State Key Laboratory of Urban Water Resources and Environment, School of Municipal & Environmental Engineering, Harbin Institute of Technology, Harbin, 150090, China; Department of Civil and Environmental Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA.
State Key Laboratory of Urban Water Resources and Environment, School of Municipal & Environmental Engineering, Harbin Institute of Technology, Harbin, 150090, China.
Chemosphere. 2016 Dec;165:100-109. doi: 10.1016/j.chemosphere.2016.09.027. Epub 2016 Sep 15.
Soil aquifer treatment (SAT) systems rely on extensive physical and biogeochemical processes in the vadose zone and aquifer for water quality improvement. In this study, the distribution, quantitative changes, as well as the speciation characteristics of heavy metals in different depth of soils of a two-year operated lab-scale SAT was explored. A majority of the heavy metals in the recharged secondary effluent were efficiently trapped by the steady-state operated SAT (removal efficiency ranged from 74.7% to 98.2%). Thus, significant accumulations of 31.7% for Cd, 15.9% for Cu, 15.3% for Zn and 8.6% for Cr were observed for the top soil after 730 d operation, leading to the concentration (in μg g) of those four heavy metals of the packed soil increased from 0.51, 46.7, 61.0 and 35.7 to 0.66, 54.2, 70.4 and 38.8, respectively. By contrast, the accumulation of Mn and Pb were quite low. The residual species were the predominant fraction of the six heavy metals (ranged for 59.8-82.4%), followed by oxidisable species. Although the Zn, Cr, Cd, Cu and Mn were efficiently bounded onto the oxide components within the soil, the percentage of the labile metal fractions (water-, acid-exchangeable and reducible metal fractions) exhibited a slight increasing after 2 Y operation. Significantly heavy metals accumulation and slightly decreasing of the proportion of the stable fractions indicated a potentially higher environmental hazard for those six heavy metals after long-term SAT operation (especially for Cu, Zn and Cd). Finally, a linear relationship between the accumulation rate of metal species and the variation of soil organic carbon concentration and water extractable organic carbon was demonstrated.
土壤含水层处理 (SAT) 系统依赖于包气带和含水层中广泛的物理和生物地球化学过程来改善水质。在这项研究中，探索了经过两年运行的实验室规模 SAT 不同深度土壤中重金属的分布、定量变化以及形态特征。再补给二级出水的大部分重金属被稳定运行的 SAT 有效截留（去除效率范围为 74.7%至 98.2%）。因此，在 730 天运行后，顶部土壤中 Cd 的积累量显著增加了 31.7%，Cu 增加了 15.9%，Zn 增加了 15.3%，Cr 增加了 8.6%，导致填充土壤中这四种重金属的浓度（μg/g）从 0.51、46.7、61.0 和 35.7 分别增加到 0.66、54.2、70.4 和 38.8。相比之下，Mn 和 Pb 的积累量较低。残余物是这六种重金属的主要形态（范围为 59.8-82.4%），其次是可氧化态。尽管 Zn、Cr、Cd、Cu 和 Mn 有效地结合到土壤中的氧化物成分中，但在 2 年运行后，易释放金属（水相、酸交换和可还原金属）的比例略有增加。重金属的大量积累和稳定比例的略微下降表明，这些六种重金属在长期 SAT 运行后具有更高的环境风险（特别是 Cu、Zn 和 Cd）。最后，证明了金属形态的积累率与土壤有机碳浓度和水可提取有机碳的变化之间存在线性关系。
