| Summary: | 博士 === 國立中興大學 === 土壤環境科學系所 === 105 === The cadmium (Cd) accumulation capacity of plant depends on not only cultivars but also on soil properties and cultivation managements. However, the geological conditions and the diversity of climate in Taiwan could render rather complicated soil properties. Hence, incidents of soils with cadmium contents fulfilling the regulation levels for food crop farmland but output rice or vegetables, e. g. peanuts and garlic, not conformed to the food regulation levels of cadmium in Taiwan occurred occasionally. Field experiment coordinating with survey on vegetable production areas was conducted to clarify main impact factors on vegetable Cd safety and propose appropriate suggestions of cultivation managements. The result indicated the Cd accumulation capacity varied among the 37 vegetable species tested, and the order of the five vegetables with the highest capacities was peanut (Arachis hypogaea L.) > spinach (Spinacia oleraceae L.) > amaranth (Amaranthus tricolor L.) > gynura (Gynura bicolor DC.) > okra (Hibiscus esculentus L.), whereas the order of the five vegetables with the lowest capacities was bitter gourd (Momordica charantia L.) < cucumber (Cucumis sativus L.) < asparagus bean (Vigna unguiculata (L.) Walp. ssp. sesquipedalis (L.) Verdc.) < snap bean (Phaseolus vulgaris L.) < sponge gourd (Luffa cylindrica Roem.). Difference of Cd accumulation capacity among different cultivars of many vegetables was not significant. However, there was significant difference of Cd accumulation capacities among some cultivars of vegetables including lettuce, Chinese cabbage, cauliflower, celery, corn, and asparagus bean. As to various vegetable groups compared, edible parts of leafy vegetables were with strong Cd accumulation capacity, while legume vegetables and fruiting vegetables were weaker Cd accumulator. Soil–plant transfer prediction models of Cd in the edible parts were derived for 29 vegetable species. According to the derived models, the 0.1M hydrochloric acid extractable Cd, Mn and Zn concentrations, and pH, served as the main factors affecting Cd concentrations in the edible parts of vegetables, whereas the CEC is less important factors. To thoroughly assess Cd concentrations in vegetables and to understand the food safety of vegetables in Taiwan, 5023 vegetable samples were collected from major vegetable production areas and another 1,254 vegetable were samples collected from potentially Cd contaminated areas in Taiwan for Cd concentration analysis. The results indicated that the percentage of vegetables with Cd concentrations exceeding the regulatory concentration was merely 0.4% for major vegetable production areas, with very less concern of food safety, while that of potentially Cd contaminated areas were up to3.4%, presenting the necessary need of concern of food safety. Based on soil–plant transfer prediction models of Cd established, we also assessed the effect of adjusting soil pH and changing vegetable varieties on cadmium concentration and its safety in vegetables. The results indicated that the food safety of vegetables grown in Taoyuan and Taichung areas could greatly be ensured by managements raising soil pH up to 7.0. However, for ensuring the food safety of vegetables grown in Changhua and Ilan areas, in addition to raising soil pH up to 7.0, selecting vegetable varieties with low Cd accumulating capacity is also needed.
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