中文摘要：

采用室内模拟方法较为系统地研究了六价水溶态铬和总铬对土壤脲酶活性的影响。结果表明，六价铬进入土壤后，水溶态含量迅速降低，降幅随培养时间延长而减缓；水溶态铬含量与外源总铬的变化呈极显著正相关；六价铬抑制土壤脲酶活性，且脲酶活性与六价水溶态铬达到极显著负相关，揭示脲酶活性可作为土壤铬污染程度的指标之一；从土壤脲酶角度获得的红壤轻度和中度污染时临界浓度，土壤总铬和水溶态铬含量分别为17．07、85．37mg·kg-1和0．78、3．88mg·kg-1；随土壤肥力降低，土壤脲酶的ED10和ED50递减。

英文摘要：

Chromium is one of the four major heavy metals to pollute environments. By simulative method, the relationship between soil urease and chromium（ Ⅵ ）including the total and the water-soluble concentrations was systematically studied. The results showed that the con- centration of water-soluble chromium （ Ⅵ）remarkably decreased at the beginning of chromium （ Ⅵ ）added in the soil, and the decreasing content was slowed down with culturing time extending. Their relationship reached remarkable significant positive correlation between watersoluble and total chromium（ Ⅵ ）concentrations in soils. Soil urease activity could be an index of soil polluted by chromium（ Ⅵ）because Cr （ Ⅵ ）significantly inhibited ttrease activity. Soil total chromium（ Ⅵ ）critical concentrations were 17.07 mg·kg-1 and 85.37 mg· kg-1, and water- soluble chromium（ VI ）critical concentrations were 0.78 mg· kg-1 and 3.88 mg· kg-1 for the slight and medium pollution by chromium（ Ⅵ ）in Red soils respectively, according to ED10 and ED50 values. Soil urease ED10 and ED50 decreased continuously with the decline of soil fertility.