表面流人工湿地微污染进水下沉积物营养盐累积特征及污染评价OA

This study investigates the spatiotemporal distribution characteristics and main influencing factors of carbon,nitrogen,and phosphorus in sediments of a large surface-flow constructed wetland during the long-term purification of lightly polluted water.Sediment samples were collected from 28 sites in Lake Yanlong,northern Jiangsu Province,and the contents of total organic carbon(TOC),total nitrogen(TN),and total phosphorus(TP)were measured.Correlation analysis among TOC,TN,and TP contents was conducted,followed by comprehensive pollution and organic pollution assessments of the sediments.Results indicated that the average contents of TP,TN,and TOC in the sediments were 529 mg/kg,953 mg/kg,and 0.85％,respectively.A highly signifi-cant positive correlation was observed between TN and TP contents(R=0.729,P＜0.01),and a significant positive correlation was found between TN and TOC contents(R=0.251,P＜0.05),suggesting that organic nitrogen and organic carbon in the sedi-ments may share common sources.Spatially,(1)along the flow direction,TP and TN contents generally decreased across different zones,with the highest nutrient concentrations and most severe pollution occurring in the pretreatment zone;(2)vertically,sedi-ments in the pretreatment and deep purification zones exhibited surface enrichment of nutrients,with the highest values concentrat-ed in the 0-30 cm layer,while the emergent and submerged plant zones showed relatively stable vertical profiles with no clear trends with depth;and(3)compared to 2017,nutrient levels in the emergent plant zone decreased along the flow direction,while TP and TOC contents increased significantly in 2023,likely attributable to high plant density,lodging,and decomposition of plant residues.Pollution assessment based on comprehensive and organic pollution index methods demonstrated that the overall sediment quality of Lake Yanlong was relatively good.With the exception of the pretreatment zone,which was moderately polluted by nitro-gen and phosphorus,other areas were classified as clean or lightly polluted.Organic pollution was light in the pretreatment and deep purification zones,while other regions were clean.These evaluation results provide a scientific basis for localized dredging op-erations.Overall,the purification performance of Lake Yanlong wetland weakened after long-term operation,with hydraulic reten-tion time and influent concentration identified as key influencing factors,and pollutants showed a clear accumulation trend.The findings offer scientific support for sediment pollution assessment and operational management of large surface-flow constructed wet-lands receiving long-term lightly polluted inflows.