中文摘要：

在35%的田间持水量下,通过模拟试验研究了外源二甲基砷酸盐（DMA）、一甲基砷酸盐（MMA）、五价无机砷[As（V）]在土壤中的形态转化.结果表明：外源砷进入土壤后,其含量均有随时间推延而逐渐下降的趋势,两种不同形态的有机砷DMA和MMA在土壤中主要发生脱甲基化过程,经150d的恒温恒湿培养,其在土壤中主要转化为As（V）,DMA处理仅在120d时检测到少量MMA,而MMA处理则在7～60d内均有少量的DMA生成.培养结束时土壤中DMA和MMA含量均显著降低（P〈0.01）,降幅分别为99.5%、94.3%,而两者的主要转化产物As（V）的含量则分别显著增加了4.61和5.15倍.表明外源有机态砷在土壤中基本上被转化为无机形态;与有机态外源砷相比,外源As（V）进入土壤后其形态基本上没有发生转化.

英文摘要：

An incubation test was conducted to study the transformation of exogenous dimethyl-arsenic acid （ DMA） ,monomethylarsenic acid （ MMA） ,and arsenate [As（ V） ]in soil under the condition of 35% of water-holding capacity. After added into soil,the concentrations of test arsenic forms all showed a decreasing trend with time. The DMA and MMA were mainly demethylated,and after 120 days incubation at constant temperature and humidity,transformed into As（ V） . A small amount of MMA was detected in the treatment with added DMA on the 120th day of incubation,and a small amount of DMA was detected in the treatment with added MMA during the period of 7-60 days incubation. By the end of the incubation test,the concentrations of added DMA and MMA in soil decreased significantly （ P 0. 01） ,with the decrement being 99. 5% and 94. 3% and the concentration of transformed As（ V） increased by 4. 61 and 5. 15 times,respectively. Comparing with DMA and MMA,the As（ V） after added into soil had less form transformation.