Effect of pH concentration on the transport of naphthalene in saturated aquifer media

Sorption is one of the primary mechanisms for retarding the movement of organic contaminants in groundwater. Sorption of hydrophobic compounds such as toluene, naphthalene, and DDT is generally assumed to be linearly proportional to solution phase concentration. In the present research naphthalene was chosen as a model compound. Batch adsorption was studied from 0.01 to 1.00 mgL −1. Transport of naphthalene through a specially designed soil column apparatus was studied from 5 to 9 pH and from 0.025 to 2.0 mgL −1 initial concentration. All transport data could be modeled using a single pH-modified Freundlich isotherm: q = 2.71(1 − σΔpH) C 0.81 r = 0.9999 where q (μg g −1 is the amount of contaminant sorbed on the soil per g of soil, C is the contaminant concentration in the flowing water, σ is a correction factor and ΔpH = pH − 7. The exponent agrees with the batch data to within one percent and the partition coefficient is within a factor of two. The implications of these results to environmental transport modelling are discussed.