Field evidence of autocatalytic iodine release from atmospheric aerosol

2021 ◽  
Author(s):  
Yee Jun Tham ◽  
Xu-Cheng He ◽  
Qinyi Li ◽  
Carlos A. Cuevas ◽  
Darius Ceburnis ◽  
...  
Keyword(s):  
Loss Rate ◽  
Heterogeneous Reaction ◽  
Marine Aerosol ◽  
Oxidation Capacity ◽  
Sea Salt Aerosol ◽  
Field Evidence ◽  
Heterogeneous Processes ◽  
Iodine Monobromide ◽  
Iodine Release ◽  
Atomic Iodine

<p>Reactive iodine plays a key role in determining the oxidation capacity of the atmosphere in addition to being implicated in the formation of new particles in the marine environment. Recycling of reactive iodine from heterogeneous processes on sea-salt aerosol was hypothesized over two decades ago but the understanding of this mechanism has been limited to laboratory studies and has not been confirmed in the atmosphere until now. Here, we report the first direct ambient observations of hypoiodous acid (HOI) and heterogeneous recycling of iodine monochloride (ICl) and iodine monobromide (IBr) at Mace Head Observatory in Ireland (53°19’ N, 9°54’ W) during the summer of 2018. A newly developed bromide based chemical ionization atmospheric pressure interface time-of-flight mass spectrometer (Br-CI-APi-TOF) was deployed to measure I<sub>2</sub>, HOI, ICl, and IBr. Significant levels of ICl and IBr, with mean daily maxima of 4.3 and 3.0 pptv (1 min-average), respectively, have been observed throughout the campaign. We show that the heterogeneous reaction of HOI on marine aerosol and subsequent production of iodine interhalogens (ICl and IBr) are much faster than previously thought. These results indicate that the fast formation of iodine interhalogens, together with their rapid photolysis, results in more efficient recycling of atomic iodine than currently estimated by the models. The photolysis of the observed ICl and IBr leads to 32% increase in the daytime average of atomic iodine production rate, thereby enhancing the average daytime iodine-catalyzed ozone loss rate by 10-20%. Our findings provide the first direct field evidence that the autocatalytic mechanism of iodine release from marine aerosol is important in the atmosphere and can have significant impacts on atmospheric oxidation capacity and new particle formation in the troposphere.</p>

scholarly journals Direct field evidence of autocatalytic iodine release from atmospheric aerosol

2021 ◽  
Vol 118 (4) ◽  
pp. e2009951118
Author(s):  
Yee Jun Tham ◽  
Xu-Cheng He ◽  
Qinyi Li ◽  
Carlos A. Cuevas ◽  
Jiali Shen ◽  
...  
Keyword(s):  
Loss Rate ◽  
Marine Boundary Layer ◽  
Heterogeneous Reaction ◽  
Marine Aerosol ◽  
Oxidation Capacity ◽  
Field Evidence ◽  
Iodine Monobromide ◽  
Iodine Release ◽  
Product Species ◽  
Atomic Iodine

Reactive iodine plays a key role in determining the oxidation capacity, or cleansing capacity, of the atmosphere in addition to being implicated in the formation of new particles in the marine boundary layer. The postulation that heterogeneous cycling of reactive iodine on aerosols may significantly influence the lifetime of ozone in the troposphere not only remains poorly understood but also heretofore has never been observed or quantified in the field. Here, we report direct ambient observations of hypoiodous acid (HOI) and heterogeneous recycling of interhalogen product species (i.e., iodine monochloride [ICl] and iodine monobromide [IBr]) in a midlatitude coastal environment. Significant levels of ICl and IBr with mean daily maxima of 4.3 and 3.0 parts per trillion by volume (1-min average), respectively, have been observed throughout the campaign. We show that the heterogeneous reaction of HOI on marine aerosol and subsequent production of iodine interhalogens are much faster than previously thought. These results indicate that the fast formation of iodine interhalogens, together with their rapid photolysis, results in more efficient recycling of atomic iodine than currently considered in models. Photolysis of the observed ICl and IBr leads to a 32% increase in the daytime average of atomic iodine production rate, thereby enhancing the average daytime iodine-catalyzed ozone loss rate by 10 to 20%. Our findings provide direct field evidence that the autocatalytic mechanism of iodine release from marine aerosol is important in the atmosphere and can have significant impacts on atmospheric oxidation capacity.

Heterogeneous formation of HONO and its impacts on haze formation in the YRD region of China

2020 ◽  
Author(s):  
Jun Zheng ◽  
Xiaowen Shi ◽  
Yan Ma
Keyword(s):  
Heterogeneous Reaction ◽  
Particle Surface ◽  
Ground Surface ◽  
Yangtze River Delta ◽  
Heterogeneous Reactions ◽  
Atmospheric Oxidation ◽  
Industrial Zone ◽  
Particle Surface Area ◽  
Oxidation Capacity ◽  
The Yrd

<p>A suite of instruments were deployed to simultaneously measure nitrous acid (HONO), nitrogen oxides (NO<sub>x</sub>= NO + NO<sub>2</sub>), carbon monoxide (CO), ozone (O<sub>3</sub>), volatile organic compounds (VOCs, including formaldehyde (HCHO)) and meteorological parameters near a typical industrial zone in Nanjing of the Yangtze River Delta region, China. High levels of HONO were detected using a wet chemistry-based method. HONO ranged from 0.03-7.04 ppbv with an average of 1.32 ±0.92 ppbv. Elevated daytime HONO was frequently observed with a minimum of several hundreds of pptv on average, which cannot be explained by the homogeneous OH + NO reaction (P<sub>OH+NO</sub>) alone, especially during periods with high loadings of particulate matters (PM<sub>2.5</sub>). The HONO chemistry and its impact on atmospheric oxidation capacity in the study area were further investigated using a MCM-box model. The results show that the average hydroxyl radical (OH) production rate was dominated by the photolysis of HONO (7.13×10<sup>6</sup>molecules cm<sup>-3 </sup>s<sup>-1</sup>), followed by ozonolysis of alkenes (3.94×10<sup>6</sup>molecules cm<sup>-3 </sup>s<sup>-1</sup>), photolysis of O<sub>3</sub>(2.46×10<sup>6</sup>molecules cm<sup>-3 </sup>s<sup>-1</sup>) and photolysis of HCHO (1.60×10<sup>6</sup>molecules cm<sup>-3 </sup>s<sup>-1</sup>), especially within the plumes originated from the industrial zone. The observed similarity between HONO/NO<sub>2</sub>and HONO in diurnal profiles strongly suggests that HONO in the study area was likely originated from NO<sub>2</sub>heterogeneous reactions. The averagenighttimeNO<sub>2</sub>to HONO conversion ratewas determined to be ~0.9% hr<sup>-1</sup>. Good correlation between nocturnal HONO/NO<sub>2</sub>and the products of particle surface area density (S/V) and relative humidity (RH), S/V×RH,supports the heterogeneous NO<sub>2</sub>/H<sub>2</sub>O reaction mechanism. The other HONO source, designated as P<sub>unknonwn</sub>, was about twice as much as P<sub>OH+NO </sub>on average and displayed a diurnal profile with an evidently photo-enhanced feature, i.e., photosensitized reactions of NO<sub>2</sub>may be an important daytime HONO source. Nevertheless, our results suggest that daytime HONO formation was mostly due to the light-induced conversion of NO<sub>2</sub>on aerosol surfaces but heterogeneous NO<sub>2</sub>reactions on ground surface dominated nocturnal HONO production. Concurred elevated HONO and PM<sub>2.5</sub>levels strongly indicate that high HONO may increase the atmospheric oxidation capacity and further promote the formation of secondary aerosols, which may in turn synergistically boost NO<sub>2</sub>/HONO conversion by providing more heterogeneous reaction sites.</p>

Kinetics of heterogeneous processes

2005 ◽  
Author(s):  
Boris S. Bokstein ◽  
Mikhail I. Mendelev ◽  
David J. Srolovitz
Keyword(s):  
Oxide Layer ◽  
Atomic Oxygen ◽  
Reaction Rate ◽  
Heterogeneous Reaction ◽  
Effective Rate Constant ◽  
Internal Oxide ◽  
Reactant Concentration ◽  
Rate Determining Step ◽  
Oxidation Reduction ◽  
Heterogeneous Processes

Most practical reactions that occur in synthesizing or processing materials are heterogeneous. These include oxidation, reduction reactions, dissolution of solids in liquids, and most solid-state phase transformations. Consider the oxidation of a metal by exposure of a solid metal to an atmosphere with a finite partial pressure of oxygen. In order for oxidation to occur, molecular oxygen must dissociate into atomic oxygen on the metal surface. In some cases, atomic oxygen diffuses into the metal and reacts to form an internal oxide, while in others, the reaction occurs at the surface. In the latter case, thickening of the oxide layer requires either metal or oxygen diffusion through the growing oxide layer. This example demonstrates that heterogeneous processes commonly involve several steps. The first step is usually the transport of a reactant through one of the phases to the interface. The second is the adsorption (segregation) or chemical reaction on the interface. Finally, the last third step is the diffusion of the products into the growing phase or the desorption of the product. Since the entire heterogeneous process is a type of complex reaction, there is usually one step that controls the rate of the process, that is, is the rate-determining step. Recall that the rate-determining step is the slowest (fastest) step for a consecutive (parallel) reaction (see Sections 8.2.1 and 8.2.2). Consider the case of a consecutive heterogeneous reaction in which one of the reactants is transported through the fluid phase to the solid–fluid interface, where a first-order reaction takes place. The reaction rate ωr in such a case is ωr=kcx, where cx is the concentration of the reactant on the interface. Since the reactant is consumed at the interface, cx is smaller than the reactant concentration far from the interface, c0. It is usually easier to measure the reactant concentration in the bulk fluid. Therefore, it is convenient, to rewrite the reaction rate in terms of the bulk concentration in the fluid and an effective rate constant . . . ωr = kcx = keffc0. (11.1) . . . It is easiest to see the relation between keff and k by considering the steady-state case.

Ozone oxidation of sulfur in sea-salt aerosol particles during the Azores Marine Aerosol and Gas Exchange experiment

1995 ◽  
Vol 100 (D11) ◽  
pp. 23075 ◽  
Author(s):  
H. Sievering ◽  
E. Gorman ◽  
T. Ley ◽  
A. Pszenny ◽  
M. Springer-Young ◽  
...  
Keyword(s):  
Gas Exchange ◽  
Aerosol Particles ◽  
Sea Salt ◽  
Marine Aerosol ◽  
Ozone Oxidation ◽  
Sea Salt Aerosol

scholarly journals Primary marine aerosol emissions: size resolved eddy covariance measurements with estimates of the sea salt and organic carbon fractions

2007 ◽  
Vol 7 (5) ◽  
pp. 13345-13400 ◽  
Author(s):  
E. D. Nilsson ◽  
E. M. Mårtensson ◽  
J. S. Van Ekeren ◽  
G. de Leeuw ◽  
M. Moerman ◽  
...  
Keyword(s):  
Wind Speed ◽  
Organic Carbon ◽  
Eddy Covariance ◽  
Sea Salt ◽  
Sea Spray ◽  
Marine Aerosol ◽  
Particle Counter ◽  
Wind Speeds ◽  
Sea Salt Aerosol ◽  
Aerosol Emissions

Abstract. Primary marine aerosol fluxes were measured using eddy covariance (EC), a condensation particle counter (CPC) and an optical particle counter (OPC) with a heated inlet. The later was used to discriminate between sea salt and total aerosol. Measurements were made from the 25 m tower at the research station Mace Head at the Irish west coast, May to September 2002. The aerosol fluxes were dominated by upward fluxes, sea spray from bubble bursting at the ocean surface. The sea salt aerosol number emissions increased two orders of magnitude with declining diameter from 1 to 0.1 μm where it peaked at values of 105 to 107 particles m−2s−1. The sea salt emissions increased at all sizes in the wind range 4 to 22 ms−1, in consistency with a power function of the wind speed. The sea salt emission data were compared to three recent sub micrometer sea salt source parameterisations. The best agreement was with Mårtensson et al. (2003), which appear to apply from 0.1 to 1.1 μm diameters in temperate water (12°C) as well as tropical water (25°C). The total aerosol emissions were independent of the wind speed below 10 ms−1, but increased with the wind above 10 ms−1. The aerosol volume emissions were larger for the total aerosol than for the sea salt at all wind speeds, while the sea salt number emissions approached the total number emissions at 15 ms−1. It is speculated that this is caused by organic carbon in the surface water that is depleted at high wind speeds. The data are consistent with an internal aerosol mixture of sea salt, organic carbon and water. Using the aerosol model by Ellison et al. (1999) (a mono-layer of organic carbon surrounding a water-sea-salt brine) we show that the total and sea salt aerosol emissions are consistent. This predict that the organic carbon fraction increase with decreasing diameter from a few % at 1 μm over 50% at about 0.5 μm to about 90% at 0.1 μm, in consistency with simultaneous chemical data by Cavalli et al. (2004). The combined models of Mårtensson et al. (2003) and Ellison et al. (1999) reproduce the observed total aerosol emissions and offer an approach to model the organic sea spray fraction.

scholarly journals The role of chlorine in global tropospheric chemistry

2019 ◽  
Vol 19 (6) ◽  
pp. 3981-4003 ◽  
Author(s):  
Xuan Wang ◽  
Daniel J. Jacob ◽  
Sebastian D. Eastham ◽  
Melissa P. Sulprizio ◽  
Lei Zhu ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Atmospheric Chemistry ◽  
Sea Salt ◽  
Tropospheric Chemistry ◽  
Mixing Ratios ◽  
Sea Salt Aerosol ◽  
Oxidation Of Methane ◽  
Heterogeneous Processes ◽  
Marine Air ◽  
Global Mean

Abstract. We present a comprehensive simulation of tropospheric chlorine within the GEOS-Chem global 3-D model of oxidant–aerosol–halogen atmospheric chemistry. The simulation includes explicit accounting of chloride mobilization from sea salt aerosol by acid displacement of HCl and by other heterogeneous processes. Additional small sources of tropospheric chlorine (combustion, organochlorines, transport from stratosphere) are also included. Reactive gas-phase chlorine Cl*, including Cl, ClO, Cl2, BrCl, ICl, HOCl, ClNO3, ClNO2, and minor species, is produced by the HCl+OH reaction and by heterogeneous conversion of sea salt aerosol chloride to BrCl, ClNO2, Cl2, and ICl. The model successfully simulates the observed mixing ratios of HCl in marine air (highest at northern midlatitudes) and the associated HNO3 decrease from acid displacement. It captures the high ClNO2 mixing ratios observed in continental surface air at night and attributes the chlorine to HCl volatilized from sea salt aerosol and transported inland following uptake by fine aerosol. The model successfully simulates the vertical profiles of HCl measured from aircraft, where enhancements in the continental boundary layer can again be largely explained by transport inland of the marine source. It does not reproduce the boundary layer Cl2 mixing ratios measured in the WINTER aircraft campaign (1–5 ppt in the daytime, low at night); the model is too high at night, which could be due to uncertainty in the rate of the ClNO2+Cl- reaction, but we have no explanation for the high observed Cl2 in daytime. The global mean tropospheric concentration of Cl atoms in the model is 620 cm−3 and contributes 1.0 % of the global oxidation of methane, 20 % of ethane, 14 % of propane, and 4 % of methanol. Chlorine chemistry increases global mean tropospheric BrO by 85 %, mainly through the HOBr+Cl- reaction, and decreases global burdens of tropospheric ozone by 7 % and OH by 3 % through the associated bromine radical chemistry. ClNO2 chemistry drives increases in ozone of up to 8 ppb over polluted continents in winter.

scholarly journals The chemistry–climate model ECHAM6.3-HAM2.3-MOZ1.0

2018 ◽  
Vol 11 (5) ◽  
pp. 1695-1723 ◽  
Author(s):  
Martin G. Schultz ◽  
Scarlet Stadtler ◽  
Sabine Schröder ◽  
Domenico Taraborrelli ◽  
Bruno Franco ◽  
...  
Keyword(s):  
Climate Model ◽  
Model Simulation ◽  
Heterogeneous Reaction ◽  
Surface Ozone ◽  
Gas Phase Chemistry ◽  
Sea Salt Aerosol ◽  
The Stability ◽  
Phase Chemistry ◽  
The Impact ◽  
Lightning Nox

Abstract. The chemistry–climate model ECHAM-HAMMOZ contains a detailed representation of tropospheric and stratospheric reactive chemistry and state-of-the-art parameterizations of aerosols using either a modal scheme (M7) or a bin scheme (SALSA). This article describes and evaluates the model version ECHAM6.3-HAM2.3-MOZ1.0 with a focus on the tropospheric gas-phase chemistry. A 10-year model simulation was performed to test the stability of the model and provide data for its evaluation. The comparison to observations concentrates on the year 2008 and includes total column observations of ozone and CO from IASI and OMI, Aura MLS observations of temperature, HNO3, ClO, and O3 for the evaluation of polar stratospheric processes, an ozonesonde climatology, surface ozone observations from the TOAR database, and surface CO data from the Global Atmosphere Watch network. Global budgets of ozone, OH, NOx, aerosols, clouds, and radiation are analyzed and compared to the literature. ECHAM-HAMMOZ performs well in many aspects. However, in the base simulation, lightning NOx emissions are very low, and the impact of the heterogeneous reaction of HNO3 on dust and sea salt aerosol is too strong. Sensitivity simulations with increased lightning NOx or modified heterogeneous chemistry deteriorate the comparison with observations and yield excessively large ozone budget terms and too much OH. We hypothesize that this is an impact of potential issues with tropical convection in the ECHAM model.

scholarly journals The role of chlorine in tropospheric chemistry

2018 ◽  
Author(s):  
Xuan Wang ◽  
Daniel J. Jacob ◽  
Sebastian D. Eastham ◽  
Melissa P. Sulprizio ◽  
Lei Zhu ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Atmospheric Chemistry ◽  
Sea Salt ◽  
Tropospheric Chemistry ◽  
Mixing Ratios ◽  
Sea Salt Aerosol ◽  
Oxidation Of Methane ◽  
Heterogeneous Processes ◽  
Marine Air ◽  
Global Mean

Abstract. We present a comprehensive simulation of tropospheric chlorine within the GEOS-Chem global 3-D model of oxidant-aerosol-halogen atmospheric chemistry. The simulation includes explicit accounting of chloride mobilization from sea-salt aerosol by acid displacement of HCl and by other heterogeneous processes. Additional sources of tropospheric chlorine (combustion, organochlorines, transport from stratosphere) are small in comparison. Reactive gas-phase chlorine Cl*, including Cl, ClO, Cl2, BrCl, ICl, HOCl, ClNO3, ClNO2, and minor species, is produced by the HCl + OH reaction and by heterogeneous conversion of sea-salt aerosol chloride to BrCl, ClNO2, Cl2, and ICl. The model simulates successfully the observed mixing ratios of HCl in marine air (highest at northern mid-latitudes) and the associated HNO3 decrease from acid displacement. It captures the high ClNO2 mixing ratios observed in continental surface air at night with chlorine of sea salt origin transported inland as HCl and fine aerosol. It simulates successfully the vertical profiles of HCl measured from aircraft, where enhancements in the continental boundary layer can again be explained by transport inland of the marine source. It does not reproduce the boundary layer Cl2 mixing ratios measured in the WINTER aircraft campaign (1–5 ppt in the daytime, low at night); the model is too high at night compared to WINTER observations, which could be due to uncertainty in the rate of the ClNO2 + Cl− reaction, but we have no explanation for the daytime observations. The global mean tropospheric concentration of Cl atoms in the model is 620 cm−3 and contributes 1.0 % of the global oxidation of methane, 20 % of ethane, 14 % of propane, and 4 % of methanol. Chlorine chemistry increases global mean tropospheric BrO by 85 %, mainly through the HOBr + Cl− reaction, and decreases global burdens of tropospheric ozone by 7 % and OH by 3 % through the associated bromine radical chemistry. ClNO2 chemistry drives increases in ozone of up to 8 ppb over polluted continents in winter.

A POTENTIAL ATOMIC IODINE LASER PUMPED BY ELECTRICALLY GENERATED 1Δ OXYGEN

1980 ◽  
Vol 41 (C9) ◽  
pp. C9-449-C9-453 ◽  
Author(s):  
G. Fournier ◽  
J. Bonnet ◽  
D. Pigache
Keyword(s):  
Iodine Laser ◽  
Atomic Iodine

Review of Flap Monitoring Technology in 2020

2020 ◽  
Vol 36 (06) ◽  
pp. 722-726
Author(s):  
Adam Jacobson ◽  
Oriana Cohen
Keyword(s):  
Head And Neck ◽  
Free Flap ◽  
Loss Rate ◽  
Early Recognition ◽  
Postoperative Patient ◽  
Free Flap Monitoring ◽  
Improved Outcomes ◽  
Vascular Compromise ◽  
Flap Monitoring ◽  
Multiple Levels

AbstractAdvances in free flap reconstruction of complex head and neck defects have allowed for improved outcomes in the management of head and neck cancer. Technical refinements have decreased flap loss rate to less than 4%. However, the potential for flap failure exists at multiple levels, ranging from flap harvest and inset to pedicle lay and postoperative patient and positioning factors. While conventional methods of free flap monitoring (reliant on physical examination) remain the most frequently used, additional adjunctive methods have been developed. Herein we describe the various modalities of both invasive and noninvasive free flap monitoring available to date. Still, further prospective studies are needed to compare the various invasive and noninvasive technologies and to propel innovations to support the early recognition of vascular compromise with the goal of even greater rates of flap salvage.

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