的逐步多元线性回归模型,并以建立的模型为基础,分析了降水中各主要离子浓度的变化对氢离子浓度的影响大小情况。由模型可以得出,硫酸根离子与硝酸根离子浓度增加时,氢离子浓度也随之增加,铵离子与钙离子浓度增加时,氢离子浓度则随之减小。氢离子变化对4种主要离子的敏感性顺序为:硝酸根>硫酸根>钙离子>铵离子。结合上海市降水化学组成特征分析结果可得,主要离子浓度的变化是导致降水pH快速下降的原因。

On analysis of Characteristics of Chemical Composition of precipitation from year 2002 to 2007 in Shanghai city, it shows the pH value is decreasing dramatically these years, and both of the ratios of SO4^2-/NO3^- and Ca^2＋/NH4^＋ have decreased. Based on the concentration of the major ions in the precipitation of Shanghai city, a stepwise linear multi - variation regression model to predict hydrogen ion is established. The influence of the variation of the concentration of the main iotas on the concentration of the H^＋ is analyzed based on the model established. Some conclusions were drawn from the modal ： the concentration of H^＋ increases with the increasing of the concentration of SO4^2- or NO3^- , while decreases with the increasing of the concentration of Ca^2＋ and NH4^＋. The intluences of the 4 main ion to the concentration of H^＋ in the order from strong to weak is NO3^- 〉 SO4^2- 〉 Ca^2＋ 〉 NH4^＋. Combine with the conclusion of analysis of characteristics of chemical composition of precipitation, it shows that the variation of the concentration of the major ions results in the dramatic decreasing of pH.