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Spatial Variability of Soil‐Gas Concentrations near and beneath a Building Overlying Shallow Petroleum Hydrocarbon–Impacted Soils
Author(s) -
Luo Hong,
Dahlen Paul,
Johnson Paul C.,
Peargin Tom,
Creamer Todd
Publication year - 2009
Publication title -
groundwater monitoring and remediation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.677
H-Index - 47
eISSN - 1745-6592
pISSN - 1069-3629
DOI - 10.1111/j.1745-6592.2008.01217.x
Subject(s) - soil gas , soil water , hydrocarbon , methane , hopanoids , environmental chemistry , soil science , soil test , geology , petroleum , spatial distribution , spatial variability , environmental science , hydrology (agriculture) , chemistry , geotechnical engineering , geomorphology , source rock , organic chemistry , structural basin , statistics , remote sensing , mathematics , paleontology
Data requirements for assessing the significance of the soil vapor intrusion pathway are evolving, and the collection and interpretation of subslab and near‐slab soil‐gas samples are under discussion. The potential for different assessment paradigms for aerobically biodegradable and recalcitrant chemicals is also frequently debated. In this work, the soil‐gas distribution beneath and around a slab‐on‐grade building overlying shallow (0.5 to >1.5 m below ground surface) petroleum hydrocarbon–impacted coarse alluvial soils was studied. The study spanned about 12 months, including the sampling of soil‐gas hydrocarbon and oxygen concentrations, subslab soil vs. building pressure differentials and included weather conditions. Three‐dimensional soil‐gas concentration “snapshots” using samples from 79 soil‐gas sampling points are presented here. Significant spatial variability was observed with hydrocarbon and oxygen concentrations ranging from about <0.01 to 200 mg/L and 0 to 21% v/v, respectively. The presence of oxygen and the depth to petroleum‐impacted soils appeared to be the dominant factors in controlling the soil‐gas distribution; the depletion of hydrocarbons over short lateral and vertical distances (<2 m) was observed in the well‐oxygenated regions. Composition data suggest preferential biodegradation of lighter compounds at some points, as reflected in the ratio of the masses of chemicals eluting on the gas chromatography between methane and pentane (C1 and C5) and all others after pentane (>C5).