Extractability of dioxins from soil: I. Extractability of dioxins from airborne particulates and humic acid fraction in soil

The extractability of dioxins (polychlorinated dibenzo- p -dioxins, polychlorinated dibenzofurans, and coplanar polychlorinated biphenyls) from airborne particulates (APs) and humic acid (HA) in soil was evaluated. APs collected from ambient atmosphere and dioxins-associated precipitated HA fraction (PHA) were extracted by pressurized liquid extraction with either toluene or acetone. Native dioxins were equivalently extracted from APs with both solvents, whereas only acetone could satisfactorily recover the 13 C-labelled compounds from metal-free PHA. The recovery rates of dioxins by toluene extraction from metal-free PHA varied with the organic carbon content of the PHA. However, even with acetone, the recovery of dioxins from metal-bound HA was poor (11–40%). These results suggest that PHA prevented the solvents from accessing sequestered dioxins. This characteristic of solid HA may influence the extractability of dioxins from humus-rich soil.