内陆干旱区降水化学变化和对沙尘天气的指示——以民乐县为例

The indicative significance of sand-dust weather and chemical change of precipitation in the inland arid area:A case of Minle county

本文对内陆干旱区(民乐县)2013年6月—2014年5月收集的降水样品p H值、EC和主要阴阳离子浓度进行了测定和分析.结果表明,民乐县降水样品的p H值的变化范围为6.84—8.78,平均值为7.41,p H值在四季中的大小顺序为:冬季>春季>秋季>夏季.而民乐县降水样品EC的平均值为167.80μS·cm^(-1),变化范围17.4—848μS·cm^(-1),四季中EC的大小顺序与p H值在四季中的大小顺序一致;p H与降水量呈正相关关系,但显著性不高,同时也与与相对湿度呈正相关关系,而p H值与气温也呈负相关关系,显著性较降水量的高.与p H值不同的是,电导率与降水量、气温和相对湿度均负相关关系;通过对典型沙尘事件的分析表明,p H值会随着沙尘事件的发生主要表现出降低的趋势,而电导率会随着沙尘事件的发生呈现增加的趋势,在沙尘事件发生后离子浓度出现最高值的离子有:Na+、Mg^(2+)、NH_4^+、Cl-和SO_4^(2-),而沙尘事件前后离子浓度变化程度由大到小的顺序为SO_4^(2-)、Cl^-、Na^+、NH_4^+和Mg^(2+).

This work determined and analyzed the p H value,EC and the concentrations of main anion and cation of precipitation samples collected from June 2013 to May 2014 in the inland arid area（Minle county）.The results showed that,the range of the p H value of the precipitation ranged from 6.84 to 8.78,and the mean was 7.41.The order for season was winter 〉spring 〉autumn 〉summer.The average of EC was 167.80 μS·cm（-1）,and the variation range was from 17.4 to848 μS·cm（-1）.The order for season was the same as p H value.The positive correlation between p H value and precipitation,but the significance was not high.Meanwhile,the positive correlation between p H value and relative humidity, but p H value and air temperature showed negativecorrelation and the significance was higher than precipitation.By contrast,EC and precipitation,air temperature and relative humidity showed negative correlation.Through the analysis of typical sand dust events,the p H value decreased and the electrical conductivity incerased with the occurrence of sand dust events.The concentrations of Na＋,Mg（2＋）,NH_4＋,Cl-and SO_4（2-）reached to the highest value after the dust events occurred.The order of ion concentration change after dust everts was SO_4（2-）、Cl-、Na＋、NH_4＋and Mg（2＋）in dust events before and after.