广东湛江湾氮磷污染时空分布特征及影响因素分析

Spatial and temporal distribution characteristics and influencing factors of nitrogen and phosphorus pollution in Zhanjiang Bay,Guangdong Province

海湾是地球上单位面积生产力最高的区域之一,保护海湾生态是推进美丽海湾建设的重要内容。根据2015—2021年湛江湾近岸海域水质监测信息数据,分析了湛江湾海水水质总体状况及其主要污染物时空分布特征,采用氮磷比(N/P)、富营养化指数法及潜在性富营养化评价方法分析了湛江湾海域富营养状态及营养盐结构,探讨了主要污染来源及其影响因素。结果表明:1)湛江湾海域水质状况较差,海水水质类别以四类及劣四类海水为主,主要污染因子为DIP及DIN,DIP年均浓度整体逐年下降,DIN年均浓度先升高后降低,DIP和DIN浓度高值区主要分布于湛江湾麻斜以北海域及东部南山水道海域,整体呈湾顶至湾外逐渐减小趋势,湛江湾水质呈现明显分异特征,可能是受到了入海河流及沿岸陆源污染输入、海湾水体中有机质生化作用、海湾地形与水动力条件等的综合影响。2)湛江湾海域DIN/DIP比值偏低,年均范围为5.33~11.16,整体上表现为氮限制,海湾北部、中部及南部海域DIN/DIP比值相对较低(比值<8),陆源减排可能是导致湛江湾营养盐结构发生变化的主要原因。3)湛江湾海水富营养化指数较高,海水已呈重度富营养化,受汛期大量陆源污染输入的影响,夏、秋季节富营养化指数相对较高。湛江湾海域潜在性富营养化等级正在由氮中等限制潜在性富营养向富营养状态转变,营养盐结构的改变可能是受到了湾顶遂溪河及沿岸生活污水、工业废水及农业等陆源污染输入的影响,改善湛江湾水质应同步推进遂溪河和其他陆源的联合治理,研究分析结果及提出的防控对策建议可为湛江湾开展精准污染治理提供有益参考和支持。

As one of the most productive places on Earth,protecting the bay is an important part of the construction of beautiful bay.Based on the point survey data of Zhanjiang Bay from 2015 to 2021,the spatial and temporal distribution characteristics of seawater quality,oncentration of active phosphate(DIP)and inorganic nitrogen(DIN)in Zhanjiang Bay were analyzed.The eutrophication and nutrient structure of Zhanjiang Bay were evaluated by the N/P ratio,eutrophication index and potential eutrophication assessment model,and discussed the main pollution sources and influencing factors.Results showed that the main area of Zhanjiang Bay were inferior to the fourth category of national sea water quality standard,and the main pollutants were DIP and DIN.The average annual concentration of DIP showed a downward trend,while DIN showed a trend of first increased and then decreased.The areas with high DIP and DIN concentrations were mainly distributed to the northern region of Maxi slope and the eastern of Nanshan waterway of Zhanjiang Bay.And the concentration of DIP and DIN showed a spatial variation trend of decreasing from inside to outside in Zhanjiang Bay.The water quality of Zhanjiang Bay shows obvious different characteristics,which may be affected by the input of terrestrial pollution into the sea and coastal rivers,the biochemical action of organic matter in the bay water,the topography and hydrodynamic conditions of the bay.The DIN/DIP ratio in Zhanjiang Bay is relatively low,ranging from 5.33 to 11.16,and nitrogen was the main potential limitation.The DIN/DIP ratio in the northern,central and southern region of Zhanjiang Bay is relatively low(N/P≤8),land-based emission reduction may be the main reason for the change of nutrient structure.The eutrophication index of Zhanjiang Bay varied from 9.35 to 46.72,has reached a severe eutrophication,with the eutrophication level slightly higher in summer and autumn than in winter and spring due to the influence of a large amount of land-based pollution input in flood season.The potential eutrophication level of Zhanjiang Bay changed from the medium nitrogen limited potential eutrophication to the eutrophication state,which may be related to the influence of Suixi River and land-based pollution of coastal domestic sewage,industrial wastewater and agricultural pollution,and changed the nutrient structure of Zhanjiang Bay.In order to improve the water quality of Zhanjiang Bay,the pollution control of Suixi River and other land-based sources should be promoted simultaneously.The research and the proposed control countermeasures can provide useful reference and support for the precise pollution control in Zhanjiang Bay.