A theoretical model for predicting the behaviour of btex in the unsaturated zone and groundwater

ZANELLO, VICTORIA; SCHERGER, LEONARDO E.; CARBAJO CASTOLDI, MICAELA; LEXOW, CLAUDIO

Journal of Urban and Environmental Engineering

Universidade Federal da Paraiba

Año: 2021 vol. 15 p. 117 - 125

Fuelling stations are one of the most important forms of soil and groundwatercontamination in urban areas around the world. In this work, a mathematical model wasapplied to assess the risk of physical media contamination (water, air and soil). Themodel is based on the chemical fuel and hydrological properties of each site. The groupof hydrocarbons selected for applying the model were monoaromatic hydrocarbons:benzene, toluene, ethylbenzene and xylenes (BTEX). A mathematical model was usedto evaluate the behavior of each compound in each partitioning phase (non aqueousliquid phase, dissolved, volatile and retained). Furthermore, it was analyze whichcompound has more affinity for each phase. Finally, mass flux of BTEX reachinggroundwater was calculated according to steady flow under two different conditions:(1) considering only sorption and volatilization, and (2) adding biodegradation. In thisstudy, it could be demonstrated that modeling BTEX behavior in soil gave good resultsfor urban areas. The methodology applied in this work could be extrapolated to any siteof the world with the same problematic. Particularly, the model could be used todetermine the distribution of BTEX in the soil profile. Moreover, results exhibit thatdissolution is the main process affecting BTEX transport in areas containing reducedunsaturated zones (less than two meters). Otherwise, when water table is placed atdeeper depths, contaminants are predominately retained in soil. In all cases, the lowestproportion of BTEX were in the volatile phase. Using this information, zones with highand low risk of contamination could be easily defined in the city of Bahia Blanca,Argentina.