Global distribution and seasonal concentration change of methyl iodide in the atmosphere

Yokouchi, Yoko; Osada, Kazuo; Wada, Makoto; Hasebe, Fumio; Agama, M.; Murakami, Ryuichi; Mukai, Hitoshi; Nojiri, Yukihiro; Inuzuka, Yoko; Toom-Sauntry, D.; Fraser, Paul J.

doi:10.1029/2008jd009861

Cited by 60 publications

(74 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The spatial disconnect between atmospheric IO and the Chl-a concentration, however, poses questions about which iodine emissions can legitimately be scaled using Chl-a distributions. Notably, some of the highest CH 3 I concentrations observed are found over the Eastern Pacific ocean (34), where deep convection also provides a transport pathway into the FT. The apparent correlation between satellite IO and Chl-a could possibly be because of the coupled effect of biological sources producing IO precursors with a longer lifetime and dynamical impacts on their distribution.…”

Section: Resultsmentioning

confidence: 99%

Detection of iodine monoxide in the tropical free troposphere

Dix

Baidar

Bresch

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

118

View full text Add to dashboard Cite

Atmospheric iodine monoxide (IO) is a radical that catalytically destroys heat trapping ozone and reacts further to form aerosols. Here, we report the detection of IO in the tropical free troposphere (FT). We present vertical profiles from airborne measurements over the Pacific Ocean that show significant IO up to 9.5 km altitude and locate, on average, two-thirds of the total column above the marine boundary layer. IO was observed in both recent deep convective outflow and aged free tropospheric air, suggesting a widespread abundance in the FT over tropical oceans. Our vertical profile measurements imply that most of the IO signal detected by satellites over tropical oceans could originate in the FT, which has implications for our understanding of iodine sources. Surprisingly, the IO concentration remains elevated in a transition layer that is decoupled from the ocean surface. This elevated concentration aloft is difficult to reconcile with our current understanding of iodine lifetimes and may indicate heterogeneous recycling of iodine from aerosols back to the gas phase. Chemical model simulations reveal that the iodine-induced ozone loss occurs mostly above the marine boundary layer (34%), in the transition layer (40%) and FT (26%) and accounts for up to 20% of the overall tropospheric ozone loss rate in the upper FT. Our results suggest that the halogen-driven ozone loss in the FT is currently underestimated. More research is needed to quantify the widespread impact that iodine species of marine origin have on free tropospheric composition, chemistry, and climate.atmospheric chemistry | oxidative capacity | halogens | heterogeneous chemistry | air-sea exchange R eactive iodine impacts atmospheric chemistry in several ways. Catalytic reaction cycles involving iodine atoms and iodine monoxide (IO; I x = I + IO) destroy tropospheric ozone, which is a primary source for OH radicals (1, 2). Halogens contribute ∼45% of the ozone loss in the remote tropical marine boundary layer (MBL) (2-4). IO further affects the oxidative capacity of the atmosphere through fast reactions with HO 2 radicals and the resulting changes in HO x (HO x = OH + HO 2 ) (1, 2). Iodine also affects NO x (NO x = NO + NO 2 ) by oxidizing NO to NO 2 (1-4). Additionally, bromine atom recycling by IO increases ozone destruction and mercury oxidation rates in the MBL, resulting in higher mercury deposition rates to ecosystems and increased availability to the food chain (2, 5, 6). Finally, in coastal regions, the formation of ultrafine aerosol particles from iodine oxides can be a source of cloud condensation nuclei that can modify Earth's albedo and thus, the radiative budget of the atmosphere (2, 7).Oceans are the main source of iodine to the atmosphere. Most current knowledge of iodine sources and chemistry is based on measurements in the MBL (3,(8)(9)(10)(11)(12)(13). IO observations at coastal MBL sites primarily link iodine sources to macroalgae (8-10). More recent studies have measured IO at open ocean sites (3, 11-13), suggesting that ther...

show abstract

Section: Resultsmentioning

confidence: 99%

Detection of iodine monoxide in the tropical free troposphere

Dix

Baidar

Bresch

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

118

View full text Add to dashboard Cite

show abstract

“…Among the organic source gases, methyl iodide (CH 3 I) is the generally most abundant one due to its comparatively long atmospheric lifetime of ∼7 days and due to sizable emissions from algae and oceanic surface waters (WMO-2006). Measurements in marine boundary layer air indicate that background CH 3 I concentrations range between 0.1 ppt and 2 ppt (Butler et al, 2007;Yokouchi et al, 2008) with higher values reported from North Atlantic coastal source regions (e.g. Peters et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Constraints on inorganic gaseous iodine in the tropical upper troposphere and stratosphere inferred from balloon-borne solar occultation observations

et al. 2009

View full text Add to dashboard Cite

show abstract

“…Methyl iodide is a very short-lived species (1-2 d) with a major oceanic source (Yokouchi et al, 2008) and minor terrestrial sources (e.g., Redeker et al, 2003;Sive et al, 2007). Its mixing ratio declined sharply with altitude, consistent with its short atmospheric lifetime (Fig.…”

Section: Minimally Enhanced Halocarbonsmentioning

confidence: 99%

Characterization of trace gases measured over Alberta oil sands mining operations: 76 speciated C2–C10 volatile organic compounds (VOCs), CO2, CH4, CO, NO, NO2, NOy, O3 and SO2

et al. 2010

View full text Add to dashboard Cite

Abstract. Oil sands comprise 30% of the world's oil reserves and the crude oil reserves in Canada's oil sands deposits are second only to Saudi Arabia. The extraction and processing of oil sands is much more challenging than for light sweet crude oils because of the high viscosity of the bitumen contained within the oil sands and because the bitumen is mixed with sand and contains chemical impurities such as sulphur. Despite these challenges, the importance of oil sands is increasing in the energy market. To our best knowledge this is the first peer-reviewed study to characterize volatile organic compounds (VOCs) emitted from Alberta's oil sands mining sites. We present high-precision gas chromatography measurements of 76 speciated C 2 -C 10 VOCs (alkanes, alkenes, alkynes, cycloalkanes, aromatics, monoterpenes, oxygenated hydrocarbons, halocarbons and sulphur compounds) in 17 boundary layer air samples collected over surface mining operations in northeast Alberta on 10 July 2008, using the NASA DC-8 airborne laboratory as a research platform. In addition to the VOCs, we present simultaneous measurements of CO 2 , CH 4 , CO, NO, NO 2 , NO y , O 3 and SO 2 , which were measured in situ aboard the DC-8.Carbon dioxide, CH 4 , CO, NO, NO 2 , NO y , SO 2 and 53 VOCs (e.g., non-methane hydrocarbons, halocarbons, sulphur species) showed clear statistical enhancements (1.1-397×) over the oil sands compared to local background valCorrespondence to: I. J. Simpson (isimpson@uci.edu) ues and, with the exception of CO, were greater over the oil sands than at any other time during the flight. Twenty halocarbons (e.g., CFCs, HFCs, halons, brominated species) either were not enhanced or were minimally enhanced (<10%) over the oil sands. Ozone levels remained low because of titration by NO, and three VOCs (propyne, furan, MTBE) remained below their 3 pptv detection limit throughout the flight. Based on their correlations with one another, the compounds emitted by the oil sands industry fell into two groups: (1) evaporative emissions from the oil sands and its products and/or from the diluent used to lower the viscosity of the extracted bitumen (i.e., C 4 -C 9 alkanes, C 5 -C 6 cycloalkanes, C 6 -C 8 aromatics), together with CO; and (2) emissions associated with the mining effort, such as upgraders (i.e., CO 2 , CO, CH 4 , NO, NO 2 , NO y , SO 2 , C 2 -C 4 alkanes, C 2 -C 4 alkenes, C 9 aromatics, short-lived solvents such as C 2 Cl 4 and C 2 HCl 3 , and longer-lived species such as HCFC-22 and HCFC-142b). Prominent in the second group, SO 2 and NO were remarkably enhanced over the oil sands, with maximum mixing ratios of 38.7 ppbv and 5.0 ppbv, or 383× and 319× the local background, respectively. These SO 2 levels are comparable to maximum values measured in heavily polluted megacities such as Mexico City and are attributed to coke combustion. By contrast, relatively poor correlations between CH 4 , ethane and propane suggest low levels of natural gas leakage despite its heavy use at the surface mining sites. Instead the elevat...

show abstract

Global distribution and seasonal concentration change of methyl iodide in the atmosphere

Cited by 60 publications

References 40 publications

Detection of iodine monoxide in the tropical free troposphere

Detection of iodine monoxide in the tropical free troposphere

Constraints on inorganic gaseous iodine in the tropical upper troposphere and stratosphere inferred from balloon-borne solar occultation observations

Characterization of trace gases measured over Alberta oil sands mining operations: 76 speciated C<sub>2</sub>–C<sub>10</sub> volatile organic compounds (VOCs), CO<sub>2</sub>, CH<sub>4</sub>, CO, NO, NO<sub>2</sub>, NO<sub>y</sub>, O<sub>3</sub> and SO<sub>2</sub>

Contact Info

Product

Resources

About