温度对汞抑制土壤脲酶动力学影响研究

以不同施肥方式、不同有机质含量的草甸棕壤和黑土4个土样为对象,研究了不同温度条件下,汞(Hg)对土壤脲酶动力学特征的影响.结果表明,同一类型、有机质含量高的土壤脲酶活性、酶促最大反应速度(V_max)和V_max/K_m均高于有机质含量低的土壤,表明有机质对脲酶的吸附能力较强;黑土V_max和V_max/K_m值总体上大于草甸棕壤,但酶活性和米氏常数(K_m)值在不同土壤类型之间规律性较差,反映出酶活性由总酶量和酶-底物亲和力等因素共同决定;黑土K_m值大小与有机质含量相一致,而草甸棕壤则相反,表明有机质含量和施肥方式均会对K_m值产生影响;在最适温度以下,随温度升高,土壤的脲酶活性、V_max和V_max/K_m值均增加;Hg对土壤脲酶表现出典型的反竞争性抑制现象;Hg对脲酶活性的抑制作用及对K_m、V_max和V_max/K_m的负效应均随温度升高而有增加的趋势,揭示出土壤对脲酶的保护能力随温度升高而有所下降.

Effect of Temperature on Kinetic of Soil Urease Inhibited by Hg

Urease kinetics inhibited by Hg in two meadow burozem, fertilized by different ways and two phaeozem soils with different organic matter content was investigated at different temperatures. The results showed that the urease activity and kinetic parameter V_max and V_max/K_m were higher in soils with high organic matter content than that in soils with low organic matter among the same soil type. It indicated that organic matter had great adsorption capacity to urease. Soil urease V_max and V_max/K_m in phaeozem were generally higher than that in meadow burozem, but urease activity and K_m were not comparable among different soil types. K_m depended on not only the organic matter content of soils, but also fertilization ways. As incubating temperature increased, urease activity, V_max and V_max/K_m value enhanced under the optical catalysis temperature. Hg behaved as uncompetitive inhibitor to soil urease in this experiment. The negative effect that Hg inhibited urease activity, K_m, V_max and V_max/K_m increased with temperature increasing, indicated that the protective capacity of soil on urease decreased with the temperature increasing.