福建省三沙湾氮、磷污染物入海量及来源结构

Nitrogen and Phosphorus Discharge Flux into the Sea and Pollution Source Structure in Sansha Bay,Fujian Province

近年来,三沙湾海域水环境质量仍不容乐观。厘清三沙湾氮、磷污染物的入海量及来源结构,对加强近岸海域生态环境统筹治理具有重要意义。因此,本研究基于土地利用、社会经济统计和污染源普查等多元数据,估算三沙湾总氮、总磷的入海量及来源结构。结果表明,2020年主要陆源(工业源、生活源、种植业源、畜禽养殖源和陆基水产养殖源)和海源(滩涂养殖、筏式养殖和网箱养殖)总氮、总磷净入海量分别为238和622 t。其中,陆源总氮、总磷入海量分别为2564和352 t,海源总氮、总磷净入海量分别为-2326和270 t。种植业作为主要的陆源,总氮、总磷入海量分别占46.4%和41.4%。不同流域总氮、总磷排放强度存在空间差异,其中交溪流域面积最大,氮、磷入海量最高。投饵型生物(如鱼类、鲍鱼和海参)养殖是海源总氮、总磷的主要来源,非投饵型贝类和大型藻类养殖可以抵消系统内部分总氮、总磷污染负荷。

It is concerning that,in recent years,there has been no appreciable improvement in the quality of seawater in Sansha Bay.A better understanding of the pollution sources of the coastal areas is essential for developing comprehensive ecological environment management approaches for Sansha Bay.Based on land use data,socialeconomic statistics and pollution source investigation data,the pollutant discharge coefficient method was used to evaluate the total nitrogen and total phosphorus fluxes into Sansha Bay,the largest bay in Fujian Province.A comprehensive and systematic analysis was conducted to investigate the composition and distribution of the pollutants.The results show that the net total nitrogen and total phosphorus fluxes produced by land-based sources(including industrial production,residents′living,cultivation,livestock and poultry breeding,and land-based fish farming)and sea-based pollution sources(including tidal flat aquaculture,raft culture,and cage culture)in 2020 were 238 and 622 tons,respectively.The primary source of the total nitrogen and total phosphorus was land-based pollution,with fluxes of 2564 and 352 tons,respectively.The fluxes of total nitrogen and total phosphorus from the primary sea-based pollution sources were-2326 and 270 tons,respectively.Cultivation was the dominant land-based source of pollution,accounting for 46.4%and 41.4%of the total nitrogen and total phosphorus fluxes,respectively.Notable heterogeneity was observed in the total nitrogen and total phosphorus fluxes across the watersheds.The Jiaoxi Watershed,with the largest watershed area,was responsible for the greatest proportion of land-based pollutant fluxes.Feed-based aquaculture(such as fish,abalone,and sea cucumber feeding)was the main sea-based pollution source,whereas the non-feeding shellfish and macroalgae can assist in the assimilation of the nitrogen and phosphorus nutrients.