Atmospheric movements of lindane (gamma-hexachlorocyclohexane) from canolafields planted with treated seed

Lindane (gamma -hexachlorocyclohexane [gamma -HCH]) is used as an insectici de in many countries. Concentrations of gamma -HCH have been found in air, water, soil, snow, and tissue samples throughout the world and concerns hav e been raised for its potential effects on human and ecosystem health. In C anada, gamma -HCH is primarily used as a treatment on canola (Brassica napu s L) seed with an estimated 455.3 Mg applied in 1997 and 510.4 Mg in 1998. The purpose of this study was to measure gamma -HCH volatilization from fie lds planted with treated canola seed. Atmospheric dry and wet deposition an d soil samples were collected for two growing seasons (1997 and 1998) from a canola field planted with treated seed. Atmospheric concentrations as hig h as 16.1 and 7.4 ng m(-3) were measured at 1 m above the canola field comp ared with maximum concentrations of 2.9 and 2.7 ng m(-3) measured above a g rass field located 2 km away (1997 and 1998, respectively). On the basis of measurements made in this study it was estimated that between 12 and 30% o f the gamma -HCH applied as canola seed treatment may volatilize and be rel eased to the atmosphere. This would create an atmospheric loading of 66.4 t o 188.8 Mg for the 6-wk period following planting, estimated from the quant ity of seed sown on the Canadian prairies in 1998. Dry deposition rates and rain concentrations as high as 2203 ng m(-2) d(-1) and 170 ng L-1 were mea sured adjacent to the canola field.