Correlations and emission ratios among bromoform, dibromochloromethane, and dibromomethane in the atmosphere

Abstract

[1] Bromoform (CHBr 3 ), dibromochloromethane (CHBr 2 Cl), and dibromomethane (CH 2 Br 2 ) in the atmosphere were measured at various sites, including tropical islands, the Arctic, and the open Pacific Ocean. Up to 40 ppt of bromoform was observed along the coasts of tropical islands under a sea breeze. Polybromomethane concentrations were highly correlated among the coastal samples, and the ratios CH 2 Br 2 /CHBr 3 and CHBr 2 Cl/ CHBr 3 showed a clear tendency to decrease with increasing CHBr 3 concentration. These findings are consistent with the observations that polybromomethanes are emitted mostly from macroalgae whose growth is highly localized to coastal areas and that CHBr 3 has the shortest lifetime among these three compounds. The relationship between the concentration ratios CHBr 3 /CH 2 Br 2 and CHBr 2 Cl/CH 2 Br 2 suggested a large mixing/ dilution effect on bromomethane ratios in coastal regions and yielded a rough estimate of 9 for the molar emission ratio of CHBr 3 /CH 2 Br 2 and of 0.7 for that of CHBr 2 Cl/CH 2 Br 2 . Using these ratios and an global emission estimate for CH 2 Br 2 (61 Gg/yr (Br)) calculated from its background concentration, the global emission rates of CHBr 3 and CHBr 2 Cl were calculated to be approximately 820(±310) Gg/yr (Br) and 43(±16) Gg/yr (Br), respectively, assuming that the bromomethanes ratios measured in this study are global representative. The estimated CHBr 3 emission is consistent with that estimated in a very recent study by integrating the sea-to-air flux database. Thus the contribution of CHBr 3 and CHBr 2 Cl to inorganic Br in the atmosphere is likely to be more important than previously thought. Citation: Yokouchi, Y., et al. (2005), Correlations and emission ratios among bromoform, dibromochloromethane, and dibromomethane in the atmosphere,

Bromocarbons in the tropical coastal and open ocean atmosphere during the 2009 Prime Expedition Scientific Cruise (PESC-09)

“…For example, Yokouchi observed mixing ratios of CHBr 3 of 0.32 to 7.1 pmol mol −1 , which is similar to our study, with a range of 1.85-5.25 pmol mol −1 for CHBr 3 . This contrasts with the study of Yokouchi et al (2005) over the western Pacific and Java Island, who observed high mixing ratios with a range of 16.3 to 31.4 pmol mol −1 at Christmas Island, and 4.2 to 43.6 pmol mol −1 at San Cristobal Island. Pyle et al (2011) also observed high mixing ratios of CHBr 3 in Malaysian Borneo (near to stations 21 and 27 in this study), with a range of 2 to 60 pmol mol −1 .…”

“…Significant correlations between brominated halocarbons have been observed in coastal air measurements, suggesting that these gases have come from the same sources (Yokouchi et al, 2005;O'Brien et al, 2009;Carpenter et al, 2009). Several studies have exploited these correlations to explore the possible source strengths of the individual species.…”

“…Several studies have exploited these correlations to explore the possible source strengths of the individual species. Carpenter et al (2003), Yokouchi et al (2005) and O'Brien et which CHBr 3 has been removed at a faster rate. Yokouchi et al (2005) used the minimum ratio of CH 2 Br 2 /CHBr 3 to define the ratio of the emission sources by assuming that the emissions came from the common sources and are constant on a regional scale.…”

“…Carpenter et al (2003), Yokouchi et al (2005) and O'Brien et which CHBr 3 has been removed at a faster rate. Yokouchi et al (2005) used the minimum ratio of CH 2 Br 2 /CHBr 3 to define the ratio of the emission sources by assuming that the emissions came from the common sources and are constant on a regional scale. If the global emission of CH 2 Br 2 is known, then that of CHBr 3 can be inferred.…”

“…More recently, Yokouchi et al (2005) reported a larger range of bromocarbon concentrations, with CHBr 3 ranging from ∼ 1 pmol mol −1 over the open ocean to ∼ 40 pmol mol −1 in the vicinity of tropical islands in the western Pacific region. Butler et al (2007a) collected data from seven open ocean cruises spanning a ten-year period, covering much of the world's oceans.…”