High arsenic groundwater has posed a severe health threat to the local people in Jianghan Plain. Several studies have been conducted to illuminate the factors and mechanism controlling seasonal variations in As concentrations. However, the quantitatively description of As adsorption has not been studied and this impedes the explanation of As reactive transport and fate in the study area. In this study, a series of adsorption experiments on natural sediments were conducted to investigate the characteristics of surface complexation reactions. The results showed that As(III) and As(V) have different adsorption behaviors on natural sediments. The HCO 3 competitive adsorption has negligible effect on As(V) adsorption in artificial groundwater (AGW), while it has significant influences on As(III) adsorption. With the increase of pH, adsorbed As(III) concentration increased and As(V) concentration decreased. The results from this study strongly suggested that different adsorption behavior of As(III) and As(V) should be considered as a important process for controlling the seasonal variation in arsenic concentration in Jianghan Plain.