Heavy metals of vegetables and soils of vegetable bases in Chongqing, Southwest China.

There is a growing concern over environmental and ecological safety in China owing to rapid urbanization and industrialization and increasing reliance on agrochemicals in the last several decades. Excessive accumulation for some essential trace elements (e.g., zinc, copper) or low concentration of toxic elements (e.g., cadmium, lead) in agricultural soils may not only result in environmental contamination but also affect food quality and safety. This study is conducted to investigate eight heavy metal elements (Cr, Ni, Cu, Zn, As, Cd, Hg, and Pb) of soils and vegetables in twenty vegetable bases in Chongqing, one of the municipalities directly under the jurisdiction of central government. The results shows that soils investigated in this study are heavily contaminated with cadmium and lead, which exceed the national (China) and local (Chongqing) background values. All the study vegetables are below the national sanitary standards for vegetables in China with one exception of lead concentration of vegetables in the district of Dadakou. All the 20 bases in this study can be divided into three groups: group 1 including Rongchang, Wanzhou, Bishan, Yubei, Jiangjin, Wansheng and Fuling, group 2 containing Dadukou, Changshou, Jiulongpo, Ba'nan, Yongchuan and Jiangbei and group 3 comprising Nan'an, Beibei, Shapingba, Dazu, Tongnan, Tongliang and Hechuan. The soil contamination is group III > group I > group II while the order of the plant contamination is reverse.