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.

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>

Iodine and Halocarbon Response of Laminaria digitata to Oxidative Stress and Links to Atmospheric New Particle Production

2005 ◽  
Vol 2 (4) ◽  
pp. 282 ◽  
Author(s):  
Carl J. Palmer ◽  
Thorsten L. Anders ◽  
Lucy J. Carpenter ◽  
Frithjof C. Küpper ◽  
Gordon B. McFiggans
Keyword(s):  
Oxidative Stress ◽  
Particle Production ◽  
Marine Boundary Layer ◽  
Oxidative Capacity ◽  
Molecular Iodine ◽  
Laminaria Digitata ◽  
Organic Iodine ◽  
Free Air ◽  
Iodine Compounds ◽  
Iodine Release

Environmental Context.Various organic iodine compounds (including CH3I, CH2ClI, CH2BrI, CH2I2) are present throughout the marine boundary layer as a result of their production from seaweeds, phytoplankton, and photolysis reactions occurring in seawater. In air, these compounds rapidly photolyse to give atomic I which subsequently reacts with ozone to form iodine oxide, potentially leading to perturbations of the tropospheric oxidative capacity and nucleation of atmospheric particles. Recent research has identified molecular iodine as an additional source of iodine atoms to coastal areas. Here we study the relative roles and controls of gaseous organic and molecular iodine release from the seaweed Laminaria digitata. Abstract.Changes in the halocarbon, I2 and particle production of the brown algal kelp Laminaria digitata as a response to different chemical stresses have been investigated. Oxidative stress (caused by either exogenous hydrogen peroxide, gaseous ozone or a solution of oligoguluronates, known elicitors of oxidative stress) caused increased halocarbon and I2 production by the seaweed. The maximum I2 release was observed under exposure to O3 (at several hundred parts per billion by volume (ppbv)), whereas oligoguluronates elicited the highest release of iodine-containing halocarbons including CH2I2. Significantly greater production of I2, compared to CH2I2, was observed at atmospheric levels of ozone. Particle production was observed only when the Laminaria samples were exposed to ozone (up to 16 000 cm−3 s−1 per gram fresh weight (FW) of seaweed with a ~2 min residence time and with a total I atom flux of 1.6 × 108 cm−3 s−1 g−1 FW from photolysis of I2); passing O3-free air over the unstressed seaweed followed by secondary mixing with ozone did not result in any measurable particle formation. Our limited data indicate that ozone elicits abiotic production of I2 from Laminaria and that there is a direct relationship between the amount of I2 released and the number of particles formed. The results support the recent hypothesis that molecular iodine rather than volatile organic iodine (e.g. CH2I2) release from exposed seaweeds is the major source of coastal new particle production.

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>

scholarly journals BrO and Br<sub>y</sub> profiles over the Western Pacific: Relevance of Inorganic Bromine Sources and a Br<sub>y</sub> Minimum in the Aged Tropical Tropopause Layer

2017 ◽  
Author(s):  
Theodore K. Koenig ◽  
Rainer Volkamer ◽  
Sunil Baidar ◽  
Barbara Dix ◽  
Siyuan Wang ◽  
...  
Keyword(s):  
Gas Phase ◽  
Marine Boundary Layer ◽  
Heterogeneous Reaction ◽  
Reaction Rates ◽  
Western Pacific ◽  
Vertical Column ◽  
Tropical Tropopause Layer ◽  
Local Maxima ◽  
Tropical Tropopause ◽  
Vertical Column Density

Abstract. We report measurements of bromine monoxide (BrO) and use an observationally constrained chemical box-model to infer total gas phase inorganic bromine (Bry) over the tropical Western Pacific Ocean (tWPO) during the CONTRAST field campaign (January–February 2014). The median tropospheric BrO Vertical Column Density (VCD) over the tWPO was measured as 1.6 × 1013 molec cm−2, compared to model predictions of 0.4 × 1013 in CAM-Chem, 0.9 × 1013 in GEOS-Chem, and 2.1 × 1013 in GEOS-Chem with a sea-salt aerosol (SSA) bromine source. The observed BrO and inferred Bry profiles is found to be C-shaped in the troposphere, with local maxima in the marine boundary layer (MBL) and in the upper free troposphere. Neither global model fully captures this profile shape. Between 6 and 13.5 km, the inferred Bry is highly sensitive to assumptions about the rate of heterogeneous bromine recycling (depends on the surface area of ice/aerosols), and the inclusion of a SSA bromine source. A local Bry maximum of 3.6 ppt (2.3–11.1 ppt, 95 % CI) is observed between 9.5 and 13.5 km in air masses influenced by recent convective outflow. Unlike BrO, which increases from the convective TTL to the aged TTL, gas phase Bry decreases from the convective TTL to the aged TTL. Analysis of gas phase Bry against multiple tracers (CFC-11, H2O / O3 ratio, and θ) reveals a Bry minimum of 2.7 ppt (2.4–3.0 ppt, 95 % CI) in the aged TTL, which is remarkably insensitive to assumptions about heterogeneous chemistry. Bry increases to 6.3 ppt (5.9–6.7 ppt, 95 % CI) in the stratospheric middleworld, and 6.9 ppt (6.7–7.1 ppt, 95 % CI) in the stratospheric overworld. The local Bry minimum in the aged TTL is qualitatively (but not quantitatively) captured by CAM-chem, and suggests a more complex partitioning of gas phase and aerosol Bry species than previously recognized. Our data provide corroborating evidence that inorganic bromine sources (e.g., SSA derived gas phase Bry) are needed to explain the gas phase Bry budget in the TTL. They are also consistent with observations of significant bromide in UTLS aerosols. The total Bry budget in the TTL is currently not closed, because of the lack of concurrent quantitative measurements of gas phase Bry species (i.e., BrO, HOBr, HBr, etc.) and aerosol bromide. These simultaneous measurements are needed 1) to quantify SSA derived Bry aloft, 2) to test Bry partitioning, and explain the gas phase Bry minimum in the aged TTL, 3) to constrain heterogeneous reaction rates of bromine, and 4) to account for all of the sources of Bry to the lower stratosphere.

Marine Aerosol Iodine Chemistry: The Importance of Soluble Organic Iodine

2005 ◽  
Vol 2 (4) ◽  
pp. 295 ◽  
Author(s):  
Alex R. Baker
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Marine Aerosol ◽  
Radiative Balance ◽  
Iodine Species ◽  
Ozone Destruction ◽  
Organic Iodine ◽  
Iodine Chemistry ◽  
Inorganic Iodine ◽  
Complex Chemistry

Environmental Context.Ozone concentrations play a large part in controlling the oxidation capacity of the marine boundary layer, while the production of new aerosol particles affects atmospheric radiative balance. Iodine has a complex chemistry in the marine atmosphere which impacts on both these processes. Much of this iodine chemistry, especially the chemical speciation of iodine in aerosol, is only poorly understood. This study explores the occurrence and abundance of organic forms of iodine, a topic that has received very little attention to date. Abstract.Iodine has a complex chemistry in aerosols in the marine boundary layer (MBL), and is involved in both ozone destruction and new aerosol particle formation processes. Work in this area has focussed almost exclusively on inorganic iodine chemistry. Results from two research cruises in the Atlantic Ocean, covering wide longitude (60°W to 0°W) and latitude (50°N to 50°S) ranges indicate that soluble organic iodine species are both widespread and abundant in marine aerosol. The reactivity of these species is yet to be determined, but may influence the concentrations of some aerosol inorganic iodine species, and may also impact on MBL ozone destruction reactions.

scholarly journals Closing the dimethyl sulfide budget in the tropical marine boundary layer during the Pacific Atmospheric Sulfur Experiment

2009 ◽  
Vol 9 (22) ◽  
pp. 8745-8756 ◽  
Author(s):  
S. A. Conley ◽  
I. Faloona ◽  
G. H. Miller ◽  
D. H. Lenschow ◽  
B. Blomquist ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Loss Rate ◽  
Dimethyl Sulfide ◽  
Marine Boundary Layer ◽  
Photochemical Oxidation ◽  
Flux Divergence ◽  
Horizontal Advection ◽  
The Pacific ◽  
Variable Surface ◽  
Atmospheric Sulfur

Abstract. Fourteen research flights were conducted with the National Center for Atmospheric Research (NCAR) C-130 near Christmas Island (2° N, 157° W) during the summer of 2007 as part of the Pacific Atmospheric Sulfur Experiment (PASE). In order to tightly constrain the scalar budget of DMS, vertical eddy fluxes were measured at various levels in the marine boundary layer (MBL) from ~30 m to the top of the mixed layer (~500 m) providing improved accuracy of the flux divergence calculation in the DMS budget. The observed mean mole fraction of DMS in the MBL exhibited the well-known diurnal cycle, ranging from 50–95 pptv in the daytime to 90–110 pptv at night. Contributions from horizontal advection are included using a multivariate regression of all DMS flight data within the MBL to estimate the mean gradients and trends. With this technique we can use the residual term in the DMS budget as an estimate of overall photochemical oxidation. Error analysis of the various terms in the DMS budget indicate that chemical losses acting on time scales of up to 110 h can be inferred with this technique. On average, photochemistry accounted for ~7.4 ppt hr −1 loss rate for the seven daytime flights, with an estimated error of 0.6 ppt hr−1. The loss rate due to expected OH oxidation is sufficient to explain the net DMS destruction without invoking the action of additional oxidants (e.g., reactive halogens.) The observed ocean flux of DMS averaged 3.1 (±1.5) μmol m−2 d−1, and generally decreased throughout the sunlit hours. Over the entire mission, the horizontal advection contribution to the overall budget was merely -0.1 ppt hr−1, indicating a mean atmospheric DMS gradient nearly perpendicular to the east-southeasterly trade winds and the chlorophyll gradient in the equatorial upwelling ocean. Nonetheless, horizontal advection was a significant term in the budget of any given flight, ranging from −1.2 to 2.5 ppt hr−1 , indicating a patchy and variable surface seawater DMS distribution, and thus needs to be accounted for in budget studies.

scholarly journals Biomass burning and marine aerosol processing over the southeast Atlantic Ocean: A TEM single particle analysis

2021 ◽  
Author(s):  
Caroline Dang ◽  
Michal Segal-Rozenhaimer ◽  
Haochi Che ◽  
Lu Zhang ◽  
Paola Formenti ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Biomass Burning ◽  
Single Particle ◽  
Marine Boundary Layer ◽  
Particle Analysis ◽  
Marine Aerosol ◽  
Potassium Salts ◽  
Aerosol Composition ◽  
Cloud Processing ◽  
Atmospheric Processing

Abstract. This study characterizes single particle aerosol composition from filters collected during the ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES) and CLoud–Aerosol–Radiation Interaction and Forcing: Year 2017 (CLARIFY-2017) campaigns. In particular the study describes aged biomass burning aerosol (BBA), its interaction with the marine boundary layer and the influence of biomass burning (BB) air on marine aerosol. The study finds evidence of BBA influenced by marine boundary layer processing as well as sea salt influenced by BB air. Secondary chloride aerosols were observed in clean marine air as well as in BB-influenced air in the free troposphere. Higher volatility organic aerosol appears to be associated with increased age of biomass burning plumes, and photolysis may be a mechanism for this increased volatility. Aqueous processing and interaction with the marine boundary layer air may be a mechanism for the presence of sodium on many aged potassium salts. By number, biomass burning potassium salts and modified sea salts are the most observed particles on filter samples. These results suggest that atmospheric processing such as photolysis and cloud processing, rather than BB fuel type, has a major role in the elemental composition and morphology of aged BBA.

scholarly journals Iodine chemistry in the troposphere and its effect on ozone

2014 ◽  
Vol 14 (23) ◽  
pp. 13119-13143 ◽  
Author(s):  
A. Saiz-Lopez ◽  
R. P. Fernandez ◽  
C. Ordóñez ◽  
D. E. Kinnison ◽  
J. C. Gómez Martín ◽  
...  
Keyword(s):  
Tropospheric Ozone ◽  
Marine Boundary Layer ◽  
Tropospheric Chemistry ◽  
Annual Average ◽  
Upper Troposphere ◽  
Ozone Loss ◽  
Iodine Chemistry ◽  
Inorganic Iodine ◽  
Iodine Oxides ◽  
Atomic Iodine

Abstract. Despite the potential influence of iodine chemistry on the oxidizing capacity of the troposphere, reactive iodine distributions and their impact on tropospheric ozone remain almost unexplored aspects of the global atmosphere. Here we present a comprehensive global modelling experiment aimed at estimating lower and upper limits of the inorganic iodine burden and its impact on tropospheric ozone. Two sets of simulations without and with the photolysis of IxOy oxides (i.e. I2O2, I2O3 and I2O4) were conducted to define the range of inorganic iodine loading, partitioning and impact in the troposphere. Our results show that the most abundant daytime iodine species throughout the middle to upper troposphere is atomic iodine, with an annual average tropical abundance of (0.15–0.55) pptv. We propose the existence of a "tropical ring of atomic iodine" that peaks in the tropical upper troposphere (~11–14 km) at the equator and extends to the sub-tropics (30° N–30° S). Annual average daytime I / IO ratios larger than 3 are modelled within the tropics, reaching ratios up to ~20 during vigorous uplift events within strong convective regions. We calculate that the integrated contribution of catalytic iodine reactions to the total rate of tropospheric ozone loss (IOx Loss) is 2–5 times larger than the combined bromine and chlorine cycles. When IxOy photolysis is included, IOx Loss represents an upper limit of approximately 27, 14 and 27% of the tropical annual ozone loss for the marine boundary layer (MBL), free troposphere (FT) and upper troposphere (UT), respectively, while the lower limit throughout the tropical troposphere is ~9%. Our results indicate that iodine is the second strongest ozone-depleting family throughout the global marine UT and in the tropical MBL. We suggest that (i) iodine sources and its chemistry need to be included in global tropospheric chemistry models, (ii) experimental programs designed to quantify the iodine budget in the troposphere should include a strategy for the measurement of atomic I, and (iii) laboratory programs are needed to characterize the photochemistry of higher iodine oxides to determine their atmospheric fate since they can potentially dominate halogen-catalysed ozone destruction in the troposphere.

scholarly journals Two-years of NO<sub>3</sub> radical observations in the boundary layer over the Eastern Mediterranean

2007 ◽  
Vol 7 (2) ◽  
pp. 315-327 ◽  
Author(s):  
M. Vrekoussis ◽  
N. Mihalopoulos ◽  
E. Gerasopoulos ◽  
M. Kanakidou ◽  
P. J. Crutzen ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Heterogeneous Reaction ◽  
Eastern Mediterranean ◽  
North Coast ◽  
Data Set ◽  
East Europe ◽  
Dinitrogen Pentoxide ◽  
Mixing Ratios ◽  
The North

Abstract. This is the first study that investigates the seasonal variability of nitrate (NO3) radicals in the marine boundary layer over the East Mediterranean Sea. An extensive data set of NO3 radical observations on the north coast of Crete for more than two years (June 2001–September 2003) is presented here. NO3 radicals follow a distinct seasonal dependency with the highest seasonally average mixing ratios in summer (5.6±1.2 pptv) and the lowest in winter (1.2±1.2 pptv). Episodes with high NO3 mixing ratios have been encountered mainly in polluted air masses originating from mainland Greece, Central and East Europe, and Turkey. Ancillary measurements of ozone, nitrogen dioxide (NO2) and meteorological parameters have been conducted and used to reveal possible relationship with the observed NO3 variability. The acquired NO2 nighttime observations provide the up-to-date most complete overview of NO2 temporal variability in the area. The data show correlations of the NO3 nighttime mixing ratios with temperature (positive), relative humidity (negative) and to a lesser extend with O3 (positive). As inferred from these observations, on average the major sink of NO3 radicals in the area is the heterogeneous reaction of dinitrogen pentoxide (N2O5) on aqueous particles whereas the homogeneous gas phase reactions of NO3 are most important during spring and summer. These observations support a significant contribution of NO3 nighttime chemistry to the oxidizing capacity of the troposphere.

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