Spatial and temporal distribution of main aquatic environment factors in Miyun Reservoir, Beijing since 1990s

Abstract

根据19902011年密云水库共12个监测点的月监测资料，采用聚类分析研究各监测点水环境相似性及空间分布特征，采用因子分析识别影响水质的主要因子并评价各采样点的综合水质.通过绝对主成分多元回归分析，获得汛期和非汛期各因子对各水质指标的贡献率.利用季节性Kendall检验及流量调节检验对密云水库库区水化学特征和水质状况时空分布特征进行了研究.结果表明：汛期水质主要受到农业营养物质的影响，其次为生物化学因素和有机物的影响.非汛期水质主要受到农牧业排放因素的影响，其次为人类活动和生物化学因素的影响.因子得分综合评价显示，汛期辛庄桥、内湖和大关桥综合水质较差，潮河、库西和白河综合水质较好.非汛期辛庄桥、石佛桥和大关桥综合水质较差，库东、套里和恒河综合水质较好.主要水质指标的年际变化规律不同，但最终都趋于平稳.与潮河、白河入库水质变化相比，库区水质变化趋势较小，上游入库水质和库区水质都整体趋好.除白河入库的总氮和总磷外，其他监测指标的变化趋势经流量调节前后基本一致，表明流量并不是引起水质趋势变化的主要因素，水质的变化主要是由于污染源变化而引起.;Monthly monitoring data of totally 12 monitoring sites in Miyun Reservoir from 1990 to 2011 were collected. Cluster analysis was used to analyze the spatial distribution of hydrogeochemical characteristics of these sites. Factor analysis was used to identify the main factors affecting water quality and evaluate the comprehensive water quality of each monitoring site. The multivariate linear regression of the absolute principal component scores (APCS-MLR) was employed to quantify the contribution rate of each factor on water quality indicators in both flood and non-flood seasons. The results indicated that:water quality was mainly affected by agricultural nutrients, biochemical factor and organics in flood season. While in non-flood season it was mainly affected by farming and husbandry emissions, human activities and biochemical factors. Factor score evaluation showed that the comprehensive water quality of Xinzhuangqiao, Neihu and Kudong were worse and that of Chaohe, Kuxi and Baihe were better in flood season. In non-flood season, the comprehensive water quality of Xinzhuangqiao, Shifoqiao and Daguanqiao were worse and that of Kudong, Taoli and Henghe were better. The interannual trends of main water quality pollutants were different, but all leveled off eventually. Water quality changed less in the reservoir compared with water quality coming from Chaohe and Baihe. Water quality of both reservoir and watershed was getting better. Changing trend of water quality indicators were basically the same before and after flow control test except for TN and TP in Baihe. It indicated that the main factor causing water quality changes was not flow but pollution source changes.