Dynamics of iodine, bromine, and chlorine in soil

Chemical forms of iodine in soil solutions under non-flooded oxidizing and flooded reducing soil conditions were quantitatively analyzed. The results showed that IO3¯ (oxidation number +5) was the dominant chemical form under non-flooded soil condition (85.8% of water soluble iodine), although most of the iodine was combined with the soil in an insoluble form. In contrast, under the flooded soil condition, a considerable portion of the insoluble iodine combined with the soils was transformed to water soluble iodine, where the concentration of soluble iodine became much higher than that under non-flooded soil condition, and I¯ (oxidation number −1) was the dominant chemical form (86.8% of water soluble iodine), followed by IO3¯ (11.9%). It was assumed that the redox potential was an important factor affecting the concentration of soluble iodine or the ratio of I¯ to IO3¯ in the soil solution.