南四湖水质空间分布特征分析与改善效果评估

根据南四湖2006年、2007年、2010年和2011年4次90个采样点的水质空间分布监测数据,采用Surfer 8.0软件绘制南四湖水质空间分布等值线图,进行南四湖及分湖区水质指标的综合比较分析和平均综合污染指数的计算与污染控制效果评估。结果表明:南四湖COD、NH3-N、TP、TN和CODMn等指标的空间分布具有北高南低的非均一性特点;2010—2011年比2006—2007年枯水期各水质指标的平均浓度下降率为38.3%,整体提高了1～2个水质类别;按GB 3838—2002《地表水环境质量标准》中Ⅲ类标准相应的平均综合污染指数进行评价,达标和基本达标湖区的比例达到63.3%;2010—2011年枯水期南四湖主要污染物分担率由大到小排序依次为TP、COD、TN、CODMn、NH3-N;水质平均综合污染指数与电导率存在很好的相关性和北高南低的污染特点,说明南四湖水污染物仍然以外源排放为主。

Analysis of spatial distribution of water quality and assessment of water quality improvement in Nansi Lake

Based on data of the spatial distribution of water quality monitored four times,in 2006,2007,2010,and 2011,at 90 sampling points in Nansi Lake,the spatial distribution of water quality in Nansi Lake and sub-lakes near the lake boundary were studied via the contours generated by Surfer 8.0.A synthetically comparative analysis of the water quality indices,a calculation of the average comprehensive pollution index,and an assessment of the effects of pollution control were conducted.The results show that water quality indices,including COD,NH3-N,TP,TN,and CODMn,in Nansi Lake exhibit an inhomogeneous distribution,with higher values found in the north and lower ones in the south.The overall water quality improved by one to two grades as the average concentration of water quality indices decreased by 38.3% in the drought seasons during the period from 2010 to 2011,compared with the values in the drought seasons during the period from 2006 to 2007.63.3% of the lake areas reached or were close to the standard level based on the evaluation of the average comprehensive pollution index corresponding to the grade III standard according to the Environmental Quality Standards for Surface Water(GB3838-2002).The main pollutants in the drought seasons during the period from 2010 to 2011 were TP,COD,TN,CODMn,and NH3-N,in sequence of their contribution rates.The strong correlation between the average comprehensive pollution index and electronic conductivity,as well as the inhomogeneous feature of the spatial distribution of pollutants,indicates that the pollution of Nansi Lake was mainly caused by exogenous discharge.