Effects of Organic and Inorganic Colloids on Iodine Mobilization in Groundwater of the Datong Basin, Northern China

In order to identify the effects of groundwater colloids on iodine mobilization in aquifer system, nine groundwater samples were in-situ filtered through successive pore-sized membranes (0.45 μm, 30 kDa and 5 kDa) using filtration technique under N2 atmosphere. Obvious decrease in groundwater iodine, Fe, Al and DOC was observed in the larger pore-sized fractions, indicating that groundwater iodine is closely associated with larger Fe-Al colloids. The analysis result of sample DT15-27 suggests that the extremely reducing condition could promote iodine dissolved in the truly dissolved phase. For low iodine groundwater, no good correlation between iodine and Fe, Al, DOC was observed for all sequential filtration steps, suggesting that groundwater iodine is trapped in the truly dissolved phase because of competitive adsorption of iron/aluminum.