Department of Agricultural Chemistry, School of Agriculture, Meiji University, 1-1-1, Higashimita, Tama, Kawasaki, Kanagawa, 214-8571, Japan.
Department of Agricultural Chemistry, School of Agriculture, Meiji University, 1-1-1, Higashimita, Tama, Kawasaki, Kanagawa, 214-8571, Japan.
Chemosphere. 2020 Jun;249:126122. doi: 10.1016/j.chemosphere.2020.126122. Epub 2020 Feb 5.
Lead (Pb) complexed with dissolved organic matter (DOM-Pb) is a dominant Pb species in soils, but it is not clear that DOM-Pb is stably immobilized by hydroxyapatite. This study investigates how DOM-Pb is immobilized by hydroxyapatite in both aqueous solutions and soils. A sorption test showed that 69.5% of DOM-Pb is removed in an aqueous solution, but less DOM-Pb is retained by hydroxyapatite compared with Pb ions. On the basis of the ratio of Pb and dissolved organic carbon before and after the sorption test, 7% of Pb was retained as DOM-Pb by hydroxyapatite, but 93% of Pb was dissociated from DOM-Pb, and was sorbed as Pb ions. The concentrations of water-soluble Pb re-released were higher in the DOM-Pb solution than those in the Pb ion solution in sandy loam soil with hydroxyapatite. A column-leaching test that flowed the DOM-Pb solution showed that Pb concentrations in leached water from sandy loam soil gradually increased after the middle stage of the test despite the presence of hydroxyapatite. The amount of water-soluble Pb re-released from soils with and without the hydroxyapatite that flowed the DOM-Pb solution was the same as or greater than that without the hydroxyapatite that flowed the Pb ion solution. This study concludes that in soils with low Pb sorption ability, some of the Pb retained as DOM-Pb is water soluble and possibly re-released despite the presence of hydroxyapatite, although most Pb in DOM-Pb is stably sorbed as Pb ions.
铅（Pb）与溶解的有机物（DOM-Pb）结合是土壤中主要的 Pb 形态，但目前尚不清楚 DOM-Pb 是否被羟磷灰石稳定固定。本研究调查了 DOM-Pb 在水溶液和土壤中是如何被羟磷灰石固定的。吸附实验表明，在水溶液中 69.5%的 DOM-Pb 被去除，但与 Pb 离子相比，羟磷灰石对 DOM-Pb 的保留量较少。根据吸附实验前后 Pb 和溶解有机碳的比值，有 7%的 Pb 被羟磷灰石作为 DOM-Pb 保留，但 93%的 Pb 从 DOM-Pb 中解离出来，被吸附为 Pb 离子。在含有羟磷灰石的砂壤土中，DOM-Pb 溶液中水溶性 Pb 再释放的浓度高于 Pb 离子溶液。用 DOM-Pb 溶液进行的柱淋滤实验表明，尽管存在羟磷灰石，但在实验中期后，淋出水中的 Pb 浓度逐渐增加。用含有和不含有流过 DOM-Pb 溶液的羟磷灰石的土壤进行淋滤实验，从土壤中再释放的水溶性 Pb 的量与不含有流过 Pb 离子溶液的羟磷灰石的土壤相同或更大。本研究得出结论，在 Pb 吸附能力较低的土壤中，尽管存在羟磷灰石，部分被保留为 DOM-Pb 的 Pb 是水溶性的，可能会被重新释放，尽管 DOM-Pb 中的大部分 Pb 被稳定地吸附为 Pb 离子。
