Injection of iodine to the stratosphere

Saiz‐Lopez, Alfonso; Baidar, Sunil; Cuevas, Carlos A.; Koenig, Theodore K.; Fernández, Rafael P.; Dix, B.; Kinnison, Douglas E.; Lamarque, Jean‐François; Rodríguez-Lloveras, Xavier; Campos, T.; Volkamer, Rainer

doi:10.1002/2015gl064796

Cited by 64 publications

(86 citation statements)

References 36 publications

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“…The tropospheric VCD of ∼ 2.3 ± 0.7 × 10 13 molec cm −2 BrO derived from this study falls in the range of other currently reported measurements, which span from ∼ 1 to 3 × 10 13 molec cm −2 Salawitch et al, 2005;Theys et al, 2007Theys et al, , 2011Coburn et al, 2011;Wang et al, 2015). The observed tropospheric BrO VCD is consistent with the VCD of 2.0 × 10 13 molec cm −2 measured by the same instrument during a previous study in the same location (Coburn et al, 2011).…”

Section: S Coburn Et Al: Mercury Oxidation From Bromine Chemistry Isupporting

confidence: 89%

“…compared ground-based and balloon-borne measurements to VCDs of BrO from the space-borne Global Ozone Monitoring Experiment (GOME) and found all platforms were consistent with a rather widespread tropospheric BrO VCD of 1-3 × 10 13 molec cm −2 once appropriate radiative transfer effects were taken into consideration. Salawitch et al (2005) and Theys et al (2011) also report satellite derived tropospheric BrO VCDs (GOME and GOME-2, respectively) for the midlatitudes of 2 × 10 13 and 1-3 × 10 13 molec cm −2 , respectively. Ground-based measurements Coburn et al, 2011) in the midlatitudes have reported BrO VCDs of 1-2 × 10 13 molec cm −2 that are comparable to the findings from satellites.…”

Section: Introductionmentioning

confidence: 99%

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Mercury oxidation from bromine chemistry in the free troposphere over the southeastern US

et al. 2016

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Abstract. The elevated deposition of atmospheric mercury over the southeastern United States is currently not well understood. Here we measure partial columns and vertical profiles of bromine monoxide (BrO) radicals, a key component of mercury oxidation chemistry, to better understand the processes and altitudes at which mercury is being oxidized in the atmosphere. We use data from a ground-based MAX-DOAS instrument located at a coastal site ∼ 1 km from the Gulf of Mexico in Gulf Breeze, FL, where we had previously detected tropospheric BrO (Coburn et al., 2011). Our profile retrieval assimilates information about stratospheric BrO from the WACCM chemical transport model (CTM), and uses only measurements at moderately low solar zenith angles (SZAs) to estimate the BrO slant column density contained in the reference spectrum (SCD Ref ). The approach has 2.6 degrees of freedom, and avoids spectroscopic complications that arise at high SZA; knowledge about SCD Ref further helps to maximize sensitivity in the free troposphere (FT). A cloud-free case study day with low aerosol load (9 April 2010) provided optimal conditions for distinguishing marine boundary layer (MBL: 0-1 km) and free-tropospheric (FT: 1-15 km) BrO from the ground. The average daytime tropospheric BrO vertical column density (VCD) of ∼ 2.3 × 10 13 molec cm −2 (SZA < 70 • ) is consistent with our earlier reports on other days. The vertical profile locates essentially all tropospheric BrO above 4 km, and shows no evidence for BrO inside the MBL (detection limit < 0.5 pptv). BrO increases to ∼ 3.5 pptv at 10-15 km altitude, consistent with recent aircraft observations. Our case study day is consistent with recent aircraft studies, in that the oxidation of gaseous elemental mercury (GEM) by bromine radicals to form gaseous oxidized mercury (GOM) is the dominant pathway for GEM oxidation throughout the troposphere above Gulf Breeze. The column integral oxidation rates are about 3.6 × 10 5 molec cm −2 s −1 for bromine, while the contribution from ozone (O 3 ) is 0.8 × 10 5 molec cm −2 s −1 . Chlorine-induced oxidation is estimated to add < 5 % to these mercury oxidation rates. The GOM formation rate is sensitive to recently proposed atmospheric scavenging reactions of the HgBr adduct by nitrogen dioxide (NO 2 ), and to a lesser extent also HO 2 radicals. Using a 3-D CTM, we find that surface GOM variations are also typical of other days, and are mainly derived from the FT. Bromine chemistry is active in the FT over Gulf Breeze, where it forms water-soluble GOM that is subsequently available for wet scavenging by thunderstorms or transport to the boundary layer.

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Section: S Coburn Et Al: Mercury Oxidation From Bromine Chemistry Isupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Mercury oxidation from bromine chemistry in the free troposphere over the southeastern US

et al. 2016

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“…Tropical annual averages have been computed between 20°N and 20°S, while the tropical Western Pacific (TWP) warm pool area in February has been used as a representative region with strong vertical convection (0° ≤ latitude ≤ 20°N; 120°E ≤ longitude ≤ 165°E). In the absence of measurements of atomic bromine or iodine in the free and upper troposphere, our CAM‐Chem halogen configuration has been validated with observed vertical profiles of the commonly targeted BrO [ Dorf et al , ] and IO [ Saiz‐Lopez et al , ] radicals in the tropical atmosphere (see supporting information).…”

Section: Resultsmentioning

confidence: 99%

On the formation of tropical rings of atomic halogens: Causes and implications

Saiz‐Lopez

Fernández

2016

Geophysical Research Letters

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Halogens produced by ocean biological and photochemical processes reach the tropical tropopause layer (TTL), where cold temperatures and the prevailing low ozone abundances favor the diurnal photochemical enhancement of halogen atoms. Under these conditions atomic bromine and iodine are modeled to be the dominant inorganic halogen species in the sunlit TTL, surpassing the abundance of the commonly targeted IO and BrO radicals. We suggest that due to the rapid photochemical equilibrium between halogen oxides and halogen atoms a natural atmospheric phenomenon evolves, which we have collectively termed “tropical rings of atomic halogens.” We describe the main causes controlling the modeled appearance and variability of these superposed rings of bare bromine and iodine atoms that circle the tropics following the Sun. Some potential implications for atmospheric oxidizing capacity are also explored. Our model results suggest that if experimentally confirmed, the extent and intensity of the halogen rings would directly respond to changes in oceanic halocarbon emissions, their atmospheric transport, and photochemistry.

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“…If iodic acid is irreversibly lost on aerosol (similar to sulfuric acid) its lifetime should only be on the order of several minutes at typical boundary layer conditions. Therefore, the presence of iodine indicates either a local iodine source or its transport from marine environments in the form of a reservoir substance, e.g., CH 3 I (the lifetime of CH 3 I is in the order of 1 week; see Saiz-Lopez et al, 2015), and subsequent release due to photolysis.…”

Section: Iodic Acid (Hio 3 ) and Oiomentioning

confidence: 99%

Observation of new particle formation and measurement of sulfuric acid, ammonia, amines and highly oxidized organic molecules at a rural site in central Germany

et al. 2016

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Abstract. The exact mechanisms for new particle formation (NPF) under different boundary layer conditions are not known yet. One important question is whether amines and sulfuric acid lead to efficient NPF in the atmosphere. Furthermore, it is not clear to what extent highly oxidized organic molecules (HOMs) are involved in NPF. We conducted field measurements at a rural site in central Germany in the proximity of three larger dairy farms to investigate whether there is a connection between NPF and the presence of amines and/or ammonia due to the local emissions from the farms. Comprehensive measurements using a nitrate chemical ionization-atmospheric pressure interface time-of-flight (CI-APi-TOF) mass spectrometer, a proton-transfer-reaction mass spectrometer (PTR-MS), particle counters and differential mobility analyzers (DMAs), as well as measurements of trace gases and meteorological parameters, were performed. We demonstrate here that the nitrate CI-APi-TOF is suitable for sensitive measurements of sulfuric acid, amines, a nitrosamine, ammonia, iodic acid and HOMs. NPF was found to correlate with sulfuric acid, while an anti-correlation with RH, amines and ammonia is observed. The anti-correlation between NPF and amines could be due to the efficient uptake of these compounds by nucleating clusters and small particles. Much higher HOM dimer (C 19 /C 20 compounds) concentrations during the night than during the day indicate that these HOMs do not efficiently self-nucleate as no nighttime NPF is observed. Observed iodic acid probably originates from an iodine-containing reservoir substance, but the iodine signals are very likely too low to have a significant effect on NPF.

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Injection of iodine to the stratosphere

Cited by 64 publications

References 36 publications

Mercury oxidation from bromine chemistry in the free troposphere over the southeastern US

Mercury oxidation from bromine chemistry in the free troposphere over the southeastern US

On the formation of tropical rings of atomic halogens: Causes and implications

Observation of new particle formation and measurement of sulfuric acid, ammonia, amines and highly oxidized organic molecules at a rural site in central Germany

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