Halogenated organic species over the tropical South American rainforest

Abstract

Abstract. Airborne measurements of the halogenated trace gases methyl chloride, methyl bromide and chloroform were conducted over the Atlantic Ocean and about 1000 km of pristine tropical rainforest in • N, 51-59 • W) in October 2005. In the boundary layer (0-1.4 km), maritime air masses, advected over the forest by southeasterly trade winds, were measured at various distances from the coast. Since the organohalogens presented here have relatively long atmospheric lifetimes (0.4-1.0 years) in comparison to the advection times from the coast (1-2 days), emissions will accumulate in air traversing the rainforest. The distributions of methyl chloride, methyl bromide and chloroform were analyzed as a function of time the air spent over land and the respective relationship used to determine net fluxes from the rainforest for one week within the long dry season.Net fluxes from the rainforest ecosystem have been calculated for methyl chloride and chloroform as 9.5 (±3.8 2σ ) and 0.35 (±0.15 2σ )µg m −2 h −1 , respectively. No significant flux was observed for methyl bromide within the limits of these measurements.The global budget of methyl chloride contains large uncertainties, in particular with regard to a possible source from tropical vegetation. Our measurements are used in a large-scale approach to determine the net flux from a tropical ecosystem to the planetary boundary layer. The obtained global net flux of 1.5 (±0.6 2σ ) Tg yr −1 for methyl chloride is at the lower end of current estimates for tropical vegetation sources, which helps to constrain the range of tropical sources and sinks (0.82 to 8.2 Tg yr −1 from tropical plants, 0.03 to 2.5 Tg yr −1 from senescent/dead leaves and a sink of 0.1 to 1.6 Tg yr −1 by soil uptake). Nevertheless, these resultsCorrespondence to: J. Williams (williams@mpch-mainz.mpg.de) show that the contribution of the rainforest ecosystem is the major source in the global budget of methyl chloride.For chloroform, the extrapolated global net flux from tropical ecosystems is 56 (±23 2σ ) Gg yr −1 , which is of minor importance compared to the total global sources and might be already contained in the soil emission term.

Influence of corona discharge on the ozone budget in the tropical free troposphere: a case study of deep convection during GABRIEL

“…Table 1 shows an overview of the various measured species and the related measurement techniques that were applied for the different instruments for the GABRIEL campaign. Further information of the measured species is reported in Stickler et al (2007), Williams et al (2007), Gebhardt et al (2008), Eerdekens et al (2009) and Martinez et al (2010). In 10 measurement flights, of 3 to 3.5 h each, the troposphere was probed in a region between 3.5 and 6 • N and between 59 and 51 • W .…”

Flux estimates of isoprene, methanol and acetone from airborne PTR-MS measurements over the tropical rainforest during the GABRIEL 2005 campaign

“…Details on the airborne instrumentation for the measurements of CO 2 , H 2 O, CO, O 3 , NO, J NO 2 , H 2 O 2 , total peroxides, OH, HO 2 , HCHO, besides VOCs can be found elsewhere (Stickler et al, 2007;Martinez et al, 2008). The measurement of volatile organic compounds by the airborne proton transfer reaction mass spectrometer (PTR-MS) are described here, whereas VOCs measured with Thermo Desorption-Gas chromatography -Mass Spectrometry (TD-GCMS) and halogenated VOC canister GC-MS analysis are described by Williams et al (2007) and Gebhardt et al (2008), respectively. A second PTR-MS was sited in the forest approximately central in the measurement region (Brownsberg, Suriname) to provide 24 h ground level data for comparison with the aircraft .…”

An aircraft gas chromatograph–mass spectrometer System for Organic Fast Identification Analysis (SOFIA): design, performance and a case study of Asian monsoon pollution outflow

“…Scheeren et al (2003) have shown that a ratio of 10 ppt ppb −1 is indicative of Asian pollution over the eastern Mediterranean. Hence the higher CH 3 Cl / CO ratios observed in P1 ([CH 3 Cl / CO] P1 = 14.1 ± 2.6 ppt ppb −1 ) compared with P2 ([CH 3 Cl / CO] P2 = 8.7 ± 1.5 ppt ppb −1 ) are indicative of pollution outflow, which may have been influenced by other strong sources such as tropical vegetation (Gebhardt et al, 2008), biofuel use (Lobert et al, 1999) or the burning of agricultural residues, waste and dung (Scheeren et al, 2002).…”

“…Problems from co-collection of ozone have been recognized previously (Goldan et al, 1995) and are documented in several studies (Bates et al, 2000;Plass-Dülmer et al, 2002;Pollmann et al, 2005;Lee et al, 2006;Apel et al, 2008;Arnts, 2008;Hellen et al, 2012). The ozone interference can be either positive via artefact formation from reaction with ozone in the sampling system (e.g.…”

“…TOGA uses a custom-built liquid nitrogen (LN 2 ) fuelled system to cool sample enrichment traps down to −130 • C enabling a sample to be taken every 2-5 min. To our knowledge, three other fast GC systems have since been designed for aircraft operation: GhostMS (Sala et al, 2014), HCG (Jäger, 2014) and µDirac (Gostlow et al, 2010). None of the three require the use of a liquid cryogen and all have been successfully operated in aircraft, Zeppelin or balloon campaigns.…”