有机酸对As(Ⅴ)在土壤中老化的影响

为了明确不同类型有机酸对土壤中砷释放及迁移转化等行为的影响,应用模拟试验方法,研究了添加乙酸、草酸、柠檬酸和腐植酸对砷在第四纪红壤中老化的影响。研究结果表明,在温度为25℃、湿度为最大田间持水量70%条件下,有机酸类型对砷在第四纪红壤中老化过程的影响不显著,但有机酸添加量对培养期间土壤有效态和结合态砷的含量具有显著影响。当乙酸的添加量为50、100 mg·kg~(-1)时,对As(Ⅴ)在土壤中的老化均有抑制作用;添加量达到200 mg·kg~(-1)时,对As(Ⅴ)的老化具有促进作用。而草酸和柠檬酸的添加量为50 mg·kg~(-1)时,对As(Ⅴ)的老化具有促进作用;添加量为100、200 mg·kg~(-1)时均抑制As(Ⅴ)的老化。腐植酸对外源砷在土壤中的老化具有抑制作用,且其对砷老化的影响远大于其他类型有机酸。当添加量在50~200 mg·kg~(-1)时,乙酸和草酸对土壤中专性吸附态砷含量有显著影响;添加量为50、100 mg·kg~(-1)时,柠檬酸和腐植酸对弱结晶水合铁铝氧化物结合态砷均有显著影响;添加量为200 mg·kg~(-1)时,乙酸、柠檬酸和腐植酸对结晶水合铁铝氧化物态砷影响显著。综上,在本试验条件下,As(Ⅴ)在第四纪红壤上老化不受有机酸类型的影响,而受有机酸添加量的影响。

Influence of organic acids on As(V)aging in soils

Incubation experiments were conducted to study the influence of different organic acids(acetic acid, oxalic acid, citric acid, and humic acid)on the aging process of arsenic(As aging)in quaternary red clay. The results indicated that the influence was not significant at 25℃and at the maximum field moisture capacity of 70%, while the organic acid amounts significantly affected available As and combined As in soils. Acetic acid added at 50 and 100 mg·kg-1 inhibited As aging in soils, while acetic acid added at 200 mg·kg-1 promoted As aging. However, oxalic acid and citric acid added at 50 mg·kg-1 promoted As aging and the inhibition was observed at 100 and 200 mg·kg-1. Ar-senic aging in soils was significantly inhibited after adding humic acid and comparatively, less significant effects were detected with other organic acids. Acetic acid and oxalic acid addition at 50~200 mg·kg-1 significantly decreased the specifically sorbed As. Citric acid and hu-mic acid added at 50~100 mg·kg-1 significantly increased the amorphous and poorly-crystalline hydrous Fe/Al oxides associated with As. Acetic acid, citric acid, and humic acid addition at 200 mg·kg-1 significantly increased the well-crystalline hydrous Fe/Al oxides associated with As. These observations will not only provide an understanding of the effects of different types of organic acids on the release, migration, and transformation of As in soil, but also will be the reference for the regulation and safe use of As-contaminated soils.