Photochemical reactions in the tropospheric aqueous phase and on particulate matter

2006 ◽  
Author(s):  
Davide Vione ◽  
Valter Maurino ◽  
Claudio Minero ◽  
Ezio Pelizzetti ◽  
Mark A. J. Harrison ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Aqueous Phase ◽  
Photochemical Reactions

Modelling the photochemical formation of high H2O2 concentrations and secondary sulfate observed during winter haze periods in the NCP

2020 ◽  
Author(s):  
Andreas Tilgner ◽  
Erik Hans Hoffmann ◽  
Lin He ◽  
Bernd Heinold ◽  
Can Ye ◽  
...  
Keyword(s):  
Air Pollution ◽  
Gas Phase ◽  
Aqueous Phase ◽  
Photochemical Reactions ◽  
Data Availability ◽  
Phase Reaction ◽  
Aerosol Composition ◽  
Chemistry Research ◽  
The Impact

<p>During winter, the North China Plain (NCP) is frequently characterized by severe haze conditions connected with extremely high PM2.5 and NOx concentrations, i.e. strong air pollution. The NCP is one of the most populated regions worldwide where haze periods have direct health effects. Tropospheric haze particles are a complex multiphase and multi-component environment, in which multiphase chemical processes are able to alter the chemical aerosol composition and deduced physical aerosol properties and can strongly contribute to air pollution. Despite many past investigations, the chemical haze processing is still uncertain and represents a challenge to atmospheric chemistry research. Recent NCP studies during autumn/winter 2017 haze periods have revealed unexpected high H<sub>2</sub>O<sub>2</sub> concentrations of about 1 ppb suggesting H<sub>2</sub>O<sub>2</sub> as a potential contributor to secondary PM2.5 mass, e.g., due to sulfur(IV) oxidation. However, the multiphase H<sub>2</sub>O<sub>2</sub> formation under such NOx concentrations is still unclear. Therefore, the present study aimed at the examination of potential multiphase H<sub>2</sub>O<sub>2</sub> formation pathways, and the feedback on sulfur oxidation.</p><p>Multiphase chemistry simulations of a measurement campaign in the NCP are performed with the box model SPACCIM. The multiphase chemistry model within SPACCIM contains the gas-phase mechanism MCMv3.2 and the aqueous-phase mechanism CAPRAM4.0 together with both its aromatics module CAPRAM-AM1.0 and its halogen module CAPRAM-HM2.1. Furthermore, based on available literature data, the multiphase chemistry mechanism is extended considering further multiphase formation pathways of HONO and an advanced HOx mechanism scheme enabling higher in-situ H<sub>2</sub>O<sub>2</sub> formations in haze particles. The simulations have been performed for three periods characterized by high H<sub>2</sub>O<sub>2</sub> concentrations, high RH and PM2.5 conditions and high measurement data availability. Several sensitivity runs have been performed examining the impact of the soluble transition metal ion (TMI) content on the predicted H<sub>2</sub>O<sub>2</sub> formation.</p><p>Simulations with the improved multiphase chemistry mechanism shows a good agreement of the modelled H<sub>2</sub>O<sub>2</sub> concentrations with field data. The modelled H<sub>2</sub>O<sub>2</sub> concentration shows a substantial dependency on the soluble TMI content. Higher soluble TMI contents result in higher H<sub>2</sub>O<sub>2</sub> concentrations demonstrating the strong influence of TMI chemistry in haze particles on H<sub>2</sub>O<sub>2</sub> formation. The analysis of the chemical production and sink fluxes reveals that a huge fraction of the multiphase HO<sub>2</sub> radicals and nearly all of the subsequently formed reaction product H<sub>2</sub>O<sub>2</sub> is produced in-situ within the haze particles and does not origin from the gas phase. Further chemical analyses show that, during the morning hours, the aqueous-phase reaction of H<sub>2</sub>O<sub>2</sub> with S(IV) contributes considerably to S(VI) formation beside the HONO related formation of sulfuric acid by OH in the gas-phase.</p><p>Finally, a parameterization was developed to study the particle-phase H<sub>2</sub>O<sub>2</sub> formations as potential source with the global model ECHAM-HAMMOZ. The performed global modelling identifies an increase of gas-phase H<sub>2</sub>O<sub>2</sub> by a factor of 2.8 through the newly identified particle chemistry. Overall, the study demonstrated that photochemical reactions of HULIS and TMIs in particles are an important H<sub>2</sub>O<sub>2</sub> source leading to increased particle sulfate formation.</p>

scholarly journals The number fraction of iron-containing particles affects OH, HO<sub>2</sub> and H<sub>2</sub>O<sub>2</sub> budgets in the atmospheric aqueous phase

2021 ◽  
Author(s):  
Amina Khaled ◽  
Minghui Zhang ◽  
Barbara Ervens
Keyword(s):  
Particulate Matter ◽  
Aqueous Phase ◽  
Aerosol Particles ◽  
Iron Concentration ◽  
Transition Metal Ions ◽  
Total Iron ◽  
Chemical Mechanism ◽  
Cloud Droplets ◽  
Iron Distribution ◽  
Total Iron Concentration

Abstract. Reactive oxygen species (ROS), such as OH, HO2, H2O2 affect the oxidation capacity of the atmosphere and cause adverse health effects of particulate matter. The role of transition metal ions (TMIs) in impacting the ROS concentrations and conversions in the atmospheric aqueous phase has been recognized for a long time. Model studies usually assume that the total TMI concentration as measured in bulk aerosol or cloud water samples is distributed equally across all particles or droplets. This assumption is contrary to single-particle measurements that have shown that only a small number fraction of particles contain iron and other TMIs (FN,Fe < 100 %) which implies that also not all cloud droplets contain TMIs. In the current study, we apply a box model with an explicit multiphase chemical mechanism to simulate ROS formation and cycling in (i) aqueous aerosol particles and (ii) cloud droplets. Model simulations are performed for the range of 1 % ≤ FN,Fe ≤ 100 % for constant pH values of 3, 4.5 and 6 and constant total iron concentration (10 or 50 . Model results are compared for two sets of simulations with FN,Fe < 100 % (FeN < 100) and 100 % (FeBulk). We find largest differences between model results in OH and HO2/O2− concentrations at pH = 6. Under these conditions, HO2 is subsaturated in the aqueous phase because of its high effective Henry's law constant and the fast chemical loss reactions of the O2− radical anion. As the main reduction of process of Fe(III) is its reaction with HO2/O2−, we show that the HO2 subsaturation leads to predicted Fe(II)/Fe(total) ratios for FN,Fe < 100 % that are lower by a factor of ≤ 2 as compared to bulk model approaches. This trend is largely independent of the total iron concentration, as both chemical source and sink rates of HO2/O2− scale with the iron concentration. The chemical radical (OH, HO2) loss in particles is usually compensated by its uptake from the gas phase. We compare model-derived reactive uptake parameters γ(OH) and γ(HO2) for the full range of FN,Fe. While γ(OH) is not affected by the iron distribution, the calculated γ(HO2) range from 0.0004 to 0.03 for FN,Fe = 1 % and 100 %, respectively. Implications of these findings are discussed for the application of lab-derived γ(HO2) in models to present reactive HO2 uptake on aerosols. As the oxidant budget in aerosol particles and cloud droplets is related to the oxidative potential, we also conclude that the iron distribution FN,Fe should be taken into account to estimate the ROS concentrations and health impacts of particulate matter that might be overestimated by bulk sampling and model approaches. Our study suggests that the number concentration of iron-containing particles may be more important than the total iron mass concentration in determining ROS budgets and uptake rates in cloud and aerosol water.

scholarly journals Effect of atmospheric ageing on volatility and ROS of biodiesel exhaust nano-particles

2015 ◽  
Vol 15 (5) ◽  
pp. 6481-6508 ◽  
Author(s):  
A. M. Pourkhesalian ◽  
S. Stevanovic ◽  
M. M. Rahman ◽  
E. M. Faghihi ◽  
S. E. Bottle ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Chemical Composition ◽  
Volatile Compounds ◽  
Photochemical Reactions ◽  
Diesel Emissions ◽  
Nano Particles ◽  
Biodiesel Fuel ◽  
Carbon Chain Length ◽  
Aerosol Formation ◽  
Oxidative Potential

Abstract. In the prospect of limited energy resources and climate change, effects of alternative biofuels on primary emissions are being extensively studied. Our two recent studies have shown that biodiesel fuel composition has a~significant impact on primary particulate matter emissions. It was also shown that particulate matter caused by biodiesels was substantially different from the emissions due to petroleum diesel. Emissions appeared to have higher oxidative potential with the increase in oxygen content and decrease of carbon chain length and unsaturation levels of fuel molecules. Overall, both studies concluded that chemical composition of biodiesel is more important than its physical properties in controlling exhaust particle emissions. This suggests that the atmospheric ageing processes, including secondary organic aerosol formation, of emissions from different fuels will be different as well. In this study, measurements were conducted on a modern common-rail diesel engine. To get more information on realistic properties of tested biodiesel particulate matter once they are released into the atmosphere, particulate matter was exposed to atmospheric oxidants, ozone and ultra-violet light; and the change in their properties was monitored for different biodiesel blends. Upon the exposure to oxidative agents, the chemical composition of the exhaust changes. It triggers the cascade of photochemical reactions resulting in the partitioning of semi-volatile compounds between the gas and particulate phase. In most of the cases, aging lead to the increase in volatility and oxidative potential, and the increment of change was mainly dependent on the chemical composition of fuels as the leading cause for the amount and the type of semi-volatile compounds present in the exhaust.

scholarly journals Measurement report: Vertical distribution of atmospheric particulate matter within the urban boundary layer in southern China – size-segregated chemical composition and secondary formation through cloud processing and heterogeneous reactions

2020 ◽  
Vol 20 (11) ◽  
pp. 6435-6453 ◽  
Author(s):  
Shengzhen Zhou ◽  
Luolin Wu ◽  
Junchen Guo ◽  
Weihua Chen ◽  
Xuemei Wang ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Particulate Matter ◽  
Vertical Distribution ◽  
Aqueous Phase ◽  
Ground Level ◽  
Urban Boundary Layer ◽  
Water Soluble ◽  
Heterogeneous Reactions ◽  
Formation Mechanisms ◽  
Autumn And Winter

Abstract. Many studies have recently been done on understanding the sources and formation mechanisms of atmospheric aerosols at ground level. However, vertical profiles and sources of size-resolved particulate matter within the urban boundary layer are still lacking. In this study, vertical distribution characteristics of size-segregated particles were investigated at three observation platforms (ground level, 118 m, and 488 m) on the 610 m high Canton Tower in Guangzhou, China. Size-segregated aerosol samples were simultaneously collected at the three levels in autumn and winter. Major aerosol components, including water-soluble ions, organic carbon, and elemental carbon, were measured. The results showed that daily average fine-particle concentrations generally decreased with height. Concentrations of sulfate and ammonium in fine particles displayed shallow vertical gradients, and nitrate concentrations increased with height in autumn, while the chemical components showed greater variations in winter than in autumn. The size distributions of sulfate and ammonium in both seasons were characterized by a dominant unimodal mode with peaks in the size range of 0.44–1.0 µm. In autumn, the nitrate size distribution was bimodal, peaking at 0.44–1.0 and 2.5–10 µm, while in winter it was unimodal, implying that the formation mechanisms for nitrate particles were different in the two seasons. Our results suggest that the majority of the sulfate and nitrate is formed from aqueous-phase reactions, and we attribute coarse-mode nitrate formation at the measurement site to the heterogeneous reactions of gaseous nitric acid on existing sea-derived coarse particles in autumn. Case studies further showed that atmospheric aqueous-phase and heterogeneous reactions could be important mechanisms for sulfate and nitrate formation, which, in combination with adverse weather conditions such as temperature inversion and calm wind, led to haze formation during autumn and winter in the Pearl River Delta (PRD) region.

Study of the distribution of 204 organic contaminants between the aqueous phase and the suspended particulate matter in treated wastewater for proper environmental control

2013 ◽  
Vol 51 (10-12) ◽  
pp. 2497-2515 ◽  
Author(s):  
Nieves Barco-Bonilla ◽  
Roberto Romero-González ◽  
Patricia Plaza-Bolaños ◽  
Antonia Garrido Frenich ◽  
José L. Martínez Vidal ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Aqueous Phase ◽  
Suspended Particulate Matter ◽  
Organic Contaminants ◽  
Environmental Control ◽  
Treated Wastewater ◽  
Suspended Particulate

scholarly journals Synoptic drivers of co-occurring summertime ozone and PM<sub>2.5</sub> pollution in eastern China

2020 ◽  
Author(s):  
Lian Zong ◽  
Yuanjian Yang ◽  
Meng Gao ◽  
Hong Wang ◽  
Peng Wang ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Surface Ozone ◽  
Eastern China ◽  
Principal Component ◽  
Photochemical Reactions ◽  
Hygroscopic Growth ◽  
Weather Patterns ◽  
Synoptic Weather ◽  
Compound Pollution ◽  
Surface O3

Abstract. In recent years, surface ozone (O3) pollution during summertime (June–August) over eastern China has become more serious, and it is even the case that surface O3 and PM2.5 (particulate matter with aerodynamic diameter &amp;leq; 2.5 μm in the air) pollution can co-occur. However, the synoptic circulation pattern related to this compound pollution remains unclear. In this study, the T-mode principal component analysis method is used to objectively classify four synoptic weather patterns (SWPs) that occur over eastern China, based on the geopotential heights at 500 hPa during summertime from 2015 to 2018. Four SWPs of eastern China are closely related to the western Pacific subtropical high (WPSH), exhibiting, significant intraseasonal and interannual variations. Note that remarkable spatial and temporal disparities of surface O3 and PM2.5 pollution are given under these four different SWPs according to the ground-level air quality and meteorological observations. In areas controlled by the WPSH or the prevailing westerlies, O3 pollution is mainly caused by photochemical reactions of nitrogen oxides and volatile organic compounds under weather conditions of high temperature, moderate humidity and slight precipitation. In particular, the warm moist flow brought by the WPSH can promote hygroscopic growth of fine particulate matter in some local areas, resulting in the increase of PM2.5 concentrations, which may form co-occurring surface O3 and PM2.5 pollution. In addition, the low boundary layer height and frequency of light-wind days are closely related to the transmission and diffusion of pollutants under the different SWPs, modulating the levels of O3–PM2.5 compound pollution. Overall, our findings demonstrate the different roles played by synoptic weather patterns in driving regional surface O3–PM2.5 compound pollution, in addition to the large quantities of emissions, and may also provide insights into the regional co-occurring high PM2.5 and high O3 level via the effects of certain meteorological factors.

scholarly journals Aqueous-Phase Production of Secondary Organic Aerosols from Oxidation of Dibenzothiophene (DBT)

Atmosphere ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 151 ◽  
Author(s):  
Yu Liu ◽  
Junchen Lu ◽  
Yanfang Chen ◽  
Yue Liu ◽  
Zhaolian Ye ◽  
...  
Keyword(s):  
Hydroxyl Radical ◽  
Aqueous Phase ◽  
Reaction Pathway ◽  
Photochemical Reactions ◽  
Oxidation Products ◽  
Gas Phase Reactions ◽  
Photo Oxidation ◽  
Oxygenated Compounds ◽  
Direct Light ◽  
Triplet Excited States

Intermediate-volatility organic compounds (IVOCs) have been recognized as an important contributor to the secondary organic aerosol (SOA) formation via gas-phase reactions. However, it is unclear whether or not IVOCs-SOA can be produced in the aqueous phase. This work investigated aqueous oxidation of one model compound of IVOCs, dibenzothiophene (DBT). Results show that DBT can be degraded by both hydroxyl radical and the triplet excited states of organic light chromophores (3C*). Aqueous dark oxidation of DBT was also possible. SOA yields of 32% and 15% were found for hydroxyl radical (OH)-mediated photo-oxidation and dark oxidation, respectively. A continuous and significant increase of oxidation degree of SOA was observed during OH photo-oxidation, but not during the dark oxidation. Factor analyses revealed that there was a persistent production of highly oxygenated compounds from the less oxygenated species. OH-initiated photochemical reactions can also produce species with a relatively large light-absorbing ability, while such photo-enhancement due to direct light irradiation and 3C*-initiated oxidation could occur, but is much less important. In the future, studies on the second-order rate constants, molecular characterization of the oxidation products from this and other IVOCs precursors are needed to better understand the role of this reaction pathway in SOA budget, air quality and climate change.

scholarly journals Aqueous-phase reactive species formed by fine particulate matter from remote forests and polluted urban air

2021 ◽  
Vol 21 (13) ◽  
pp. 10439-10455
Author(s):  
Haijie Tong ◽  
Fobang Liu ◽  
Alexander Filippi ◽  
Jake Wilson ◽  
Andrea M. Arangio ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Transition Metal ◽  
Metal Ions ◽  
Aqueous Phase ◽  
Organic Molecules ◽  
Fine Particulate Matter ◽  
Fulvic Acids ◽  
Transition Metal Ions ◽  
Relative Fraction ◽  
Fine Particulate

Abstract. In the aqueous phase, fine particulate matter can form reactive species (RS) that influence the aging, properties, and health effects of atmospheric aerosols. In this study, we explore the RS yields of aerosol samples from a remote forest (Hyytiälä, Finland) and polluted urban locations (Mainz, Germany; Beijing, China), and we relate the RS yields to different chemical constituents and reaction mechanisms. Ultra-high-resolution mass spectrometry was used to characterize organic aerosol composition, electron paramagnetic resonance (EPR) spectroscopy with a spin-trapping technique was applied to determine the concentrations of ⚫OH, O2⚫-, and carbon- or oxygen-centered organic radicals, and a fluorometric assay was used to quantify H2O2. The aqueous H2O2-forming potential per mass unit of ambient PM2.5 (particle diameter < 2.5 µm) was roughly the same for all investigated samples, whereas the mass-specific yields of radicals were lower for sampling sites with higher concentrations of PM2.5. The abundances of water-soluble transition metals and aromatics in ambient PM2.5 were positively correlated with the relative fraction of ⚫OH and negatively correlated with the relative fraction of carbon-centered radicals. In contrast, highly oxygenated organic molecules (HOM) were positively correlated with the relative fraction of carbon-centered radicals and negatively correlated with the relative fraction of ⚫OH. Moreover, we found that the relative fractions of different types of radicals formed by ambient PM2.5 were comparable to surrogate mixtures comprising transition metal ions, organic hydroperoxide, H2O2, and humic or fulvic acids. The interplay of transition metal ions (e.g., iron and copper ions), highly oxidized organic molecules (e.g., hydroperoxides), and complexing or scavenging agents (e.g., humic or fulvic acids) leads to nonlinear concentration dependencies in aqueous-phase RS production. A strong dependence on chemical composition was also observed for the aqueous-phase radical yields of laboratory-generated secondary organic aerosols (SOA) from precursor mixtures of naphthalene and β-pinene. Our findings show how the composition of PM2.5 can influence the amount and nature of aqueous-phase RS, which may explain differences in the chemical reactivity and health effects of particulate matter in clean and polluted air.

Photochemical Aging of Atmospheric Particulate Matter in the Aqueous Phase

2021 ◽  
Author(s):  
Frank Leresche ◽  
Joseph R. Salazar ◽  
David J. Pfotenhauer ◽  
Michael P. Hannigan ◽  
Brian J. Majestic ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Aqueous Phase ◽  
Atmospheric Particulate Matter ◽  
Atmospheric Particulate ◽  
Photochemical Aging
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