CNRS-UMR 6118, Géosciences Rennes, University of Rennes 1, Avenue du Général Leclerc, 35042 Rennes Cedex, France.
J Colloid Interface Sci. 2009 Nov 15;339(2):390-403. doi: 10.1016/j.jcis.2009.07.046. Epub 2009 Jul 25.
Colloidal dissolved organic carbon (DOC) is an important carrier phase for trace elements (TE) in subsurface environments. As suggested by previously published field observations, preferential sorption of DOC onto mineral surfaces tends to enrich the solid phase in humic acids. This DOC fractionation may affect the mobility of TE. pH is known to play an important role in the stability of colloids. This study was therefore dedicated to identifying the influence of DOC fractionation on TE mobility. Sequential extraction has been used to provide information on the possible TE carriers within soil (as exchangeable, weak acid soluble, reducible, oxidizable, and nonextractible metal fractions). Batch experiments were carried out to investigate the influence of pH on the detachment of colloids and associated TE. Different groups of elements were identified according to TE behavior during pH changes. Several elements displayed increasing concentrations with decreasing pH. These concentrations can represent an important fraction of the total soil concentration. By contrast, other elements showed increasing concentrations following increasing pH, in association with an increasing amount of colloids in soil solution. Concerning this latter group, two colloidal carrier phases were identified during the pH increase: (i) the first one concerned the majority of elements, which were associated with humic substances remaining in solution, and (ii) the second one involved several TE rather associated with nanooxides. Therefore, DOC fractionation plays a key role in the TE concentration in soil solution during pH changes.
胶体溶解有机碳（DOC）是地下环境中微量元素（TE）的重要载体相。先前的野外观察表明，DOC 优先吸附到矿物表面往往会使固相富里酸化。这种 DOC 分馏可能会影响 TE 的迁移性。pH 值在胶体稳定性中起着重要作用。因此，本研究旨在确定 DOC 分馏对 TE 迁移性的影响。连续提取已被用于提供土壤中可能的 TE 载体信息（如可交换的、弱酸可溶的、可还原的、可氧化的和不可提取的金属部分）。批实验用于研究 pH 值对胶体和相关 TE 脱附的影响。根据 pH 变化过程中 TE 的行为，确定了不同的元素组。一些元素的浓度随 pH 值降低而增加。这些浓度可以代表土壤总浓度的一个重要部分。相比之下，其他元素的浓度随 pH 值升高而增加，与土壤溶液中胶体数量的增加有关。对于后者组，在 pH 值升高期间鉴定出两种胶体载体相：（i）第一种涉及与仍留在溶液中的腐殖物质相关的大多数元素，和（ii）第二种涉及与纳米氧化物相关的几种 TE。因此，DOC 分馏在 pH 值变化过程中对土壤溶液中 TE 浓度起着关键作用。
