颤蚓扰动对湖泊沉积物中镉迁移转化的影响机制研究

Heavy metal pollution has become one of the main aspects of water environmental deterioration in our country. Macroinvertebrate activity can alter the physical and chemical properties of sediments, further influencing the environmental behaviors of heavy metals across the sediment-water interface. However, the coupling relationship between the key physicochemical properties of sediment and the transport and transformation of heavy metals in sediments under bioturbation has not been well understood by far. .Our experimental was based on indoor microcosms, selecting tubificid, a typical pollution resistant species, as the bioturbation agents and cadmium (Cd), a typical kind of heavy metal pollutants in sediment, as the target pollutant. The aims of this study were to: investigate the physicochemical properties of sediments and its change tendency under bioturbation based on the monitoring data; reveal the effect of tubificids bioturbation on transport and transformation characteristics of Cd in sediments through analyzing the concentration of different Cd fractionation in sediment and water phase; reveal the mechanism for the influence of physicochemical properties change of sediment caused by tubificids on environmental behaviors of Cd through the analysis of the relationship between the key physicochemical indexes and the content of different Cd fractions in sediment and water phase. .This study will help to explore the mechanism for the influence of bioturbation on environmental behaviors of heavy metal and provide theoretical foundation for the evaluation of the potential ecological risk in lake sediments.

重金属污染已成为我国主要水环境问题之一。底栖动物扰动可通过改变水体沉积物的理化性质影响重金属的环境行为，而生物扰动下沉积物关键理化性质的变化特征与重金属迁移转化过程之间的耦合关系尚不清楚。.项目选取常见底栖动物耐污种颤蚓为扰动生物，以典型水体重金属污染物镉（Cd）为研究对象，探讨颤蚓扰动对沉积物中Cd迁移转化的影响机制。通过对颤蚓扰动过程中沉积物/水相关键理化性质指标的动态监测，探讨颤蚓扰动下沉积物微环境的变化特征及趋势；通过分析沉积物/水相中不同赋存形态Cd的含量变化，识别颤蚓扰动对水环境中Cd迁移、转化和释放的影响特征及规律；通过分析沉积物/水相中不同形态Cd含量与关键理化性质指标间的相关关系，揭示生物扰动通过改变沉积物理化环境特征影响Cd迁移转化的作用机制。.本研究有助于揭示水环境中生物扰动和沉积物中重金属环境行为之间的耦合关系，为湖泊重金属污染的潜在生态风险评价提供理论依据。

水体沉积物是重金属污染物的重要汇，其具有不可降解性、生物累积及低浓度毒性效应等特点，重金属污染已成为我国主要水环境问题之一。底栖动物作为水生态系统的重要组成部分和关键界面因子，可通过摄食、钻行、筑穴等改变沉积物的理化性质，进而对重金属污染物的赋存形态、释放等产生影响，而目前关于二者之间的耦合关系尚不清楚。项目选取常见底栖动物颤蚓和环棱螺为扰动生物，以典型水体重金属污染物为研究对象，对扰动下沉积物/水相关键理化性质及重金属形态和含量进行了监测，探讨了生物扰动下沉积物理化环境的变化特征，识别了扰动对水环境中重金属迁移和释放的影响特征，初步揭示了生物扰动改变沉积物理化性质和影响重金属迁移转化的作用机制。研究表明，颤蚓生物扰动可增加沉积物孔隙率和渗透性，但未对沉积物内氧气的空间分布造成显著改变；颤蚓扰动可导致沉积物表层结构粗糙，稳定性变差，且能够改变沉积物粒度和成分比，但影响作用不显著。颤蚓扰动组水体中总Cd的浓度呈先升后下趋势，水体中颗粒态Cu含量和浊度具有显著的正相关性，且颗粒态Cu含量在实验后期始终保持在极低水平，无显著的释放现象发生。颤蚓扰动组中沉积物表层总Cd含量均低于初始值，且明显高于对照组。对照组沉积物表层可交换态Cd和碳酸盐结合态Cd的含量均低于扰动组，沉积物中有机物/硫化物结合态Cd的含量均比较低，其受到生物扰动作用的影响不显著。环棱螺可以加速系统中悬浮颗粒物的沉降，水体中溶解态Cu浓度24h内降低至1.04±0.37 μg/L，颗粒态Cu含量在第48h降低至0.13±0.02 μg/L，且和水体浊度具有显著的正相关性。环棱螺扰动对表层沉积物理化特性和重金属赋存形态无显著影响，其肌肉组织对重金属的富集作用较弱，而其内脏团组织对重金属的富集作用明显，28d实验后三种重金属的含量均显著高于投放前，内脏团中Cd含量达到0.88±0.02mg/kg dw。本研究有助于揭示水环境中生物扰动和沉积物中重金属环境行为之间的耦合关系，为湖泊重金属污染的潜在生态风险评价提供依据。