Abstract: For the sake of investigating the heavy metal contamination of vegetable and exploring effects of soil properties on soil heavy metal accumulation in Lanzhou City, Gansu Province, the study was conducted in Yuzhong County, Gaolan County, Yongdeng County, Qilihe District, Anning District, Xigu District and Honggu District. On the basis of the field and laboratory experiments, the soil heavy metal pollution of Cr, Cd, Hg, Pb and As to the vegetable soil were quantitative analysis by employing mathematical model, and evaluation of soil heavy metal contamination and their distribution were analyzed by combining improved Matter Element Analysis Model and toxic response factor. At the same time, the heavy content in 118 samples involved 36 kinds of vegetable with 6 categories, such as leaf vegetables, solanaceous fruits, gourd vegetables, rhizome vegetables, bean vegetables and allium vegetables, were tested to conduct the health risk assessment of heavy metals and discuss the dominant or recessive risk to human health by Target hazard quotients(THQ).The key results from the study were summarized as follows:The average content of Cd, Hg, Pb, As and Cr of vegetable soils in Lanzhou City were 0.22 mg·kg-1, 0.07 mg·kg-1, 26.40 mg·kg-1, 11.23 mg·kg-1 and 65.47 mg·kg-1 ,respectively. The contents of Cd and Hg were 1.57 and 2.69 times higher than the background values, indicating that Cd and Hg were the main pollution elements and significant accumulated in soil. However, The contents of Cr, Cd, Hg, Pb and As lower than secondary standard of Soil Environmental Quality Standard, indicating that the fields were apt for vegetables. According to the improved Matter Element Analysis Model, the single assessment results of heavy metals in different surveyed districts were mainly “still clean” or “clean”, except the concentration of Pb in Qilihe districts, being slightly polluted. The integrated assessment results in surveyed districts and Lanzhou city were “still clean”. This study further showed that compared with the value of the limited food contaminants（GB2762-2005）, the concentration of Cd and Pb in leaf vegetables, Cr and Pb in onion and garlic vegetables, Pb in melons vegetables and rhizome vegetables was higher than standard value, being 14.8% and 27.9%，22.2% and 22.2%，14.3%and 7.1%,respectively, but the concentration of Cr in fruit-vegetable and beans was lower than the value of the given standard, indicating that Pb,Cd and Cr were the main pollution elements in vegetable. Health risk assessment showed that the heavy metals of vegetables in Lanzhou could be conform to the corresponding standard.The THQs (Target hazard quotients)of several heavy metals of vegetables in Lanzhou were below 1.0. However, there was a higher health risk of heavy metals in children and a potential risk lurks in adults, arisen from the higher THQ of heavy metals in vegetables consumed by children and lower THQ of heavy metals in vegetables consumed by adults. The THQ of Pb and Cr were 0.418 and 0.693 and THQ was 1.338 in vegetables consumed by children, which was much higher than that in vegetables consumed by adults.

Key words: heavy metals, spatial assessment, Matter Element Model, health risk assessment