Batch experiments were carried out to investigate the effects of initial atrazine concentrations and consecutive desorption steps on the desorption characteristics of atrazine from a sandy loam soil.As initial atrazine concentration increased,the average percentage of atrazine desorption on the sandy loam soil ranged gradually from 23.1% to 38.5% after five consecutive desorption steps.The values of the Freundlich capacity parameter,kdes,derived from the initial concentration and time-dependent desorption isotherm were consistently higher than those associated with sorption.The opposite trend was observed only for the values of nonlinear parameter,ndes,from the initial concentration-dependent desorption isotherms.Atrazine hydrolysis to hydroxyatrazine and bound residue formation were mainly responsible for the observed hysteresis in its sorption and desorption isotherms.For the initial concentration-dependent desorption isotherms,as initial atrazine concentration increased,the values of hysteretic coefficients ω and λ decreased,and H values increased.However,the relationships between initial atrazine concentration and hysteretic coefficients were not pronounced for ω,H,or λ.For the time-dependent desorption isotherms,λ and H values increased as the atrazine desorption step proceeded.The correlation between hysteretic coefficient and desorption step was highly significant for λ(P < 0.0001),but not for H.