Biogeochemical Behaviour Of Iodine By ¹²⁵â…  Tracer And The Stability Of Biological Iodine In Plant

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).