丹江口水库淅川库区大气降水中无机离子特征及来源解析

Characteristics and Source Apportionment of Inorganic Ions in Precipitation in Xichuan Area of Danjiangkou Reservoir

大气降水中水化学组成深刻影响着地表水体水质和水生态系统的物质循环.为探究丹江口水库降水中无机离子的化学组分和来源贡献,以丹江口水库淅川库区为研究区,通过野外调查、原位观测和室内分析,研究了降水中无机离子(F^(−)、Cl^(−)、NO_(3)^(−)、SO_(4)^(2−)、Na^(+)、NH_(4)^(+)、K^(+)、Ca^(2+)和Mg^(2+))的浓度特征.结果表明:丹江口水库淅川库区降水中无机离子浓度大小表现为NH_(4)^(+)(170.0μeq/L)>Ca^(2+)(115.4μeq/L)>SO_(4)^(2−)(112.9μeq/L)>NO_(3)^(−)(94.2μeq/L)>Na^(+)(61.1μeq/L)>Mg^(2+)(25.9μeq/L)>F−(12.2μeq/L)>K^(+)(11.8μeq/L)>Cl−(10.3μeq/L),其中NH_(4)^(+)、Ca^(2+)、SO_(4)^(2−)、NO_(3)−和Na^(+)浓度占总离子浓度的90.2%;相关性分析表明不同无机离子浓度之间存在显著相关性(P<0.05),富集因子分析表明陆源人类活动对无机离子浓度的影响较大;正定矩阵因子分析表明,农业源、工业燃煤、土壤扬尘、化石燃料燃烧和生物质燃烧是无机离子的重要来源,其中NH_(4)^(+)和SO_(4)^(2−)的主要来源分别为农业源(56.3%)和化石燃料燃烧(78.7%).研究显示,丹江口水库淅川库区降水中无机离子组分以NH_(4)^(+)、Ca^(2+)、SO_(4)^(2−)、NO_(3)−为主,其主要受陆源人类活动(农业活动和化石燃料燃烧)的影响.

Danjiangkou Reservoir is the drinking water source of the National South-North Water Diversion Project and the largest artificial fresh lake in Asia.It aims to alleviate the water shortages and maintain sustainable social and economic development in northern China.Hence,both government and public have been increasingly concerned about the water quality of Danjiangkou Reservoir,which can be significantly affected by the chemical composition of precipitation.However,until now,less attention has been paid on the chemical characteristics of precipitation and its source apportionment in the large scale reservoir.In addition,a certain water-retention time and huge water surface of the reservoir allow more pollutants to enter the water body through precipitation.This study aimed to discuss the chemical composition and source apportionment of inorganic ions in precipitation in Danjiangkou Reservoir.The Xichuan area of Danjiangkou Reservoir was selected as the study area,and the precipitation from six sites around the reservoir was collected and the concentrations of inorganic ions(F^(−),Cl^(−),NO_(3)^(−),SO_(4)^(2−),Na^(+),NH_(4)^(+),K^(+),Ca^(2+)and Mg^(2+))were measured based on field investigation,in-situ observation and laboratory analysis.The results showed that the concentrations of inorganic ions in the precipitation were in the following order:NH_(4)^(+)(170.0μeq/L)>Ca^(2+)(115.4μeq/L)>SO_(4)^(2−)(112.9μeq/L)>NO_(3)^(−)(94.2μeq/L)>Na^(+)(61.1μeq/L)>Mg^(2+)(25.9μeq/L)>F^(−)(12.2μeq/L)>K^(+)(11.8μeq/L)>Cl−(10.3μeq/L).The contents of NH_(4)^(+),Ca^(2+),SO_(4)^(2−),NO_(3)−and Na^(+)accounted for 90.2%of the total inorganic ions.Correlation analysis showed that there was significant correlation among the nine inorganic ions.Terrigenous human activities had a greater impact on inorganic ions based on enrichment factor analysis.Positive matrix factorization model analysis indicated that agricultural sources,industrial coal combustion,soil dust,fossil fuel combustion and biomass combustion were the important sources of inorganic ions.The main sources of NH_(4)^(+)and SO_(4)^(2−)were agricultural sources(56.3%)and fossil fuel combustion(78.7%),respectively.These results indicated that the chemical composition of inorganic ions in the precipitation is mainly composed of NH_(4)^(+),Ca^(2+),SO_(4)^(2−)and NO_(3)−,which were significantly affected by terrigenous human activities(agricultural activity and fossil fuel combustion).It is suggested that the control measures of agricultural activities and the substitution of fossil fuels are essential to decrease the risks of water pollution in the reservoir.Furthermore,more long-term studies are necessary to understand the relation between control measures,chemical composition of precipitation and water quality of Danjiangkou Reservoir.