崇明河网水质污染的空间差异性分析

Application of Principal Component Analysis in Evaluation of Water Quality of Chongming Island

采用主成分分析方法,对崇明岛河网水系61个采样点、12个水质指标进行分析,通过提取占累计方差率85%以上的5个主成分,即氮素营养指数,藻类生长指数,营养水平指数,铵吸收因子及水色指数,研究水体污染的空间分布特征,分析崇明河网水系的主要污染源与区域间差异。结果表明,氮素营养指数和藻类生长指数是影响崇明水质的主要因子,崇明岛大面积的农业面源污染对硝态氮的贡献作用明显,对水质影响较大;特殊的水文及水动力条件对藻类生长和分布也产生了明显影响。从区域水系而言,崇明岛水质南部优于北部,西部优于东部。

The principal component analysis was used to deal with the data for 12 water quality indexes collected in August of 2009 at 61 sample points in Chongming Island.The five principal components with a total variance of over 85% were extracted from the original monitoring data,there were nitrogen nutrient index,algae growth index,eutrophication level index,ammonium absorption factor,and chrominance index.Besides,the spatial distribution characteristic of the various factors were studied,the major pollution sources of Chongming river network water were summed up.It was concluded that the nitrogen nutrient index and the algae growth index were the key factors to effecting water quality of Chongming Island,based on the analysis,it could be inferred that large areas of agricultural non-point pollution has a big contribution on NO3-N,and greater impact on water quality.Specific hydrological conditions of Chongming Island have also a greater impact on the growth and distribution of algae.From the regional water system,in Chongming Island,the south is better than the north,the west than the east.