通过品种选择降低稻米对总汞和甲基汞的吸收

Reducing Total Mercury and Methylmercury Accumulation in Brown Rice by Selection of Rice Cultivars

筛选对总汞（THg）和甲基汞（Me Hg）低积累的水稻品种对解决Hg污染稻田的利用和保障稻米安全具有重要意义。选择在贵州省清镇市水晶化工集团附近Hg污染稻田（THg浓度为7.4 mg/kg,Me Hg浓度为2.9 ng/g）种植20个水稻品种,用原子荧光法（AFS）和气象色谱联合冷原子荧光法（GC-CVAFS）测定水稻组织THg和Me Hg浓度。结果发现,20个水稻品种大米对THg（F=7.2,P〈0.001）和Me Hg（F=2.8,P〈0.01）的吸收呈现显著的品种差异,平均THg浓度为20.02 ng/g（范围10.3～36.25 ng/g）,平均Me Hg浓度为2.48 ng/g（范围1.91～3.95 ng/g）。此外,有10个品种大米THg浓度是低于食品安全标准（GB 2762-2012中的限值〈20 ng/g）;通过对人体摄取Me Hg量的评估发现,即使食用Me Hg浓度最高的水稻品种每天所摄取的Me Hg量也仅为0.022 ng/g,远低于联合国粮农组织和世界卫生组织下的食品添加剂联合专家委员会（JECFA）（0.23 ng/g）和美国环保总局（EPA）（0.1 ng/g）的标准,20个水稻品种大米Me Hg浓度都是相对安全的。研究结果表明,在因化工厂导致的中低度Hg污染稻田中,通过筛选对THg和/或Me Hg低积累的水稻品种去降低稻米Hg污染的方法是有效可行的。

It is of great significance to screen rice cultivars with low total mercury（THg） and methylmercury（MeHg） for the safety of rice grown in Hg-contarninated fields. Twenty rice cultivars were cultivated in paddy field of Qingzhen nearby the Guizhou Organic Chemical Factory, where metallic mercury was used as a catalyst to produce acetic acid. The digested samples were taken for THg analysis by atomic fluorescence spectrometry （AFS）, and MeHg was detected by GC-CVFAS. The result of the analysis showed that there were significant cultivar variations for THg （F=7.2, p〈0.001） and MeHg （F= 2.8, p〈0.01） at the paddy fields. The mean THg and MeHg concentrations of brown rice were 20.02 ng/g （ranging from 10.3 to 36.25 ng/g） and 2.48 ng/g （ranging from 1.91 to 3.95 ng/g）. Moreover, there were 10 cultivars with lower brown rice THg, which were under the permitted limit of the maximum levels of contaminants in the relevant national standard （GB 2762-2012）. Additionally, an assessment of MeHg exposure to human was conducted; it was found that for the peak value of MeHg in brown rice, the MeHg intake of 0.022 ng/g of body weight per day, which is lower than the new dietary reference dose （RID） of 0.23 ng/g of body weight per day for MeHg recommended by Joint FAO/WHO Expert Committee on Food Additives （JECFA）, meanwhile lower than the RfD of 0.1 ng/g of body weight per day for high MeHg exposure recommended by U.S. EPA. So, these rice cultivars were considered low risk for humans MeHg exposure. In general, the investigation proved the selection of rice cultivar was an effective method in reducing THg and MeHg in rice.