Industrial emissions of trichloroethene, tetrachloroethene, and dichloromethane: Reactive Chlorine Emissions Inventory

The identified emissions of the title compounds come predominantly from their use in industrial and commercial processes. Trichloroethene and tetrachloroethene have also been found as byproducts of gasoline and coal combustion; these sources were also considered but shown to be insignificant compared with industrial releases. Global emissions during 1990, amounting to 0.241±0.013 Tg of trichloroethene, 0.366±0.020 Tg of tetrachloroethene, and 0.583±0.032 Tg of dichloromethane (0.195±0.010, 0.313±0.017, and 0.487±0.027 Tg as chlorine, respectively) have been assigned to individual countries and thence to a 1° latitude × 1° longitude grid based on a combination of three data sets: regional sales data that were available on a continental scale; economic activity in the form of national Gross Domestic Products; and the population distribution within each country. For those countries where they were available, data for the quantities and locations of reported emissions were also incorporated. Uncertainty in the distributed emissions is ±4% relative to countries with the largest emissions. The results, which are complementary to the marine fluxes and releases from biomass burning reported by Khalil et al [this issue] and Lobert et al [this issue], respectively, are recorded here as maps and are also available from the Global Emissions Inventory Activity web site at http://groundhog.sprl.umich.edu/geia/rcei. While the industrial regions of North America, Europe, and Japan are the largest sites of anthropogenic emissions, there are also significant sources in the developing nations of Asia; in contrast, anthropogenic emissions within the southern hemisphere are much smaller and more widely dispersed. The total emissions of dichloromethane appear to match the observed atmospheric concentrations, but about 25% of the flux of tetrachloroethene calculated from observations remains unaccounted, and significant extra emissions of trichloroethene are necessary to effect a balance. The known sources have been examined thoroughly in this work, and so it is reasonably certain that the additional emissions are not a deliberate result of human activity; however, there is no means of discriminating their origin unequivocally, and the missing quantities may be inadvertent byproducts of anthropogenic activities.