钱塘江兰溪段地表水质季节变化特征及源解析

季节变化对水质的影响评价是流域水质管理的重要内容之一.选取钱塘江兰溪段6个监测点位为研究对象,测定了2010和2011年丰水期和枯水期12个水质指标,采用因子分析技术识别关键污染因子及来源的季节变异特征,并基于层次聚类分析和改进的模糊数学方法进行不同季节关键污染因子空间差异性分析和水质综合评价.结果表明,枯水期关键污染因子为来源于城镇集中式生活污水处理厂、纺织业等点源的CODMn、BOD5和NH4+-N,丰水期为来源于农业面源的NH4+-N、TP和工业点源的CODMn；枯水期和丰水期关键污染因子存在空间差异性,无论枯水期还是丰水期,费垅为重污染区域,横山、洋港和将军岩为轻度污染区域；其不同之处在于枯水期女埠和西门码头为中度污染区域,而丰水期则为轻度污染区域；关键污染因子综合水质丰水期优于枯水期,丰水期16.7％的监测点位综合水质归属于V类,而枯水期50％的监测点位综合水质归属于V类.

Seasonal variations and source identification of surface water quality in Lanxi segment of Qiantang River

Assessment of seasonal changes in surface water quality is an important aspect for water quality management in watershed. Surface water quality data for 12 physical and chemical parameters collected from 6 monitoring sites in Lanxi segment, Qiantang River during the dry and wet seasons in 2010 and 2011 were analyzed. The factor analysis (FA) technique was applied to identify seasonal variations of the key pollution factors and sources of surface water. Hierarchical cluster analysis (HCA) was used to analyze the spatial variations of the key pollution factors in different seasons, and the comprehensive water quality of the key pollution factors was assessed based on improved fuzzy mathematics. The results show that in the dry seasons the key pollutants were COD_Mn, BOD₅ and NH₄⁺-N from point sources, such as urban centralized sewage treatment plant, textile industry, etc. In the wet seasons, the main pollutants were NH₄⁺-N, TP and COD_Mn. NH₄⁺-N and TP were related to agricultural non-point sources, whereas COD_Mn was possibly related to industrial point sources. The main pollutants of different monitoring sites in the dry and wet seasons had a spatial heterogeneity. Feilong was considered as the highly polluted site, Hengshan, Yanggang and Jiangjunyan were considered as slightly polluted sites both in the dry and wet seasons. Nvbu and Ximenmatou were considered as the moderately polluted sites in the dry season, but in wet season these sites were considered as the slightly polluted sites. The comprehensive water quality in the wet season was better than in the dry season. Water quality was classified as Grade V on 50% of the monitoring sites in the dry season and on 16.7% of the sites in the wet season.