scholarly journals Soluble Iodine Speciation in Marine Aerosols Across the Indian and Pacific Ocean Basins

2021 ◽  
Vol 8 ◽  
Author(s):  
Elise S. Droste ◽  
Alex R. Baker ◽  
Chan Yodle ◽  
Andrew Smith ◽  
Laurens Ganzeveld
Keyword(s):  
Oxidative Capacity ◽  
Anthropogenic Emissions ◽  
Marine Aerosols ◽  
Climate Feedbacks ◽  
Ph Measurements ◽  
Air Masses ◽  
Aerosol Acidity ◽  
Coarse Mode ◽  
Halogen Chemistry ◽  
Iodine Speciation

Iodine affects the radiative budget and the oxidative capacity of the atmosphere and is consequently involved in important climate feedbacks. A fraction of the iodine emitted by oceans ends up in aerosols, where complex halogen chemistry regulates the recycling of iodine to the gas-phase where it effectively destroys ozone. The iodine speciation and major ion composition of aerosol samples collected during four cruises in the East and West Pacific and Indian Oceans was studied to understand the influences on iodine’s gas-aerosol phase recycling. A significant inverse relationship exists between iodide (I–) and iodate (IO3–) proportions in both fine and coarse mode aerosols, with a relatively constant soluble organic iodine (SOI) fraction of 19.8% (median) for fine and coarse mode samples of all cruises combined. Consistent with previous work on the Atlantic Ocean, this work further provides observational support that IO3– reduction is attributed to aerosol acidity, which is associated to smaller aerosol particles and air masses that have been influenced by anthropogenic emissions. Significant correlations are found between SOI and I–, which supports hypotheses that SOI may be a source for I–. This data contributes to a growing observational dataset on aerosol iodine speciation and provides evidence for relatively constant proportions of iodine species in unpolluted marine aerosols. Future development in our understanding of iodine speciation depends on aerosol pH measurements and unravelling the complex composition of SOI in aerosols.

scholarly journals Determining the Role of Acidity, Fate and Formation of IEPOX-Derived SOA in CMAQ

Atmosphere ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 707
Author(s):  
Petros Vasilakos ◽  
Yongtao Hu ◽  
Armistead Russell ◽  
Athanasios Nenes
Keyword(s):  
Significant Influence ◽  
Organic Aerosol ◽  
Liquid Water Content ◽  
Anthropogenic Emissions ◽  
So2 Emissions ◽  
Aerosol Acidity ◽  
A Value ◽  
Future Emission ◽  
The Impact

Formation of aerosol from biogenic hydrocarbons relies heavily on anthropogenic emissions since they control the availability of species such as sulfate and nitrate, and through them, aerosol acidity (pH). To elucidate the role that acidity and emissions play in regulating Secondary Organic Aerosol (SOA), we utilize the 2013 Southern Oxidant and Aerosol Study (SOAS) dataset to enhance the extensive mechanism of isoprene epoxydiol (IEPOX)-mediated SOA formation implemented in the Community Multiscale Air Quality (CMAQ) model (Pye et al., 2013), which was then used to investigate the impact of potential future emission controls on IEPOX OA. We found that the Henry’s law coefficient for IEPOX was the most impactful parameter that controls aqueous isoprene OA products, and a value of 1.9 × 107 M atm−1 provides the best agreement with measurements. Non-volatile cations (NVCs) were found in higher-than-expected quantities in CMAQ and exerted a significant influence on IEPOX OA by reducing its production by as much as 30% when present. Consistent with previous literature, a strong correlation of isoprene OA with sulfate, and little correlation with acidity or liquid water content, was found. Future reductions in SO2 emissions are found to not affect this correlation and generally act to increase the sensitivity of IEPOX OA to sulfate, even in extreme cases.

scholarly journals Identification of the Aerosol Types over Athens, Greece: The Influence of Air-Mass Transport

2010 ◽  
Vol 2010 ◽  
pp. 1-15 ◽  
Author(s):  
D. G. Kaskaoutis ◽  
P. G. Kosmopoulos ◽  
H. D. Kambezidis ◽  
P. T. Nastos
Keyword(s):  
Winter Season ◽  
Saharan Dust ◽  
Dust Particles ◽  
Hysplit Model ◽  
Air Mass ◽  
Back Trajectories ◽  
Air Masses ◽  
Local Pollution ◽  
Coarse Mode ◽  
Aerosol Types

Aerosol optical depth at 550 nm () and fine-mode (FM) fraction data from Terra-MODIS were obtained over the Greater Athens Area covering the period February 2000–December 2005. Based on both and FM values three main aerosol types have been discriminated corresponding to urban/industrial aerosols, clean maritime conditions, and coarse-mode, probably desert dust, particles. Five main sectors were identified for the classification of the air-mass trajectories, which were further used in the analysis of the ( and FM data for the three aerosol types). The HYSPLIT model was used to compute back trajectories at three altitudes to investigate the relation between -FM and wind sector depending on the altitude. The accumulation of local pollution is favored in spring and corresponds to air masses at lower altitudes originating from Eastern Europe and the Balkan. Clean maritime conditions are rare over Athens, limited in the winter season and associated with air masses from the Western or Northwestern sector. The coarse-mode particles origin seems to be more complicated proportionally to the season. Thus, in summer the Northern sector dominates, while in the other seasons, and especially in spring, the air masses belong to the Southern sector enriched with Saharan dust aerosols.

scholarly journals Chemical and meteorological influences on the lifetime of NO<sub>3</sub> at a semi-rural mountain site during PARADE

2016 ◽  
Vol 16 (8) ◽  
pp. 4867-4883 ◽  
Author(s):  
N. Sobanski ◽  
M. J. Tang ◽  
J. Thieser ◽  
G. Schuster ◽  
D. Pöhler ◽  
...  
Keyword(s):  
Loss Rate ◽  
Trace Gases ◽  
Meteorological Conditions ◽  
Biogenic Emissions ◽  
Anthropogenic Emissions ◽  
Air Masses ◽  
Mixing Ratios ◽  
Criegee Intermediates ◽  
Mountain Site ◽  
Meteorological Influences

Abstract. Through measurements of NO2, O3 and NO3 during the PARADE campaign (PArticles and RAdicals, Diel observations of mEchanisms of oxidation) in the German Taunus mountains we derive nighttime steady-state lifetimes (τss) of NO3 and N2O5. During some nights, high NO3 (∼ 200 pptv) and N2O5 (∼ 1 ppbv) mixing ratios were associated with values of τss that exceeded 1 h for NO3 and 3 h for N2O5 near the ground. Such long boundary-layer lifetimes for NO3 and N2O5 are usually only encountered in very clean/unreactive air masses, whereas the PARADE measurement site is impacted by both biogenic emissions from the surrounding forest and anthropogenic emissions from the nearby urbanised/industrialised centres. Measurement of several trace gases which are reactive towards NO3 indicates that the inferred lifetimes are significantly longer than those calculated from the summed loss rate. Several potential causes for the apparently extended NO3 and N2O5 lifetimes are examined, including additional routes to formation of NO3 and the presence of a low-lying residual layer. Overall, the most likely cause of the anomalous lifetimes are related to the meteorological conditions, though additional NO3 formation due to reactions of Criegee intermediates may contribute.

scholarly journals Active and widespread halogen chemistry in the tropical and subtropical free troposphere

2015 ◽  
Vol 112 (30) ◽  
pp. 9281-9286 ◽  
Author(s):  
Siyuan Wang ◽  
Johan A. Schmidt ◽  
Sunil Baidar ◽  
Sean Coburn ◽  
Barbara Dix ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Oxidative Capacity ◽  
Free Troposphere ◽  
Mercury Deposition ◽  
Tropical Eastern Pacific ◽  
Ice Clouds ◽  
Bromine Oxide ◽  
Halogen Chemistry ◽  
Model Predictions ◽  
Wet Scavenging

Halogens in the troposphere are increasingly recognized as playing an important role for atmospheric chemistry, and possibly climate. Bromine and iodine react catalytically to destroy ozone (O3), oxidize mercury, and modify oxidative capacity that is relevant for the lifetime of greenhouse gases. Most of the tropospheric O3 and methane (CH4) loss occurs at tropical latitudes. Here we report simultaneous measurements of vertical profiles of bromine oxide (BrO) and iodine oxide (IO) in the tropical and subtropical free troposphere (10°N to 40°S), and show that these halogens are responsible for 34% of the column-integrated loss of tropospheric O3. The observed BrO concentrations increase strongly with altitude (∼3.4 pptv at 13.5 km), and are 2–4 times higher than predicted in the tropical free troposphere. BrO resembles model predictions more closely in stratospheric air. The largest model low bias is observed in the lower tropical transition layer (TTL) over the tropical eastern Pacific Ocean, and may reflect a missing inorganic bromine source supplying an additional 2.5–6.4 pptv total inorganic bromine (Bry), or model overestimated Bry wet scavenging. Our results highlight the importance of heterogeneous chemistry on ice clouds, and imply an additional Bry source from the debromination of sea salt residue in the lower TTL. The observed levels of bromine oxidize mercury up to 3.5 times faster than models predict, possibly increasing mercury deposition to the ocean. The halogen-catalyzed loss of tropospheric O3 needs to be considered when estimating past and future ozone radiative effects.

scholarly journals Halogen chemistry reduces tropospheric O<sub>3</sub> radiative forcing

2017 ◽  
Vol 17 (2) ◽  
pp. 1557-1569 ◽  
Author(s):  
Tomás Sherwen ◽  
Mat J. Evans ◽  
Lucy J. Carpenter ◽  
Johan A. Schmidt ◽  
Loretta J. Mickley
Keyword(s):  
Tropospheric Ozone ◽  
Radiative Forcing ◽  
Observational Evidence ◽  
Anthropogenic Emissions ◽  
Transport Models ◽  
Model Calculations ◽  
Halogen Chemistry ◽  
Tropospheric O3 ◽  
Observational Record ◽  
Surface O3

Abstract. Tropospheric ozone (O3) is a global warming gas, but the lack of a firm observational record since the preindustrial period means that estimates of its radiative forcing (RFTO3) rely on model calculations. Recent observational evidence shows that halogens are pervasive in the troposphere and need to be represented in chemistry-transport models for an accurate simulation of present-day O3. Using the GEOS-Chem model we show that tropospheric halogen chemistry is likely more active in the present day than in the preindustrial. This is due to increased oceanic iodine emissions driven by increased surface O3, higher anthropogenic emissions of bromo-carbons, and an increased flux of bromine from the stratosphere. We calculate preindustrial to present-day increases in the tropospheric O3 burden of 113 Tg without halogens but only 90 Tg with, leading to a reduction in RFTO3 from 0.43 to 0.35 Wm−2. We attribute  ∼ 50 % of this reduction to increased bromine flux from the stratosphere,  ∼ 35 % to the ocean–atmosphere iodine feedback, and  ∼ 15 % to increased tropospheric sources of anthropogenic halogens. This reduction of tropospheric O3 radiative forcing due to halogens (0.087 Wm−2) is greater than that from the radiative forcing of stratospheric O3 (∼ 0.05 Wm−2). Estimates of RFTO3 that fail to consider halogen chemistry are likely overestimates (∼ 25 %).

The natural aerosol over Northern Europe and its relation to anthropogenic emissions—implications of important climate feedbacks

Tellus B ◽  
2008 ◽  
Vol 60 (4) ◽  
pp. 473-484 ◽  
Author(s):  
P. Tunved ◽  
J. Stroöm ◽  
M. Kulmala ◽  
V.-M. Kerminen ◽  
M. Dal Maso ◽  
...  
Keyword(s):  
Northern Europe ◽  
Anthropogenic Emissions ◽  
Climate Feedbacks ◽  
Natural Aerosol

scholarly journals Examining the effects of anthropogenic emissions on isoprene-derived secondary organic aerosol formation during the 2013 Southern Oxidant and Aerosol Study (SOAS) at the Look Rock, Tennessee ground site

2015 ◽  
Vol 15 (15) ◽  
pp. 8871-8888 ◽  
Author(s):  
S. H. Budisulistiorini ◽  
X. Li ◽  
S. T. Bairai ◽  
J. Renfro ◽  
Y. Liu ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Anthropogenic Emissions ◽  
Strongly Correlated ◽  
Particle Phase ◽  
Aerosol Formation ◽  
Aerosol Acidity ◽  
Southeastern Us

Abstract. A suite of offline and real-time gas- and particle-phase measurements was deployed at Look Rock, Tennessee (TN), during the 2013 Southern Oxidant and Aerosol Study (SOAS) to examine the effects of anthropogenic emissions on isoprene-derived secondary organic aerosol (SOA) formation. High- and low-time-resolution PM2.5 samples were collected for analysis of known tracer compounds in isoprene-derived SOA by gas chromatography/electron ionization-mass spectrometry (GC/EI-MS) and ultra performance liquid chromatography/diode array detection-electrospray ionization-high-resolution quadrupole time-of-flight mass spectrometry (UPLC/DAD-ESI-HR-QTOFMS). Source apportionment of the organic aerosol (OA) was determined by positive matrix factorization (PMF) analysis of mass spectrometric data acquired on an Aerodyne Aerosol Chemical Speciation Monitor (ACSM). Campaign average mass concentrations of the sum of quantified isoprene-derived SOA tracers contributed to ~ 9 % (up to 28 %) of the total OA mass, with isoprene-epoxydiol (IEPOX) chemistry accounting for ~ 97 % of the quantified tracers. PMF analysis resolved a factor with a profile similar to the IEPOX-OA factor resolved in an Atlanta study and was therefore designated IEPOX-OA. This factor was strongly correlated (r2 > 0.7) with 2-methyltetrols, C5-alkene triols, IEPOX-derived organosulfates, and dimers of organosulfates, confirming the role of IEPOX chemistry as the source. On average, IEPOX-derived SOA tracer mass was ~ 26 % (up to 49 %) of the IEPOX-OA factor mass, which accounted for 32 % of the total OA. A low-volatility oxygenated organic aerosol (LV-OOA) and an oxidized factor with a profile similar to 91Fac observed in areas where emissions are biogenic-dominated were also resolved by PMF analysis, whereas no primary organic aerosol (POA) sources could be resolved. These findings were consistent with low levels of primary pollutants, such as nitric oxide (NO ~ 0.03 ppb), carbon monoxide (CO ~ 116 ppb), and black carbon (BC ~ 0.2 μg m−3). Particle-phase sulfate is fairly correlated (r2 ~ 0.3) with both methacrylic acid epoxide (MAE)/hydroxymethyl-methyl-α-lactone (HMML)- (henceforth called methacrolein (MACR)-derived SOA tracers) and IEPOX-derived SOA tracers, and more strongly correlated (r2 ~ 0.6) with the IEPOX-OA factor, in sum suggesting an important role of sulfate in isoprene SOA formation. Moderate correlation between the MACR-derived SOA tracer 2-methylglyceric acid with sum of reactive and reservoir nitrogen oxides (NOy; r2 = 0.38) and nitrate (r2 = 0.45) indicates the potential influence of anthropogenic emissions through long-range transport. Despite the lack of a clear association of IEPOX-OA with locally estimated aerosol acidity and liquid water content (LWC), box model calculations of IEPOX uptake using the simpleGAMMA model, accounting for the role of acidity and aerosol water, predicted the abundance of the IEPOX-derived SOA tracers 2-methyltetrols and the corresponding sulfates with good accuracy (r2 ~ 0.5 and ~ 0.7, respectively). The modeling and data combined suggest an anthropogenic influence on isoprene-derived SOA formation through acid-catalyzed heterogeneous chemistry of IEPOX in the southeastern US. However, it appears that this process was not limited by aerosol acidity or LWC at Look Rock during SOAS. Future studies should further explore the extent to which acidity and LWC as well as aerosol viscosity and morphology becomes a limiting factor of IEPOX-derived SOA, and their modulation by anthropogenic emissions.

scholarly journals Speciation of <sup>127</sup>I and <sup>129</sup>I in atmospheric aerosols at Risø, Denmark: insight into sources of iodine isotopes and their species transformations

2015 ◽  
Vol 15 (17) ◽  
pp. 25139-25173 ◽  
Author(s):  
L. Y. Zhang ◽  
X. L. Hou ◽  
S. Xu
Keyword(s):  
Atmospheric Aerosols ◽  
Significant Proportion ◽  
Speciation Analysis ◽  
Secondary Emission ◽  
Water Soluble ◽  
Marine Aerosols ◽  
Total Iodine ◽  
European Continent ◽  
Air Masses ◽  
Iodine Species

Abstract. Speciation analysis of iodine in aerosols is a very useful approach for understanding geochemical cycling of iodine in the atmosphere. In this study, overall iodine species, including water-soluble iodine species (iodide, iodate and water-soluble organic iodine), NaOH-soluble iodine and insoluble iodine have been determined for 129I and 127I in the aerosols collected at Risø, Denmark, between March and May 2011 (shortly after the Fukushima nuclear accident) and in December 2014. The measured concentrations of total iodine are in the range of 1.04–2.48 ng m−3 for 127I and (11.3–97.0) × 105 atoms m−3 for 129I, and 129I / 127I atomic ratios of (17.8–86.8) × 10−8. The contribution of Fukushima-derived 129I (peak value of 6.3 × 104 atoms m−3) is estimated to be negligible (less than 6 %) compared to the total 129I concentration in northern Europe. The concentrations and species of 129I and 127I in the aerosols are found to be strongly related to their sources and atmospheric pathways. Aerosols that were transported over the contaminated ocean, contained higher amounts of 129I than aerosols transported over the European continent. The high 129I concentrations of the marine aerosols are attributed to secondary emission from heavily 129I-contaminated seawater rather than primary gaseous release from nuclear reprocessing plants. Water-soluble iodine was found to be a minor fraction to total iodine for both 127I (7.8–13.7 %) and 129I (6.5–14.1 %) in ocean-derived aerosols, but accounted for 20.2–30.3 % for 127I and 25.6–29.5 % for 129I in land-derived aerosols. Iodide was the predominant form of water-soluble iodine, accounting for more than 97 % of the water-soluble iodine. NaOH-soluble iodine seems to be independent of the sources of aerosols. The significant proportion of 129I and 127I found in NaOH-soluble fractions is likely bound with organic substances. In contrast to water-soluble iodine however, the sources of air masses exerted distinct influences on insoluble iodine for both 129I and 127I, with higher values for marine air masses and lower values for terrestrial air masses.

scholarly journals A better understanding of hydroxyl radical photochemical sources in cloud waters collected at the puy de Dôme station: experimental vs. modeled formation rates

2015 ◽  
Vol 15 (10) ◽  
pp. 13923-13955 ◽  
Author(s):  
A. Bianco ◽  
M. Passananti ◽  
H. Perroux ◽  
G. Voyard ◽  
C. Mouchel-Vallon ◽  
...  
Keyword(s):  
Hydroxyl Radical ◽  
Solar Spectrum ◽  
Oxidative Capacity ◽  
Xenon Lamp ◽  
Air Masses ◽  
Naturally Occurring ◽  
Field Campaigns ◽  
Experimental Values ◽  
Nitrite Nitrate ◽  
Yield Formation

Abstract. The oxidative capacity of the cloud aqueous phase is investigated during three field campaigns from 2013 to 2014 at the top of the puy de Dôme station (PUY) in France. Forty-one cloud samples are collected, and the corresponding air masses are classified as highly marine, marine and continental. Hydroxyl radical (HO·) formation rates (RHO·f) are determined using a photochemical setup (Xenon lamp that can reproduce the solar spectrum) and a chemical probe coupled with spectroscopic analysis that can trap all of the generated radicals for each sample. Using this method, the obtained values correspond to the total formation of HO· without its chemical sinks. These formation rates are correlated with the concentrations of the naturally occurring sources of HO·, including hydrogen peroxide, nitrite, nitrate and iron. The total hydroxyl radical formation rates are measured as ranging from approximately 2 × 10−11 to 4 × 10−10 M s−1, and the hydroxyl radical quantum yield formation (ΦHO·) is estimated between 10−4 and 10−2. Experimental values are compared with modeled formation rates calculated by the model of multiphase cloud chemistry (M2C2), considering only the chemical sources of the hydroxyl radicals. The comparison between the experimental and the modeled results suggests that the photoreactivity of the iron species as a source of HO· is overestimated by the model, and H2O2 photolysis represents the most important source of this radical (between 70 and 99%) for the cloud water sampled at the PUY station (primarily marine and continental).

scholarly journals Long-term trends of surface ozone and its influencing factors at the Mt. Waliguan GAW station, China, Part 2: Variation mechanism and links to some climate indices

2017 ◽  
Author(s):  
Wanyun Xu ◽  
Xiaobin Xu ◽  
Meiyun Lin ◽  
Weili Lin ◽  
Jie Tang ◽  
...  
Keyword(s):  
Southeast Asia ◽  
Trajectory Analysis ◽  
Surface Ozone ◽  
Eastern China ◽  
Sunspot Cycle ◽  
Anthropogenic Emissions ◽  
Climate Indices ◽  
Air Masses ◽  
Long Term Trends

Abstract. Interannual variability and long-term trends of tropospheric ozone are both of environmental and climate concerns. Ozone measured at Mt. Waliguan Observatory (WLG, 3816 m asl) on the Tibetan Plateau over the period 19947ndash;2013 has increased significantly by 0.2–0.3 ppbv year-1 during spring and autumn, but shows a much smaller trend in winter and no significant trend in summer. Here we explore the factors driving the observed ozone changes at WLG using backward trajectory analysis, chemistry-climate model hindcast simulations (GFDL-AM3), a trajectory-mapped ozonesonde dataset and various climate indices. A stratospheric ozone tracer implemented in GFDL-AM3 indicates that stratosphere-to-troposphere transport (STT) can explain ~ 70 % of the observed springtime ozone increase at WLG, consistent with an increase in the NW air mass frequency inferred from the trajectory analysis. Enhanced STT associated with the strengthening of the mid-latitude jet stream contributes to the observed high-ozone anomalies at WLG during the springs of 1999 and 2012. During autumn, observations at WLG are more heavily influenced by polluted air masses originated from Southeast Asia than in the other seasons. Rising Asian anthropogenic emissions of ozone precursors is the key driver of increasing autumnal ozone observed at WLG, as supported by the GFDL-AM3 model with time-varying emissions, which captures the observed ozone increase (0.26 ± 0.11 ppbv year-1). AM3 simulates a greater ozone increase of 0.38 ± 0.11 ppbv year-1 at WLG in autumn under conditions with strong transport from Southeast Asia and shows no significant ozone trend in autumn when anthropogenic emissions are held constant in time. During summer, WLG is mostly influenced by easterly air masses but these trajectories do not extend to the polluted regions of eastern China and have decreased significantly over the last two decades, which likely explains why summertime ozone measured at WLG shows no significant trend despite ozone increases in Eastern China. Analysis of the Trajectory-mapped Ozonesonde dataset for the Stratosphere and Troposphere (TOST) and trajectory residence time reveals increases in direct ozone transport from the eastern sector during autumn, which adds to the autumnal ozone increase. We further examine the links of ozone variability at WLG to the QBO, the North Atlantic Oscillation (NAO), the East Asian summer monsoon (EASM) and the sunspot cycle. Our results suggest that the 2–3 year, 3–7 year and 11 year periodicities are linked to QBO, EASMI and NAO and the sunspot cycle, respectively. A multivariate regression analysis is performed to quantify the relative contributions of various factors to surface ozone concentrations at WLG. Through an observational and modelling analysis, this study demonstrates the complex relationships between surface ozone at remote locations and its dynamical and chemical influencing factors.

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