Studies On Speciation And Influencing Factors Of Iodine In Environmental Water System

Iodine is an essential microelement which can composes hormone of thyroidgland, and it is very important for metabolism and human body's growth development.Environmental water system is a medium of elementary transformation andtransference in circle of geochemistry, and it is an important source of iodine forhuman body. Therefor, the study on speciation of iodine in environmental watersystem can offer theoretic basis for transferred conditions and rules of iodine inentironment. And it can truly evaluate the influence of iodine on surroundings andecosystem. There are many analytical methods for study of iodine. Inductivelycoupled plasma mass spectrometry (ICP-MS) has been a preferred technique foranalysis of various trace elements in environmental geochemistry owing to its lowlimits of detection, few interferences, high sensitivity and precision, widely dynamiclinearity. The combination of other separation technique with its specific detectiontechniques has become most effective methods for iodine speciation of some specialsamples.The speciation of iodine in environmental water system was selected as target inthis dissertation. Two new methods had been established, one was inductively coupledplasma mass spectrometry technique for determination of total iodine, the other wasion chromatography coupled with inductively coupled plasma mass spectrometrytechnique for speciation analysis of iodine. On the basis of these methods, thecontents of total iodine and its speciation in environmental water system includingseawater, lake water, groundwater and atmosphere precipitation etc had been studied.Finally, the influencing factors which could affect the speciation of iodine, the reasonsof speciation tansform and behaviors in environmental geochemistry of iodine hadbeen discussed.The major results are described as follows:(1) On the basis of summarization on the source, distributing, circle of geochemistry of iodine and the relation of iodine to the human health, progress in thestudy of analytical methods for total iodine and its speciation had been summarized inditail.(2) An analytical method was established for total iodine by ICP-MS with Lu asinternal standard. The stadard curve of total iodine, established on the optimalinstrumental operating parameters which were adjusted by mixed criterion solution,had wide linear ranges which reached to five magnitude, the detection limit of iodinewas0.0218μg/L, the precision was high wih RSD=3.85%, the method was alsovalidated using certified reference materials, and the results were in good agreementwith the certified values, which showed the veracity of method was good.(3) A fast analytical method was developed for speciation of iodine by shortcolumn ion chromatography (IC) coupled with inductively plasma mass spectrometry(ICP-MS). The optimal separation conditions were obtained after optimization whichwere separation column, Dionex Ion PacAG11(4×50mm); mobile phase,8mmol/L(NH4)2CO3solution; flow rate,1.5mL/min; injection volume,20μL. Under theoptimal separation conditions and ICP-MS detector, IO₃^-and I-both had wide linearranges (0.1-100μg/L), good linearity (r2>0.9996), low detection limits (0.015μg/Land0.081μg/L for IO₃^-and I-, respectively), high precision (RSD<4.3%), shortseparation time (nearly170s).(4) The established short column IC coupled with ICP-MS for Speciation ofiodide and iodate was applied to determination of iodized salts collected from localmarkets and human urine samples collected from volunteers. The results showed thatiodine in the iodized salts firstly existed as IO₃^-and was all transformed to I-after themetabolizing cycle in the human body, which would supply basis to further study onmetabolizing mechanism of IO₃^-in organism (human). The dangers of IDD inChangchun City was inexistent from the contents of urine iodine.(5) The contents, speciation, reasons of speciation and their behaviors inenvironmental geochemistry of iodine in different environmental water system hadbeen studied by the proposed method in this work. As the results revealed, thecontents and speciation of iodine in different environmental water system weredifferent from each other. In a word, the content of iodine in seawater was higher thanthat in land water. The iodine were existed as IO₃^-and I-in seawater and ChangchunSouth lake water, and the contents were moderate. Changchun was section of iodine deficiency which judged by atmospheric precipitation, the total content of IO₃^-and I-was fewer than half of total iodine. Changchun was section of moderate iodine whichjudged by tap water and groundwater, however, the existent speciations of iodine inthese two waters were IO₃^-for tap water and I-for groundwater, respectively, nealyboth were100%.(6) The infulence of pH value, oxidation-reduction surroundings, salinity andcontent of organic substance on the speciation tansform of iodine had been studied.The results showed that speciation of IO₃^-had remarkable relativity with the contentsof oxidant, salinity and organic substance, by contraries, it had no relativity withwater temperature between0-50oC and pH value between4-10. However, thespeciation of I-had good relativity with all factors, especially with content of oxidant,salinity and content of organic substance. The theoretic species of iodine according tothe diagram of Eh-pH were different to the real species of iodine in environmentalwater system, which revealed that the speciation of iodine in environmental watersystem had been significantly affected by geographical position and environmentalconditions.