Abstract
The Oxford Clay from Bletchley, the Kimmeridge Clay from Kimmeridge Bay, Dorset, and Tertiary mud (Wittering Formation) from Whitecliff, Isle of Wight, United Kingdom were used as sorbent samples because of their distinctive organic material characteristics (Amorphous organic matter rich and/or phytoclast rich). Organic material was isolated for identification and analysis using a non-acid extraction method (heavy liquid) extraction and traditional methods involving HF digestion. These organic materials were then used to determine influences of extraction on hydrophobic organic contaminants, (toluene and naphthalene) sorption. Organic petrology classification was applied to identify the various types of isolated organic material. Amorphous organic matter from the Kimmeridge Clay displayed a higher sorption capacity (Sorption–desorption distribution coefficient (Kd), Kd = 6,481, 59, 670; for toluene and naphthalene, respectively) compared to literature values. Amorphous organic matter-rich sorbent extracts demonstrated a higher absorption capacity than the phytoclast-rich sorbents (e.g., Wittering Formation, Kd = 219, 10, 134; for toluene and naphthalene, respectively). Implications of results in landfill design/risk assessment and modelling are discussed.
Highlights
Modern landfills are designed with engineered barriers to prevent pollution of surface and groundwater
KCHF: hydrofluoric acid (HF) digestion residues from the Kimmeridge Clay (KC) OxCHF: HF digestion residues from the Oxford Clay (OxC) WFHF: HF digestion residues from the WF OMHL: Organic matter extracted by heavy liquid from KC, OxC and WF KCHL: OM separated from the KC by heavy liquid OxCHL: OM separated from the OxC by heavy liquid WFHL: OM separated from the Wittering Formation by heavy liquid
The sorption capacity measured by the linear sorption coefficients (Kd) for toluene and naphthalene on KC were significantly higher than other natural sorbents in the literature
Summary
Modern landfills are designed with engineered barriers to prevent pollution of surface and groundwater. Low permeability barriers such as engineered clay liners may be used to limit transport of leachate or attenuate the concentration of pollutants by processes such as sorption (Fishman et al 2012; Simoes et al 2011). Simoes et al (2011) found that hydrophobic organic contaminants (HOCs) present in landfill leachate (such as naphthalene, toluene and tetrachloromethane) sorbed to clay materials used as barriers in landfills. Sorption of HOCs to Oxford Clay (OxC) was much stronger than predicted from contaminant hydrophobicity and this was attributed to the organic matter characteristics of the clay barrier material
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