The water quality during high-water season, normal-water season and low-water season in 20 monitoring sections of Ningbo urban river was analyzed by using the principal component analysis based on 8 indicators, including dissolved oxygen, permanganate index, BODS, ammonia nitrogen, copper, zinc, phenol and oil. Three factors with 84.02% of accumulated contribution rates were extracted from the original data, which include organic matter factor, ammonia and heavy metal matter factor, volatile phenol factor. The result shows that the ratio up to the standard of water quality in three seasons are 20% ,50% , 80% respectively, and the order of pollution degree from high to low is low-water season, normal-water season, high-water season. Most of the water sections which can't reach the standards are located in Yinzhou River, Zhongda River and downstream of Yin River. The results consist with the actual situation.%选取宁波市区20个监测断面作为研究对象,选择溶解氧、高锰酸盐指数、五日生化需氧量、氨氮、铜、锌、挥发酚、石油类作为评价指标,利用主成分分析法分别对其枯水期、平水期、丰水期进行综合水质评价.根据计算结果提取了3个主成分因子(有机物因子、氨氮和重金属因子、挥发酚因子),累计方差贡献率达到84.02％,基本保留了选取指标的有效信息.结果发现,各监测断面污染状况均显示为枯水期＞平水期＞丰水期,枯水期、平水期、丰水期断面达标率分别为20％、50％、80％,主要超标水域为鄞州河网、中大河、鄞江下游,评价结果与实际情况相符合.
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