河口是海陆交汇的复杂生境交错带，对于河口水质的特征研究有助于完善对整个流域的水质分析。本研究通过对东江流域河口河网区2009年的7月（丰水期）和12月（枯水期）的盐度、总磷、总氮、氨氮、硝态氮、高锰酸钾指数及叶绿素a的浓度变化分析，归纳出河口段水质时空变化特征，通过各水质指标的相关性分析研究了东江河口段水质指标与水体富营养化的关系，并结合单因子水质评价了东江河口段水质状况。结果显示：1.东江河口段与河网区界线可能位于东莞市沙田镇附近；2.总氮、氨氮、硝态氮以及总磷的含量在枯水期都明显高于丰水期含量，而叶绿素a的变化是丰水期含量显著高于枯水期含量，高锰酸钾指数两期在变化不显著；3.东江流域枯水期河口段及河网段均为V类水甚至劣V类水，丰水期在河口段为V类水，在河网区为IV类水。对研究区段水质污染源分析表明东江河口段水质主要受周围工业和居民聚集区所排放的工业污水和生活废水的影响，而河网区水质主要受周边农田灌溉的影响制约。各水质指标的相关性显示总磷、氨氮与河流富营养化密切相关。

Estuary is a complex ecotone of land of sea. The research of the estuarine characteristic helps to improve the water quality of the entire basin. The study summed up the spatial and temporal variations of estuary by the thickness of salinity, TN, TP, NH4-N, NO3-N, CODMn and chlorophyll a of July and December in 2009, and the relation between water quality and eutrophication by correlation analysis, and assess water quality by single factor index method. The result showed that the boundary of estuary and drainage network may be located near Shatian Town, Dongguan. The thickness of TN, NH4-N, NO3-N and TP during the dry season is higher than wet season. The thickness of chlorophyll is higher during the wet season. And the variations of CODMn aren’t obvious. The water quality of estuary and drainage network is the level of V or less V during the dry season. Analysis showed that the sources of water pollution of estuary are the waste water from industry and population centers. And water pollution of drainage network is effected by farms. The correlation analysis showed the relation between eutrophication and TN, TP.