Soot–water distribution coefficients for polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and polybrominated diphenylethers determined with the soot cosolvency-column method

For many types of hydrophobic compounds, sorption non-linearity and solid–water distributions in the field well above expectations from organic matter partitioning models have lead to the proposition that strong adsorption to soot surfaces may not be limited to polycyclic aromatic hydrocarbons but may extend as a significant process for many aromatic compound classes. Here, the soot–water distribution coefficients (Ksc) were determined with the soot cosolvency-column method for homolog series of five polychlorinated dibenzo-p-dioxins (PCDDs), five polychlorinated dibenzofurans (PCDFs) and for two polybrominated diphenylethers (PBDEs). All compounds exhibited significantly stronger association with soot carbon than expected from estimates of their bulk organic-carbon normalized partition coefficients (Koc). The Ksc/Koc ratios (at aqueous concentrations of around 0.1–1 μg/l) were for PCDDs (up to tetrachlorination) 19–130 (median 25), for PCDFs (also up to tetrachlorination) 150–490 (median 300), and for both the tetra- and pentabrominated PBDEs a factor of 60. The particularly strong soot sorption for the PCDFs is of similar enhancement factors as previously elucidated for polycyclic aromatic hydrocarbons. Compound-class specific correlations between logKsc and octanol–water partition coefficients (logKow) were significant for both PCDDs and PCDFs (and with R2>98%). These may prove useful for anticipating variable fractions of dissolved exposures between different environmental regimes and putative remediation objects.