than that for atrazine. The higher affinity of 2-azidoatrazine to the soil is probably related to the increasing ability of the 2-azidoatrazine to perform H-bonding due to the substitution of Cl by N3 group. The Kd values calculate for atrazine in the presence of 2-azidoatrazine were lower indicating that 2-azidoatrazine successfully competed with atrazine. Hence, the presence of NaN3 affects indirectly the sorption of atrazine due to competitive effect of its derivative.