Thermal transformation is an effective remediation measure to stabilize soil Pb and other heavy metals via transformation into less soluble compounds. This study aimed to determine the solubility of Pb in soils subjected to heating at a range of temperatures (100–900 °C) in relation to the changes in Pb speciation using XAFS spectroscopy. Lead solubility in the contaminated soils after thermal treatment corresponded well to the chemical species of Pb present. As the temperature was increased to 300 °C, cerussite and Pb associated with humus started to decompose in the soils. As the temperature was further increased to 900 °C, the amount of water and HCl extractable Pb decreased significantly from the soils, whereas Pb-bearing feldspar started to occur, accounting for nearly 70% of the soil Pb. During thermal treatment, Pb species in the soils were little affected by Fe oxides that showed a significant phase transformation into hematite. Our study proposes the following underlying mechanisms for Pb immobilization in thermally treated soils: i) thermally labile Pb species such as PbCO₃ and Pb associated with humus start to decompose at temperatures around 300 °C, ii) aluminosilicates with crystalline and poorly ordered structures undergo thermal decomposition at temperatures around 400 °C, iii) liberating Pb in the soil is then associated with a Si and Al rich liquid derived from thermally decomposed aluminosilicates at higher temperatures, and iv) the formation of Pb-feldspar like minerals is enhanced at 900 °C.

热转化是一种有效的修复措施，通过转化为难溶性化合物来稳定土壤中的铅和其他重金属。本研究旨在利用 XAFS 光谱法确定在一定温度范围 (100–900 °C) 下加热的土壤中 Pb 的溶解度与 Pb 形态变化的关系。热处理后污染土壤中铅的溶解度与存在的铅的化学形态非常一致。当温度升至 300 °C 时，与腐殖质相关的白铅矿和铅开始在土壤中分解。当温度进一步升高到900℃时，土壤中水和HCl可萃取Pb的量显着减少，而含铅长石开始出现，占土壤Pb的近70%。在热处理过程中，土壤中的铅形态几乎不受铁氧化物的影响，铁氧化物表现出显着的相转变为赤铁矿。我们的研究提出了热处理土壤中 Pb 固定的以下基本机制： i) 热不稳定 Pb 物质，例如 PbCO₃和与腐殖质相关的 Pb 在 300 °C 左右的温度下开始分解，ii) 具有结晶和不良有序结构的铝硅酸盐在 400 °C 左右的温度下经历热分解，iii) 释放土壤中的 Pb 然后与 Si 和 Al 结合iv) 在 900 °C 下，类铅长石矿物的形成增强。