Abstract: Effects of soil Pb pollution on growth of Brassica chinensis and Ipomoea aquatica and soil urease activities were investigated in three different soils through pot experiment in the greenhouse.The results show that biomass of Brassica chinensis and Ipomoea aquatica growing in red soil decreased with increasing soil Pb concentration, but did not change much with soil Pb concentration when they grew in meadow brown soil and gray lime soil.Pb concentrations in both the aerial part and roots of vegetables increased with soil Pb concentration,but the latter was higher than the former in Pb concentration. Statistic analysis indicates that Pb concentration in the former had significant negative correlation with soil pH.Pb mobility in red soil was higher than in gray lime soil and in meadow brown soil.Soil urease activities were enhanced with increasing Pb concentration in meadow brown soil and gray lime soil,but obviously reduced in red soil,which suggests limitation of using soil urease in characterizing soil Pb pollution.With Brassica chinensis as indicator and the national standard for hygiene of vegetable and food as the basis for calculation,the critical value of Pb contamination in the three soils was 387 mg·kg^-1 for meadow brown soil,245 mg·kg^-1 for gray lime soil,and 45 mg·kg^-1 for red soil,respectively.

Key words: Brassica chinensis, Ipomoea aquatica, Pb, uptake, urease