铜对土壤脲酶活性特征的影响

铜是土壤中的"双重元素",为了从土壤酶角度探讨其生态毒理,采用模拟方法较为系统地研究了铜对土壤脲酶活性及酶促反应参数的影响。结果表明,(1)土壤肥力水平越高,脲酶活性越大,铜的加入导致土壤脲酶活性降低越大,除5号土样外,铜的质量浓度与土壤脲酶活性达显著或极显著负相关,表明土壤脲酶活性可作为土壤铜污染程度的监测指标之一;供试土壤铜轻微和严重污染时,铜质量浓度分别为94.00~151.75和470.40~759.28mg/kg;尿素浓度对土壤生态剂量值影响不大,生态剂量总体呈现土娄土大于红壤。(2)除4号土样外,土壤脲酶最大反应速度(Vmax)、最大反应速度/米氏常数(Vmax/Km)和反应速度常数(k)值,随铜质量浓度的增加呈显著或极显著降低,Km值则略有增加,说明铜对土壤脲酶的作用机理为混合型抑制,其中包含微弱的竞争性抑制,但以非竞争性抑制为主。可见,土壤脲酶及其参数在一定程度可表示土壤铜的污染程度。

Soil urease activity affected by copper

Copper is a double element in the soil.In order to investigate the copper eco-toxicity by means of soil enzyme,the relationship between soil urease and copper is systematically studied by using simulative method.The results showed that soil urease activity was increased with the improvement of soil fertility.But the urease activity was remarkably reduced by the introduction of copper into soil,and the relationship between them was up to the significant negative correlation level so that soil urease activity could be used as a testing index of soil polluted by copper.Calculated copper ecological dose ED10 and ED50 values,which could be used as different polluted levels,were 94.00-151.75 and 470.40-759.28 mg/kg in soils tested.Urea concentration showed little effect on ecological dose.The kinetic parameters such as Vmax,Vmax/Km and k were reduced with the increase of copper concentration,and their relationship was up to the significant negative correlation levels,except the increased Km value.It was proved that the copper reaction mechanism was a mixed inhibition,including both competitive and non-competitive effect,while the non-competitive mechanism was more important.Our results demonstrated that soil urease could be used as an indicator for soil copper pollution.