Impact of carbonaceous materials in soil on the transport of soil-bound PAHs during rainfall-runoff events

Polycyclic Aromatic Hydrocarbons (PAHs) transported from contaminated soils by surface runoff pose significant risk for aquatic ecosystems. Based on a rainfall-runoff simulation experiment, this study investigated the impact of carbonaceous materials (CMs) in soil, identified by organic petrology analysis, on the transport of soil-bound PAHs under rainfall conditions. The hypothesis that composition of soil organic matter significantly impacts the enrichment and transport of PAHs was proved. CMs in soil, varying significantly in content, mobility and adsorption capacity, act differently on the transport of PAHs. Anthropogenic CMs like black carbon (BC) largely control the transport, as PAHs may be preferentially attached to them. Eventually, this study led to a rethink of the traditional enrichment theory. An important implication is that CMs in soil have to be explicitly considered to appropriately model the nonpoint source pollution of PAHs (possibly other hydrophobic chemicals as well) and assess its environmental risk. •Composition of SOM significantly impacts the enrichment and transport of PAHs.•Anthropogenic carbonaceous materials in soil largely control the transport of PAHs.•The classic enrichment theory is invalid if anthropogenic CMs are abundant in the soil.•Organic petrology analysis introduced to study the fate and transport of PAHs. Anthropogenic carbonaceous materials in soil, especially black carbon, largely control the transport of soil-bound PAHs during rainfall-runoff events.