Adsorption in soil of organic contaminants, such as pesticides, is a time-dependent process, which can be relevant for understanding and predicting the potential pollution risk of different water sources. The adsorption behavior of six different pesticides with a wide range of physicochemical properties (log K_OW 1.26–5.8) was evaluated in up to three different soils with low organic carbon (OC) content (≤1.2%). Pesticide sorbed amounts were fitted to several mathematical models to unravel the mechanisms involved in the adsorption process. The linear distribution constants revealed that pendimethalin and the pyrethroid insecticides were strongly retained in soil, whereas the other three compounds were moderately or weakly adsorbed. In the three soils, the pseudo second order model described more accurately the sorption kinetics of all the contaminants. The more hydrophobic pesticides (log K_OW ≥ 4.6) presented lower kinetic rates as compared with the other compounds under study. Both Elovich and intraparticle diffusion models reflected a strong contribution of a rapid initial adsorption on soil surface for thiacloprid, dimethenamid and fenarimol. For the hydrophobic pesticides this contribution was moderate according to the intraparticle diffusion model. Therefore, slower diffusion into the soil micropores was more relevant for the more hydrophobic compounds and for the bigger molecules, and less significant for the more polar pesticides because almost 90% of the total amount adsorbed was achieved in the rapid initial stage.

土壤中对有机污染物（如农药）的吸附是一个随时间变化的过程，与理解和预测不同水源的潜在污染风险有关。六种具有多种理化特性的农药的吸附行为（log K _OW在多达三种有机碳含量低（≤1.2％）的不同土壤中进行了评估（1.26-5.8）。将农药的吸附量与几个数学模型进行拟合，以阐明吸附过程中涉及的机理。线性分布常数表明，二甲戊乐灵和拟除虫菊酯类杀虫剂在土壤中保留强，而其他三种化合物被中等或弱吸收。在这三种土壤中，伪二级模型更准确地描述了所有污染物的吸附动力学。疏水性更高的农药（log K _OW 与研究中的其他化合物相比，≥4.6）的动力学速率更低。Elovich和颗粒内扩散模型均反映了噻虫啉，丁二烯胺和苯那莫尔在土壤表面快速快速吸附的重要作用。对于疏水性农药，根据颗粒内扩散模型，这种贡献是中等的。因此，对于疏水性更高的化合物和较大的分子而言，向土壤微孔中扩散的速度越慢，对极性较大的农药的影响就越小，因为几乎90％的总吸附量是在快速的初始阶段获得的。