Distribution of Iodine in Soil-Water System in the Gandak Basin, Bihar

The vast tract in Gandak basin in north Bihar is known iodine deficient area and the population is prone to dreaded and endemic disease like goiter. The present study provides an in-depth account of the iodine content of the Gandak basin in terms of spatial and seasonal variation in both soil and water system in one of the most fertile and thickly populated part of Mid-Ganga basin. In surface water, iodine content ranges from 1.56 ug/1 to 5.52 jjg/1, while in groundwater which is the only source for drinking, it varies from 2.1 ug/1 to 4.56 ug/1. In addition to iodine, pH, dissolved oxygen, Ca, Mg and CI of water were also analyzed. Only pH is found to have good correlation with iodine. In soil, the iodine content ranges between 3.65 ug/gm to 12.59 (ig/gm. Seasonwise, there is considerable variation in iodine content both in surface and groundwater. During monsoon it reduces considerably in surface water due to dilution and in groundwater it reduces owing to heavy recharge of the aquifer system through infiltration. In soil, there is no definite pattern in seasonal variation in iodine content. Spatially iodine decreases towards south in both groundwater and river water. In major part of the study area, the iodine content is deficient and ranges between 3 and 4 ug/1. The cause of low iodine is attributed to repeated floods and erosion of top soil which is the main source of iodine to the groundwater system.