State Key Laboratory of Biogeology and Environmental Geology & School of Environmental Studies, China University of Geosciences, Wuhan, 430074, China; Hubei Key Laboratory of Mine Environmental Pollution Control and Remediation, School of Environmental Science and Engineering, Hubei Polytechnic University, Huangshi, 435003, China.
State Key Laboratory of Biogeology and Environmental Geology & School of Environmental Studies, China University of Geosciences, Wuhan, 430074, China.
Environ Pollut. 2022 Aug 1;306:119391. doi: 10.1016/j.envpol.2022.119391. Epub 2022 May 2.
Identifying the bioavailability and release-desorption mechanism of heavy metals (HMs) in soil is critical to understand the release risk of HMs. Simultaneously, the mechanistic investigation of affecting the bioavailability of HMs in soil is necessary, such as the grain-size distribution and soil mineralogy. Herein, the bioavailability of HMs (Cu, Cd, Ni, Pb, and Zn) in different area soils near a typical copper-smelter was evaluated by the sequential extraction technique (BCR), diffusive gradients in thin-films (DGT), and DGT-induced fluxes in sediments (DIFS) model. Results showed that the HMs proportion of the residual fraction in all soils was the highest. The average bioavailability concentration (C) of Cu and Cd in industrial soil was the highest, with 45.12 μg· L and 9.06 μg· L. The result of DIFS model revealed that the decreased order of the mean value of desorption rate constant (K) was Cd > Zn > Ni > Cu > Pb, 5.91 × 10, 4.96 × 10, 2.89 × 10, 9.64 × 10, and 8.69 × 10, respectively. According to the spatial distribution of release potential (R-value), the release potential of labile-Cu in agricultural soil was the highest, which was mainly attributed to fertilizer application in farmland. Simultaneously, the reduced hydroxyl was also related to the agricultural activities, resulting in the weakened adsorption capacity of HMs by soil. Redundancy analysis (RDA) results showed that the bioavailability of Cd, Ni, and Zn was mainly driven by soil pH, while the bioavailability of Cu and Pb was primarily driven by dissolved organic carbon (DOC). Meanwhile, carbonate minerals had a positive correlation with the bioavailability of Cd, Ni, and Zn, which could promote the release of HMs in mining soil as chemical weathering progresses. In conclusion, this study provides a structured method which can be used as a standard approach for similar scenarios to determine the geochemical fractionation, bioavailability, and release kinetics of heavy metals in soils.
确定土壤中重金属（HM）的生物可利用性和释放解吸机制对于理解 HM 的释放风险至关重要。同时，有必要研究影响土壤中 HM 生物可利用性的机制因素，如粒度分布和土壤矿物学。在此，采用连续提取技术（BCR）、薄膜扩散梯度技术（DGT）和沉积物扩散梯度诱导通量技术（DIFS）模型评估了典型铜冶炼厂附近不同区域土壤中 HM（Cu、Cd、Ni、Pb 和 Zn）的生物可利用性。结果表明，所有土壤中残渣态的 HM 比例最高。工业土壤中 Cu 和 Cd 的平均生物可利用性浓度（C）最高，分别为 45.12μg·L 和 9.06μg·L。DIFS 模型的结果表明，解吸速率常数（K）的平均值降低顺序为 Cd>Zn>Ni>Cu>Pb，分别为 5.91×10、4.96×10、2.89×10、9.64×10和 8.69×10。根据释放潜力（R 值）的空间分布，农田土壤中易释放的 Cu 的释放潜力最高，这主要归因于农田施肥。同时，还原羟基也与农业活动有关，导致土壤对 HM 的吸附能力减弱。冗余分析（RDA）结果表明，Cd、Ni 和 Zn 的生物可利用性主要受土壤 pH 值驱动，而 Cu 和 Pb 的生物可利用性主要受溶解有机碳（DOC）驱动。同时，碳酸盐矿物与 Cd、Ni 和 Zn 的生物可利用性呈正相关，随着化学风化的进行，可促进采矿土壤中 HM 的释放。总之，本研究提供了一种结构化的方法，可作为类似场景下确定土壤中重金属地球化学形态、生物可利用性和释放动力学的标准方法。
