Department of Environmental Engineering, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, PR China.
Department of Environmental Engineering, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, PR China.
Environ Pollut. 2024 Jun 1;350:124005. doi: 10.1016/j.envpol.2024.124005. Epub 2024 Apr 20.
Simultaneously stabilizing of arsenic (As) and cadmium (Cd) in co-contaminated soil presents substantial challenges due to their contrasting chemical properties. Schwertmannite (Sch) is recognized as a potent adsorbent for As pollution, with alkali modification showing promising results in the simultaneous immobilization of both As and Cd. This study systematically investigated the long-term stabilization efficacy of alkali-modified Sch in Cd-As co-contaminated farmland soil over a 200-day flooding-drying period. The results revealed that As showed significant mobility in flooded conditions, whereas Cd exhibited increased soil availability under drying phases. The addition of Sch did not affect the trends in soil pH and Eh fluctuations; nonetheless, it led to an augmentation in the levels of amorphous iron oxides and SO concentration in soil pore water. At a dosage of 0.5% Sch, there was a notable decrease in the mobility and soil availability of As and Cd under both flooding (34.5% and 53.6% at Day 50) and drying conditions (27.0% and 29.4% at Day 130), primarily promoting the transformation of labile metal(loid) fraction into amorphous iron oxide-bound forms. Throughout the flooding-drying treatment period, Sch maintained stable mineral morphology and mineralogical phase, highlighting its long-term stabilization effect. The findings of this study emphasize the promising application of Sch-based soil remediation agents in mitigating the challenges arising from As-Cd co-contamination. Further research is warranted to explore their application in real farmland settings and their impact on the uptake of toxic metal(loid)s by plants.
由于砷（As）和镉（Cd）的化学性质相反，同时稳定受污染土壤中的砷和镉存在很大的挑战。水钠锰矿（Sch）被认为是一种有效的砷污染吸附剂，碱改性在同时固定砷和 Cd 方面显示出有前景的结果。本研究系统研究了碱改性 Sch 在 Cd-As 复合农田土壤中的长期稳定效果，在 200 天的淹水-干燥期内。结果表明，砷在淹水条件下表现出显著的移动性，而 Cd 在干燥阶段表现出增加的土壤可用性。Sch 的添加并没有影响土壤 pH 和 Eh 波动的趋势，但导致土壤中无定形氧化铁和 SO 浓度的增加。在 0.5%Sch 的剂量下，As 和 Cd 的流动性和土壤可用性在淹水（第 50 天为 34.5%和 53.6%）和干燥条件（第 130 天为 27.0%和 29.4%）下都有明显下降，主要促进了不稳定金属（类）形态向无定形氧化铁结合形态的转化。在整个淹水-干燥处理期间，Sch 保持稳定的矿物形态和矿物相，突出了其长期稳定的效果。本研究的结果强调了基于 Sch 的土壤修复剂在缓解 As-Cd 复合污染带来的挑战方面的应用前景。需要进一步研究以探索它们在实际农田环境中的应用及其对植物吸收有毒金属（类）的影响。
