Abstract: It is important for safe use of polluted soils and amendment of the soil environment quality standard to study absorption and enrichment of heavy metals by crops.Samples of lettuce(Lactuca sativa var.angustana Irish) plants and their rhizospheric soils were collected for analysis of accumulation of Cu,Zn,Cd and Pb in lettuce,and absorption and enrichment of Zn and Cd by lettuce in complex contaminated soil.Results show that in terms of accumulation,contents of the four elements in lettuce was in the order of root>leaf>stem,and Zn>Cu>Cd>Pb,with the bioconcentration factors(BCF) being Cd≈Zn>Cu>Pb.The ability of the lettuces of absorbing and accumulating heavy metals varied significantly with the sampling sites.The response models that may depict transfer of Zn and Cd in the soil-lettuce system are non-linear ones;and somewhat differ between the two elements and between parts of the lettuce plant.However,all the responses of the two elements in various parts of the lettuce plant can be described with a cubic curve equation.The absorption of Zn and Cd by lettuce is not only affected by elements themselves,but also by co-existent elements,and the effect of the co-existent elements depends on their concentration in the soils.

Key words: lettuce, heavy metal, complex contamination, response model, absorption, enrichment