Monitoring of cadmium pollution by carrot

从除冲绳外的46个县的232个市町村采集了373份胡萝卜样品。根据地理特征和植被状况，将46个都道府县划分为9个道（北海道、东北、关东、北陆、东海、近畿、四国、中国和九州）。镉评估的可靠性为7.4%，在10个重复分析的同一样品批次的变异系数。每10个胡萝卜样品（0.1g）中加入0.04μg镉进行回收试验。平均回收率为103%，373个胡萝卜样品中镉含量的频率分布左偏，作对数变换。Cd的几何平均值（GM）为24.4 ng/g湿重，几何标准差（GSD）为2.2。计算了日本9个省胡萝卜样品Cd含量的GM和GSD。采用Ryan方法进行多重比较。中国胡萝卜中Cd含量最高（36.7 ng/g），其次是东北胡萝卜（36.1 ng/g）。镉含量最低的是来自近畿的胡萝卜（15.8 ng/g）。中国和东北胡萝卜Cd含量显著高于日本和近畿胡萝卜（p<0.05）。Cd含量以潮土最高（171.9ng/g），以形成土最低（50.1ng/g），20个样品中水稻Cd含量与胡萝卜Cd含量的相关系数为0.492（p<0.05），表明胡萝卜是世界各国监测Cd污染的理想指示食品。

373 carrot samples were collected from 232 cities, towns and villages in 46 prefectures other than Okinawa. According to geographical features and vegetation, the 46 prefectures were divided into 9 provinces : Hokkaido, Tohoku, Kanto, Hokuriku, Tokai, Kinki, Shikoku, Chugoku and Kyushu.Cadmium (Cd) in the solutions was measured by a flameless atomic absorption spectrophotometer (AAS) (Hitachi Z9000) at a wavelength of 228.8 nm. The reliability of Cd assessment was 7.4%, in terms of the coefficient of variation of 10 repeated analyses of the same sample lot. A recovery test was conducted by adding 0.04μg of Cd to each ten carrot sample (0.1 gram). The recovery rate was 103% on average.As the frequency distribution of Cd content in the 373 carrot samples was skewed to the left, a logarithmic transformation was made. Geometric mean (GM) and the geometric standard deviation (GSD) of Cd were 24.4 ng/g wet weight and 2.2, respectively. The range was 2.1 to 179.1 ng/g wet weight.GMs and GSDs of the Cd contents of carrot samples from 9 provinces in Japan are calculated. Multiple comparison by the Ryan's method was conducted. Cd was highest (36.7 ng/g) in carrots from Chugoku, followed Tohoku (36.1 ng/g). Cd was lowest (15.8 ng/g) in carrots from Kinki. Cd contents of carrots from Chugoku and Tohoku were significantly higher than those of carrots from Hkuriku and Kinki (p<.05).Cd contents of carrots by soil type are also calculated. The highest Cd level was in the soil type Fluvisol (171.9 ng/g), and the lowest (50.1 ng/g) was in Cambisol.The correlation coefficient of Cd in rice and Cd in carrot using 20 samples was 0.492 (p<.05).The authors conclude that carrots are an ideal indicator food for monitoring of Cd pollution in other countries of the worlds as opposed to rice.