Abstract
Thirty-five sewage sludge samples collected across Canada were analyzed for 18 polycyclic aromatic hydrocarbons (PAHs), 17 congeners of polychlorinated biphenyls (PCBs) and seven selected chlorinated compounds. Samples were prepared by accelerated solvent extraction and standard column cleanup procedures using silica gel and Florisil. Gas chromatography with electron-capture detection was used for the determination of PCBs. Gas chromatography/mass spectrometry with electron-impact ionization and methane negative ion chemical ionization were used for the detection of PAHs and the chlorinated compounds, respectively. PAHs were detected in nearly all samples, with a total concentration ranging from 0.14 to 209 µg/g (median 3.65 µg/g) on a dry weight basis. Phenanthrene, fluoranthene and pyrene were present at the highest concentrations, with medians ranging from 0.56 to 0.58 µg/g. PCBs were also found in all samples, with a total PCB concentration ranging from 31 to 323 ng/g. The most abundant PCBs (congeners 52, 101 and 110) had median concentrations of 12 ng/g or above. While pentachlorobenzene and hexachlorobenzene were observed in all sludge, at low ng/g levels, no other less chlorinated benzenes have been detected in the same samples. Octachlorostyrene was only found in the Ontario samples, with concentrations ranging from 0.3 to 11.5 ng/g (median 0.9 ng/g). For the chlorinated insecticides, only p,p'-DDE, α- and γ-chlordane were found on a more regular basis, with median concentrations of 12.0, 0.4 and 0.8 ng/g, respectively. These results suggest that the above toxic chemicals are occurring in Canadian sewage samples and are persistent enough to survive the existing sewage treatment processes.
