Department of Geology and Geoenvironment, NKUA, Athens, 15784, Greece.
Environ Geochem Health. 2021 Jul;43(7):2483-2503. doi: 10.1007/s10653-020-00542-1. Epub 2020 Feb 24.
Clays have been widely applied in contaminated soils in order to reduce the mobility of potentially toxic elements (PTEs), such as Pb, Zn and Cu. In the present study, three Fe-rich clays from Greece were selected as amendments of three contaminated soils with distinct physicochemical and mineralogical characteristics. The amendments consisted of palygorskite-rich (PCM), Fe-smectite-rich (SCM) and natural palygorskite/Fe-smectite-rich (MCM) clays. The changes induced in the environment of the soil-PTE-clay system were assessed by examining the water-labile fraction of Pb, Zn and Cu, as well as the bioaccessibility of Pb, in the contaminated soils. The initial water-leachable concentrations of PTEs in soil were within the range 1826-6160 μg/kg Pb, 152-645 μg/kg Cu and 370-4052 μg/kg Zn. All three Fe-rich clays exhibited high retention efficiency toward PTEs, following the order Pb (55-70%) > Zn (45-55%) > Cu (0-45%). The high reactive surface area of the clay particles acted as a substrate for the deposition of Fe-Al oxides with a concomitant removal of PTEs that were transported through the colloidal fraction. Furthermore, the decrease in relative bioaccessibility of Pb (5-10% compared to the control) suggests dissolution of primary clays followed by entrapment of the element in secondary Fe-rich precipitates. In conclusion, the use of Fe-rich clays as soil amendments may have a positive effect in reducing the environmentally significant PTE fraction in soils, especially when different clay phases coexist.
粘土已广泛应用于污染土壤中，以降低潜在有毒元素（PTEs）的迁移性，如 Pb、Zn 和 Cu。在本研究中，选择了来自希腊的三种富铁粘土作为三种具有不同物理化学和矿物学特性的污染土壤的改良剂。改良剂由富坡缕石（PCM）、富铁蒙脱石（SCM）和天然坡缕石/富铁蒙脱石（MCM）粘土组成。通过检查污染土壤中 Pb、Zn 和 Cu 的水不稳定部分以及 Pb 的生物可利用性，评估了土壤-PTE-粘土系统环境中发生的变化。土壤中 PTE 的初始水可提取浓度在 1826-6160μg/kg Pb、152-645μg/kg Cu 和 370-4052μg/kg Zn 范围内。三种富铁粘土对 PTE 均表现出高的保留效率，顺序为 Pb（55-70%）>Zn（45-55%）>Cu（0-45%）。粘土颗粒的高反应表面积充当 Fe-Al 氧化物沉积的基质，同时去除通过胶体部分运输的 PTE。此外，Pb 的相对生物可利用性降低（与对照相比降低 5-10%）表明原生粘土的溶解，随后元素被捕获在次生富铁沉淀物中。总之，将富铁粘土用作土壤改良剂可能会对减少土壤中具有环境意义的 PTE 部分产生积极影响，特别是当不同的粘土相共存时。
