长江口及其邻近海域富营养化水平评价

根据2004年4个季度2、5、8、11月的调查资料,选择化学耗氧量、溶解氧、活性磷酸盐、溶解无机氮和叶绿素a作为评价因子,利用人工神经网络模型对长江口及其邻近海域的营养水平进行评价。结果表明,富营养化区域主要集中在口门附近,富营养化程度由口门向东和东北方向递减。富营养化范围几乎均分布在盐度小于20的一侧,并随着长江冲淡水的变化而发生季节性的变化。5月和8月的富营养化比较严重,且都有转向东北的趋势,可能与5月进入丰水期长江冲淡水转向有关。断面分布表明,各个季度月由河口向东,富营养化评价等级由高到低,垂直方向则呈现复杂的变化。分析表明影响富营养化的主要评价指标是溶解无机氮。

Assessment of eutrophication in the Yangtze River estuary and its adjacent waters

According to the investigations of four mid-months (Feb.,May,Aug.,and Nov.)of seasons in 2004,we choose COD,DO,PO₄-P,DIN,Chl-a as assessing indexes,and use the artificial neural network to assess eutrophication in the Yangtze River estuary and its adjacent waters.The results show that the waters of eutrophication mainly concentrate round the rivermo uth,and the extent of eutrophication gradually decreases from the rivermouth to the east and northeast.The areas of eutrophication are almost distributed in the side of salinity bellowed 20 and have seasonal variations along with the changes of Yangtze River diluted water.The phenomenon of eutrophication is more serious in May and August than in other months,and both have the trend of turning around to the northeast,which may be caused by the diluted water turnaround with the flood coming in May.The transection distributions of eutrophication in each rmnth indicate that the grades of eutrophication change from high to low level,from rivermouth to the east,and it has complex variations in the vertical direction.The analysis shows that DIN is the main control factor for the assessment results of eutrophication.