低质量分数Pb对冬小麦幼苗根微域土壤酶活性、微生物量C及土壤呼吸的影响

通过土壤盆栽试验,研究不同w(Pb)(0、50、120、180、230mg/kg)对冬小麦幼苗期根微域土壤酶活性、土壤微生物量C和土壤呼吸强度的影响。结果表明,在小麦幼苗期,Pb对土壤脱氢酶产生极显著(P<0.01)抑制作用,对脲酶、碱性磷酸酶和转化酶的抑制作用相对较弱,对多酚氧化酶的影响表现为激活-抑制-激活的作用,土壤酶活性对Pb的敏感程度为脱氢酶>脲酶>转化酶>多酚氧化酶>碱性磷酸酶;麦苗生长24d时,土壤微生物量C和土壤呼吸强度与未处理土壤相比有所增加,随后则降低,土壤代谢商与土壤微生物量C的变化趋势相反;土壤w(Pb)在低于国家"土壤环境质量标准"规定的Ⅱ类土壤环境基准值时仍会显著影响冬小麦幼苗根微域土壤生理生化功能。

Effects of Low Mass Fraction of Pb on Soil Enzyme Activities, Microbial Biomass C and Soil Respiration in Wheat Seedlings Rhizosphere

Effects of low doses of w(Pb)(< 350 mg/kg) on soil enzyme activities,microbial biomass C,and soil respiration in wheat seedlings rhizosphere were studied with the pot experiment.The result showed that the low w(Pb) concentration significantly inhabited the dehydrogenase activity,and the influence on urease,alkaline phosphatase,and invertase activities was insignificant.However,the effect on polyphenol oxidase activity showed the pattern of activation-inhabitation-activation.The order of the response of rhizosphere soil enzyme activities to low w(Pb) concentration was dehydrogenase > urease > invertase > polyphenol oxidase > alkaline phosphatase.The soil microbial biomass C and soil respiration increased significantly under the stress of w(Pb) at the first 24 days and then decreased.The response of soil respiration quotient to low doses of w(Pb) was opposite to that of soil microbial biomass C.The result indicated that the low dose of w(Pb)(<350 mg/kg) can obviously influence the soil biochemical characters in winter wheat seedling rhizosphere.