环保疏浚是治理湖泊污染底泥,消减内源污染的重要手段,而科学合理确定疏浚范围的控制指标是保证治理效果和工程经济性的关键,但现阶段相关技术标准对底泥中持久性有机污染物(POPs)的控制指标并未予以明确。研究结合相关技术指南和规程,以长江流域鸭儿湖复合污染底泥为研究对象,通过收集梳理国内外相关学者的研究成果,对底泥中的二噁英、甲基汞及短链氯化石蜡(SCCPs)等持久性有机污染物(POPs)进行分析。分析结果表明:对于不具备渔业功能的湖泊,建议二噁英总毒性质量比和SCCPs质量比控制指标分别为5~10 ng/kg和900 ng/g;对于具备渔业功能的湖泊,建议参考地区背景值提高控制指标标准;对于底泥表层甲基汞质量比>5 ng/g的区域,应限制渔业养殖功能。根据湖泊功能提出的技术建议,为复合污染底泥修复补充了理论依据,也为今后同类湖泊治理项目的实施提供了一定的经验和借鉴。

[Objective] Focusing on the composite-polluted sediments of Ya’er Lake in the Yangtze River Basin, this study aims to address the lack of control indicators for persistent organic pollutants (POPs) in environmental dredging projects. [Methods] A systematic analysis was conducted on the distribution characteristics and ecological risks of three typical pollutants: dioxins, methylmercury, and short-chain chlorinated paraffins (SCCPs). Based on the functional zoning of the lake, differentiated control indicators were proposed. The research methodology integrated comparative analysis of domestic and international standards (including China’s GB 36600—2018, Beijing’s DB11T 811—2011, and standards from Germany and Netherlands), analysis of pollutant migration and transformation mechanisms, and ecological risk assessment models. [Results]The concentration distributions of POPs in Ya’er Lake sediments were measured (dioxins: 1-50 ng/kg, methylmercury: 2-8 342 ng/g, SCCPs: 300-2 000 ng/g). Combined with the co-distribution patterns of heavy metal pollution, the response relationship between pollutant concentrations and lake functions was established. The results showed that control indicators for dioxins should be strictly graded according to lake functions: 10 ng/kg for lakes of landscape and storage functions (aligned with China’s Class I construction land standards), 5 ng/kg for lakes used for agricultural irrigation (referencing German agricultural land standards), and 1 ng/kg for lakes used for fishery purposes (based on background values and Dutch standards). For methylmercury control, the limitations of existing total mercury standards needed to be overcome. It was proposed that when the surface sediment methylmercury concentrations exceeded 5 ng/g, fishery activities should be restricted, with dry excavation identified as the preferred dredging method to minimize secondary pollution risks. For SCCPs control, a threshold of 900 ng/g was first proposed for non-fishery lakes (derived from ecological risk thresholds), while lakes used for fishery purposes required dynamic adjustments based on surrounding agricultural land data. The research demonstrated three breakthroughs: (1) it established for the first time China’s control indicator system for POPs in lake sediments, filling technical gaps in standards like GB 36600—2018 for dredging projects. (2) It revealed a high spatial correlation (R²>0.85) between POPs and heavy metal pollution in Ya’er Lake, proving that dredging according to existing heavy metal standards could simultaneously control POPs risks, thereby significantly reducing remediation costs. (3) It proposed a “function-pollutant-process” integrated control theory, offering a new paradigm for composite pollution remediation. [Conclusion] The conclusions indicate that differentiated control indicators can balance remediation costs and ecological safety. Dioxin standards for fishery water use must be an order of magnitude stricter than current soil standards, methylmercury risk control should be decoupled from total mercury metrics, and SCCPs thresholds must account for water solubility. The study provides critical scientific basis for the revision of standards such as the Technical Specifications for Environmental Dredging of Polluted Lake Sediments, and its methodology can be extended to remediation practices for other composite-polluted lakes globally.