In this study, we examined the influence of dissolved organic matter (humic and fulvic acids) on arsenic (As) mobilization from two Class F coal fly ashes under oxic and anoxic conditions. Batch leaching experiments were conducted to examine As leaching behavior and changes in As aqueous and solid phase speciation after exposure to humic and fulvic acids for up to 4 weeks (ash/buffer ratio = 0.01 g/mL). Under oxic conditions, mobilized As concentrations increased compared to the organic-free controls and were positively correlated with percent aliphatic carbon and oxygen/carbon ratio of the humic and fulvic acids, suggesting both non-specific hydrophobic association of the organic matter with the surface of the fly ash particles and competitive desorption between negatively charged organic functional groups and As anions adsorbed to mineral surfaces. Under anoxic conditions, organic matter enhanced the reductive dissolution of As-bearing iron oxides such as hematite, resulting in increased As mobilization. X-ray absorption spectroscopy indicated that the majority of As in the leached and unleached fly ash was As(V) (≥90%), with As(V)-ferrihydrite precipitation occurring under all leaching conditions tested. Our results demonstrated that humic and fulvic acids are capable of mobilizing As from fly ash under both oxic and anoxic conditions, though redox appeared to be a larger driver of As mobilization compared to dissolved organic matter (DOM). DOM is a parameter which should be considered in risk assessment strategies for fly ash that is exposed to water (e.g., subsurface infiltration) or released to aquatic systems.

在这项研究中，我们研究了在有氧和无氧条件下，两种F类粉煤灰中溶解的有机物（腐殖酸和黄腐酸）对砷（As）迁移的影响。进行分批浸出实验以检查暴露于腐殖酸和黄腐酸达4周（灰分/缓冲液比= 0.01 g / mL）后As的浸出行为以及As水和固相形态的变化。在有氧条件下，与不含有机物的对照相比，动员的As浓度增加，并且与腐殖酸和富里酸的脂肪族碳百分比以及氧/碳比呈正相关，这表明有机物与粉煤灰颗粒表面的非特异性疏水缔合以及带负电的有机官能团和吸附在矿物表面的As阴离子之间的竞争性解吸。在缺氧条件下，有机物增强了含砷铁氧化物（如赤铁矿）的还原溶解，从而增加了As的迁移。X射线吸收光谱表明，浸出和未浸出的粉煤灰中的大部分As为As（V）（≥90％），并且在所有测试的浸出条件下均发生As（V）-水铁矿沉淀。我们的结果表明，腐殖酸和富里酸能够在有氧和无氧条件下从粉煤灰中迁移出As，尽管与溶解有机物（DOM）相比，氧化还原似乎是As迁移的更大驱动力。