上海市不同区县中小河道氮磷污染特征

以上海11个区县,共19条河道、65个点位进行1a的氮磷污染情况调查。结果表明:(1)上海河道为不完全感潮型河网水系。潮汐、降雨对氮磷污染物的分布影响具有时间差异性。(2)上海河道区县之间氮磷污染差异大(P0.05)。氮磷浓度从中心城区河道依次向外呈现"圆环状"稀释扩散趋势。黄浦江以南河道水质好于黄浦江以北河道;近江苏的河道总体氮磷浓度水平高于近浙江的河道(上海东南部)(P0.05)。水体中污染物浓度、扩散、降解与人为扰动和城镇化程度密切相关。(3)聚类分析(Cluster Analysis,CA)结果显示上海市河道污染水平在点位之间区别不大,而多维尺度分析(Multidimensional Scaling,MDS)显示上海市河道污染水平在点位之间具有一定差异,并与水质评价结果一致。(4)经生态修复后的河道水质优于修复前(P0.05),说明上海市人工水生态修复措施和生态型驳岸建设对改善河道水质有潜在价值。

Distribution of nitrogen and phosphorus in medium and small rivers of shanghai

To assess nitrogen and phosphorus pollution in rivers of Shanghai, this study explored 65 water samples from 11 rivers in 19 districts of Shanghai from July 2012 to July 2013. The results showed that Shanghai rivers display incomplete tidal and river network characteristics under the effect of tide and rainfall, which caused temporal distribution differences of nitrogen and phosphorus pollutants. This combination of factors also affected the biodegradation in the rivers. Rainfall and tide had a diluting effect in the rivers during the experiment. There was a significant difference between the rivers of Shanghai in the nitrogen and phosphorus concentrations (P<0.05). In general, the difference appeared in a ring-like form on the map of the river network, with suburban rivers having lower concentrations of nitrogen and phosphorus than the urban rivers. Rivers located in southern sections of the Huangpu River have better water quality compared to the northern parts, and the concentration of nitrogen and phosphorus in rivers near the Jiangsu Province (northwest of Shanghai, near the estuary of the Yangtze River) were higher than in the sections near the Zhejiang Province (southeast of Shanghai) (P<0.05). Such distribution of pollutants reflected the close relationship between the concentration of pollutants and urbanization level. Cluster analysis (CA) did not find a significant difference in pollutants between the rivers of Shanghai, whereas multidimensional scaling, opposite to the CA, supported the results of the water quality assessment. Water quality of rivers after ecological restoration improves compared to the state before or to the rivers without ecological restoration (P<0.05), indicating that ecological restitution has potential in improving the water quality of rivers.