Adsorption and Distribution of Selected High Molecular Weight Polycyclic Aromatic Hydrocarbons in a Typical Coastal Sand Deposit

Abstract

Contaminant migration study through soil medium is a veritable tool for a match towards sustainable groundwater protection. It is also essential to predict the fate and Transport of pollutants and to evaluate pollution risks. In this study, migration and distribution of High Molecular Weight (HMW) Polycyclic Aromatic Hydrocarbons (PAHs) through a coastal sand deposit of a wetland was investigated. Flow simulation of the PAHs to determine the migration of the selected HMW was carried out by soil column method. With the help of gravity, the PAHs polluted wastewater collected from the study site was made to pass through a soil column. The analysis of the pore water collected as exit solution showed apparent concentration differences of various selected (HMW) PAHs from the original concentrations. The relative concentrations with respect to pore water assumed dome curves in which various selected (HMW) PAH concentrations rose gradually to the peak then decreased and tailed down with increasing pore volume effluents. The observed concentration differences was attributed to adsorption. Concentration values of the PAHs adsorbed onto the soil is of the following order; Benzo(b)flouranthene>Benzo(K)flourathene>1,2,3-cd pyrene >Dibenzo(a,h)anthrene> Benzo(a)pyrene > Chrysene > Benzo(a)anthrene. Distribution of the selected (HMW) PAHs within the soil column was also investigated. There was significant percentage asymmetric fixation of Benzo(b)flouranthene, Benzo(a)pyrene, Chrysene, 1,2,3-cd pyreneand Benzo(K)flourathene at the upper segment (0-4 and 4-9 cm) of the soil column. On the other hand, retentions of Dibenzo(a,h)anthrene and Benzo(a)anthrene were equally significant at the lower segment (9-15 cm). Despite the asymmetric fixation of Benzo(a)pyrene and Chrysene at the upper segment of the column, their concentrations and that of Benzo(a)anthrene) compound were significant in the exit solution. However, Migration and distributions of the HMW PAHs on the soil under investigation were essentially the functions of their chemical structures, solubility and to an extent the molecular weights. Given the distribution and migration pattern of the selected (HMW), Dibenzo(a,h)anthrene, Benzo(a)pyrene, Chrysene and Benzo(a)anthrene have great potentials to migrate further down the subsurface and to the aquifer to compromise the integrity of the groundwater in the wetland.