Enhanced containment of polycyclic aromatic hydrocarbons through organic modification of soils

A methodology to enhance the containment of polycyclic aromatic hydrocarbons (PAHs) in pervious pavement systems was developed through the chemical modification of a typical Rhode Island glacial outwash soil. In addition, the PAH-retaining capacity of different structural components of pervious pavements was evaluated using column experiments in terms of PAH retention. Two methods were used for soil amendments. The first method was a direct modification of the porous matrix using quaternary ammonium cations through an ion exchange process. The second method involved blending the soil with a commercial organoclay (PM-199; CETCO Oil Field Services). These amendments successfully increased the soil's fraction of organic carbon (f_oc) by at least 70%. To quantify the efficiency of these amended soils to sorb PAHs, a series of batch isotherms and column experiments were conducted on unmodified and modified soils. These studies demonstrated that, through the synthetic modification, the sorption of PAH was increased by up to 20-fold. The Langmuir (α, β) and Freundlich (K_F, n) isotherm coefficients calculated from batch studies were higher when compared with column experiments. Overall, the organoclay-glacial outwash blend exhibited the greatest K_F value of 114.2. Breakthrough curves obtained using HYDRUS 1D were compared with measured data. The column experiments conducted on porous concrete and aggregate demonstrated that these materials have a minimal contribution to the overall containment of PAH in pervious pavement systems. © 2013 American Institute of Chemical Engineers Environ Prog, 2013