Assessment of groundwater contamination risk by BTEX from residual fuel soil phase

Abstract

The aim of this work is to assess the risk of groundwater contamination associated with BTEX dissolution from fuels as a residual phase. Numerical simulations of sixty scenarios were carried out with the software HYDRUS 2D/3D. Groundwater contamination risk was analyzed given the combination of different porous media textures (silt loam, sandy loam and clay), water fluxes (0.5%, 1% or 3% Rainfall), water table depths (1.5, 2.5, 5 or 8 m below ground surface) and biodegradation rate (active or null). Risk was calculated comparing leachate concentrations to the aquifer and limits established by an international guideline for human drinking water. In all cases, benzene and toluene had the highest mobility in the dissolved phase. Contrary, xylene and ethylbenzene tended to concentrate close to the source zone. These two compounds predominantly concentrated in the solid phase. Calculated risk was proportional to the water flux rate and inversely proportional to the unsaturated thickness. Without biodegradation, in fine-grained sediments risk was very high for shallow aquifers (> 1.5 m depth) and moderate or low for deeper aquifers. However, in sandy loam sediments risk was classified as very high for aquifers up to 8 m deep. When biodegradation was considered, leached concentrations were greatly reduced in the three textures. BTEX concentration in Bahía Blanca City´s aquifer showed acceptable agreement with simulated scenarios. The most sensitive parameters to model results were biodegradation > foc > water table depth > Ks. This study is important for assessing the risks and developing management strategies for fuel contaminated sites.

A theoretical model for predicting the behaviour of BTEX in the unsaturated zone and groundwater (Bahía Blanca, Argentina).

“…The mobility of BTEX compounds is closely related to the physico-chemical characteristics and subsoil properties of each site. (Zanello et al 2021).…”

“…In turn, Rodrigo- Ilarri et al (2018) quantified the concentrations of BTEX in the UZ, by means of a one-dimensional mathematical model that is solved through the application of VLEACH. Zanello et al (2021) studied the risk of groundwater contamination related to residual fuel phase in the study area, using HYDRUS 2D/3D. In this work, a mathematical model was evaluated as a tool to assess the risk of contamination of the physical environment (soil and groundwater).…”

A Critical Review of the Modelling Tools for the Reactive Transport of Organic Contaminants

“…Despite numerous studies and years of research into hydrocarbon migration, the process remains in the discovery phase. When hydrocarbons enter an aquifer, they move downward under gravity through a vadose zone and partition into subsequent phases [99][100][101][102]:…”

Reactive Transport Modeling for Exploring the Potential of Water Quality Sensors to Estimate Hydrocarbon Levels in Groundwater

“…The European Union has identified millions of leaking storage tanks (European Commission, 2001). The current practice of manually collecting groundwater samples is expensive and has associated health risks (US EPA, 2003; Wu et al., 2017; Zanello et al., 2021). As a result, we need a reliable, low maintenance, and low‐cost technology that enables the early detection and real‐time monitoring of contaminants in groundwater.…”