我国两种典型土壤汞的安全阈值研究——以根茎类蔬菜为例

Food Safety Thresholds of Mercury for Two Typical Soils of China ——A Case Study for Rootstalk Vegetables

选择我国广泛种植的12个根茎类蔬菜品种(萝卜、胡萝卜和马铃薯各4个品种)和2种典型土壤(江西的红壤和天津的潮土),通过温室盆栽试验,设置汞(Hg)添加浓度为现行《土壤环境质量标准GB 15618-1995》二级标准的1倍和2倍,研究不同根菜品种对Hg的敏感性差别,并利用物种敏感性分布法(species sensitivity distribution,SSD)推导两种土壤的Hg安全阈值。结果表明:根菜产量指标对土壤Hg污染的敏感性存在品种间差异,红壤上的三红八寸参胡萝卜在2倍Hg添加处理下可食部位Hg含量超过食品安全国家标准(0.01 mg/kg),潮土中所有品种均未超标。与土壤类型相比,品种对萝卜、胡萝卜和马铃薯中Hg含量影响均最大。利用BurrⅢ型分布拟合12个根菜品种富集Hg的SSD曲线,通过食品安全国家标准反推,计算出红壤和潮土上保护95%的品种不超标的HC5值即安全阈值分别为0.53 mg/kg和1.2 mg/kg。本研究可为我国土壤重金属环境质量标准的修订提供重要参考。

In this study, twelve cultivars of widely cropped rootstalk vegetables （4 cultivars each for radish, carrot and potato） and two typical soils （red soil and fluvo-aquic soil） were selected to study the sensitivity differences for mercury （Hg） through a greenhouse pot experiment. Two Hg addition treatments were applied, including low （equal to the national soil limit for Hg）, and high （two folds of the soil limit for Hg） additions according to the second grade soil （the highest allowable soil heavy metal concentration for vegetable production; 0.3, 0.5, and 1.0 mg/kg for soils with pH〈6.5, 6.5〈pH〈7.5, and pH〉7.5） of the Chinese Soil Environmental Quality Standard. The soil thresholds were then derived using species sensitivity distribution （SSD）. The results indicated that biomass of edible part under Hg exposures varied with cultivars. Under high Hg addition treatment, Hg concentration in carrot cultivar Three red 8-inch grown in red soil, none in fluvo-aquic soil, exceeded the food safety standard （0.01 mg/kg）. Cultivar consistently exhibited the largest effect on the Hg concentration in edible part compared with soil type. The SSD curves for Hg were fitted with Burr Ⅲ distribution based on the bioconcentration factor （ratio of Hg concentration in plant to that in soil） of the twelve cultivars. The 5% hazardous concentrations （HCS） were then derived inversely from the food safety standard. The Hg thresholds for red soil and fluvo-aquic soil were 0.53 and 1.2 mg/kg, respectively. This work provides an important reference for the revision of the soil environmental quality standard for heavy metals in China.