黑河上中游水质时空分异特征及污染源解析

在黑河上中游主要河道设置33个水样监测点，分别于2017年5月（平水期）、8月（丰水期）、12月（枯水期）进行水质调查，运用GIS和水质标识指数法对水环境质量进行评价，并采用多元统计的方法分析了水质时空分布特征及潜在污染物来源.结果表明：区域内水质类别以Ⅱ类和Ⅲ类为主，并具有一定的时空分异性.时间上水体污染程度表现为枯水期 > 平水期 > 丰水期，空间上表现为上游支流区 > 上游干流区 > 中游.依据土地利用类型将33个采样点划分为放牧与工矿企业用地（A组）、水库建设用地（B组）和农业与城镇人居用地（C组）.结合因子分析和主成分回归分析得出，NH₃-N、BOD₅和COD_Mn是该区域的典型污染物，其中A组污染源主要来自于有机物，其次是营养盐；B组水体主要受到机物和营养物的蓄积污染，而自然因素的影响相对较弱；C组主要是生物化学污染，其次为非点源营养盐污染.研究表明，人类活动依然是影响水质变差的主要因素，虽然大坝的拦截效应能改善下泄水质，但常年累积于库底的沉积物随环境变化有二次污染的潜在风险，如沉积物中营养盐的活化释放等问题.

Spatio-temporal characteristics and source identification of water pollutants in the upper and middle reachers of Heihe River

Thirty-three water sampling sites in Heihe River of the upper and middle reachers were set to characterize its water quality with spatiotemporal distribution. Water sampling trips were conducted in May (wet period), August (flow period), December (dry period) of 2017. Spatial and seasonal variations of water quality were analyzed by using the multivariate statistical methods and water quality were assessed by employing the comprehensive water quality identification index. The results indicated that the main types of water quality in the region were Class II and Class III, it also had a certain space-time differentiation. In temporal terms, the order of pollution was dry period > wet period > flow period; the spatial pollution situation was the upper tributary > the lower main stream > the middle reaches. According to landscape difference, the sampling sites were divided into 4groups:grazing and industrial area (Group A), reservoir area (Group B), agriculture and urban area (Group C). The results of factor analysis and APCS-MLR show that NH3-N, BOD5 and CODMn were typical pollutants in this region, and the pollution sources of group A were mainly from organic matter, followed by nutrients; the water quality of group B was mainly polluted by the accumulation of organic matter and nutrients, while the influence of natural factors were relatively weak; group C was mainly polluted by biochemistry, followed by non-point source nutrients pollution. The results show that human activities were still the main factors affecting the deterioration of water quality. Although the interception effect of dams could improve the quality of discharge water, the pollutants accumulated in the reservoir area all the year round have the potential risk of secondary pollution with the change of environment, such as the activation and release of nutrients in sediments.