撒施阻控材料快速去除上覆水Cd对的室内模拟研究

Laboratory simulation study on Cd rapid removal from the overlying water through scattering resistance materials

湘中矿区塘、水库等灌溉水体及其底泥重金属超标问题日益凸显,研究选取石灰、水稻秸秆生物炭和人造沸石等3种环境友好型土壤重金属阻控材料,通过室内玻璃柱模拟静止水体实验探讨水面缓慢撒施阻控材料对上覆水重金属Cd去除与底泥Cd有效性影响。为期60 d的实验结果显示,1%(0~20 cm表层底泥质量分数)的单一石灰、生物炭、沸石与石灰+生物炭+人造沸石配方(质量比1∶1∶1)4种处理均可明显快速去除上覆水中水溶态Cd质量浓度,其中石灰效果最佳,沸石效果最差,石灰与3种阻控剂组配处理均可使上覆水中水溶态Cd质量浓度由20μg·L^(-1)以上降至10μg·L^(-1),符合我国灌溉水Cd的限定标准。阻控材料自然沉积在底泥表面后对5 cm处底泥水溶液Cd质量浓度具有一定的消减效应,沸石效果优于石灰、生物炭处理,其中"石灰+生物炭+沸石"的不同粒径阻控材料组配方式效果最佳。石灰、生物炭、沸石及3种阻控剂组配处理60 d后底泥pH值依然略高于对照,差异不显著,但可交换态Cd含量明显低于对照。结果可为塘库型水体上覆水及底泥Cd等重金属污染的生态风险降低及控制措施研究提供科学参考与方法指导。

Heavy metal pollution of irrigation water and pond and reservoir sediment has been increasing. Lime, rice straw-derived biochar, and artificial zeolite are three kinds of soil heavy metal pollution resistance control materials, which were proven to be environmentally friendly, were selected to assess the rapid removal ef- ficiency of Cd in overlying water and sediment Cd availability through water surface broadcasting under laboratory indoor glass column stationary water body simulation. Results of a 60 day period showed that all four treatments- lime, biochar, and zeolite treatments and a lime ＋ biochar ＋ zeolite （weight ratio 1 ： 1 ： 1 ） combination treat- ment-at a 1% mass ratio （0 to 20 cm sediment） application amount could quickly reduce the water soluble-Cd concentration from overlying water. Treatment with lime gave the best removal efficiency, followed by bioehar and zeolite treatments. Lime treatment and the combination treatment obviously decreased the water soluble-Cd con- centration from above 20 μg·L^-1 to below 10 μg·L^-1 , which conforms to the irrigation water Cd limit standard in China. The three kinds of environmentally friendly resistance materials showed a consistent reduction effect on a 5 em site with a sediment slurry solution containing Cd on the sediment surface from natural material deposits. A treatment combining the three materials showed the best reduction efficiency, and individually used zeolite showed better performance than that of lime and biochar. Results also revealed that the sediment pH in the four treatments was still slightly higher than that of the control experiment after 60 days. Though non-significant differ- ences were observed, the exchangeable Cd was obviously decreased compared to that in the control experiment. The results provide some scientific references and guidance for reducing the ecological risks in ponds, overlying reservoir water, and sediments polluted by heavy metal Cd.