Eawag, Swiss Federal Institute of Aquatic Science and Technology, Ueberlandstrasse 133, CH-8600 Duebendorf, Switzerland.
Environ Sci Technol. 2011 Jan 1;45(1):255-61. doi: 10.1021/es101189d. Epub 2010 Dec 9.
The long-term speciation of Zn in contaminated soils is strongly influenced by soil pH, clay, and organic matter content as well as Zn loading. In addition, the type of Zn-bearing contaminant entering the soil may influence the subsequent formation of pedogenic Zn species, but systematic studies on such effects are currently lacking. We therefore conducted a soil incubation study in which four soils, ranging from strongly acidic to calcareous, were spiked with 2000 mg/kg Zn using either ZnO (zincite) or ZnS (sphalerite) as the contamination source. The soils were incubated under aerated conditions in moist state for up to four years. The extractability and speciation of Zn were assessed after one, two, and four years using extractions with 0.01 M CaCl(2) and Zn K-edge X-ray absorption fine structure (XAFS) spectroscopy, respectively. After four years, more than 90% of the added ZnO were dissolved in all soils, with the fastest dissolution occurring in the acidic soils. Contamination with ZnO favored the formation of Zn-bearing layered double hydroxides (LDH), even in acidic soils, and to a lesser degree Zn-phyllosilicates and adsorbed Zn species. This was explained by locally elevated pH and high Zn concentrations around dissolving ZnO particles. Except for the calcareous soil, ZnS dissolved more slowly than ZnO, reaching only 26 to 75% of the added ZnS after four years. ZnS dissolved more slowly in the two acidic soils than in the near-neutral and the calcareous soil. Also, the resulting Zn speciation was markedly different between these two pairs of soils: Whereas Zn bound to hydroxy-interlayered clay minerals (HIM) and octahedrally coordinated Zn sorption complexes prevailed in the two acidic soils, Zn speciation in the neutral and the calcareous soil was dominated by Zn-LDH and tetrahedrally coordinated inner-sphere Zn complexes. Our results show that the type of Zn-bearing contaminant phase can have a significant influence on the formation of pedogenic Zn species in soils. Important factors include the rate of Zn release from the contaminant phases and effects of the contaminant phase on bulk soil properties and on local chemical conditions around weathering contaminant particles.
在受污染土壤中，锌的长期分异强烈受土壤 pH 值、粘土和有机质含量以及锌负荷的影响。此外，进入土壤的含锌污染物的类型可能会影响随后形成的土壤成因锌物种，但目前缺乏对此类影响的系统研究。因此，我们进行了一项土壤培养研究，其中四种土壤，从强酸性到石灰性，用氧化锌（锌矿）或闪锌矿（闪锌矿）作为污染源，用 2000mg/kg 的锌进行了接种。在潮湿状态下，在充气条件下培养了长达四年。分别使用 0.01M CaCl₂ 和 Zn K 边 X 射线吸收精细结构（XAFS）光谱提取法，在一年、两年和四年后评估了 Zn 的可提取性和形态。四年后，所有土壤中添加的 ZnO 中有超过 90%溶解，在酸性土壤中溶解最快。用 ZnO 污染有利于形成含锌层状双氢氧化物（LDH），即使在酸性土壤中也是如此，而形成锌叶状硅酸盐和吸附态锌的程度较小。这可以用溶解的 ZnO 颗粒周围局部升高的 pH 值和高 Zn 浓度来解释。除了石灰性土壤外，ZnS 的溶解速度比 ZnO 慢，四年后仅达到添加 ZnS 的 26%至 75%。ZnS 在两种酸性土壤中的溶解速度比在近中性和石灰性土壤中慢。此外，这两种土壤中形成的 Zn 形态明显不同：在两种酸性土壤中，与羟基插层粘土矿物（HIM）和八面体配位的 Zn 吸附配合物结合的 Zn 占主导地位，而中性和石灰性土壤中的 Zn 形态则以 Zn-LDH 和四面体配位的内球 Zn 配合物为主。我们的结果表明，含锌污染物相的类型会对土壤中土壤成因锌物种的形成产生重大影响。重要因素包括污染物相从污染物中释放锌的速度以及污染物相对土壤性质和风化污染物颗粒周围局部化学条件的影响。
