Effects of soil colloids on adsorption and migration of benzo(a)pyrene on contaminated sites under runoff infiltration processes

In the environment, soil colloids are widespread and possess a significant adsorption capacity. This makes them capable of transporting different pollutants, presenting a potential risk to human and ecological well-being. This study aimed to examine the adsorption and co-migration characteristics of benzo(a)pyrene (BaP) and soil colloids in areas contaminated with organic substances, utilizing both static and dynamic batch experiments. In the static adsorption experiments, it was observed that the adsorption of BaP onto soil colloids followed the pseudo-second-order kinetic model (R2=0.966), and the adsorption isotherm conformed to the Langmuir model (R2=0.995). The BaP and soil colloids primarily formed bonds through π-π interactions and hydrogen bonds. The dynamic experimental outcomes revealed that elevating colloids concentration contributed to increased BaP mobility. When the concentration of soil colloids in influent was 500 mg L-1, the mobility of BaP was 23.2 % compared to that without colloids of 13.4 %. Meanwhile, the lowering influent pH value contributed to increased BaP mobility. When the influent pH value was 4.0, the mobility of BaP was 30.1 %. The BaP’s mobility gradually declined as the initial concentration of BaP in polluted soil increased. When the initial concentration of BaP in polluted soil was 5.27 mg kg-1, the mobility of BaP was 39.1 %. This study provides a support for controlling BaP pollution in soil and groundwater.