砷在水环境中的形态转化受到许多物理化学因素的制约,并产生毒害程度不同的环境效应.对多种因素进行研究,寻找将高毒的As(Ⅲ)向低毒的As(Ⅴ)转化的有利条件,并控制As(Ⅴ)向As(Ⅲ)的转化.结果表明,自然敞口放置3d的As(Ⅲ)溶液中没有As(Ⅴ)的出现,As(Ⅲ)向As(Ⅴ)的转化是一个缓慢的过程.锰矿、粉煤灰等天然矿物能氧化As(Ⅲ),从而降低毒性.酸性或碱性条件都有利于As(Ⅲ)向As(Ⅴ)的转化,转化率超过90％.温度、可见光、超声波等外界条件对砷形态转化有一定影响.紫外光照射3d后的As(Ⅲ)完全转化成As(Ⅴ),且As(Ⅴ)没有向As(Ⅲ)转化,因此紫外光是降低砷毒性的有利条件.Fe2+能将As(Ⅴ)还原,升高水体砷的毒性；而Fe3+能将As(Ⅲ)氧化,并生成氢氧化物将砷吸附.%Transformation of arsenic species in aquatic environment is controlled by many physical-chemical factors, and it can results in different toxic effects to environment. This paper studied many factors which affect arsenic species transformation, and discussed the method to decrease toxicity, such as found the conditions beneficial for the transformation from high-toxic As( Ⅲ ) to low-toxic As( V ) and control the conversion from As( V ) to As( Ⅲ ). The results showed that there was no As( V ) found in As( Ⅲ ) solution after 3 d of placement, indicated that the transformation of As( Ⅲ ) to As( V ) was very slow under the natural condition. Manganese ore and fly ash were both beneficial to transformation of As( Ⅲ ) to As( V ). The conversion rate of As( Ⅲ ) to As( V ) was above 90% both in the a-cidic and alkaline condition. Temperature, visible light and ultrasonic all had little effect on the arsenic species transformation. UV-light made As( Ⅲ ) completely transformed into As( V ) after 3 d of illumination, and the conversion was nonreversible. Fe2+ in water body could restore As( V ), and increased the arsenic toxicity. But Fe3+ could oxidize As(Ⅲ) and adsorbed arsenic, then decreased the arsenic toxicity.
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