• 关键词：水分  砷  土壤碱性磷酸酶  动力学参数  水稻土

• 基金项目：国家自然科学基金(No.41571245);西北农林科技大学基本科研业务费科研创新重点项目(No.ZD2013012);国家高技术研究发展计划项目(No.2012AA101402)

• 谢伟
• 1. 西北农林科技大学资源环境学院, 杨凌 712100;2. 农业部西北植物营养与农业环境重点实验室, 杨凌 712100

• 和文祥
• 1. 西北农林科技大学资源环境学院, 杨凌 712100;2. 农业部西北植物营养与农业环境重点实验室, 杨凌 712100

• 王紫泉
• 西北农林科技大学资源环境学院, 杨凌 712100

• 谭向平
• 西北农林科技大学资源环境学院, 杨凌 712100

• 卢冠男
• 西北农林科技大学资源环境学院, 杨凌 712100

• 杜威
• 西北农林科技大学资源环境学院, 杨凌 712100

• 韦革宏
• 西北农林科技大学生命学院, 杨凌 712100

• 摘要：为研究水分条件对砷抑制土壤碱性磷酸酶动力学特征的影响,本文采用室内模拟培养试验方法,以江苏水稻土为供试土壤,在35%、65%、110%最大持水量(WHC)下,利用酶动力学手段较为系统地分析了砷污染下水分对土壤碱性磷酸酶动力学参数及机理的影响.结果表明:碱性磷酸酶动力学参数K_m随砷浓度增加而增大,V_max(110%WHC)、V_max/K_m、k则相应降低,表明砷污染从本质上抑制了酶促反应的进行.K_m、V_max、V_max/K_m、k、K_i随水分含量增加而减小,表明水分含量升高虽增加了酶-底物亲和力,但最终减缓了酶促反应的发生.Y=A/(1+B×C)模型较好拟合了动力学参数V_max/K_m(Y)与土壤砷浓度(C)的关系,表明V_max/K_m在一定程度上可表征不同水分下土壤砷污染程度,并计算获得水稻土砷轻度污染临界值为20.45 mg·kg^-1,此值与国家土壤质量标准中的二级污染标准较为接近.干燥(35%WHC)和湿润(65%WHC)下砷抑制碱性磷酸酶活性机理为完全竞争性抑制,淹水(110%WHC)下则为以完全非竞争性抑制为主的线性混合抑制作用.研究表明,各个酶动力学参数可分别从不同角度揭示砷抑制碱性磷酸酶活性机理上的差异,水分主要通过影响K_m、V_max而改变抑制机理.

• Abstract：Soil moisture affects the kinetic characteristics of alkaline phosphatase inhibition in the presence of arsenic. A simulation experiment was carried out to investigate the effects of soil moisture on the kinetic characteristics of alkaline phosphatase inhibited by arsenic at three soil moisture levels:35%, 65% and 110% of the maximum water holding capacity (WHC). The results showed that the kinetic parameter K_m increased with the increase of arsenic concentration in soils, while V_max (110%WHC)、V_max/K_m、kdecreased, indicating that arsenic essentially inhibited the enzymatic reaction. K_m、V_max、V_max/K_m、kdecreased with the increase of soil moisture, showing that higher water content increased enzyme and substrate affinity, but slowed down the enzymatic reaction. The model Y=A/(1+B×C) described the relationship between kinetic parameter V_max/K_m (Y)and arsenic concentration (C) very well, indicating that V_max/K_m could be a good bio-indicator for arsenic pollution in soils at different soil moisture conditions. The calculated ecological dose 10% (ED₁₀) of paddy soil was 20.45 mg·kg^-1, which was close to the national standard (25 mg·kg^-1). There was a complete-competitive inhibition mechanism of arsenic on soil alkaline phosphatase under drought (35%WHC) and moist (65%WHC) conditions, while the mechanism was completely non-competitive inhibition combined with linear mixed inhibition under flooding condition (110%WHC). This study showed that kinetic parameters revealed the differences of mechanism of arsenic on alkaline phosphatase. Soil moisture mainly affected the kinetic parameters (K_m and V_max), thereby changing the inhibition mechanism of arsenic on soil enzyme.

• Key words：soil moisture  arsenic  soil alkaline phosphatase  kinetic parameter  paddy soil

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