Mathematical model to predict the natural attenuation of petroleum hydrocarbons from vertical soil temperature profiles

Abstract

Petroleum hydrocarbons are commonly found in contaminated sites as Liquid Non-Aqueous Phase Liquids (LNAPL). LNAPL natural biodegradation processes are known as Natural Source Zone Depletion (NSZD). NSZD kinetics may reveal that natural LNAPL biodegradation is the most efficient, economic and sustainable available remediation practice. Recent studies demonstrated that soil temperature can be used for measuring NSZD. In this paper, the theoretical data on soil heat transport, related to LNAPL biodegradation rates, is presented. Under this theorical background, we present a new model. This model accounts for differences on soil thermal properties, with little increments on computational cost. Based on synthetic data generated on a numerical model, we compared the model with those proposed by Warren and Bekins (2015) and Stockwell (2015). A comparative analysis of the Warren and Bekins (2015) and Stockwell (2015) models measured only 30 and 51% of the heat at the source of the contamination, respectively. Results indicate that thermal conductivity vertical variation is an important parameter is an important parameter to consider when measuring NSZD from soil temperature.