Analysis study of the forms of water iodine in areas with excessive iodine in water in Henan Province.

Objective To investigate the forms of water iodine in areas with excessive iodine in water of Henan Province. Methods From December 2013 to January 2014, 50 water plants in 4 cities (Puyang, Xinxiang, Kaifeng and Shangqiu cities) of Henan Province were selected from the areas with excessive iodine in water where iodized salt and centralized water supply were stopped for more than 5 years. In each selected water plant, 3 water samples were collected. I2-Starch Spectrophotometer was used to measure the iodine content and identify the forms of iodine in water samples. Results A total of 403 water samples were collected and ultimately 286 samples met the requirement (water iodine ≥80 μg/L). Among the 286 samples, iodine existed in the forms of iodide in 6 water samples, of both iodate and iodide in 139 water samples, and of iodate in 141 water samples. In water samples with iodine content lower than 150 μg/L, the proportions of forms of iodide and both iodate and iodide, were 26.67% (12/45) and 73.33% (33/45), respectively. In water samples with iodine content between 150-299 μg/L, the proportions of the forms of iodide, both iodate and iodide, and iodate, were 4.88% (6/123), 79.67% (98/123) and 24.39% (30/123), respectively. In water samples with iodine content higher than 300 μg/L, the proportions of the forms of iodide and both iodate and iodide, were 18.18% (2/11) and 81.81% (9/11), respectively. Conclusions In areas with excessive water iodine in Henan Province, iodine mainly exists in the forms of iodate, or both iodate and iodide. No sample is found to contain periodate. Key words: Drinking water; Iodine; Chemical, analysis