Reaction Of HNO3 Research Articles

Sulfinamide Formation from the Reaction of Bacillithiol and Nitroxyl.

Bacillithiol (BSH) replaces glutathione (GSH) as the most prominent low-molecular-weight thiol in many low G + C gram-positive bacteria. BSH plays roles in metal binding, protein/enzyme regulation, detoxification, redox buffering, and bacterial virulence. Given the small amounts of BSH isolated from natural sources and relatively lengthy chemical syntheses, the reactions of BSH with pertinent reactive oxygen, nitrogen, and sulfur species remain largely unexplored. We prepared BSH and exposed it to nitroxyl (HNO), a reactive nitrogen species that influences bacterial sulfur metabolism. The profile of this reaction was distinct from HNO oxidation of GSH, which yielded mixtures of disulfide and sulfinamide. The reaction of BSH and HNO (generated from Angeli's salt) gives only sulfinamide products, including a newly proposed cyclic sulfinamide. Treatment of a glucosamine-cysteine conjugate, which lacks the malic acid group, with HNO forms disulfide, implicating the malic acid group in sulfinamide formation. This finding supports a mechanism involving the formation of an N-hydroxysulfenamide intermediate that dehydrates to a sulfenium ion that can be trapped by water or internally trapped by an amide nitrogen to give the cyclic sulfinamide. The biological relevance of BSH reactivity toward HNO is provided through in vivo experiments demonstrating that Bacillus subtilis exposed to HNO shows a growth phenotype, and a strain unable to produce BSH shows hypersensitivity toward HNO in minimal medium cultures. Thiol analysis of HNO-exposed cultures shows an overall decrease in reduced BSH levels, which is not accompanied by increased levels of BSSB, supporting a model involving the formation of an oxidized sulfinamide derivative, identified in vivo by high-pressure liquid chromatography/mass spectrometry. Collectively, these findings reveal the unique chemistry and biology of HNO with BSH in bacteria that produce this biothiol.

NH3and HNOxFormation and Loss in Nitrogen Fixation from Air with Water Vapor by Nonequilibrium Plasma

The current global energy crisis indicated that increasing our insight into nonfossil fuel nitrogen fixation pathways for synthetic fertilizer production is more crucial than ever. Nonequilibrium plasma is a good candidate because it can use N2 or air as a N source and water directly as a H source, instead of H2 or fossil fuel (CH4). In this work, we investigate NH3 gas phase formation pathways from humid N2 and especially humid air up to 2.4 mol % H2O (100% relative humidity at 20 °C) by optical emission spectroscopy and Fourier-transform infrared spectroscopy. We demonstrate that the nitrogen fixation capacity is increased when water vapor is added, as this enables HNO2 and NH3 production in both N2 and air. However, we identified a significant loss mechanism for NH3 and HNO2 that occurs in systems where these species are synthesized simultaneously; i.e., downstream from the plasma, HNO2 reacts with NH3 to form NH4NO2, which rapidly decomposes into N2 and H2O. We also discuss approaches to prevent this loss mechanism, as it reduces the effective nitrogen fixation when not properly addressed and therefore should be considered in future works aimed at optimizing plasma-based N2 fixation. In-line removal of HNO2 or direct solvation in liquid are two proposed strategies to suppress this loss mechanism. Indeed, using liquid H2O is beneficial for accumulation of the N2 fixation products. Finally, in humid air, we also produce NH4NO3, from the reaction of HNO3 with NH3, which is of direct interest for fertilizer application.

Quantifying the formation pathways of nitrate in size-segregated aerosols during winter haze pollution

Nitrate (NO3−) is an important acidic component in haze pollution. The NO3− formation pathways for bulk aerosols have been studied thoroughly, leaving the size-segregated NO3− formation mechanisms underexplored. By coupling nitrate dual isotopes with aerosol chemical compositions, we studied size-segregated aerosols collected during winter haze pollution events at Chengdu, China. Different formation mechanisms for the size-segregated NO3− were analyzed. For fine particles (0.43–2.1 μm), NO3− was dominantly formed under NH4+ enriched conditions, during which the SIAR (stable isotope analysis in R) model suggested that N2O5 hydrolysis, NO3 + VOCs (volatile organic compounds) and NO2 + OH homogeneous reactions contributed 38–42 %, 32–38 %, and 22–30 % of NO3− production, respectively. For coarse particles (>3.3 μm), majority of NO3− was produced through the reaction of gas-phase HNO3 with CaCO3 (63–71 %). This work revealed differential formation pathways of size-segregated NO3− and provided quantitative insights on information on NO3− formation during the haze pollution.

Reaction Kinetics of Criegee Intermediates with Nitric Acid

This work investigated the reaction kinetics of HNO3 with four Criegee intermediates (CIs): CH2OO, (CH3)2COO, methyl vinyl ketone oxide (MVKO), and methacrolein oxide (MACRO). Our results show that these reactions are extremely fast with rate coefficients of (1.51 ± 0.45) × 10-10, (3.54 ± 1.06) × 10-10, (3.93 ± 1.18) × 10-10, and (3.0 ± 1.0) × 10-10 cm3 s-1 for reactions of HNO3 with CH2OO, (CH3)2COO, syn-MVKO, and anti-MACRO, respectively. This is consistent with previous results for the reactions between CIs and carboxylic acids, but the rate coefficient of CH2OO + HNO3 in the literature [Foreman Angew. Chem. 2016, 128, 10575] was found to be overestimated by a factor of 3.6. In addition, we did not observe any significant pressure dependence in the HNO3 reactions with CH2OO and (CH3)2COO under 100-400 Torr. Our results indicate that in a dry area with severe NOx pollution, the reactions of CIs with HNO3 and their products may be worthy of attention, but these reactions may be insignificant under high-humidity conditions. However, CI reactions with HNO3 may not play an important role in the atmospheric removal processes of HNO3 because of the low concentrations of CIs.

Chemical Characteristics of Water-Soluble Inorganic Ions in Different Types of Asian Dust in Wajima, a Background Site in Japan

Two Asian dust (AD) events were observed in March 2021 (AD1: 16 March 2021 00:00 UTC~17 March 2021 12:00 UTC and AD2: 28 March 2021 00:00 UTC~31 March 2021 12:00 UTC). To determine the chemical characteristics of water-soluble inorganic ions (WSIIs) in different types of Asian dust, the total suspended particulates (TSP) were collected at Kanazawa University Wajima Air Monitoring Station (KUWAMS), a background site in Japan from 27 February to 4 March, 2021. Based on the lidar observations and the backwards trajectory analysis results, AD events were divided into two types: ADN (aerosols were mainly mineral dust) and ADP (aerosols were mixtures of spherical particles). During ADs, the concentrations of the TSP and WSII increased, with the highest TSP concentration in ADN (38.6 μg/m3) and the highest WSII concentration in ADP (5.82 μg/m3). The increase in (cations)/(anions) during AD indicates that the input of AD aerosol buffered the aerosol acidity. Additionally, a significant increase in Cl depletion, along with ADN events, was found (Cl depletion = 73.8%). To comprehensively analyse the different types of ADs on WSIIs, we refer to the previous data from 2010 to 2015 at KUWAMS. As a result, the increased Cl depletion was caused by the heterogeneous reaction of HNO3 with sea salt when the air mass passed over the Japanese Sea. Additionally, the chemical form of SO42− was highly dependent on the source and pathway, while SO42− mainly came from natural soil dust in ADN and from anthropogenic emissions in ADP. The enhancement of secondary NO3− was observed in AD via the heterogeneous hydrolysis of N2O5.

High-Resolution Measurements of SO2, HNO3 and HCl at the Urban Environment of Athens, Greece: Levels, Variability and Gas to Particle Partitioning

High-resolution measurements of sulfur dioxide (SO2), nitric acid (HNO3), and hydrochloric acid (HCl) were conducted in Athens, Greece, from 2014 to 2016 via a wet rotating annular denuder system paired with an ion chromatograph. Decreased mean annual levels of SO2 and HNO3 (equal to 3.3 ± 4.8 μg m−3 and 0.7 ± 0.6 μg m−3, respectively) were observed relative to the past, whereas for HCl (mean of 0.4 μg m−3 ) no such comparison was possible as the past measurements are very scarce. Regional and local emission sources regulated the SO2 levels and contributed to both the December and the July maxima of 6.6 μg m−3 and 5.5 μg m−3, respectively. Similarly, the significant enhancement at noon and during the winter nighttime was due to transported SO2 and residential heating, respectively. The oxidation of NO2 by OH radicals and the heterogeneous reactions of HNO3 on sea salt seemed to drive the HNO3 and HCl formation, respectively, whereas nighttime biomass burning affected only the former by almost 50%. During summer, the sulfate anions dominated over the SO2, in contrast to the chloride and nitrate ions that prevailed during the winter and were linked to the aerosol acidity that influences their lifetime as well as their impact on ecosystems.

Can a Nitrosyl of a Mn(II)-Porphyrin Complex Release Nitroxyl/HNO?

In general, the nitrosyl complexes of Mn(II)-porphyrinate having the {Mn(NO)}6 configuration are not considered as HNO or nitroxyl (NO-) donors because of [MnI-NO+] nature. A nitrosyl complex of Mn(II)-porphyrin, [Mn(TMPP2-)(NO)], 1 [TMPPH2 = 5,10,15,20-tetrakis-4-methoxyphenylporphyrin], is shown to release HNO in the presence of HBF4. It is evidenced from the characteristic reaction of HNO with triphenylphosphine and isolation of the [(TMPP2-)MnIII(H2O)2](BF4), 2. This is attributed to the fact that H+ from HBF4 polarizes the NO group whereas the BF4- interacts with metal ion to stabilize the Mn(III) form. These two effects cooperatively result in the release of HNO from complex 1. In addition, complex 1 behaves as a nitroxyl (NO-) donor in the presence of [Fe(dtc)3] (dtc = diethyldithiocarbamate anion) and [Fe(TPP)(Cl)] (TPP = 5,10,15,20-tetraphenylporphyrinate) to result in [Fe(dtc)2(NO)] and [Fe(TPP)(NO)], respectively.

Review of Comprehensive Measurements of Speciated NOy and its Chemistry: Need for Quantifying the Role of Heterogeneous Processes of HNO3 and HONO

ABSTRACT To improve the credibility of chemistry schemes employed in chemical transport models (CTMs) aiming at predicting ozone mixing ratios in urban, rural, and regional scales, validation of models not only by observational data of O3 and NOx but also by individual species of reactive nitrogen NOy is necessary because the formation and dissipation of O3 in the atmosphere occur via reactions accompanying the transformation of NOx and NOy. The disagreement of the simulated results of CTM with observational data of HNO3 and HONO have often been reported, and this paper reviews previous studies on the heterogeneous “renoxification” reaction of gaseous HNO3 to form NO, NO2, and/or HONO; the formation of HONO from the heterogeneous dark reaction of NO2 and H2O, and the photolysis of adsorbed HNO3 and NO3– on surfaces. For the further validation of CTMs with individual species of NOy, previous field studies of comprehensive observation of NOy speciation in ground-based and aircraft campaigns have also been reviewed. Studies combining observations of speciated NOy and model simulations need to be performed to improve chemistry models used in CTMs.

Reaction of Nitroxyl (HNO) with Hydrogen Sulfide and Hydropersulfides

Nitroxyl (HNO) has gained a considerable amount of attention because of its promising pharmacological effects. The biochemical mechanisms of HNO activity are associated with the modification of regulatory thiol proteins. Recently, several studies have suggested that hydropersulfides (RSSH), presumed signaling products of hydrogen sulfide (H2S)-mediated thiol (RSH) modification, are additional potential targets of HNO. However, the interaction of HNO with reactive sulfur species beyond thiols remains relatively unexplored. Herein, we present characterization of HNO reactivity with H2S and RSSH. The reaction of H2S with HNO leads to the formation of hydrogen polysulfides and sulfur (S8), suggesting a potential role in sulfane sulfur homeostasis. Furthermore, we show that hydropersulfides are more efficient traps for HNO than their thiol counterparts. The reaction of HNO with RSSH at varied stoichiometries has been examined with the observed production of various dialkylpolysulfides (RSSnSR) and other nitrogen-containing dialkylpolysulfide species (RSS-NH-SnR). We do not observe evidence of sulfenylsulfinamide (RS-S(O)-NH2) formation, a pathway expected by analogy with the known reactivity of HNO with thiol.

The influence of upslope fog on hygroscopicity and chemical composition of aerosols at a forest site in Taiwan

This study investigated the influence of upslope fog formation on the chemical composition and single hygroscopicity parameter (κ) of rural aerosols from Dec. 1st to Dec. 24th, 2018 at the Xitou forest site (23.67°N, 120.80°E, 1178 m above sea level (a.s.l.)) in central Taiwan. The aerosol chemical compositions were monitored using a mini compact time-of-flight aerosol mass spectrometer (mini-C-ToF-AMS), and the ambient aerosol particles were collected by a 13-stage micro-orifice uniform deposit impactor (MOUDI) for a Fourier-transform infrared spectrometer with an attenuated total reflectance accessory (FTIR-ATR) analysis. κ of aerosols was derived from the comparison of AMS pToF size distribution and FTIR-ATR measurement using the κ-Köhler equation. Our results show that the moderate correlation between OOA and CO provided evidence of upstream anthropogenic emission and time-lagged aged secondary organic aerosol transport by the daytime sea breeze and valley wind. Larger particles (Dva ~800 nm–1.0 μm) had a higher fog scavenging removal efficiency (62% for organic and 81% for nitrate, respectively), and smaller particles (Dva ~100 nm–700 nm) could remain growth through gas-to-aqueous partition. The submicrometer nitrate particles were likely significantly formed via gas-particle partitioning as HNO3(aq) or NH4NO3 while the larger micrometer-sized sea salt-like nitrate particles might be formed via heterogeneous reaction of gaseous HNO3 with deliquesced sea salt particles. The inconsistency of submicrometer nitrate between real-time AMS and offline FTIR-ATR measurements indicates that the evaporation loss of HNO3 or NH4NO3 during MOUDI filter sampling could lead to the unavailable κp−NO3 (κ for nitrate-containing particles) retrieval. The average κp-org (organics-containing particles) was 0.19 ± 0.12 (r2 ≥ 0.8) and nearly overlapped with κp−SO4 (0.22 ± 0.08) (sulfate-containing particles) during misty daytime, indicating that aerosols were more likely internally mixed particles to have similar hygroscopicity and physical mixing state property.

Day–night variation and size distribution of water-soluble inorganic ions in particulate matter in Ulsan, South Korea

In the present study, 11 size classes of particulate matter were collected from a semi-rural site in the industrial city of Ulsan, South Korea in 2019 to investigate the size distribution and day–night variation of water-soluble inorganic ions (WSIIs). Approximately 70% of the detected WSIIs were found in fine particles, with Na+, Ca2+, Cl−, and NO3− dominant (~70%) in coarse particles and SO42−, NO3−, and NH4+ (SNA) dominant (~70%) in fine particles. Monthly variation in total WSIIs was observed, with the highest average concentration found in April for both coarse (2.71 μg/m3) and fine particles (5.75 μg/m3). Given that this month is characterized by prevailing southeasterly winds, these high levels may represent the adverse effects of industrial activity. Coefficients of divergence for individual WSIIs exhibited large variability, which is indicative of significant day–night differences in meteorology, chemistry, and source contributions. The size distributions of Na+, K+, F−, Cl−, NO3−, and SO42− were bimodal, while Mg2+, Ca2+, and NH4+ were unimodal. Peaks were generally found at 1.8–5.6 μm and 0.18–0.56 μm for coarse and fine particles, respectively. By plotting the linear relationship between the mole charge ratios of SNA, we found that coarse NO3− particles were mainly the result of heterogeneous reactions between HNO3 and sea salts or crustal species, while the homogeneous reaction of HNO3 and NH3 played a crucial role in the formation of fine NO3− particles. In conclusion, though day–night variation in WSIIs was apparent, especially in SNA, the formation pathways for both coarse and fine particles were similar for day and night. Based on the verification of the formation mechanisms for WSIIs at this semi-rural site, the influence of industrial activity on the secondary formation of PM in urban and industrial areas can be investigated further.

Atmospheric chemical loss processes of isocyanic acid (HNCO): a combined theoretical kinetic and global modelling study

Abstract. Isocyanic acid (HNCO) is a chemical constituent suspected to be harmful to humans if ambient concentrations exceed ∼1 ppbv. HNCO is mainly emitted by combustion processes but is also inadvertently released by NOx mitigation measures in flue gas treatments. With increasing biomass burning and more widespread usage of catalytic converters in car engines, good prediction of HNCO atmospheric levels with global models is desirable. Little is known directly about the chemical loss processes of HNCO, which limits the implementation in global Earth system models. This study aims to close this knowledge gap by combining a theoretical kinetic study on the major oxidants reacting with HNCO with a global modelling study. The potential energy surfaces of the reactions of HNCO with OH and NO3 radicals, Cl atoms, and ozone were studied using high-level CCSD(T)/CBS(DTQ)//M06-2X/aug-cc-pVTZ quantum chemical methodologies, followed by transition state theory (TST) theoretical kinetic predictions of the rate coefficients at temperatures of 200–3000 K. It was found that the reactions are all slow in atmospheric conditions, with k(300K)≤7×10-16 cm3molecule-1s-1, and that product formation occurs predominantly by H abstraction; the predictions are in good agreement with earlier experimental work, where available. The reverse reactions of NCO radicals with H2O, HNO3, and HCl, of importance mostly in combustion, were also examined briefly. The findings are implemented into the atmospheric model EMAC (ECHAM/MESSy Atmospheric Chemistry) to estimate the importance of each chemical loss process on a global scale. The EMAC predictions confirm that the gas-phase chemical loss of HNCO is a negligible process, contributing less than 1 % and leaving heterogeneous losses as the major sinks. The removal of HNCO by clouds and precipitation contributes about 10 % of the total loss, while globally dry deposition is the main sink, accounting for ∼90 %. The global simulation also shows that due to its long chemical lifetime in the free troposphere, HNCO can be efficiently transported into the UTLS by deep convection events. Daily-average mixing ratios of ground-level HNCO are found to regularly exceed 1 ppbv in regions dominated by biomass burning events, but rarely exceed levels above 10 ppt in other areas of the troposphere, though locally instantaneous toxic levels are expected.

Heterogeneous Chemistry of CaCO3 Aerosols with HNO3 and HCl.

Calcite (CaCO3) aerosols often serve as an idealized proxy for calcium-rich mineral dust. Their use has also previously been proposed for stratospheric solar radiation management (SSRM). Little is known about the heterogeneous chemistry of calcite aerosols with trace gases HNO3 and HCl and therefore their potential impact on stratospheric ozone (O3). Here we report the results of an experimental study of the uptake of HNO3 and HCl onto submicron CaCO3 particles in two different flow reactors. Products and reaction kinetics were observed by impacting aerosolized CaCO3 onto ZnSe windows, exposing them to the reagent gases at a wide range of concentrations, at 296 K and under dry conditions, and analyzing the particles before and after trace gas exposure using Fourier transform infrared spectroscopy (FTIR). A Ca(OH)(HCO3) termination layer was detected in the form of a HCO3- peak in the FTIR spectra, indicating a hydrated surface even under dry conditions. The results demonstrate the reaction of HNO3 with Ca(OH)(HCO3) to produce Ca(NO3)2, water, and CO2. HCl reacted with Ca(OH)(HCO3) to produce CaCl2 and also water and CO2. The depletion of the Ca(OH)(HCO3)/Ca(CO3) signal due to reaction with HNO3 or HCl followed pseudo-first-order kinetics. From the FTIR analysis, the reactive uptake coefficient for HNO3 was determined to be in the range of 0.013 ≤ γHNO3 ≤ 0.14, and that for HCl was 0.0011 ≤ γHCl ≤ 0.012 within the reported uncertainty. The reaction of HCl with airborne CaCO3 aerosols was also studied in an aerosol flow tube coupled with a quadrupole chemical ionization mass spectrometer (CIMS) under similar conditions to the FTIR study, and γHCl was determined to be 0.013 ± 0.001. Following previous modeling studies, these results suggest that the reactions of HCl and HNO3 with calcite in the stratosphere could ameliorate the potential for stratospheric solar radiation management to lead to stratospheric ozone depletion.

Effects of NH3 and alkaline metals on the formation of particulate sulfate and nitrate in wintertime Beijing

Sulfate and nitrate from secondary reactions remain as the most abundant inorganic species in atmospheric particle matter (PM). Their formation is initiated by oxidation (either in gas phase or particle phase), followed by neutralization reaction primarily by NH3, or by other alkaline species such as alkaline metal ions if available. The different roles of NH3 and metal ions in neutralizing H2SO4 or HNO3, however, are seldom investigated. Here we conducted semi-continuous measurements of SO42−, NO3−, NH4+, and their gaseous precursors, as well as alkaline metal ions (Na+, K+, Ca2+, and Mg2+) in wintertime Beijing. Analysis of aerosol acidity (estimated from a thermodynamic model) indicated that preferable sulfate formation was related to low pH conditions, while high pH conditions promote nitrate formation. Data in different mass fraction ranges of alkaline metal ions showed that in some ranges the role of NH3 was replaced by alkaline metal ions in the neutralization reaction of H2SO4 and HNO3 to form particulate SO42− and NO3−. The relationships between mass fractions of SO42− and NO3− in those ranges of different alkaline metal ion content also suggested that alkaline metal ions participate in the competing neutralization reaction of sulfate and nitrate. The implication of the current study is that in some regions the chemistry to incorporate sulfur and nitrogen into particle phase might be largely affected by desert/fugitive dust and sea salt, besides NH3. This implication is particularly relevant in coastal China and those areas with strong influence of dust storm in the North China Plain (NCP), both of which host a number of megacities with deteriorating air quality.

On the role of Fe(III) ions on the reduction mechanisms of concentrated nitric acid

The reduction mechanism of concentrated HNO3 (4 mol L−1) was investigated on a gold electrode at 40 °C by coupling electrochemical methods (cyclic voltammetry, chrononamperometry and electrochemical impedance spectroscopy) with chemical analysis of solution by Raman spectroscopy and the gas analysis by mass spectrometry. It was demonstrated that in such conditions, Fe(III) promotes the catalytic reduction reactions of concentrated HNO3. This was ascribed to the fact that Fe(III) modifies the chemical equilibrium in concentrated nitric acid by generating reduced species of nitric acid such as NO2. Then, the presence of these species catalyses the reduction of nitric acid with a mechanism which can tuned depending on the concentration in Fe(III) and the applied potential.

Comparison of surface ozone simulation among selected regional models in MICS-Asia III – effects of chemistry and vertical transport for the causes of difference

Abstract. In order to clarify the causes of variability among the model outputs for surface ozone in the Model Intercomparison Study Asia Phase III (MICS-Asia III), three regional models, CMAQ v.5.0.2, CMAQ v.4.7.1, and NAQPMS (abbreviated as NAQM in this paper), have been selected. Detailed analyses of monthly averaged diurnal variation have been performed for selected grids covering the metropolitan areas of Beijing and Tokyo and at a remote oceanic site, Oki. The chemical reaction mechanism, SAPRC99, used in the CMAQ models tended to give a higher net chemical ozone production than CBM-Z used in NAQM, agreeing with previous studies. Inclusion of the heterogeneous “renoxification” reaction of HNO3 (on soot surface)→NO+NO2 only in NAQM would give a higher NO concentration resulting in a better agreement with observational data for NO and nighttime O3 mixing ratios. In addition to chemical processes, the difference in the vertical transport of O3 was found to affect the simulated results significantly. Particularly, the increase in downward O3 flux from the upper layer to the surface after dawn was found to be substantially different among the models. Larger early morning vertical transport of O3 simulated by CMAQ 5.0.2 is thought to be the reason for higher daytime O3 in July in this model. All three models overestimated the daytime ozone by ca. 20 ppbv at the remote site Oki in July, where in situ photochemical activity is minimal.

Seasonal characteristics of chemical compositions and sources identification of PM2.5 in Zhuhai, China.

Fine particulate matter is associated with adverse health effects, but exactly which characteristics of PM2.5 are responsible for this is still widely debated. We evaluated seasonal dynamics of the composition and chemical characteristics of PM2.5 in Zhuhai, China. PM2.5 characteristics at five selected sites within Zhuhai city were analyzed. Sampling began on January 10, 2015, and was conducted for 1year. The ambient mass concentration, carbon content (organic and elemental carbon, OC and EC), level of inorganic ions, and major chemical composition of PM2.5 were also determined. Average concentrations of PM2.5 were lower than the National Ambient Air Quality Standard (NAAQS) 24-h average of 65μg/m3. The daily PM2.5 concentration in Zhuhai city exhibited clear seasonal dynamics, with higher daily PM2.5 concentrations in autumn and winter than in spring and summer. Carbon species (OC and EC) and water-soluble ions were the primary components of the PM2.5 fraction of particles. Apart from OC and EC, chemical species in PM2.5 were mainly composed of NH4+ and SO42-. There was a marked difference between the summer and winter periods: the concentrations of OC and EC in winter were roughly 3.4 and 4.0 times than those in summer, while NH4+, SO42-, NO3-, and Na+ were 3.2, 4.5, 28.0, and 5.7 times higher in winter than those in summer, respectively. The results of chemical analysis were consistent with three sources dominating PM2.5: coal combustion, biomass burning, and vehicle exhaust; road dust and construction; and from reaction of HCl and HNO3 with NH3 to form NH4Cl and NH4NO3. However, additional work is needed to improve the mass balance and to obtain the source profiles necessary to use these data for source apportionment.

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

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.

Chemical characteristics of haze particles in Xi'an during Chinese Spring Festival: Impact of fireworks burning

Fireworks burning releases massive fine particles and gaseous pollutants, significantly deteriorating air quality during Chinese Lunar New Year (LNY) period. To investigate the impact of the fireworks burning on the atmospheric aerosol chemistry, 1-hr time resolution of PM2.5 samples in Xi'an during the winter of 2016 including the LNY were collected and detected for inorganic ions, acidity and liquid water content (LWC) of the fine aerosols. PM2.5 during the LNY was 167±87μg/m3, two times higher than the China National Ambient Air Quality Standard (75μg/m3). K+ (28wt.% of the total ion mass) was the most abundant ion in the LNY period, followed by SO42− (25wt.%) and Cl− (18wt.%). In contrast, NO3− (34wt.%) was the most abundant species in the haze periods (hourly PM2.5>75μg/m3), followed by SO42− (29.2wt.%) and NH4+ (16.3wt.%), while SO42 - (35wt.%) was the most abundant species in the clean periods (hourly PM2.5<75μg/m3), followed by NO3− (23.1wt.%) and NH4+ (11wt.%). Being different from the acidic nature in the non-LNY periods, aerosol in the LNY period presented an alkaline nature with a pH value of 7.8±1.3. LWC during the LNY period showed a robust linear correlation with K2SO4 and KCl, suggesting that aerosol hygroscopicity was dominated by inorganic salts derived from fireworks burning. Analysis of correlations between the ratios of NO3−/SO42− and NH4+/SO42− indicated that heterogeneous reaction of HNO3 with NH3 was an important formation pathway of particulate nitrate and ammonium during the LNY period.

The Chemistry Climate Model ECHAM6.3-HAM2.3-MOZ1.0

The chemistry climate model ECHAM-HAMMOZ contains a detailed representation of tropospheric and stratospheric reactive chemistry and state-of-the-art parametrisations of aerorols 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 ten-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 (O&lt;sub&gt;3&lt;/sub&gt;) and carbon monoxide (CO) from Infrared Atmospheric Sounding Interferometer (IASI) and Ozone Monitoring Instrument (OMI), Microwave Limb Sounder (MLS) observations of temperature, nitric acid (HNO&lt;sub&gt;3&lt;/sub&gt;), chlorine monoxide (ClO), and O&lt;sub&gt;3&lt;/sub&gt; for the evaluation of polar stratospheric processes, an ozone sonde climatology, surface ozone observations from the Tropospheric Ozone Assessment Report (TOAR) database, and surface CO data from the Global Atmosphere Watch network. Global budgets of ozone, hydroxide (OH), nitrogen oxides (NO&lt;sub&gt;x&lt;/sub&gt;), aerosols, clouds, and radiation are analyzed and compared to the literature. ECHAM-HAMMOZ performs well in many aspects. However, in the base simulation, lightning NO&lt;sub&gt;x&lt;/sub&gt; emissions are very low, and the impact of the heterogeneous reaction of HNO&lt;sub&gt;3&lt;/sub&gt; on dust and seasalt 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.