Quantifying the spatial variability of factors affecting natural attenuation of hydrocarbons in the unsaturated zone is important to (i) performing a reliable risk assessment and (ii) evaluating the possibility for bioremediation of petroleum-polluted sites. Most studies to date have focused on the shallow unsaturated zone. Based on a data set comprising analysis of about 100 soil samples taken in a 16 m-deep unsaturated zone polluted with volatile petroleum compounds, we statistically and geostatistically analysed values of essential soil properties. The subsurface of the site was highly layered, resulting in an accumulation of pollution within coarse sandy lenses. Air-filled porosity, readily available phosphorous, and the first-order rate constant (k(1)) of benzene obtained from slurry biodegradation experiments were found to depend on geologic sample characterization (P<0.05), while inorganic nitrogen was homogenously distributed across the soil stratigraphy. Semivariogram analysis showed a spatial continuity of 4-8.6 m in the vertical direction, while it was 2-5 times greater in the horizontal direction. Values of k(1) displayed strong spatial autocorrelation. Even so, the soil potential for biodegradation was highly variable, which from autoregressive state-space modeling was partly explained by changes in soil air-filled porosity and gravimetric water content. The results suggest considering biological heterogeneity when evaluating the fate of contaminants in the subsurface.
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http://dx.doi.org/10.1016/j.jhazmat.2010.03.042 | DOI Listing |
PLoS One
January 2025
Water Resources Engineering Department, College of Engineering, Salahaddin University, Erbil, Iraq.
This paper addresses the mechanical characteristics of a passive earth pressure problem taking into account water retention curve (SWRC) hysteresis. Both hydraulic (drying and wetting cycles) and mechanical hysteresis were considered. Parametric studies were carried out at various air entry values (AEV = 5-30 kPa), different wall frictions (δ = 0, 0.
View Article and Find Full Text PDFEnviron Monit Assess
January 2025
Chinese-Israeli International Center for Research and Training in Agriculture, China Agricultural University, Beijing, People's Republic of China.
Specific yield (S) is an essential hydrogeological parameter in groundwater-related modeling and estimation. In this study, we proposed several new analytical expressions of S to characterize the nonlinear variations of S under shallow groundwater environments, encompassing S for three-layered soil, transition zone S, and flux-dependent S (in Boussinesq-type equation). The proposed S expression for three-layered soils expanded the applicability of previous expressions for homogeneous soil.
View Article and Find Full Text PDFSci Total Environ
January 2025
Univ. Orléans, CNRS, BRGM, ISTO, UMR 7327, F-45071, Orléans, France. Electronic address:
Mine tailing deposits pose a global problem, as they may contain metal contaminants in various geochemical forms and are likely to be leached from the surface into the underlying groundwater, which can result in health and/or environmental risks. Unfortunately, little is currently known regarding the water flow and mass balance related to leaching in the vadose zone as these factors are still difficult to measure at the field scale. A pilot-scale experiment was run in a 1 m instrumented column for 6 months to address this issue.
View Article and Find Full Text PDFChemosphere
January 2025
Department of Civil Engineering, Indian Institute of Technology Delhi, New Delhi, Delhi, 110016, India. Electronic address:
The establishment of site-specific target limits (SSTLs) for old municipal solid waste (MSW) dumpsites is essential for defining remediation goals in a scientifically rigorous manner. However, a standardized framework for achieving this is currently lacking. This study proposes a comprehensive framework that integrates high-resolution site characterization (HRSC) tools, targeted sampling, and contaminant transport modeling to derive SSTLs.
View Article and Find Full Text PDFSci Total Environ
January 2025
Aquatic Geomicrobiology, Institute of Biodiversity, Friedrich Schiller University, Jena, Germany; Cluster of Excellence Balance of the Microverse, Friedrich Schiller University Jena, Jena, Germany; German Center for Integrative Biodiversity Research (iDiv) Halle-Jena_Leipzig, Germany. Electronic address:
More than 90% of earth's microbial biomass resides in the continental subsurface, where sedimentary rocks provide the largest source of organic carbon (C). While many studies indicate microbial utilization of fossil C sources, the extent to which rock-organic C is driving microbial activities in aquifers remains largely unknown. Here we incubated oxic and anoxic groundwater with crushed carbonate rocks from the host aquifer and an outcrop rock of the unsaturated zone characterized by higher organic C content, and compared the natural abundance of radiocarbon (C) of available C pools and microbial biomarkers.
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