Bromoform in the tropical boundary layer of the Maritime Continent during OP3

Abstract

Abstract. We report measurements of bromoform made by gas chromatography during the OP3 campaign in 2008. Measurements were made simultaneously for a few days at the World Meteorological Organization (WMO) Global Atmospheric Watch (GAW) site in the Danum Valley, a rainforest location in Sabah, Borneo, and at a nearby coastal site at Kunak. Background values at Kunak were higher than those measured in the rainforest (2-5 ppt compared with 1 ppt) and excursions away from the background were very much higher, reaching 10 s of ppt. Measurements of C 2 Cl 4 , an industrial tracer, showed no significant difference in background at the two sites. Modelling using two different models can reproduce a number of the observed features. The data are consistent with a strong, local coastal source of bromoform in eastern Sabah and can be used to infer the strength of the source of bromoform in South East Asia. However, they provide only a very weak constraint on global emissions. The global model results highlight the difficulty for short-lived species of extrapolating limited duration, local measurements to a global source.

The impact of local surface changes in Borneo on atmospheric composition at wider spatial scales: coastal processes, land-use change and air quality

“…(a) Variability in CHBr 3 CHBr 3 measured at Bukit Atur during OP3 ranged from about 0.6 to 3 ppt, with most measurements around 1 ppt (see Pyle et al [69] for much more detail). Good consistency was found between the two mDirac GC-ECDs and the GC-MS measurements.…”

“…We consider two example studies, the first of which [69] has explored the source strength of bromoform in South East Asia and the second has determined the total amount of short-lived bromine in the boundary layer of the Maritime Continent, which could potentially be lifted in deep convection towards the stratosphere.…”

“…Two mDirac GC-ECDs [70] were used in Sabah: one was based at the Bukit Atur global atmospheric watch (GAW) site in the Danum Valley, and the other was used in a series of short, exploratory deployments at different locations in the rainforest as well as at the coastal town of Kunak [69]. A GC-MS system operating primarily in negative ion chemical ionization mode [71] was co-located at Bukit Atur making measurements during both periods, while a second GC-MS was used to analyse the whole air samples collected on the BAe-146 aircraft during the July detachment [72].…”

Isotopic composition of polyhalomethanes from marine macrophytes – systematic effects of the halogen substituents on isotopic composition

“…[59] Isotope effects in chemical reactions involving 14 C are generally assumed to be 1.9 times larger than those involving 13 C, [60,61] suggesting a 13 C-KIE of ,27 %. We found no information on the carbon isotope effect of the enolisation, the rate-limiting step of the halogenation.…”

“…However, the current emissions estimates for these climaterelevant compounds remain fairly uncertain owing to the large spatial and temporal variability in observed halocarbon mixing ratios and fluxes. This is, in particular, true for short-lived halocarbons such as iodomethane (CH 3 I) and bromoform (tribromomethane, CHBr 3 ), [8][9][10][11][12][13][14] with the largest uncertainties in the known sources being observed for coastal and near-shore emissions. [15] Despite the uncertainties in global halocarbon emission budgets, it is well accepted that in the marine realm, diverse autotrophic organisms contribute to halocarbon production.…”