Beak Douglas G, Basta Nicholas T, Scheckel Kirk G, Traina Samuel J
School of Environment and Natural Resources, The Ohio State University, Columbus, OH 43209, USA.
J Environ Qual. 2006 Oct 27;35(6):2075-83. doi: 10.2134/jeq2005.0467. Print 2006 Nov-Dec.
Lead (Pb) sorption onto oxide surfaces in soils may strongly influence the risk posed from incidental ingestion of Pb-contaminated soil. Lead was sorbed to model oxide minerals of corundum (alpha-Al(2)O(3)) and ferrihydrite (Fe(5)HO(8).4H(2)O). The Pb-sorbed minerals were placed in a simulated gastrointestinal tract (in vitro) to simulate ingestion of Pb-contaminated soil. The changes in Pb speciation were determined using extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge spectroscopy (XANES). Both corundum (sorption maximum of 2.13 g kg(-1)) and ferrihydrite (sorption maximum of 38.6 g kg(-1)) have been shown to sorb Pb, with ferrihydrite having a very high affinity for Pb. The gastric bioaccessible Pb for corundum was >85% for corundum when the concentration of Pb was >200 mg kg(-1). Bioaccessible Pb was not detectable at </=200 mg kg(-1). Bioaccessible Pb ranged from 53 to 88% for ferrihydrite. The bioaccessible Pb was below detection limits for the intestinal phase in the ferrihydrite system. Solid phase speciation identified both inner- (mononuclear bidentate) and outer-sphere species for Pb sorbed to corundum, while only an inner-sphere (mononuclear bidentate) complex was found for ferrihydrite. Although corundum and ferrihydrite can bind Pb, they fail to significantly reduce gastric bioaccessible Pb but do reduce intestinal bioaccessible Pb. Treatment of Pb-contaminated soil with corundum or ferrihydrite may reduce Pb solubility under field soil conditions of pH > 4. However, much of the sorbed Pb will become bioaccessible under gastric conditions (pH 1.5-2.5) if this soil is ingested. Caution should be used before using these materials to remediate a soil where soil ingestion is an important exposure pathway.
土壤中铅（Pb）在氧化物表面的吸附可能会强烈影响因意外摄入受铅污染土壤而带来的风险。铅被吸附到刚玉（α-Al₂O₃）和水铁矿（Fe₅HO₈·4H₂O）的模型氧化物矿物上。将吸附了铅的矿物置于模拟胃肠道（体外）中，以模拟摄入受铅污染的土壤。使用扩展X射线吸收精细结构（EXAFS）和X射线吸收近边光谱（XANES）来确定铅形态的变化。已表明刚玉（最大吸附量为2.13 g kg⁻¹）和水铁矿（最大吸附量为38.6 g kg⁻¹）都能吸附铅，其中水铁矿对铅具有非常高的亲和力。当铅浓度>200 mg kg⁻¹时，刚玉的胃生物可利用铅含量>85%。在≤200 mg kg⁻¹时，未检测到生物可利用铅。水铁矿的生物可利用铅含量在53%至88%之间。在水铁矿体系中，肠道阶段的生物可利用铅低于检测限。固相形态分析确定了吸附在刚玉上的铅既有内层（单核双齿）物种也有外层物种，而水铁矿仅发现了内层（单核双齿）络合物。尽管刚玉和水铁矿都能结合铅，但它们并不能显著降低胃生物可利用铅，不过能降低肠道生物可利用铅。在pH>4的田间土壤条件下，用刚玉或水铁矿处理受铅污染的土壤可能会降低铅的溶解度。然而，如果摄入这种土壤，大部分吸附的铅在胃环境（pH 1.5 - 2.5）下会变得具有生物可利用性。在使用这些材料修复土壤摄入是重要暴露途径的污染土壤之前，应谨慎行事。
