Antoniadis Vasileios, McKinley John D, Zuhairi Wan Y W
Dep. of Agricultural Development, Democritus Univ. of Thrace, Pantazidou 193, GR-682 00, Orestiada, Greece.
J Environ Qual. 2007 Jan 9;36(1):53-60. doi: 10.2134/jeq2006.0134. Print 2007 Jan-Feb.
The distribution coefficient, Kd, is often used to quantify heavy metal mobility in soils. Batch sorption or column infiltration tests may be used to measure Kd. The latter are closer to natural soil conditions, but are difficult to conduct in clays. This difficulty can be overcome by using a laboratory centrifuge. An acceleration of 2600 gravities was applied to columns of London Clay, an Eocene clay sub-stratum, and Cu, Ni, and Zn mobility was measured in centrifuge infiltration tests, both as single elements and in dual competition. Single-element Kd values were also obtained from batch sorption tests, and the results from the two techniques were compared. It was found that Kd values obtained by batch tests vary considerably depending on the metal concentration, while infiltration tests provided a single Kd value for each metal. This was typically in the lower end of the range of the batch test Kd values. For both tests, the order of mobility was Ni>Zn>Cu. Metals became more mobile in competition than when in single-element systems: Ni Kd decreased 3.3 times and Zn Kd 3.4 times when they competed with Cu, while Cu decreased only 1.2 times when in competition with either Ni or Zn. Our study showed that competitive sorption between metals increases the mobility of those metals less strongly bound more than it increases the mobility of more strongly bound metals.
分配系数Kd通常用于量化土壤中重金属的迁移性。批量吸附或柱渗透试验可用于测量Kd。后者更接近自然土壤条件，但在粘土中难以进行。使用实验室离心机可以克服这一困难。对始新世粘土底层伦敦粘土柱施加2600重力加速度，并在离心机渗透试验中测量铜、镍和锌的迁移性，包括单一元素和二元竞争情况。还通过批量吸附试验获得了单一元素的Kd值，并对两种技术的结果进行了比较。结果发现，批量试验获得的Kd值根据金属浓度有很大差异，而渗透试验为每种金属提供了一个单一的Kd值。这通常处于批量试验Kd值范围的下限。对于两种试验，迁移性顺序均为镍>锌>铜。与单一元素体系相比，金属在竞争中迁移性更强：镍与铜竞争时Kd降低3.3倍，锌与铜竞争时Kd降低3.4倍，而铜与镍或锌竞争时仅降低1.2倍。我们的研究表明，金属之间的竞争性吸附对结合较弱金属迁移性的增加幅度大于对结合较强金属迁移性的增加幅度。
