On the spatial and temporal variations in atmospheric concentrations of hexachlorobenzene and hexachlorocyclohexane isomers at several locations in the province of Ontario, Canada

Abstract Hexachlorobenzene (HCB), as well as α- and γ-hexachlorocyclohexane (HCH) have been measured at seven sites in Ontario, Canada during the years 1985–1989. While two of the locations were close to a suspected source of the organochlorines, five were sites that reflected the non-urban airshed loadings which are considered to be regionally representative of the Great Lakes. At the non-urban locations, the γ-HCH (lindane) and α-HCH concentrations ranged from 15 to 190 pg m −3 (mean of 47 pg m −3 ) and 50 to 660 pg m −3 (mean of 240 pg m −3 ), respectively. The HCB concentrations varied from 20 to 310 pg m −3 (mean of 94 pg m −3 ). At the suspected source locations, the α:γ HCH ratio was less than unity while at locations distant from known or suspected sources, the α:γ ratio was usually greater than 7. At the non-urban locations, the highest concentrations of the α- and γ-HCH isomers were observed during the summer and the lowest concentrations were seen during the winter. The concentration of HCB, however, remained relatively constant throughout the year.