Vegetable is an indispensible component of human daily diet,and contamination of vegetables by heavy metals directly threatens human health.In this study,116 vegetable samples were collected from 12 administrative districts of Guangzhou City for analysis of six heavy metals,Cu,Zn,Pb,Cd,Ni,Cr.A combination of single factor evaluation and Nemero Index analysis was employed to determine specific heavy metals exceeding allowable standards and analyze the characteristics of pollution.Risk of exposure was utilized to assess human health risks originating from eating locally planted vegetables contaminated by heavy metals.The results showed that contents of Cu,Zn in the 8 sorts of vegetables were below the standards of maximum allowable content and the contents of heavy mental Cr of up to 91.67% vegetable samples were higher than their standard.Lettuce sativa var.angustana Irish,Luffa acutangula L.,Lycopersicon esculentum Mill.and Daucus carota L.were the 4 species of Pb exceeding vegetables,with the exceed ratio reaching up to 35.71% and Daucus carota L.exceeded the target value most seriously.Only the content of Cd in Lycopersicon esculentum Mill.was over-standard,with the rate of 31.25%.And the highest rate of over-standard of the content of Ni in 3 species of vegetables,which included Lactuca sativa L.,Ipomoea aquatica Forsk and Brassica parachinensis,reached 8.33%.For the contamination level of the eight kinds of vegetable,Lactuca sativa L.,Ipomoea aquatica Forsk,Brassica parachinensis,Raphanus sativus L.and Daucus carota L.were put into the class of alarming,while Lettuce sativa var.angustana Irish,Luffa acutangula L.and Lycopersicon esculentum Mill.were classified as secure.Heavy metals' comprehensive pollution degree of 4 species of vegetables presented a trend of leafy vegetables >rootstalk vegetables >stem vegetables >solanaceous fruits.Health risk assessment showed that Guangzhou citizens eat more frequently Ipomoea aquatica Forsk and Lactuca sativa L.and Brassica parachinensis were prone to higher accumulation of heavy metals,and the dietary intake of heavy metal Cr might cause harm to human health and intake of Cd would bring potential health risk to the human body.Risk of exposure to heavy metal through oral ingestion of vegetables was proved to be higher for children than adults.
Keywords: Guangzhou; health evaluation; heavy metal; pollution characteristic; vegetable.