Distribution and genesis of high iodine shallow groundwater in Henan section of Guohe Basin

By analyzing 249 groups of shallow groundwater samples in Henan section of Guohe Basin, it is found that the area of high iodine shallow groundwater covers 5 818.9 km², accounting for 51.97％ of the total. It is widely distributed in the north and northeast of the study area, followed by the east of Taikang County. Iodine in the shallow groundwater of the study area is mainly sourced from the Quaternary loose sediments. The combination of climate condition, the groundwater flow field constrained by topography and the groundwater pumping for crops irrigation is the prerequisite for the gradual concentration of iodine in the shallow groundwater.