Department of Biology, Ecophysiology, Biochemistry and Toxicology Group, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerpen, Belgium.
Water Res. 2012 May 1;46(7):2205-14. doi: 10.1016/j.watres.2012.01.052. Epub 2012 Feb 4.
In order to evaluate the effect of improved oxygen concentrations in overlying surface water on the redox status, sediment geochemistry and metal bioavailability in metal-polluted sediments a 54 days lab experiment with two different experimental treatments was conducted (90% and 40% O(2)). Changes in redox potential (Eh) in the sediment were monitored over time. At 6 different time points (after 0, 2, 5, 12, 32 and 54 days) and at 4 sediment depths (0-1, 1-4, 4-8 and 8-15 cm), acid volatile sulfides (AVS), simultaneously extracted metals (SEM) and total organic carbon (TOC) were measured and metal release to overlying surface water was determined. Labile metal species in both water and sediment were measured using Diffusive Gradients in Thin films (DGT). Our results showed that elevated oxygen levels in overlying surface water led to an Eh increase in the sediment of the 90% O(2) treatment from 0 to ± 200 mV while AVS concentrations in the upper sediment layer decreased by 70%. Following AVS oxidation metal availability in the pore water was highly elevated after 54 days. However, Cu remained strongly bound to the sediment during the whole experiment. Only a limited metal release to the overlying surface water was noticed, which was due to the fact that SEM(tot) concentrations in the sediment did not yet exceeded AVS levels ([SEM(tot) - AVS]/f(OC) = 0) after 54 days. Additionally, adsorption on Fe and Mn hydroxides and particulate organic carbon also slowed down any potential metal release. Our results indicated that increasing oxygen concentrations due to general water quality improvements can enhance the mobility of trace metals which may result in the leaching of sediment-bound metals to overlying surface water, even in undisturbed watercourses.
为了评估表层水中氧气浓度提高对氧化还原状态、沉积物地球化学和金属生物有效性的影响，进行了一项为期 54 天的实验室实验，采用两种不同的实验处理方法（90%和 40%O2）。随着时间的推移，监测了沉积物中氧化还原电位（Eh）的变化。在 6 个不同的时间点（0、2、5、12、32 和 54 天后）和 4 个沉积物深度（0-1、1-4、4-8 和 8-15 cm），测量了酸可挥发性硫（AVS）、同时提取的金属（SEM）和总有机碳（TOC），并确定了金属向表层水中的释放量。使用薄膜扩散梯度技术（DGT）测量了水和沉积物中的可利用金属物种。我们的结果表明，表层水中氧气水平的升高导致 90%O2 处理的沉积物 Eh 从 0 增加到±200 mV，而上层沉积物中的 AVS 浓度降低了 70%。在 AVS 氧化后，54 天后孔隙水中的金属可用性大大提高。然而，Cu 在整个实验过程中仍与沉积物紧密结合。仅注意到有限的金属释放到表层水中，这是由于在 54 天后，沉积物中的 SEM（tot）浓度尚未超过 AVS 水平（[SEM（tot）-AVS]/f（OC）=0）。此外，Fe 和 Mn 氢氧化物和颗粒有机碳的吸附也减缓了任何潜在的金属释放。我们的结果表明，由于水质普遍改善而增加氧气浓度可以提高痕量金属的迁移性，这可能导致沉积物结合的金属浸出到表层水中，即使在未受干扰的河道中也是如此。
