Abstract
Vertical atmospheric layering is included in a previously described, zonally averaged global multimedia distribution model. This model is used to simulate the fate of α‐hexachlorocyclohexane (α‐HCH), the main ingredient of the technical HCH pesticide mixture, for the 50 years of its large‐scale use (1947−1997). Worldwide historic emission estimates are compiled, assigned to 10 climate zones, and used as input in model calculations. The performance of the model is evaluated by comparing calculated and measured concentrations in the atmosphere and seawater. A major focus is on the arctic and northern temperate environment, and emphasis is also placed on absolute levels, time trends, latitudinal profiles, and air‐water exchange. In general, simulated and observed concentrations agree within one order of magnitude. Deviations are explained by the zonal averaging characteristics of the model and uncertainties associated with the environmental degradation rates of α‐HCH. In both model results and observations, the dramatic decrease in the global emission of α‐HCH is reflected in rapidly decreasing concentrations in the atmosphere and seawater, except in the Arctic Ocean, which apparently is the last refuge for α‐HCH in the global environment. The model thus provides an illustration of the response characteristics of the global system to the reduced emissions of α‐HCH. Its application to other chemicals with reduced emission is discussed.