FeSO4对铬污染土的稳定特性及风险评价试验研究

采用硫酸亚铁（FeSO4）对铬污染土进行稳定化处理。选用浸出试验、Cr(VI)残留值试验和形态提取试验，研究了粒径和有机质对铬污染土稳定特性的影响规律。试验结果表明，粒径和有机质对铬污染土稳定特性有较大影响。粒径的减小可显著降低稳定土中Cr(VI)和总Cr的浸出浓度及稳定土中Cr(VI)的含量；当污染土粒径小于2 mm时，Fe(II)/Cr(VI)摩尔比为3，稳定土中Cr(VI)和总Cr的浸出浓度分别为4.68、8.9 mg/L，均低于我国《危险废弃物鉴别标准 浸出毒性鉴别》（GB/T5085.3－2007）的限值。有机质添加量的增加可明显降低稳定土中Cr(VI)和总Cr的浸出浓度及Cr(VI)的含量。当Fe(II)/Cr(VI)摩尔比为3时，有机质的添加量为5%，稳定土中Cr(VI)的含量为28.3 mg/kg，低于我国《土壤环境质量标准》（GB15618－2008）中工业和商业用地限值（30 mg/kg）；当有机质的添加量为10%时，稳定土中Cr(VI)的含量为4.8 mg/kg，低于居住用地限值（5 mg/kg）。形态提取试验结果表明：粒径的减小可降低弱酸提取态的铬含量，增加可还原态的铬含量，而对可氧化态和残渣态的铬含量影响不大；有机质可促使弱酸提取态、可还原态的铬转化为可氧化态的铬，而残渣态的铬变化不大。稳定土中铬从活性态向较稳定态转化，是铬稳定土稳定特性和环境风险变化的根本原因。

Stabilization characteristics and risk assessment of hexavalent chromium-contaminated soils by ferrous sulfate treatment

Ferrous sulfate (FeSO4) was used to stabilize chromium-contaminated soils. Leaching test, alkaline digestion test and sequential extraction test were conducted to investigate the effects of particle size and organic dosage on the stability properties and risk assessment of FeSO4-treated chromium-contaminated soils, respectively. Results showed that the leaching concentration (hexavalent chromium and total chromium) and hexavalent chromium content decreased significantly with the decrease of particle size, but decreased with the increase of organic dosage. When Fe(II)/Cr(VI) molar ratio was three, the Cr(VI) and total Cr leaching concentrations were about 4.68 mg/L and 8.9 mg/L, respectively, which were lower than the Identification standards for hazardous wastes: identification for extraction toxicity (GB/T5085.3－2007) of China. Furthermore, when Fe(Ⅱ)/Cr(VI) molar ratio was three and organic dosage was 5%, the amount of Cr(VI) in the soil was 28.3 mg/kg, lower than the threshold allowed by Environmental quality standards for soils (GB15618－2008) for industrial and commercial reuse of China (Cr(VI)<30 mg/kg). However, the residential land reuse (Cr(VI)<5 mg/kg) was only achieved by adding the organic dosage of 10%. Sequential extraction test showed that with the decrease of particle size, the weak acid-soluble fraction of Cr content decreased, the Cr content in the reducible state increased, while the Cr content in the oxidisable state was slightly affected. In addition, organic matter transformed Cr from weak acid-soluble fraction and reducible fraction to oxidisable fraction. The changing in the stability properties and risk assessment of stabilized soil can be attributed to the change of chromium speciation.