Abstract：
Though both iron (hydr)oxides and soil organic matter (SOM) significantly influence heavy metal behaviors in soils, studies on the characteristics of natural minerals and the synergic effects of the two on Cr(VI) transformation are limited. This study investigated Cr(VI) retention mechanisms in four soils from tropical and subtropical regions of China based on a comprehensive characterization of Fe (hydr)oxides. These soils exhibited varying quantities of hematite, ferrihydrite and goethite, with distinct Al substitution levels and varied exposed crystallographic facets. Adsorption experiments revealed a positive correlation between Fe (hydr)oxide content and Cr(VI) fixation amount on colloid, which was influenced by the mineral types, Al substitution levels and facet exposures. Further, Cr(VI) was sequestered on soil by adsorption and reduction. In soils enriched with crystalline Fe (hydr)oxides, Cr(VI) reduction was primarily governed by SOM, while in soils enriched with poorly crystalline Fe (hydr)oxides, mineral-associated Fe(II) also contributed to Cr(VI) reduction. Aging experiments demonstrated that SOM and mineral-associated Fe(II) expedited Cr (VI) passivation and diminished the Cr leaching. These results improve our understanding of natural Fe (hydr)oxide structures and their impact on Cr(VI) behavior in soils, and shed light on complex soil-contaminant interactions and remediation of Cr(VI) polluted soils.
摘要：
尽管铁（hydr）氧化物和土壤有机质（SOM）都显着影响土壤中的重金属行为，关于天然矿物的特性以及两者对Cr（VI）转化的协同作用的研究有限。本研究基于Fe（hydr）氧化物的综合表征，研究了中国热带和亚热带地区四种土壤中Cr（VI）的保留机制。这些土壤显示出不同数量的赤铁矿，水铁矿和针铁矿，具有不同的Al取代水平和不同的暴露晶面。吸附实验表明，Fe（hyr）氧化物含量与胶体上Cr（VI）固定量之间存在正相关关系，受矿物类型的影响，铝替代水平和方面暴露。Further,Cr（VI）通过吸附和还原在土壤中被螯合。在富含结晶铁(氢)氧化物的土壤中，Cr(VI)还原主要受SOM控制，而在富含结晶不良的铁(氢)氧化物的土壤中，矿物伴生的Fe（II）也有助于Cr（VI）的还原。老化实验表明，SOM和矿物伴生的Fe（II）加速了Cr（VI）的钝化并减少了Cr的浸出。这些结果提高了我们对天然Fe（hydr）氧化物结构及其对土壤中Cr（VI）行为的影响的理解。并阐明了复杂的土壤-污染物相互作用和Cr（VI）污染土壤的修复。
