常用水环境质量评价方法分析与比较

为比较水环境质量评价方法的适用性和局限性, 在分析几种常用评价方法的基础上, 利用2008 年长江流域和淮河流域190 个国控断面水质监测数据对单因子评价法、平均污染指数法、内梅罗指数法、灰色关联分析、模糊综合评价、物元可拓评价法、综合水质标识指数法等7 种方法进行实证研究。结果表明:①指标权重的选择对评价结果影响有限, 73.7%的断面评价等级没有因权重发生变化, 但物元可拓法对权重变化较为敏感。②当评价指标污染程度相当时, 平均污染指数法较为适合;当某指标污染程度较为突出时, 内梅罗指数更为恰当。但两者评价结果吻合程度较高, 相关系数达0.94, 且水质越差, 结果越接近。③分级评分法和单因子评价法评价结果差异较大, 仅有10%左右的断面评价等级一致, 且水质越差, 各种方法所得的评价等级差别越大。④各种评价方法具有一定的关联性和互补性, 评价等级相关系数在0.7 左右。综合各种评价方法理论上的优缺点并结合环境管理需求, 单因子评价法和综合水质标识指数法是两种优选方法, 在水环境质量评价中可以组合使用。

Comparisons of Some Common Methods for Water Environmental Quality Assessment

In order to compare the applicability and limitation of some common methods for water environmental quality assessment,we analyzed seven common methods,such as single-factor assessment,average pollution index,Nemerow index,grey correlation analysis,fuzzy comprehensive assessment,matter element extension assessment,comprehensive water quality identification index,based on the water quality monitoring data of 190 surface water sections under national monitoring program in the Yangtze River drainage basin and Huaihe drainage basin.The main results could be summarized as follows.(1) Index weight had little effect on the assessment result.Among the 190 surface water sections under national monitoring program,73.7% did not change distinctly.Matter element extension assessment method was sensitive to index weight.(2) When the assessment factors ’pollution extent was similar,the average pollution index had the advantage.While the specific factor’s pollution extent was outstanding,the Nemerow index was more suitable.The result of average pollution index conformed to the result of Nemerow index,and the correlation coefficient was 0.94.The correlation coefficient was increasing when the water pollution was more serious.(3) The results of grading score method and single-factor assessment had significant difference.There were only about 10% of the 190 sections whose results were consistent.And the difference was bigger while the water quality is getting worse.(4) The results of the seven methods were correlative to a certain extent.The correlation coefficient of assessment rank was 0.7 or so.Based on an overall consideration of the advantages and disadvantages of these methods,and according to the requirement of environmental management,the single-factor assessment method and water quality identification index are the optimal methods.Therefore,these two methods could be used in combination when assessing water quality.