Extinguishing Petroleum Vapor Intrusion and Methane Risks for Slab‐on‐ground Buildings: A Simple Guide

Abstract

This column reviews the general features of PHT3D Version 2, a reactive multicomponent transport model that couples the geochemical modeling software PHREEQC-2 (Parkhurst and Appelo 1999) with three-dimensional groundwater flow and transport simulators MODFLOW-2000 and MT3DMS (Zheng and Wang 1999). The original version of PHT3D was developed by Henning Prommer and Version 2 by Henning Prommer and Vincent Post (Prommer and Post 2010). More detailed information about PHT3D is available at the website http://www.pht3d.org.The review was conducted separately by two reviewers. This column is presented in two parts.

Advancing “Autonomous” sensing and prediction of the subsurface environment: a review and exploration of the challenges for soil and groundwater contamination

“…Soil gas: Gases in shallow soils have been deemed critical for agricultural purposes (Gliński and Stępniewski 1985 ) but gained importance as a shallow survey tool to map subsurface volatile organic compounds (VOCs) as a measure of subsurface contamination in soil and groundwater (Marrin and Kerfoot 1988 ; Barber et al 1990a ; Davis et al 1991 ) and for contaminant vapour risks (Davis et al 2021 ). Recently, soil gas sampling has become a strong focus for quantifying the rate of natural source zone depletion of petroleum light nonaqueous phase liquids (LNAPLs) in the subsurface (Sookhak Lari et al 2017 ; Davis et al 2022 ), since VOC and oxygen consumption, and methane and carbon dioxide production are strong indicators of LNAPL biodegradation processes and rates (Garg et al 2017 ; Sookhak Lari et al 2019 ).…”

“…Another example is that of Davis et al ( 2009b ), whereby, based on field data, biodegradation of petroleum vapours in vadose zone soils was observed to occur rapidly compared to transport processes, and was approximated as an instantaneous rate, leading to the assumption of all vapour and oxygen consumption being at a single point in the soil profile. This reduced the number of parameters and processes considerably, allowing the effects of buildings to be represented simply (Davis et al 2021 ), with outcomes independent of soil type, moisture content or reaction kinetics. This is despite a single component vapour being assumed and layering not being accommodated in the model.…”

“…Spatial textural or soil/aquifer structural changes might be determined using in ground, downhole or surface geophysical methods (Barber et al 1991 ; García-Rincón et al 2020 ) or perhaps drone or satellite mounted sensors (Roy et al 2017 ; Kelleher et al 2018 ). As currently configured the VOC probes measure the full mixture of volatiles and so for this petroleum example would not individually report a critical risk driver such as benzene, but that may not be a critical issue if the VOC probes were deployed for single VOC contaminants such as trichloroethene (Benker et al 1997 ; Basu et al 2009 ) of if benzene was shown by other measures (such as oxygen) to be degrading adequately (Davis et al 2021 ). Similarly, the probes as configured did do not measure methane separately to VOCs.…”

“…As currently configured the VOC probes measure the full mixture of volatiles and so for this petroleum example would not individually report a critical risk driver such as benzene, but that may not be a critical issue if the VOC probes were deployed for single VOC contaminants such as trichloroethene (Benker et al 1997 ; Basu et al 2009 ) of if benzene was shown by other measures (such as oxygen) to be degrading adequately (Davis et al 2021 ).…”