Enrichment of heavy metals in vegetables and risk assessment of human health in the vicinity of an abandoned coal mine

【Objective】Studying the heavy metal pollution and human health risks of farmland vegetables around abandoned coal mines would provide a reference for the selection of vegetable planting varieties in the vicinity of the coal mines and the development of agricultural resources around coal mines.【Method】 The heavy metal contents including copper（Cu），zinc（Zn），lead（Pb），cadmium（Cd），chromium（Cr），nickel（Ni）and manganese（Mn）of Allium chrysanthum（wild onion）， Allium sativum（garlic sprouts）， Allium fistulosum（green Chinese onion）， Raphanus sativus（white radish）， Ipomoea batatas（sweet potato）， Brassica napus（rape）， Brassica pekinensis（Chinese cabbage）， Malva verticillata（mallow）， Pisum sativum（pea）leaf and corresponding rhizosphere soil were analyzed by inductively coupled plasma emission spectrometer. The pollution level of heavy metals in vegetables and their enrichment degrees were assessed， further the local vegetable potential health hazards to the public were evaluated using health risk index（HRI）and hazard index（HI）.【Result】The soil around an abandoned coal mine in western Chongqing was mainly polluted by four heavy metals， namely Cu， Zn， Pb and Cd. The content of Cd was 2.2-9.1 times higher than the background value of Chongqing soil. The accumulation index of Pb and Cd showed that the soil was moderately polluted or above. The comprehensive ecological risk of Chinese cabbage plots was the highest（302.635）， showing a high potential ecological risk. Compared with the relevant standards， the contents of Pb， Zn， Cr and Ni in edible parts of leafy vegetables（rape， Chinese cabbage， mallow and pea leaf）and aromatic vegetables（wild onion， garlic sprouts and green Chinese onion）were higher， and the single factor pollution index of Pb and Ni elements was the main contributing element in the cumulative value of all kinds of vegetables， with the contribution rates of 20.51%-48.73% and 16.93%-42.59%， respectively. Except for wild onion， the heavy metal enrichment ability of all kinds of vegetables showed the order of leaf vegetables＞root tubers＞spices. Except for garlic sprouts and green Chinese onion， the HIs of other seven kinds of vegetables were greater than 1， and the HIs of children were higher than those of adults. The HIs of leaf vegetables were the largest for children and adults， and the HRI of Cr and Pb were the main contributing elements of HI， with the contribution rates of 40.06%-64.97% and 17.15%- 33.52%， respectively. There were certain human health risks with intaking them.【Conclusion】The mining of an abandoned coal mine in western Chongqing aggravates the heavy metal pollution in the surrounding farmland soil， resulting in different degrees of heavy metal pollution in vegetables， thereinto consumption of leafy vegetables cause a higher risk. So， it is advised to choose not planting leafy vegetables in the farmland surrounding the coal mine area to reduce the intake of heavy metals.