School of Chemistry and Chemical Engineering, Shanghai University of Engineering Science, Shanghai 201620, China.
State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
Int J Environ Res Public Health. 2022 Aug 7;19(15):9721. doi: 10.3390/ijerph19159721.
The alkali digestion pretreatment method in the United States Environmental Protection Agency (USEPA) Method 3060A could underestimate the content of Cr(VI) in Cr-contaminated soils, especially for soils mixed with chromite ore processing residue (COPR), which leads to a misjudgment of the Cr(VI) level in soils after remediation, causing secondary pollution to the environment. In this study, a new pretreatment method to analyze Cr(VI) concentration in contaminated soils was established. The impacts of soil quality, particle size, alkali digestion time and the rounds of alkali digestion on Cr(VI) detection in contaminated soils was explored and the alkali digestion method was optimized. Compared with USEPA Method 3060A, the alkaline digestion time was prolonged to 6 h and multiple alkali digestion was employed until the amount of Cr(VI) in the last extraction was less than 10% of the total amount of Cr(VI). Because Cr(VI) in COPR is usually embedded in the mineral phase structure, the hydration products were dissolved and Cr(VI) was released gradually during the alkaline digestion process. The amount of Cr(VI) detected showed high correlation coefficients with the percentage of F1 (mild acid-soluble fraction), F2 (reducible fraction) and F4 (residual fraction). The Cr(VI) contents detected by the new alkaline digestion method and USEPA Method 3060A showed significant differences for soil samples mixed with COPR due to their high percentage of residual fraction. This new pretreatment method could quantify more than 90% of Cr(VI) in Cr-contaminated soils, especially those mixed with COPR, which proved to be a promising method for Cr(VI) analysis in soils, before and after remediation.
美国环保署（USEPA）方法 3060A 中的碱消解预处理方法可能会低估铬污染土壤中 Cr(VI)的含量，特别是对于混合有铬铁矿加工残渣（COPR）的土壤，这会导致对修复后土壤中 Cr(VI)水平的错误判断，从而对环境造成二次污染。在本研究中，建立了一种新的预处理方法来分析污染土壤中 Cr(VI)的浓度。探讨了土壤质量、粒径、碱消解时间和碱消解轮数对污染土壤中 Cr(VI)检测的影响，并对碱消解方法进行了优化。与 USEPA 方法 3060A 相比，将碱消解时间延长至 6 小时，并进行多次碱消解，直到最后一次提取的 Cr(VI)量小于总 Cr(VI)量的 10%。由于 COPR 中的 Cr(VI)通常嵌入在矿物相结构中，在碱消解过程中，水合产物被溶解，Cr(VI)逐渐释放。检测到的 Cr(VI)量与 F1（弱酸可溶部分）、F2（可还原部分）和 F4（残留部分）的百分比具有很高的相关性。由于 F4（残留部分）的百分比很高，新的碱消解方法和 USEPA 方法 3060A 检测到的混合有 COPR 的土壤样品的 Cr(VI)含量存在显著差异。由于新的预处理方法可以定量检测超过 90%的 Cr(VI)在铬污染土壤中，特别是那些混合有 COPR 的土壤，因此它被证明是一种有前途的土壤修复前后 Cr(VI)分析方法。
