Environmental Soil Chemistry Research Group, Department of Plant and Soil Sciences, University of Delaware, Newark, Delaware 19716, USA.
Environ Sci Technol. 2010 Jan 1;44(1):302-8. doi: 10.1021/es902332b.
The formation of mixed metal-aluminum hydroxide surface precipitates is a potentially significant uptake route for trace metals (including Co, Ni, and Zn) in environmental systems. This paper investigates the effect of mixed Ni-Al hydroxide precipitate formation and aging on Ni solubility and bioavailability in laboratory contaminated soils. Two Delaware agricultural soils were reacted with a 3 mM Ni solution for 12 months at pH's above and below the threshold for mixed Ni-Al hydroxide formation. Ni speciation was determined at 1, 6, and 12 months using X-ray absorption spectroscopy (XAS). Precipitate solubility was examined through desorption experiments using HNO3 and EDTA as desorbing agents, whereas metal bioavailability was assessed using a Ni-specific bacterial biosensor. For both soils, the formation of Ni-Al hydroxide surface precipitates resulted in a reduction in the fraction of desorbed and bioavailable Ni. However, precipitate dissolution was greater, particularly with EDTA, than in published studies on isolated soil clay fractions, and less affected by aging processes. These results suggest that mixed Ni-Al hydroxide phases forming in real world environments may be both longer-lasting and more susceptible to ligand-promoted dissolution than previously expected.
混合金属-氢氧化铝表面沉淀物的形成是环境系统中痕量金属（包括 Co、Ni 和 Zn）的一种潜在重要的吸收途径。本文研究了混合 Ni-Al 氢氧化物沉淀的形成和老化对实验室污染土壤中 Ni 溶解度和生物可利用性的影响。两种特拉华州农业土壤与 3mM Ni 溶液在高于和低于混合 Ni-Al 氢氧化物形成阈值的 pH 下反应 12 个月。使用 X 射线吸收光谱（XAS）在 1、6 和 12 个月时确定了 Ni 的形态。通过使用 HNO3 和 EDTA 作为解吸剂的解吸实验研究了沉淀物的溶解度，而使用 Ni 特异性细菌生物传感器评估了金属的生物可用性。对于这两种土壤，Ni-Al 氢氧化物表面沉淀物的形成导致解吸和生物可利用的 Ni 分数减少。然而，与已发表的关于分离土壤粘土部分的研究相比，沉淀的溶解程度更大，特别是使用 EDTA，并且受老化过程的影响较小。这些结果表明，在实际环境中形成的混合 Ni-Al 氢氧化物相可能比以前预期的更持久，并且更容易受到配体促进的溶解。
