Read Full Article (file size: 537511 bytes)    Cited by

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 107, NO. D19, 8015, doi:10.1029/2001JD001121, 2002

Methyl chloride and other chlorocarbons in polluted air during INDOEX

H. A. Scheeren

Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, Netherlands

J. Lelieveld

Atmospheric Chemistry Department, Max Planck Institute for Chemistry, Mainz, Germany

J. A. de Gouw

Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, Netherlands

C. van der Veen

Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, Netherlands

H. Fischer

Atmospheric Chemistry Department, Max Planck Institute for Chemistry, Mainz, Germany

Abstract

Methyl chloride (CH₃Cl) is the most abundant, natural, chlorine-containing gas in the atmosphere, with oceans and biomass burning as major identified sources. Estimates of global emissions suffer from large uncertainties, mostly for the tropics, partly due to a lack of measurements. We present analyses of whole-air canister samples for selected nonmethane hydrocarbons and chlorocarbons. The samples were collected from an aircraft during the Indian Ocean Experiment (INDOEX) campaign over the northern Indian Ocean in February and March 1999. The CH₃Cl results are correlated to selected nonmethane hydrocarbons and in situ measurements of carbon monoxide (CO) and acetonitrile (CH₃CN). We relate high mixing ratios of ∼750 pmol mol⁻¹ of CH₃Cl to biomass burning, as observed in polluted air masses from India and Southeast Asia. We infer a relatively high enhancement ratio relative to CO, ΔCH₃Cl/ΔCO ≈1.74 ± 0.21 × 10⁻³ mol mol⁻¹. The CH₃Cl levels relate to the extensive biofuel use in India and Southeast Asia, notably the burning of agricultural waste and dung with a comparatively high chlorine content. It appears that CH₃Cl emissions from biofuel consumption in India and Southeast Asia have been underestimated in the past. Furthermore, we observed enhanced dichloromethane (CH₂Cl₂) and trichloromethane (CHCl₃) levels, correlating with high CO, acetylene (C₂H₂) and CH₃Cl, indicating that biomass burning is a small but significant source of these species.

Published 4 September 2002.

Index Terms: 0322 Atmospheric Composition and Structure: Constituent sources and sinks; 0315 Atmospheric Composition and Structure: Biosphere/atmosphere interactions; 0365 Atmospheric Composition and Structure: Troposphere—composition and chemistry; 0368 Atmospheric Composition and Structure: Troposphere—constituent transport and chemistry; 0312 Atmospheric Composition and Structure: Air/sea constituent fluxes (3339, 4504).

Read Full Article (file size: 537511 bytes)    Cited by

Citation: Scheeren, H. A., J. Lelieveld, J. A. de Gouw, C. van der Veen, and H. Fischer (2002), Methyl chloride and other chlorocarbons in polluted air during INDOEX, J. Geophys. Res., 107(D19), 8015, doi:10.1029/2001JD001121.

Copyright 2002 by the American Geophysical Union.