珠三角地区城市黑臭水体沉积物磷-铁-硫耦合与释放机理研究

Black and odorous problems in the Pearl River Delta city waters are serious, and there is an urgent need to carry out targeted governance by exploring the causes of blackwater. At present, the understanding of the formation mechanism of black and odorous water is incomplete, especially lacking analysis from the perspective of sediment. The migration and diffusion of P, Fe and S in sediments is closely related to the black and odorous material source processes. Black materials are mainly from suspended particles adsorbing the black FeS, and the main odorous materials are H2S, NH3 or other smelly gases. Therefore, understanding the coupling and release mechanisms of P-Fe-S is helpful to explore the causes of black and odour by sediments. The key to this understanding is to obtain the spatial distribution of P, Fe and S accurately. In this project, the DGT technique, which can simulate the migration processes of target ions in sediments, combined with the Zr-oxide DGT film having the highest capacity currently known, will be used to synchronously obtain the high resolution spatial distribution and dynamics of P, Fe and S in sediments. By analyzing the consistency and correlation of P-Fe-S spatial distributions and their simultaneous release, the coupling and release mechanisms of the three will be studied, and then the causes of black and odour by sediments would be excavated. The results will be of great significance to the endogenous pollution control and repair in black and odorous water bodies.

珠三角地区城市水体黑臭问题严重，迫切需要从深入探讨黑臭成因的角度开展针对性的治理。目前人们对黑臭水体形成机制的认识还不全面，尤其缺少沉积物角度的分析。沉积物中P、Fe、S的迁移扩散与致黑臭物质的物源过程密切相关。致黑物质主要是附了黑色FeS的悬浮颗粒，致臭物质主要是H2S、NH3等有异味的气体。因此，弄清沉积物中P-Fe-S的耦合与释放机制，有助于挖掘沉积物的致黑臭机理。而准确获取P、Fe、S的空间分布及动力学信息则是深入研究三者耦合关系的关键。本项目拟采用能模拟目标离子在沉积物中迁移扩散过程的DGT技术，结合目前已知容量最高的Zr-oxide DGT膜，同步获取沉积物 P、Fe、S 高分辨空间分布及动力学信息；通过分析沉积物中P-Fe-S空间分布趋势的一致性、相关性及同步释放等研究三者的耦合与释放机制，挖掘沉积物内源释放与黑臭形成机理。研究结果对黑臭水体内源污染治理与修复具有重要的意义。

珠三角地区城市水体黑臭问题严重，迫切需要从深入探讨黑臭成因的角度开展针对性地治理。目前人们对黑臭水体形成机制的认识还不全面，尤其缺少沉积物角度的分析。沉积物中P、Fe、S的迁移扩散与致黑臭物质的物源过程密切相关。本项目选择珠三角地区典型黑臭水体，判断水体的黑臭等级和沉积物的污染程度；基于DGT技术同步获取沉积物中P、Fe、S 的高分辨空间分布；通过原位测定结合模拟实验明确P、Fe、S 的耦合机制；揭示沉积物中致黑臭物质的转化过程与致黑臭机理。结果表明，珠三角地区黑臭水体受到严重的耗氧类污染和磷污染，底泥受到有机污染和还原物质污染也较严重。P和Fe在沉积物-水界面附近有相似的变化趋势，部分点位的P和Fe在整个浓度剖面上同步变化且显著相关（R=0.67–0.93, p < 0.01），证实了磷铁之间的耦合关系在黑臭底泥中普遍存在。室内好氧－厌氧模拟实验进一步证实了磷铁之间的耦合关系，即铁的还原导致磷的释放。P和S也出现了同步变化的现象，证实了Fe还原菌与S还原菌在沉积物微尺度下同时存在。沉积物中的P、Fe和S主要表现为由沉积物向上覆水释放。Fe的释放通量较大，硫的释放通量较小，但S耗氧速率高于Fe耗氧速率。室内培养实验得出Fe2+在底泥再悬浮的情况下能够引起水体短时间内迅速耗氧，但不足以维持耗氧速率大于复氧速率，而S2-能够引起水体持续发生黑臭，是引起水体缺氧和发生黑臭的关键因子。综合以上结论，分析了黑臭水体的形成机理： （i）COD和氨氮的耗氧以及大量硫酸盐的输入是主要的外在驱动因素；（ii）沉积物中的铁硫还原形成硫化亚铁并伴有磷释放是主要的内在驱动因素。本研究基于DGT技术在黑臭河流底泥中进行了成功应用，并揭示了底泥中磷铁硫的耦合与致黑臭机理。相关研究结果对黑臭水体治理具有一定的指导意义。