Lead J R, Hamilton-Taylor J, Davison W
Institute of Environmental and Natural Sciences, Lancaster University, UK.
Sci Total Environ. 1998 Jan 19;209(2-3):193-9.
Sequential extractions, according to a modified scheme proposed by Tessier et al. (Tessier A, Campbell PGC, Bisson M. Sequential extraction procedure for the speciation of trace metals. Anal Chem 1979;51:844-851), were performed on suspended particulate material (SPM) from the River Mersey, North-West England. The resulting solid-phase fractions were spiked with trace levels of Cd and Cu and their metal-binding properties were investigated as a function of pH. The results indicated that metal binding decreased as the material was successively extracted, i.e. the unextracted fraction bound the most metal, while the particles which had undergone all of the extractions bound the least metal. This effect was attributed to the loss of particle mass during the extractions and to the relative metal affinities of the newly exposed surfaces. The exposure of new potential binding sites was not an overriding influence on metal binding. The strongest binding of Cd appears to be to the nominal manganese oxyhydroxide phase, with no measurable binding of Cd by the residual mineral fraction. By contrast, the nominal iron and manganese oxyhydroxides, organic material and the residual mineral fraction all appear to affect Cu binding significantly. The effect of the extractions on the particles was also investigated by transmission electron microscopy. Micrographs indicated that the biological material in the sample had undergone significant alteration after treatment with the first and second extractants (acetate and hydroxylamine, respectively), i.e. before removal of the nominal organic fraction. These changes in biological material may affect metal binding, complicating the interpretation in terms of simple mineral and organic phases.
根据Tessier等人提出的改进方案（Tessier A, Campbell PGC, Bisson M. Sequential extraction procedure for the speciation of trace metals. Anal Chem 1979;51:844 - 851），对英格兰西北部默西河的悬浮颗粒物（SPM）进行了连续萃取。将痕量水平的镉和铜加入到所得的固相组分中，并研究了它们作为pH函数的金属结合特性。结果表明，随着物料的连续萃取，金属结合能力下降，即未萃取的组分结合的金属最多，而经过所有萃取的颗粒结合的金属最少。这种效应归因于萃取过程中颗粒质量的损失以及新暴露表面的相对金属亲和力。新潜在结合位点的暴露对金属结合不是主要影响因素。镉的最强结合似乎是与标称的羟基氧化锰相，而残余矿物组分对镉没有可测量的结合。相比之下，标称的铁和锰的羟基氧化物、有机物质和残余矿物组分似乎都对铜的结合有显著影响。还通过透射电子显微镜研究了萃取对颗粒的影响。显微照片表明，在用第一种和第二种萃取剂（分别为乙酸盐和羟胺）处理后，即去除标称有机组分之前，样品中的生物材料发生了显著变化。生物材料的这些变化可能会影响金属结合，使基于简单矿物和有机相的解释变得复杂。
