Historical α-HCH budget in the Arctic Ocean: the Arctic Mass Balance Box Model (AMBBM)

An Arctic Mass Balance Box Model (AMBBM) has been developed to calculate a sequential historical α-hexachlorocyclohexane (α-HCH) budget in the Arctic Ocean from its introduction in the 1940s up to the present. The AMBBM is created in the context of the Arctic as a receptor, and has three major components: the air concentration module, the loading from Arctic river module and the transport/transformation module. The results of the model provide a more complete depiction of the behavior of α-HCH within the Arctic Ocean. Model output includes annual concentrations in Arctic air and water, annual α-HCH loading to, removal from the Arctic Ocean and annual cumulative burden of α-HCH in the Arctic waters from 1945 to 2000. Our model results compare well with published data in the 1980s and 1990s and show that the α-HCH burden in the Arctic Ocean started to accumulate in the early 1940s and reached the highest value of 6670 t in 1982, 1 year before China banned the use of technical HCH. Since then the burden of α-HCH in Arctic waters has decreased quickly by an average annual rate of approximately 270 t y−1 during the 1990s, decreasing from 4220 t in 1990 to 1550 t in 2000. The complete elimination of α-HCH from Arctic waters would require another two decades. The total loading between 1945 and 2000 was 27 700 t accounting for approximately 0.6% of total global α-HCH emission from agricultural land to the atmosphere. Differences in loadings of α-HCH to the North American Arctic Ocean and Eurasian Arctic Ocean are also discussed.