NMHCs and halocarbons in Asian continental outflow during the Transport and Chemical Evolution over the Pacific (TRACE‐P) Field Campaign: Comparison With PEM‐West B

Abstract

We present an overview of the spatial distributions of nonmethane hydrocarbons (NMHCs) and halocarbons observed over the western north Pacific as part of the NASA GTE Transport and Chemical Evolution over the Pacific (TRACE‐P) airborne field campaign (February–April 2001). The TRACE‐P data are compared with earlier measurements from the Pacific Rim during the Pacific Exploratory Mission‐West B (PEM‐West B), which took place in February–March 1994, and with emission inventory data for 2000. Despite the limited spatial and temporal data coverage inherent to airborne sampling, mean levels of the longer‐lived NMHCs (including ethane, ethyne, and benzene) were remarkably similar to our results during the PEM‐West B campaign. By comparison, mixing ratios of the fire extinguisher Halon‐1211 (CF2ClBr) increased by about 50% in the period between 1994 and 2001. Southern China (south of 35°N), and particularly the Shanghai region, appears to have been a substantial source of Halon‐1211 during TRACE‐P. Our previous analysis of the PEM‐West B data employed methyl chloroform (CH3CCl3) as a useful industrial tracer. However, regulations have reduced its emissions to the extent that its mixing ratio during TRACE‐P was only one‐third of that measured in 1994. Methyl chloroform mixing ratio “hot spots,” indicating regions downwind of continuing emissions, included outflow from the vicinity of Shanghai, China, but particularly high emission ratios relative to CO were observed close to Japan and Korea. Tetrachloroethene (C2Cl4) levels have also decreased significantly, especially north of 25°N, but this gas still remains a useful indicator of northern industrial emissions. Methyl bromide (CH3Br) levels were systematically 1–2 pptv lower from 1994 to 2001, in accord with recent reports. However, air masses that had been advected over Japan and/or South Korean port cities typically exhibited elevated levels of CH3Br. As a consequence, emissions of CH3Br from Japan and Korea calculated employing CH3Br/CO ratios and scaled to CO emission inventory estimates, were almost as large as for all of south China (south of 35°N). Total east Asian emissions of CH3Br and CH3Cl were estimated to be roughly 4.7 Gg/yr and 167 Gg/yr, respectively, in 2001.

Aerosol composition of the tropical upper troposphere

“…This rate constant is appropriate for a wide variety of gas phase organics species, in particular, aldehydes, ketones, peroxides, and unsaturated hydrocarbons (DeMore, 2006;Atkinson et al, 2006). In other studies, the most abundant nonmethane hydrocarbons (NMHCs) in the remote upper troposphere (<12 km) were ethane, ethyne, propane, and short chain oxygenated species: methanol, acetone, acetaldehyde, and methyl peroxide (Blake et al, 2003a;Singh et al, 2004). Total NMHC levels were 1-5 ppbv.…”

Estimate of anthropogenic halocarbon emission based on measured ratio relative to CO in the Pearl River Delta region, China

“…(Barletta et al, 2006;Blake et al, 2003). d The lowest 20-th percentile of the dataset for Guangzhou and Xinken are also shown here.…”

Injection heights of springtime biomass-burning plumes over peninsular Southeast Asia and their impacts on long-range pollutant transport

“…Two NASA aircraft were deployed during the campaign: the DC-8 (12 km ceiling) and the P-3B (7 km ceiling). BC absorption was measured on both aircraft at 565 nm using particle soot absorption photometers (Radiance Research) and corrected for scattering (Bond et al, 1999;. We calculated BC concentrations by assuming a mass absorption efficiency of 7.5 m 2 g −1 (Bond et al, 2013) and converting to standard temperature and pressure conditions (298 K and 1013 hPa, STP).…”