Quantifying hysteresis of atrazine desorption from a sandy loam soil

Batch experiments were earned 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 k(des) 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 n(des) 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 omega and lambda decreased, and H values increased However, the relationships between initial atrazine concentration and hysteretic coefficients were not pronounced for omega, H, or lambda For the time, dependent desorption isotherms lambda and H values increased as the atrazine desorption step proceeded The correlation between hysteretic coefficient and desorption step was highly significant for lambda (P < 0 0001) but not for H