佛山市南海区本土种植蔬菜重金属污染现状及对人体健康的风险分析

目的测定佛山市南海区本土土壤、灌溉水和蔬菜重金属含量水平，对经蔬菜途径摄入重金属暴露接触人体的健康风险进行评估。方法2009年7月至2010年9月在佛山市南海区8个镇（街）内分别按照东南西北中的地理位置进行布点，共设调查点40个，每个调查点分别对土壤、灌溉水及蔬菜进行随机抽样。分析蔬菜样品的铅、镉、总汞、铬、无机砷含量水平以及种植地土壤样品和灌溉水样品的铅、铜、镉、锌、总汞、铬、总砷含量水平，并用单因子污染评价指数、尼梅罗污染指教评价蔬菜中重金属污染程度，用靶标危害系数（THQ）评估人体通过食物摄入重金属的风险。结果共采集本土种植的叶菜类、根茎类、瓜豆类共47种品种241份样品，本土种植的蔬菜超标率为46．47％（112／241），其中总汞、铅、镉、无机砷、铬超标率分别为36．93％（89／241）、8．30％（20／241）、5．81％（14／241）、3．730k（9／241）、O．41％（1／241）。从重金属羊因子污染评价指数分级来看，总汞的超标情况最严重，重污染占21．16％（51／241）；从尼梅罗污染指数来看，叶菜类、根茎类、瓜豆类总汞含量均为重污染，综合指数分别为19．17、14．53、15．62。居民经食用本土种植蔬菜日均铅、镉、总汞、铬、无机砷摄入量（DI值）均未超过FAO／WHO每日允许量（ADI值），但叶菜中总汞、铅、镉分别占ADI值的17．26％、12．95％、22．41％。THQ结果显示蔬菜中5种重金属的THQ均〈1，但叶菜类铅、镉的THQ值也达0．541、0．575；3类蔬菜中无机砷的THQ值分别为0．751、0．902、0．563。采集土壤241份样品，存在1种以上重金属超标84份，超标率34．85％（84／241）。镉超标率最高为29．05％（70／241），且最高超出限量标准的17倍，其次为总汞7．47％（18／241）。采集灌溉水样品40份，重金属超标5份，超标率12．50％，均为总汞超标。结论南海区蔬菜中重金属污染对人体健康存在潜在风险，控制饮用水源和灌溉水及土壤汞污染是降低本土蔬菜汞含量的有效途径。

Heavy metal contamination of vegetables grown in Nanhai District and risk analysis on humanhealth

Objective 3＇0 detect heavy metal levels in local soil, irrigation water and vegetables and assess the health risks of exposure to heavy metals from the vegetable intake. Methods In July 2009 to September 2010, 40 survey points were selected in accordance with the geographical positions of the east, south, west and north at eight towns of Nanhai District, Foshan City. Samples of soil, irrigation water and vegetables were randomly collected at each survey point. Contents of lead, cadmium, mercury, chromium, and inorganic arsenic in vegetable samples, and lead, copper, cadmium, zinc, total mercury, chromium, and total arsenic in soil and irrigation water samples were detected. Results A total of 241 samples were collected from 47 varieties of locally planted leafy vegetables, roots kind, and melon bean, of which, 46.47% （112/241 ） exceeded the standard. Exceeding standard rates of total mercury, lead, cad- mium, inorganic arsenic, and chromium of the samples were 36. 93% （ 89/241 ） , 8.30% （ 20/241 ） ,5.81% （ 14/241 ） , 3.73% （9/241） , and 0. 41% （ 1/241 ） , respectively. Evaluated by the single factor evaluation index classification of heavy metal pollution, the contamination of total mercury was the most se- rious, with 21.16% （51/241） of heavy pollution; the Nemerow pollution indices were 19. 17, 14. 53, and 15.62 for total mercury contents of leaf vegetables, roots kind, and melon bean, respectively, contaminated heavily. The daily intake （DI） of lead, cadmium, mercury, chromium, and inorganic arsenic of local vegetables consumed by residents did not exceed the FAO/WHO acceptable daily intake （ADI）, But the ADI of total mercury, lead, and cadmium of leafy vegetables accounted for 17. 26%, 12. 95% , and 22. 41% , respectively. The target hazard quotients （THQ） of 5 heavy metals in vegetables were 〈 1. Out of 241 soil samples, 84 had more than one heavy metal exceeding the standard （34. 85% ,84/241 ）. The exceeding standard rate of cadmium was the highest （29. 05% ,70/241 ）, 17 times beyond the limit, fol- lowed by total mercury （7.47% , 18/241 ）. Of 40 irrigation water samples, total mercury contents of 5 samples （ 12.50% ） exceeded the standard. Conclusion Heavy metal contamination of vegetable exists potential risk to human health. It is an effective way to control mercury pollution in water resources, irrigation water and soil to reduce local vegetables mercury levels.