湘南某矿区蔬菜中Pb、Cd污染状况及健康风险评估

Contamination status of Pb and Cd and health risk assessment on vegetables in a mining area in southern Hunan

通过采集湘南某矿区周边农田中种植的蔬菜和对应耕作层土壤样品,探究了农田蔬菜Pb、Cd的污染状况,蔬菜和土壤重金属含量之间的相关性,蔬菜中重金属对人体的健康风险。结果表明:(1)污染区土壤重金属污染非常严重,叶菜类蔬菜重金属超出了食品卫生标准限值,但是果菜类蔬菜中重金属没有超出食品卫生标准限值。(2)不同蔬菜不同器官所含Pb、Cd有明显差异;不同种类蔬菜Pb、Cd含量不同,一般是叶菜类>果菜类;同种蔬菜不同部位重金属含量的顺序也不同,一般为根>茎>叶>果,或根>叶>茎>果。(3)二类蔬菜中重金属Pb、Cd的富集系数顺序为叶菜类>果菜类。(4)蔬菜中Pb、Cd含量与土壤中相对应元素含量均无显著相关性。(5)就农产品安全性而言,果菜类蔬菜比叶菜类蔬菜更适合在此矿区栽培。

Vegetables, including leafy vegetables and fruit, are of importance to human health. In order to evaluate the heavy metal contamination status and associated health risks of vegetables, 57 vegetables （34 spring vegetables and 23 winter vegetables） and 34 corresponding soil samples （sampled with the spring vegetables） were collected from farmland surrounding a mining area in southern Hunan, China. Analysis was carried out to determine the correlation between the heavy metal content of vegetables and soils, to enable assessment of the potential health risk to local inhabitants consuming the vegetables grown in the contaminated soils. The results showed that ： （ 1 ） The measured maximum total Pb and Cd in the soils were up to 1251.9 mg/kg （the corresponding soil to the three-colored amaranth） and 13.2 mg/kg （the corresponding soil to the kidney bean）, respectively. The average concentration of total Pb and Cd in all soils were 841.7 mg/kg and 6.5 mg/kg, respectively, which were 3.37 and 21.67 times the standard allowable concentration of Pb and Cd for vegetable soils in China （pH level〈 6.5, Pb 〈 250 mg/kg, Cd 〈 0.3 mg/kg; Environment Quality Standard for Soil Heavy Metals GB15168--1995, Grade II）. It suggested that contamination from heavy metals in these soils was very serious. （2） Vegetables grown on the contaminated soils were rich in Pb and Cd in different plant organs. The highest levels of heavy metals were 5.03 mg/kg for total Pb and 2.92 mg/kg for total Cd in the edible parts of garlic and three-colored amaranth, respectively, which exceeded the maximum levels of the China National Food Sanitation Standards for total Pb （GB14935--94, 0.2 mg/kg） and Cd （GB 15201--94, 0.05 mg/kg）. The heavy metal content of leafy vegetables, not fruit, exceeded the China National Food Sanitation Standards for Heavy Metals. The contents of total Pb and Cd in different organs of the vegetables were quite different and generally followed a sequence of root 〉 stem 〉 leaf 〉 fruit, or root 〉 leaf 〉 stem 〉 fruit. Pb and Cd contents in leafy vegetables were generally higher than those in fruits. （3） The order of bioaccumulation factors （BFs） of heavy metals in the two vegetable types was leafy vegetables 〉 fruits. Based on fresh weight, the average BFs of Pb varied within （0.7--8.4） × 10-3 for leafy vegetables and （0--0.02） ×10-3 for fruits, and those of Cd varied within （15.4--895.2） ×10-3 for leafy vegetables and （0.04--38.1） × 10-3 for fruits, which signified that the average BFs of Pb and Cd for leafy vegetables was greater than those for fruit vegetables. （4） The correlations were not significant between the heavy metal content in vegetables and those in soils ; however, total Pb and Cd in the edible parts of vegetables presented a higher significant correlation level （R2= 0.821 ; n = 18, R200 = 0.590）. （5） The results of the risk assessment on vegetables indicated that the hazard quotient （HQ） for total Pb and Cd in the edible parts of leafy vegetables were 1.70 and 3.73, respectively, 34.00 times and 53.28 times higher than those of the fruits （0.005 and 0.070）. In relation to suitability of agricultural products in this mining area, fruits were more suitable for planting than leafy vegetables.