Understanding the mechanism of arsenic mobilization from sediments to groundwater is important for drinking water supply and water quality management in endemic arsenicosis areas, such as the Jianghan alluvial plain in the middle reaches of the Yangtze river. Sediment samples from three boreholes in Jianghan Plain were collected for bulk geochemistry analysis and OSL dating. Sedimentological processes and palaeo-climatic optima after the Last Glacial Maximum have created favorable conditions for the formation of high-As aquifer systems. Bulk sediment geochemistry results indicated that As was correlated with sulfur in the pre-LGM sediments and by contrast As was correlated with iron in the post-LGM sediments. The intense chemical weathering led to sulfur depletion after the LGM could contribute to the As enrichment in the Holocene and upper Pleistocene aquifer.