Mufalo Walubita, Arima Takahiko, Igarashi Toshifumi, Ito Mayumi, Sato Tsutomu, Tomiyama Shingo, Nyambe Imasiku, Silwamba Marthias, Nakata Hokuto, Nakayama Shouta, Ishizuka Mayumi
Division of Sustainable Resources Engineering, Faculty of Engineering, Hokkaido University, Sapporo, 060-8628, Japan.
Department of Materials Chemistry, National Institute of Technology, Asahikawa College, Asahikawa, 071-8142, Japan.
Environ Geochem Health. 2025 Jun 16;47(7):271. doi: 10.1007/s10653-025-02581-y.
Stabilizing toxic elements in mine wastes is a practical strategy for countermeasures against improper disposal. Kabwe, Zambia, one of Africa's most lead (Pb)-polluted cities, faces severe contamination from historic zinc plant residues (ZPRs). This study validates the chemical stabilization of Pb and zinc (Zn) in ZPRs using half-burnt dolomite (HbD) in four embankments, two of which were treated with 10% HbD. The embankments were constructed with/without covering soil and a bottom adsorption layer containing soil with HbD (pilot-scale experiments). Five years after construction, batch experiments were conducted to evaluate the leaching behavior of Pb, Zn, and other coexisting ions from the embankments. Mechanisms of stabilization were investigated via surface binding characterization, mineralogical/elemental analysis, sequential extraction, and thermodynamic modeling of the leachates. The ZPRs were mainly composed of anglesite (PbSO₄), gypsum (CaSO₄·2H₂O) and quartz (SiO₂), with elevated Pb and Zn contents ranging from 55,700 to 73,800 mg/kg and 16,500 to 25,300 mg/kg, respectively. Untreated-ZPRs indicated that Zn leaching was driven by the dissolution of soluble Zn-sulfates in mildly acidic conditions, whereas Pb remained immobile due to its association as PbSO₄. In ZPRs-HbD-treated, stabilization of Pb and Zn was facilitated by the decrease in their exchangeable phases and enhanced incorporation into stable carbonate phases, along with binding with Fe-oxyhydroxides, confirmed by X-ray photoelectron spectroscopy. Pilot-scale experiments demonstrated that the bottom soil adsorption layer could effectively sequester leached Pb and Zn from untreated-ZPRs by stabilizing them in the soil matrix-carbonate and Fe-oxyhydroxide phases. Furthermore, the results suggest that a soil cover could form a protective barrier for oral ingestion-induced bioaccessible Pb and Zn in the stabilized residues. Given the extent of legacy pollution in Kabwe, this stabilization technique coupled with a soil cover presents a promising solution for ZPRs contamination from legacy mines.
稳定矿山废弃物中的有毒元素是应对不当处置的一项切实可行的策略。赞比亚的卡布韦是非洲铅污染最严重的城市之一，面临着历史悠久的锌厂残渣（ZPRs）带来的严重污染。本研究在四个堤坝中使用半煅烧白云石（HbD）验证了ZPRs中铅（Pb）和锌（Zn）的化学稳定化，其中两个堤坝用10%的HbD进行了处理。堤坝的建造有无覆盖土壤以及底部吸附层，底部吸附层包含含有HbD的土壤（中试规模实验）。建造五年后，进行了批次实验以评估堤坝中Pb、Zn和其他共存离子的浸出行为。通过表面结合表征、矿物学/元素分析、顺序提取以及渗滤液的热力学建模研究了稳定化机制。ZPRs主要由铅矾（PbSO₄）、石膏（CaSO₄·2H₂O）和石英（SiO₂）组成，Pb和Zn含量升高，分别为55700至73800毫克/千克和16500至25300毫克/千克。未处理的ZPRs表明，在弱酸性条件下，Zn的浸出是由可溶性硫酸锌的溶解驱动的，而Pb由于以PbSO₄形式存在而保持不移动。在ZPRs-HbD处理中，Pb和Zn的稳定化通过其可交换相的减少以及增强纳入稳定的碳酸盐相而得到促进，同时与铁羟基氧化物结合，这通过X射线光电子能谱得到证实。中试规模实验表明，底部土壤吸附层可以通过将未处理ZPRs中浸出的Pb和Zn稳定在土壤基质 - 碳酸盐和铁羟基氧化物相中，有效地隔离它们。此外，结果表明土壤覆盖层可以为稳定化残渣中因经口摄入而具有生物可利用性的Pb和Zn形成保护屏障。鉴于卡布韦遗留污染的程度，这种稳定化技术与土壤覆盖层相结合为遗留矿山的ZPRs污染提供了一个有前景的解决方案。
