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

Citation:
Simmonds, PG, Manning AJ, Cunnold DM, McCulloch A, O'Doherty S, Derwent RG, Krummel PB, Fraser PJ, Dunse B, Porter LW, Wang RHJ, Greally BR, Miller BR, Salameh P, Weiss RF, Prinn RG.  2006.  Global trends, seasonal cycles, and European emissions of dichloromethane, trichloroethene, and tetrachloroethene from the AGAGE observations at Mace Head, Ireland, and Cape Grim, Tasmania. Journal of Geophysical Research-Atmospheres. 111

Date Published:

Sep

Keywords:

atlantic, chloroform, gases, methyl-chloride, nonmethane hydrocarbons, reactive chlorine, trace, troposphere, united-states, variability, volatile organic-compounds

Abstract:

[1] In situ observations ( every 4 hours) of dichloromethane (CH(2)Cl(2)) from April 1995 to December 2004 and trichloroethene (C(2)HCl(3)) and tetrachloroethene (C(2)Cl(4)) from September 2000 to December 2004 are reported for the Advanced Global Atmospheric Gases Experiment (AGAGE) station at Mace Head, Ireland. At a second AGAGE station at Cape Grim, Tasmania, CH(2)Cl(2) and C(2)Cl(4) data collection commenced in 1998 and 2000, respectively. C(2)HCl(3) is below the limit of detection at Cape Grim except during pollution episodes. At Mace Head CH(2)Cl(2) shows a downward trend from 1995 to 2004 of 0.7 +/- 0.2 ppt yr(-1) ( ppt: expressed as dry mole fractions in 10(12)), although from 1998 to 2004 the decrease has been only 0.3 +/- 0.1ppt yr(-1). Conversely, there has been a small but significant growth of 0.05 +/- 0.01 ppt yr(-1) in CH(2)Cl(2) at Cape Grim. The time series for C(2)HCl(3) and C(2)Cl(4) are relatively short for accurate trend analyses; however, we observe a small but significant decline in C(2)Cl(4) (0.18 +/- 0.05 ppt yr(-1)) at Mace Head. European emissions inferred from AGAGE measurements are compared to recent estimates from industry data and show general agreement for C(2)HCl(3). Emissions estimated from observations are lower than industry emission estimates for C(2)Cl(4) and much lower in the case of CH(2)Cl(2). A study of wildfires in Tasmania, uncontaminated by urban emissions, suggests that the biomass burning source of CH(2)Cl(2) may have been previously overestimated. All three solvents have distinct annual cycles, with the phases and amplitudes reflecting their different chemical reactivity with OH as the primary sink.

Notes:

n/a

Website

DOI:

10.1029/2006jd007082

Scripps Publication ID:

D18304