College of Biological and Environmental Engineering, Zhejiang University of Technology, Hangzhou, China.
Environ Toxicol Chem. 2011 Dec;30(12):2682-7. doi: 10.1002/etc.672. Epub 2011 Oct 12.
A poor understanding of tributyltin (TBT) sorption on sediments has hindered an accurate evaluation of its environmental fate. The present study determined TBT sorption by a freshwater sediment (BH) and a coastal marine sediment (TZ) as influenced by pH, salinity, and biochar (BC) amendment into TZ. The isotherms were essentially linear, with K(OC) values in the range of 10(4) to 10(5) L/kg. Tributyltin sorption at pH 3.56 and 8.00 occurred mainly via partitioning. It reached maxima at pH equal to its pK(a) (=6.25) because of added ion exchange. A salinity increase from 5 to 35 practical salinity units enhanced TBT sorption at pH 3.56 and 8.00 on TZ by approximately 30% and on BH by approximately 80%, ascribed to the salting-out effect that reduced the solubilities of tributyltin hydroxide (TBTOH) and tributyltin chloride (TBTCl). At pH 6.25, the same salinity increase reduced TBT sorption on TZ by approximately 20% but enhanced TBT sorption on BH by approximately 35%. This was attributed to the enhancing role of salting out and the reducing role of metal competition for ion exchange. Tributyltin was two orders of magnitude more effectively sorbed by BC than by total organic carbon of TZ, mainly because of the high level of surface area of the BC. Although BC affinity for TBT may be significantly diminished when present in TZ, it was considered to be the primary contributor to TBT sorption from water. Biochar may thus be used to immobilize TBT in sediment for potential remediation.
对三丁基锡（TBT）在沉积物上吸附的认识不足，阻碍了对其环境归宿的准确评估。本研究测定了淡水沉积物（BH）和沿海海洋沉积物（TZ）对 TBT 的吸附，考察了 pH、盐度和向 TZ 添加生物炭（BC）对 TBT 吸附的影响。等温线基本呈线性，K（OC）值在 10（4）到 10（5）L/kg 范围内。在 pH 3.56 和 8.00 时，TBT 的吸附主要通过分配作用发生。由于加入了离子交换，当 pH 等于其 pK(a)（=6.25）时，TBT 的吸附达到最大值。盐度从 5 增加到 35 个实用盐度单位，在 pH 3.56 和 8.00 时，增加了 TZ 对 TBT 的吸附约 30%，增加了 BH 对 TBT 的吸附约 80%，这归因于盐析效应，降低了三丁基锡羟化物（TBTOH）和三丁基锡氯化物（TBTCl）的溶解度。在 pH 6.25 时，相同的盐度增加使 TZ 对 TBT 的吸附减少了约 20%，但增加了 BH 对 TBT 的吸附约 35%。这归因于盐析的增强作用和金属竞争离子交换的还原作用。BC 对 TBT 的吸附比 TZ 中的总有机碳有效两个数量级，主要是因为 BC 的表面积水平较高。尽管 BC 对 TBT 的亲和力在 TZ 中可能会显著降低，但它被认为是从水中吸附 TBT 的主要贡献者。因此，生物炭可用于固定沉积物中的 TBT，以进行潜在的修复。
