【作者】 严爱兰；

【导师】 翁焕新；

【作者基本信息】 浙江大学 ， 环境科学， 2008， 博士

【摘要】 碘是人体必需的微量元素,人体缺碘可以导致一系列生理紊乱及生物功能异常,引起甲状腺肿和克汀病,特别是影响儿童生长发育,造成智力残疾,人体补碘已成为全球范围的一个公共卫生问题。本文利用同位素示踪技术、箱式模型、组织化学定位法以及常规物理化学实验法研究了碘在土壤-植物系统中的生物地球化学迁移和转化特征,以及碘在植物体内的形态分布和活化机制,探讨了利用农业生物强化法提高蔬菜中碘的含量以改善人体碘的营养水平,为富碘蔬菜的筛选及碘的农业生物强化法的产业化应用推广,从而探询更为高效、安全的人体自然补碘补碘新途径提供理论上和技术上的科学依据。主要的研究结果如下:在浸泡海带的过程中发现,浸泡出的海带碘量与浸泡时间的长短、浸泡水量、浸泡温度与浸泡液的酸碱度均有一定的关系,而浸泡时间与浸泡温度影响最为显著。浸泡8小时后,溶出的总碘趋于一稳定值,而浸泡温度在40—45℃时浸泡液碘含量达到极值。运用同位素(¹²⁵I)示踪技术很好的模拟了碘在土壤中的迁移和扩散行为。迁移实验结果表明引入土壤的¹²⁵I随深度呈指数衰减,绝大部分¹²⁵I（青紫泥97.73%,小粉土93.98%）集中在土壤0～10cm表层内,青紫泥中¹²⁵I在垂直方向上的衰减快于小粉土,淋溶试验的结果表明,青紫泥土壤中对碘的保存能力大于小粉土。运用箱式模型分析了土壤—青菜生态系统中¹²⁵I的生物地球化学迁移与转化。结果表明土壤和青菜中¹²⁵I的动态分布服从指数变化方程,土壤和青菜中的碘可以相向迁移,青菜中碘的积累量即为土壤和青菜中碘迁移量的差值。水培条件下,青菜、辣椒和茄子根部都能迅速吸收¹²⁵I并向地上部分输送,各部位¹²⁵I的比活度大小顺序是根＞茎＞叶＞果,青菜（叶菜类）可食部分对碘的累积明显高于茄子和辣椒（果菜类）。在含¹²⁵I水培液中培养96h后,青菜运输指数达到23.7,辣椒和茄子的运输指数分别为8.9和3.6。大棚实验表明蔬菜可以吸收累积外源碘,供试蔬菜可食部位对碘的吸收均随着海藻碘肥添加浓度的提高而增加,不同类型蔬菜可食部位对碘的吸收能力存在明显的差异,对碘的积累能力叶菜类＞茎菜类＞根菜类＞果菜类。对比外源碘KI和海藻碘肥的施肥效果,施用外源碘KI土壤中的碘具有较高的生物有效性,施用海藻碘肥土壤中的碘具有更长的持效性。海藻碘肥是培育含碘蔬菜更为理想的外源碘,而且土施比喷施更有利于碘的累积。在空心菜植株体内,有机碘和无机碘共存,水不溶性碘占49.61%,水溶性碘占50.39%,其中水溶性碘有66.72%以碘离子（I-）的形式存在,蛋白质结合碘占所吸收的碘为3.68%,非蛋白质结合碘为82.32%。空心菜中的碘大部分存在于细胞可溶部分,占全株碘总量的59.0%-60.1%,细胞器和细胞壁中的碘分别占全株碘总量的19.2%-19.5%和20.4%-21.8%。空心菜吸收I^-能够增加维生素C的含量,空心菜吸收了IO₃^-和CH₂ICOO^-后,会使空心菜的维生素C含量降低,空心菜在吸收了IO₃^-和I^-后,会不同程度地提高体内硝酸盐含量。在同样的烹饪条件下,碘盐和碘菜相比,碘盐中的碘损失明显高于碘菜中的碘损失。蔬菜作为富碘作物的材料可以以多种方式满足动物和人类对碘的需求,具有明显的应用价值。更多还原

【Abstract】 Iodine is an essential microelement for human health,which has been well established that environmental iodine deficiency can cause a number of health problems known as iodine deficiency disorders（IDD）,including endemic goiter,cretinism,mental retardation,brain damage and foetal abnormalities among others.Iodine deficiency disorders（IDD） are believed to be one of the commonest preventable human health problems.In the studies,the isotope-tracer techniques,model-box method,tissue-chemistry-orientation method and the general experiment method have been carried to investigate the biogeochemistry behavior of ¹²⁵I in the soil-plant system and transfer behavior of iodine,and it is also carried out for seeking effective alternatives of iodine biofortification to prevent IDDs.Experimental results provide theoretical and technical evidence for identifying efficient plant species as target crops for iodine supplementation.The main conclusions obtained from our studies are as follows:In the course of soaking kelp,the iodine content in the liquid dissolved from the kelp was related with soaking time,soaking water volume,soaking temperature and soaking liquid pH value,while soaking time and soaking temperature were remarkable.After kelp being soaked for 8h,the total iodine content reached to a constant As time past,the iodine content had become a constant and tend to be decline and the temperature was between 40—45℃,the total iodine in the liquid had reached the extremum.The isotope tracer technique was well enough to simulate the biogeochemistry behavior of ¹²⁵I in the soil.The results showed that ¹²⁵I introduced into the soil inclined with the soil depth,but most of the applied ¹²⁵I remained in the 0～10cm from surface layer.The leach experiment showed that the soil conservation iodine ability of the paddy soil was better than which in the sandy soil.The behavior of biogeochemical transportation and translation of ¹²⁵I in soil-Chinese cabbage ecosystem was studied by using the model-box method.The dynamics of concentration of ¹²⁵I in the soil-crop ecosystem can be described successfully using exponential function.¹²⁵I in each compartment could move to each other and the content of ¹²⁵I in crop was the remains of transportation.In the nutrition liquid,the root of Chinese-cabbage,cayenne and eggplant could absorb ¹²⁵I quickly and transported the ¹²⁵I up to the above-ground part.The iodine concentration coefficient in different tissue types ranks as root＞stem＞leaf＞fruit.The cumulate iodine in the edible in the Chinese-cabbage was visible more than in the cayenne and eggplant,and the transportation exponential were 23.7,8.9 and 3.6 respectively applied in ¹²⁵I liquid for 96h.The field experiment results showed the greenstuff could absorbe exogenous iodine in soil.The iodine absorbed by the experiment greenstuff in edible parts was added when enhanced the concentration of the seaweed composite iodine fertilizer.The different greenstuff has the different capability of accumulated iodine and which ranked as:the leaf-greenstuff＞stem-greenstuff＞root-greenstuff＞fruit-greenstuff.Compared with the exogenous iodine of the seaweed composite iodine fertilizer and KI fertilizer,applying KI fertilizer is apparently faster than those with seaweed composite in decreased rates of residual and available iodine,and iodine release from seaweed composite maintains relative stability during the whole culture period,demonstrating a longtime efficacy. The seaweed composite iodine fertilizer is recommended due to its advantages in low toxicity and a longtime efficacy as well as a relatively low cost,Compare with the method of spray and embedding the seaweed composite iodine fertilizer,embedding iodine fertilizer was prior to iodine cumulation in the greenstuff.Both organic and inorganic iodine existed in water spinach tissue after iodine uptake. Half of iodine uptake by water spinach was water insoluble iodine which occupied 49.61%, and water soluble iodine accounted for 50.39%in the total iodine.In the form of water soluble iodine,the main iodine form is I^- which occupied 66.72%of the total water soluble iodine in all forms of iodine,only 3.68%were protein iodine in water spinach,and 82.32% were nonprotein iodine.In the existed iodine form in water spinach,most of iodine existed in cell dissolved part which accounting for 59%-60.1%and 19.2%-19.5%and 20.4%o-21.8% iodine in the total absorbed existed in organelle and cell wall,respectively.Ascorbic Acid will increase when water spinach absorbs I^- whereas applying IO₃^- and CH₂ICOO^- ascorbic acid will decrease and nitrate will enhance in some extent.Under the same cooking condition,compared iodide-salt with iodide- vegetable,the loss of iodine from iodide-salt was higher than which from iodide-vegetable.The iodide-vegetable provide a simple and safe alternative method of supplementing iodine and preventing iodine deficiency disorders（IDD）.更多还原