Integration of geophysical, geochemical and microbiological data for a comprehensive small-scale characterizationof an aged LNAPL-contaminated site

Abstract

Characterization of aged hydrocarbon-contaminated sites is often a challenge due to the heterogeneity of subsurface conditions. Geoelectrical methods can aid in the characterization of such sites due to their non-invasive nature, but need to be supported by geochemical and microbiological data. In this study, a combination of respective methods was used to characterize an aged light non-aqueous phase liquid-contaminated site, which was the scene of a crude oil blow-out in 1994. As a consequence, a significant amount of crude oil was released into the subsurface. Complex resistivity has been acquired, both along single boreholes and in cross-hole configuration, in a two-borehole test site addressed with electrodes, to observe the electrical behaviour at the site over a two-year period (2010-2011). Geoelectrical response has been compared to results of the analysis of hydrocarbon contamination in soil and groundwater samples. Geochemical parameters of groundwater have been observed by collecting samples in a continuous multi-channel tubing (CMT) piezometer system. We have also performed a biological characterization on soil samples by drilling new boreholes close to the monitoring wells. Particular attention has been given to the characterization of the smear zone that is the sub-soil zone affected by the seasonal groundwater fluctuations. In the smear zone, trapped hydrocarbons were present, serving as organic substrate for chemical and biological degradation, as was indicated by an increase of microbial biomass and activity as well as ferrogenic-sulfidogenic conditions in the smear zone. The results show a good agreement between the intense electrical anomaly and the peaks of total organic matter and degradation by-products, particularly enhanced in the smear zone.

Microcosm evaluation of bioaugmentation and biostimulation efficacy on diesel‐contaminated soil

“…Particularly, the soil has been sampled at a depth of about 3 m from the ground surface in an uncontaminated sector of the site. The absence of any contamination effect of the crude oil leakage in that soil has been previously assessed . The geographical position of the test site is shown in Fig.…”

Hydrogeophysical characterization of shallow light non‐aqueous phase liquid contamination at a karst aquifer

“…However, the incorporation of geophysical and geochemical methods allows researchers to enhance site evaluations used to devise remediation plans (Arato et al . ).…”

“…Therefore, several applications of geophysical and geochemical methods have been implemented to characterize LNAPL phases in different geological environments (Arato et al . ; Mitsuhata et al . ; Koroma, Arato and Godio ).…”

“…Performing site assessments using conventional methods, such as drilling or chemical sampling, can be particularly expensive, spatially limited, and labour-intensive. However, the incorporation of geophysical and geochemical methods allows researchers to enhance site evaluations used to devise remediation plans (Arato et al 2014).…”

New approaches for low-invasive contaminated site characterization, monitoring and modelling

“…As in practice, the problem definition and strategy development for monitoring and characterization is ideally done in dialogue with the end-users, to ascertain compatibility between the investigation and its practical aims, French et al (2014) address in particular this exchange of information. Next come several papers (Cassiani et al 2014, Giampalo et al 2014, Arato et al 2014, in which geophysical techniques are used together with conventional approaches to characterize the subsoil in much more detail than is possible with conventional approaches alone, yet with a definite need to provide translation functions or data that relate such geophysical data to ground truth.…”