2,4-D对土壤酶活性的影响

Impacts of 2,4-D on Soil Enzymatic Activity

2,4-D是人类最早使用的一种有机氯除草剂,其环境效应一直是人们关注的课题之一。通过室内模拟试验方法,研究了2,4-D对土壤酶活性的影响。结果发现,2,4-D可显著降低土壤脲酶的活性,起初酶活性有一个浓度迟缓期,活性变化较小,随后则表现出较强的抑制效应;3种模型拟合均达到了显著或极显著相关,揭示出土壤脲酶在一定程度上可表征2,4-D污染的程度,从侧面反映出其机理为完全抑制;得到土壤严重污染时2,4-D浓度为5.88～15.15mg·L-1。土壤转化酶效应无规律性变化,其对2,4-D反应较为迟钝。土壤碱性磷酸酶随农药浓度变化,先激活,后抑制,最后又激活;采用一元二次模型拟合,除4号土样外,其余均达到显著或极显著相关,表明磷酸酶活性与土壤污染状况有着密切的关系。土壤肥力水平对农药的生态毒理有重要的影响。

As organic chlorine herhicides, 2,4-D was used earlier on agriculture, therefore, it＇ s environmental influence has been receiving an important topic to be studied. By simulation, the present investigation studied the relationship between 2,4-D and enzymatic activity in a selected soil. The results showed as follows： 2,4-D remarkably decreased soil urease activity. Soil urease activity varied less at low 2,4-D concentrations, then was more severely inhibited as its contents increased. The three equations had significant or remarkable significant correlation between soil urease activity and 2,4-D concentration. It may be suggested that soil urease activity be an index of soil polluted by 2, 4-D, and their reaction mechanism was full inhibition. The critical concentrations was in a range of 5.88-15.15 mg·L^-1 when soil samples were severely polluted by 2,4-D. In addition, soil invertase activity had not a regular change, reflecting the enzyme was not sensitive to 2,4- D. It was also discovered that soil alkaline phosphatase activity was activated at lower concentrations, but inhibited at higher concentrations and activated at the highest concentrations. The regression equation was significant or remarkable significant correlation except No.4 sample, i.e. alkaline phosphatase activity had a closer relationship with soil fertility. Further, soil fertility exhibited more important effect on the ecological toxicity of pesticides.