基于WQI法的宁夏湖泊藻类爆发过程水环境质量变化及溯源探究

Study on water environmental quality change and source tracing of algae bloom in lakes of Ningxia based on WQI method

为研究西北地区封闭式湖泊水环境质量变化特征和污染物来源特征,以夏季湖泊水体藻类爆发过程为研究对象,对该湖泊水体主要污染物进行连续性过程监测.研究结果表明,在夏季水环境质量变化过程中波动性较大的监测指标主要为COD_(Cr)、CODMn和叶绿素,WQI范围为29.4—36.2,均值为33,位于良好等级.通过综合分析,叶绿素a监测浓度与WQI具有一定程度的相关性(r=0.5781,P<0.05);11项指标在9个不同区域呈现不同程度的相关性,9个监测点位的相关率达到15%—44%,水温和大部分监测指标呈负相关,而CODMn、COD_(Cr)及溶解氧与水体叶绿素浓度呈现较强的正相关性.同时,综合分析结果60.9%—84.7%的污染主要来源于两方面,TN、TP、F可能来源于黄河补水,CODMn、COD_(Cr)、NH3-N和叶绿素a可能来源于水体藻类爆发过程的影响,还有15.3%—39.1%污染来源不确定.

In order to study the variation characteristics of water environment quality and pollutant source characteristics of closed lakes in northwest China,the algal bloom process of the lake water body in summer was taken as the research object,and the continuous process monitoring of the main pollutants in the lake water body was conducted.The research results show that the monitoring indexes with high fluctuation are mainly COD_(Cr),CODMn and chlorophyll in the process of water environment quality change in summer.The WQI range is 29.4—36.2,with an average value of 33,which is a good grade.Through comprehensive analysis,the monitored concentration of chlorophyll a has a certain degree of correlation with WQI(r=0.5781,P<0.05);The 11 indicators showed different degrees of correlation in 9 different regions,and the correlation rate of 9 monitoring points reached 15%—44%.Water temperature and most of the monitoring indicators showed negative correlation,while CODMn,COD_(Cr)and dissolved oxygen showed strong positive correlation with the concentration of chlorophyll in water.At the same time,the comprehensive analysis results show that 60.9%to 84.7%of the pollution is mainly from two aspects:TN,TP and F may come from the replenished water of the Yellow River.CODMn,COD_(Cr),NH3-N and chlorophyll a may come from the influence of algae outbreak process in water body;and 15.3%to 39.1%of the pollution sources are uncertain.