Although black carbon only counts for about 9% of organic carbon in sediment, it dominates the sorption of many hydrophobic organic compounds and greatly reduces their bioavailability. In this study, we measured isotherms of 19 organic compounds with diverse functional groups (for example, ketone, ether, phenol, amine, chlorinated) on a well characterized model black carbon (NIST diesel soot) by frontal chromatography. Based on these soot-water partition coefficients at different sorbate activities, a sorbate-concentration dependent polyparameter linear free energy relationship was found: log10 KBC, soot (L/kg) = (4.39±0.12) V + (-3.33±0.13) B + (-0.35±0.02) log10 a × E +(-2.13±0.11) (N=95, R2=0.94, SE=0.20), where V is McGowan’s characteristic volume for the sorbate; B is the hydrogen basicity; E is the excess molar refraction and a is sorbate's activity in water (saturated = 1). This relationship shows that molecular size of sorbate is the predominant factor forcing its partition into soot, while its basicity (electron donating capacity) discourages this process. Also, sorbate's polarizability increased its adsorption, especially at lower chemical activities. Using this relationship, soot-water partition coefficients of other organic compounds of interest (e.g., atrazine) at various concentrations may be estimated.

Investigating soot-water partition coefficients of organic compounds using frontal chromatography and polyparameter linear free energy relationship

250th National Meeting (2015)

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