Liu Cheng, Fan Chengxin, Shen Qiushi, Shao Shiguang, Zhang Lei, Zhou Qilin
State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, PR China; University of Chinese Academy of Sciences, Beijing, 100049, PR China.
State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, PR China.
Chemosphere. 2016 Feb;144:2329-35. doi: 10.1016/j.chemosphere.2015.11.010. Epub 2015 Nov 21.
Environmental dredging is often used in river mouth areas to remove heavy metals. However, following dredging, high levels of metal-adsorbed suspended particulate matter (SPM) originating from polluted inflowing rivers might adversely affect the sediment-water interface (SWI). Here, we conducted a 360-day-long experiment investigating whether the riverine SPM adversely affects dredging outcome in a bay area of Lake Chaohu, China. We found that the heavy metal concentrations in the post-dredging surface sediment increased to pre-dredging levels for all metals studied (As, Cd, Cr, Cu, Ni, Pb, and Zn) after the addition of SPM. In addition, the increased concentrations were mostly detected in the relatively bioavailable non-residual fractions. Of the metals studied, the rate of increase was the greatest for Zn and Cd (482.98% and 261.07%, respectively), mostly in the weak acid extractable fraction. These results were probably due to certain characteristics of SPM (fine grain size, and high concentrations of organic matter and heavy metals) and the good oxic conditions of the SWI. Furthermore, As was the only metal for which we observed an increasing trend of diffusive flux across the SWI. However, the flux was still significantly lower than that measured before dredging. In conclusion, the quantity and character of riverine metal-adsorbed SPM affect metal re-contamination across the post-dredging SWI, and this information should be incorporated into the management schemes of dredging projects dedicated to reducing metal contamination in similar areas.
环境疏浚常用于河口地区以去除重金属。然而，疏浚后，来自受污染流入河流的大量吸附金属的悬浮颗粒物（SPM）可能会对沉积物 - 水界面（SWI）产生不利影响。在此，我们进行了一项为期360天的实验，研究河流中的SPM是否会对中国巢湖某湾区的疏浚结果产生不利影响。我们发现，添加SPM后，所有研究金属（砷、镉、铬、铜、镍、铅和锌）的疏浚后表层沉积物中的重金属浓度均恢复到疏浚前水平。此外，增加的浓度大多在相对生物可利用的非残留部分中检测到。在所研究的金属中，锌和镉的增加速率最大（分别为482.98%和261.07%），主要在弱酸可提取部分。这些结果可能归因于SPM的某些特性（细粒度、高有机质和重金属浓度）以及SWI的良好有氧条件。此外，砷是我们观察到在SWI上扩散通量呈增加趋势的唯一金属。然而，该通量仍显著低于疏浚前测量的值。总之，河流中吸附金属的SPM的数量和特性会影响疏浚后SWI上的金属再污染，并且该信息应纳入旨在减少类似地区金属污染的疏浚项目管理方案中。
