Influence of aquatic sediment on copper migration in various overlying waters in Karst region
岩溶地区水体沉积物对铜在不同类型上覆水中迁移的影响

The influence of aquatic sediment on copper migration behavior in supercarbonate-rich water (SCRW) and eutrophic water (ETW) was studied using de-ionized water (DIW) as the control. The water body in Karst region, known as its high supercarbonate concentration, suffers from eutrophication. In this study, six sub-systems with three overlying waters (SCRW, ETW, DIW) in the presence or absence of the aquatic sediment were investigated. Copper was selected as the target metal because of its wide use in daily life, industry, and agriculture. The results showed that the presence of aquatic sediment significantly affected the copper migration process, which followed sediment+DIW] > SCRW] > sediment+ETW] > sediment+SCRW] > ETW] > DIW]. Copper migration rate in each system was simulated by the first derivatives of Langmuir extended model. Our results showed that the initial copper migration rate was also accelerated in the presence of aquatic sediment. Copper migration rate was the highest in sediment+SCRW] during 0~1.8 h, and in sediment+DIW] between 1.8~42 h. From 42 h to 240 h, there was no significant difference (p>0.05) between various systems. In conclusion, aquatic sediment is able to enhance the heavy metal buffering capacity in no-Karst region water bodies. However, in SCRW water, aquatic sediment poses a negative effect on heavy metal buffering capacity. Aquatic sediment can also accelerate the initial (0~42 h) copper migration rate. Due to all reasons mentioned above, the current environmental risk assessment about sediment dredging in Karst region needs to be re-established.