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Identification of dominating factors affecting vadose zone vulnerability by a simulation method

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ABSTRACT

The characteristics of vadose zone vulnerability dominating factors (VDFs) are closely related to the migration and transformation mechanisms of contaminants in the vadose zone, which directly affect the state of the contaminants percolating to the groundwater. This study analyzes the hydrogeological profile of the pore water regions in the vadose zone, and conceptualizes the vadose zone as single lithologic, double lithologic, or multi lithologic. To accurately determine how the location of the pollution source influences the groundwater, we classify the permeabilities (thicknesses) of different media into clay-layer and non-clay-layer permeabilities (thicknesses), and introduce the maximum pollution thickness. Meanwhile, the physicochemical reactions of the contaminants in the vadose zone are represented by the soil adsorption and soil degradability. The VDFs are determined from the factors and parameters in groundwater vulnerability assessment. The VDFs are identified and sequenced in simulations and a sensitivity analysis. When applied to three polluted sites in China, the method improved the weighting of factors in groundwater vulnerability assessment, and increased the reliability of predicting groundwater vulnerability to contaminants.

No MeSH data available.


Conceptualized vadose zone structures of the sites in the case study (generated by Microsoft Office 2010 software for Windows 2003/XP/VISTA/7).
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f8: Conceptualized vadose zone structures of the sites in the case study (generated by Microsoft Office 2010 software for Windows 2003/XP/VISTA/7).

Mentions: The chromium slag dump (Site 1) occupies a chromium industry founded in the 1980s. Chromium slags are stored in the open environment with no anti-seepage measures. The leachate directly enters the vadose zone through eluviation. The vadose zone is a 4 m-thick layer of silty clay, with a permeability coefficient of 3.3 × 10−5 cm/s. The annual average groundwater table is approximately 4 m. Based on the available information, the vadose zone structure is classified as single lithologic type (Fig. 8). The chromium concentration was 400 mg/L in the leachate (recorded in the leachate monitoring results) and 55 mg/mL in the groundwater monitoring well, which is located 20 m downgradient of the dump. Therefore, the dump poses serious threats to the groundwater.


Identification of dominating factors affecting vadose zone vulnerability by a simulation method
Conceptualized vadose zone structures of the sites in the case study (generated by Microsoft Office 2010 software for Windows 2003/XP/VISTA/7).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5384093&req=5

f8: Conceptualized vadose zone structures of the sites in the case study (generated by Microsoft Office 2010 software for Windows 2003/XP/VISTA/7).
Mentions: The chromium slag dump (Site 1) occupies a chromium industry founded in the 1980s. Chromium slags are stored in the open environment with no anti-seepage measures. The leachate directly enters the vadose zone through eluviation. The vadose zone is a 4 m-thick layer of silty clay, with a permeability coefficient of 3.3 × 10−5 cm/s. The annual average groundwater table is approximately 4 m. Based on the available information, the vadose zone structure is classified as single lithologic type (Fig. 8). The chromium concentration was 400 mg/L in the leachate (recorded in the leachate monitoring results) and 55 mg/mL in the groundwater monitoring well, which is located 20 m downgradient of the dump. Therefore, the dump poses serious threats to the groundwater.

View Article: PubMed Central - PubMed

ABSTRACT

The characteristics of vadose zone vulnerability dominating factors (VDFs) are closely related to the migration and transformation mechanisms of contaminants in the vadose zone, which directly affect the state of the contaminants percolating to the groundwater. This study analyzes the hydrogeological profile of the pore water regions in the vadose zone, and conceptualizes the vadose zone as single lithologic, double lithologic, or multi lithologic. To accurately determine how the location of the pollution source influences the groundwater, we classify the permeabilities (thicknesses) of different media into clay-layer and non-clay-layer permeabilities (thicknesses), and introduce the maximum pollution thickness. Meanwhile, the physicochemical reactions of the contaminants in the vadose zone are represented by the soil adsorption and soil degradability. The VDFs are determined from the factors and parameters in groundwater vulnerability assessment. The VDFs are identified and sequenced in simulations and a sensitivity analysis. When applied to three polluted sites in China, the method improved the weighting of factors in groundwater vulnerability assessment, and increased the reliability of predicting groundwater vulnerability to contaminants.

No MeSH data available.