Comparative assessment of the global fate of α- and β-hexachlorocyclohexane before and after phase-out.
Technical hexachlorocyclohexane (HCH) was one of the most widely used pesticides during the 20th century. Although production and use were phased-out during the 1990s, two of its major components, α- and β-HCH, are still ubiquitous in the environment. Here, we have collected and analyzed data on concentrations of α- and β-HCH in the atmosphere and oceans, including spatial and temporal trends and seasonalities. We apply a global fate and transport model to both isomers over the period 1950 to 2050 to rationalize current levels and trends at remote locations with estimated emissions and to forecast into the near future. Our model results indicate that secondary emissions from soils and oceans are currently controlling the observed rates of decline in the atmosphere. β-HCH is declining more slowly than α-HCH due to its higher persistence, and we hypothesize that it will eventually become the predominant isomer of HCH in the environment. The model reproduces over 70% of measured concentrations of α-HCH in air and ocean water within factors of 3 and 5, respectively, and over 70% of measured concentrations of β-HCH within factors of 8 and 20, respectively. The model results are only weakly sensitive to climate change-induced trends in Arctic sea-ice cover and temperature.
Institute for Chemical and Bioengineering, Swiss Federal Institute of Technology Zurich, Wolfgang-Pauli Strasse 10, 8093 Zurich, Switzerland.
Henry
H
Wöhrnschimmel
Pascal
P
Tay
Harald
H
von Waldow
Hayley
H
Hung
Yi-Fan
YF
Li
Matthew
M
Macleod
Konrad
K
Hungerbuhler
D000393:Air Pollutants / Q000032:analysis*; D004784:Environmental Monitoring; D001556:Hexachlorocyclohexane / Q000032:analysis*; D008962:Models, Theoretical; D009792:Oceans and Seas; D010575:Pesticides / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis*
D000393:Air Pollutants; D010575:Pesticides; D014874:Water Pollutants, Chemical; C040534:alpha-hexachlorocyclohexane; D001556:Hexachlorocyclohexane; C023888:beta-hexachlorocyclohexane