Tropospheric concentrations of the chlorinated solvents, tetrachloroethene and trichloroethene, measured in the remote northern hemisphere

Global trends, seasonal cycles, and European emissions of dichloromethane, trichloroethene, and tetrachloroethene from the AGAGE observations at Mace Head, Ireland, and Cape Grim, Tasmania

“…The 12‐box model suggests upper tropospheric mole fractions in 0–30°N of 22 ppt in 1992 but only 7 ppt values in the lower stratosphere in early 1992, it is therefore unclear whether there is inconsistency with the Schauffler et al [1993] values of 14.9 ppt at the tropical tropopause at that time. There is good agreement with the Dimmer et al [2001] baseline values in the Arctic in July/September 1997. Encouragingly there was a 15–20% decrease in the mixing ratios of CH 2 Cl 2 observed at several of the NOAA NH monitoring sites from 1996 to 1999 which is in line with the approximately 20% decline in the Mace Head observations post 1998 [ Thompson et al , 2004].…”

“…They confirm that, as seen in the AGAGE measurements, the C 2 Cl 4 values in 2001–2003 are 10–15% less than the values in 2000. The AGAGE measurements at Mace Head are approximately 25% larger than the Dimmer et al [2001] measurements in the Arctic in August/September, 1997 and in the North Atlantic in April/May, 1998 if the McCulloch et al [1999] emissions are used. The currently observed AGAGE C 2 Cl 4 mixing ratios are lower than those reported by Wiedmann et al [1994] for 1982–1989 ( McCulloch et al [1999] do not provide emission estimates before 1988) and Blake et al [1996a].…”

“… Koppmann et al [1993] measured NH mixing ratios of 3 ± 1 ppt in 1989. Average baseline concentrations observed at Ny Ålesund, Spitzbergen, (78°N, 11°E) during the summer of 1997 were 0.12 ± 0.03 ppt, and during the CHAOS cruise in 1998; C 2 HCl 3 concentrations were 1.58 ± 0.45 for the remote Atlantic and Arctic oceans [ Dimmer et al , 2001]. Yokouchi et al [1996] reported measurements at Alert, Canada (1992–1994) from 0.01 ppt in summer to about 8 ppt in winter.…”

“…Tetrachloroethene exhibits a strong interhemispheric gradient [ Wang et al , 1995; Rudolph et al , 1996] with an estimated tropospheric mixing ratio of 5–15 ppt in the NH and 0.7–1.5 ppt in the SH [ Ko and Poulet , 2003]. Dimmer et al [2001] reported an average baseline concentration of 4.26 ± 0.84 ppt during the 1998 CHAOS cruise in the northeastern Atlantic and Arctic oceans (April–May 1998); during a separate field campaign (July–September 1997) at Ny Ålesund (Norwegian Arctic) much lower concentrations of 1.77 ± 0.07 ppt were observed. Approximately 1 year (March 1998 to January 1999) of high‐frequency C 2 Cl 4 and C 2 HCl 3 measurements have been reported for the northeastern United States with clean background C 2 Cl 4 and C 2 HCl 3 levels around 2 and 3 ppt respectively and polluted levels up to 90 and 140 ppt respectively; surface emissions have been estimated from the data during pollution events [ Kleiman and Prinn , 2000].…”

Emission patterns and spatiotemporal variations of halocarbons in the Pearl River Delta region, southern China

“…Due to their short atmosphere lifetimes (0.01 and 0.27 years, respectively) [ Warneck , 2000] and low impact on stratospheric ozone, they are not controlled by the Montreal Protocol, but they are hazardous and toxic organic compounds affecting human health (Agency for Toxic Substances and Diseases Registry, http://www.atsdr.cdc.gov/toxfaqs/index.asp). In addition, Dimmer et al [2001] reported possible oceanic emissions of TCE in subtropical oceans. Methyl chloride (CH 3 Cl) and methyl bromide (CH 3 Br) have both strong anthropogenic and natural sources.…”