Abstract: In order to investigate the effects of organic arsenic on alfalfa seed germination,arsenic accumulation and the passivation and restoration effect of bentonite on organic arsenic pollution,clean soil samples were used as control in the present experiment,two levels of arsenic exposure were set up and different levels of sodium bentonite and calcium bentonite were added to the arsenic exposure group. The results indicated that the germination rate of alfalfa seeds was significantly reduced by exposure to 150 mg·kg^-1 arsanilic acid (P<0.05). The germination index,vigor index,root length and bud length of alfalfa seeds were significantly decreased by exposure to 75 mg·kg^-1 and 150 mg·kg^-1 arsanilic acid (P<0.05),and the accumulation of arsenic in roots and shoots were significantly promoted (P<0.05). Adding bentonite could significantly promote alfalfa seed germination index,vigor index,root length and bud length (P<0.05),meanwhile reduce arsenic accumulation in roots and shoots (P<0.05). Arsenic accumulation in alfalfa tended to be stable when the addition level of bentonite was 1.0%. Sodium-based bentonite was better than calcium-based bentonite in arsenic pollution remediation. In conclusion,when the exposure level of organic arsenic was above 75 mg·kg^-1,the germination of alfalfa seeds was significantly inhibited. In the meanwhile,bentonite could reduce the migration of arsenic from soil to alfalfa and its biological toxicity.

Key words: Arsenic stress, Bentonite, Alfalfa, Seed germination, Arsenic accumulation

摘要： 为探讨有机砷对紫花苜蓿（Medicago sativa）种子萌发、砷积累的影响及膨润土的钝化修复作用，试验以洁净土样为对照，设置两个砷暴露水平，并在砷暴露组添加不同水平的钠基膨润土和钙基膨润土。结果表明，与对照组相比，150 mg·kg^-1阿散酸暴露显著降低紫花苜蓿种子发芽率（P<0.05），75 mg·kg^-1和150 mg·kg^-1阿散酸暴露显著降低紫花苜蓿种子发芽指数、活力指数、根长和芽长（P<0.05），同时，显著促进了砷在根部和地上部的积累（P<0.05）。添加膨润土能够显著促进紫花苜蓿种子发芽指数、活力指数、根长和芽长（P<0.05），降低根部和地上部砷积累量（P<0.05），以添加量1.0%时紫花苜蓿砷积累量趋于稳定；钠基膨润土对砷污染的修复效果好于钙基膨润土。总之，有机砷暴露水平75mg·kg^-1以上时对紫花苜蓿种子萌发有显著抑制作用，膨润土能够减少土壤砷向紫花苜蓿的迁移，降低其生物毒性。

关键词: 砷胁迫, 膨润土, 紫花苜蓿, 种子萌发, 砷积累