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

为研究岩溶地区河流湖库在底泥疏浚前后水体沉积物对外源性重金属污染物环境行为的影响,以重金属铜为例模拟沉积物存在或缺失条件下重金属在岩溶地区常见水体中的迁移试验,结果表明:在富碳酸氢盐水(supercarbonate-rich water, SCRW)、富营养化水(eutrophic water, ETW)、对照(去离子水,de-ionized water, DIW)3种上覆水体与水体沉积物存在或缺失构成的6个系统中,沉积物的有无对铜从上覆水中迁出量具有显著影响,表现为沉积物+DIW]>SCRW]>沉积物+ETW]>沉积物+SCRW]>ETW]>DIW].使用Langmuir扩展方程对浓度-时间函数进行拟合后考察其一阶导数研究沉积物对重金属迁出速率的影响,结果表明:不同的沉积物+上覆水]系统对铜的迁移速率的影响存在明显差异,具体表现为:在0~1.8 h内, 铜在沉积物+SCRW]系统中的迁出速率最高,在1.8~42 h内,铜在沉积物+DIW]中的迁出速率最高,在42 h后各个系统中的迁出速率均较低不具有显著性差异(p>0.05),直至240 h均保持稳定.说明在外来重金属的输入没有得到有效控制的情况下,沉积物的存在可使水体对外来重金属具有更好的缓冲能力且可有效加快上覆水中重金属(铜)初期(0~48 h)的迁出速率,因此现有的岩溶地区水体沉积物疏浚工程环境风险评价体系需要进行修正.

Influence of aquatic sediment on copper migration in various overlying waters in Karst region

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.