Global gridded emission inventories of α-hexachlorocyclohexane

Emission factors of alpha-hexachlorocyclohexane, the major isomer of technical hexachlorocyclohexane (HCH) for spray events and tilling events, are distributed on a 1 degrees x1 degrees longitude and latitude grid system. Estimations of global gridded alpha-HCH emissions in 1980 and 1990 due to 15 consecutive years of application of technical HCH are presented. The total global usage of alpha-HCH was estimated to be around 290 kt in 1980 and 59 kt in 1990. Total global alpha-HCH emissions in 1980 were 184 kt, 92.5% of which was contributed by the current use of alpha-HCH in 1980 and 7.5%, by the residues due to the use of technical HCH since 1966. Total global alpha-HCH emissions in 1990 were 44 kt, 93% of which was contributed by the current use of alpha-HCH in 1990 and 7%, by the residues due to the use of technical HCH since 1976. In 1980 approximately 74% of the global alpha-HCH emissions originated in the Northern Hemisphere midlatitudes, followed by around 19% in the Northern Hemisphere tropics, while in 1990 approximately 54% of the global alpha-HCH emissions originated in the Northern Hemisphere tropics, followed by around 37% in the Northern Hemisphere midlatitudes. Emissions of alpha-HCH were strongly localized in Asia. Among total global alpha-HCH emissions, 85% and 75% originated in Asia in 1980 and 1990, respectively. Study of trends of alpha-HCH residue shows that alpha-HCH can remain in the soil for more than 10 years after its ban in countries such as China and Japan. The trends of alpha-HCH concentration in the soils in the Kitakyushu District, Japan, and Taihu Lake basin, China, estimated from our model fit the monitoring data in the same areas quite well. Qualitative uncertainty estimates have also been assigned on a regional basis.