北京市蔬菜和菜地土壤砷含量及其健康风险分析

通过对北京市蔬菜和菜地土壤砷含量状况进行大规模调查,研究了蔬菜和土壤砷含量及其健康风险,并筛选出抗砷污染能力强的蔬菜品种。根据蔬菜的消费量并兼顾品种多样性的原则,在北京市规模化蔬菜栽培基地(采集蔬菜及土壤样品)和蔬菜批发市场(蔬菜样品)共采集93种蔬菜400多份蔬菜样品和39个土壤样品系统地分析其砷含量。研究发现:北京市菜地土壤砷含量范围和平均含量分别为4.44￣25.3和9.40mg/kg,明显超过北京市土壤砷背景值;北京市蔬菜砷含量最高达0.479mg/kg,平均含量为0.028mg/kg,均未超过《食品中砷限量卫生标准》(GB4810-94)的限量值,但其中有2个蔬菜样品(萝卜和大蒜)砷含量超过WHO/FAO制订的限量标准。北京市蔬菜砷含量在东偏北方向(偏转11o-30o)存在明显的"U"型趋势分布。裸露地蔬菜砷含量显著高于设施蔬菜。油菜、萝卜、小白菜、大葱、芥菜、黄瓜、大白菜和甘蓝抗砷污染能力较弱,而辣椒、云架豆、冬瓜、茄子、菠菜、西红柿、芹菜等抗砷污染能力则较强。北京市居民从蔬菜中摄入砷平均值为0.016mg/(人·d),蔬菜砷对北京市部分人群存在一定的健康风险。

A Survey of Arsenic Concentrations in Vegetables and Soils in Beijing and the Potential Risks to Human Health

In order to assess the risks to human health posed by elevated concentrations of arsenic in vegetables, and to identify pollution-tolerant vegetable varieties, a large scale survey of arsenic levels in soils and vegetables planted or sold in Beijing was conducted. Thirty-nine soil samples were collected from gardens and fields used to grow vegetable plants. In addition, 93 varieties of more than 400 fresh vegetable samples were obtained from vegetable stalls, supermarkets and wholesale outlets. Arsenic concentrations were measured using hydride generation atomic fluorescence spectroscopy (HG-AFS). Arsenic concentrations in soils ranged from 4.44 to 25.3 mg kg^-1, with arithmetic and geometric means of 9.40 and 8.79 mg kg^-1, respectively. Compared with the background arsenic concentrations of soil from Beijing, there appeared to be a significant accumulation of arsenic in soil collected from gardens/fields that produce vegetables. Arsenic concentrations in the edible plant portions ranged from less than the analytical detection limit (0.1 μg kg^-1 fresh weight) to 0.479 mg kg^-1 fresh weight, with a mean of 0.028 mg kg^-1 fresh weight. In all of the samples, arsenic was less than the Tolerance Limit of Arsenic in Foods for China (TLAFC) of 0.5 mg kg^-1 fresh weight. The TLAFC is the maximum permissible concentration of arsenic in vegetables that will be consumed by people. The highest level of arsenic detected in a vegetable plant was 0.479 mg kg^-1, which was measured in a radish (Raphanus sp.) sample obtained from the Fengtai District of Beijing. Arsenic was detected at 0.331 mg kg^-1 in a garlic sample collected from Shandong Province, which is higher than the standard of 0.25 mg kg^-1 set by WHO/FAO. The spatial distribution of arsenic concentrations in vegetables planted in Beijing presented apparently a "U-shaped" pattern at the northeast deflection angle of 11o-30o. The arsenic concentration in field-grown vegetables was significantly higher than the concentration of those planted in a greenhouse.Results of hierarchical cluster analysis on the arsenic bioconcentration factor (BCF) in vegetables indicated that the plants sampled could be separated into two groups based on BCF. Rape (Brassica campestris), radish (Raphanus sp.), pakchoi (Brassica chinensis), onion (Allium fistulosum), mustard (Brassica juncea), cucumber (Cucumis sativus), Chinese cabbage (Brassica pekinensis) and cabbage (Brassica caulorapa) had higher arsenic BCFs while chili (Capsicum annuum), beans round trellis (Vigna unguiculata), wax gourd (Beninacasa hispida), eggplant (Solanum sp.), spinach (Spinacia oleracea), tomato (Lycopersicon esculentum) and celery (Apium graveolens) had lower arsenic BCFs. The average ingestion rate of arsenic from vegetables was 0.016 mg/person/day for people of Beijing. Consuming vegetables with elevated arsenic concentrations may pose a health risk to local residents, particularly the young, elderly, or ill.