黔江区降水化学组份变化趋势及相关性分析研究

通过对重庆市黔江区"十二五"期间320个降水样品的pH值和化学组成成分等特征进行了研究,结果表明,五年间黔江区降水pH范围为4.71~7.81,电导率范围为21.8~42.5 μS/cm-1,平均值33.4 μS/cm-1.降水pH和电导率的Spearman秩相关系数法检验表明,pH的rs为正值,电导率的rs为负值,五年期间大气降水中总离子当量浓度有所下降,降水酸雨环境得到有效控制.SO2-4是降水中主要阴离子,占阴离子总量的74.3%,Ca2+是降水中主要阳离子,占阳离子总量的31.4%.黔江区酸雨为硫酸型或燃煤型酸雨,SO2-4/NO-3浓度比均值为7.13,SO2-4/NO-3比值在2013年达最大值,之后呈现减小趋势,黔江区汽车尾气和工业排放的NOx对降水的影响在变大.在99.0%的置信水平下,降水离子浓度总和与电导率线性相关显著.相关性研究表明:降水中SO2-4、NH+4、Ca2+、Mg2+、F-主要来自煤燃烧.Mg2+、Na+与Cl-即来源于地壳源又来自于海洋远源传输,人类活动对黔江区降水影响较大.

Tendency and Correlations of ChemicalComposition in Precipitation in Qianjiang District

Comprehensive study was conducted on pH and chemical composition of the 320 precipitation samples derived from 2011 to 2015 in Qianjiang District of Chongqing.The results showed a wave range of 4.71 to 7.81 of the precipitation pH, and a range of 21.8 to 42.5μS/cm-1 of the conductivity with an average value of 33.4 uS/cm-1 of the precipitation samples.Spearman rank correlation coefficient method analysis on the pH and conductivity indicated a positive rs of pH but a negative rs of conductivity.The total ion equivalent concentration decreased, which indicates an effectively controlled acid rain environment.SO2-4 was the main anion with a 74.3 percent of the total mass measured anions in precipitation, and Ca2 was the main cation, accounting for 31.4% of the total cations.Sulfuric and coal type acid appeared in Qianjiang District, the average concentration ratio of SO2-4 / NO-3 was 7.13, and the value reached the maximum in 2013, then showed an decreasing trend in the following years, which indicated an increasing effect of NOx from vehicle exhaust and industrial emission.Significant linear correlation of the total ion concentration and conductivity at confidence level of 99.0%.Correlation analysis showed that SO2-4, NH+4, Ca2+, Mg2+ and F-in precipitation mainly come from coal combustion.Mg2+, Na+ and Cl-was derived from the crustal source and the far ocean source.Human activities have great impacts on precipitation.