Source Apportionment of Brown Carbon Absorption by Coupling Ultraviolet-Visible Spectroscopy with Aerosol Mass Spectrometry

The impact of brown carbon (BrC) on climate has been widely acknowledged but remains uncertain, because either its contribution to absorption is being ignored in most climate models or the associated mixed emission sources and atmospheric lifetime are not accounted for. In this work, we propose positive matrix factorization as a framework to apportion the contributions of individual primary and secondary organic aerosol (OA) source components of BrC absorption, by combining long-term aerosol mass spectrometry (AMS) data with concurrent ultraviolet-visible (UV-vis) spectroscopy measurements. The former feature time-depend ent factor contributions to OA mass, and the latter consist of wavelength-dependent absorption coefficients. Using this approach for a full-year case study, we estimate for the first time the mass absorption efficiency (MAE) of major light-absorbing water soluble OA components in the atmosphere. We show that secondary biogenic OA contributes negligibly to absorption despite dominating the mass concentration in the summer. In contrast, primary and secondary wood burning emissions are highly absorbing up to 500 nm. The approach allowed us to constrain their MAE within a confined range consistent with previous laboratory work, which can be used in climate models to estimate the impact of BrC from these emissions on the overall absorption.The impact of brown carbon (BrC) on climate has been widely acknowledged but remains uncertain, because either its contribution to absorption is being ignored in most climate models or the associated mixed emission sources and atmospheric lifetime are not accounted for. In this work, we propose positive matrix factorization as a framework to apportion the contributions of individual primary and secondary organic aerosol (OA) source components of BrC absorption, by combining long-term aerosol mass spectrometry (AMS) data with concurrent ultraviolet-visible (UV-vis) spectroscopy measurements. The former feature time-depend ent factor contributions to OA mass, and the latter consist of wavelength-dependent absorption coefficients. Using this approach for a full-year case study, we estimate for the first time the mass absorption efficiency (MAE) of major light-absorbing water soluble OA components in the atmosphere. We show that secondary biogenic OA contributes negligibly to absorption despite dominating the mass concentration in the summer. In contrast, primary and secondary wood burning emissions are highly absorbing up to 500 nm. The approach allowed us to constrain their MAE within a confined range consistent with previous laboratory work, which can be used in climate models to estimate the impact of BrC from these emissions on the overall absorption.Peer reviewe

Quantification of levoglucosan and its isomers by High Performance Liquid Chromatography - Electrospray Ionization tandem Mass Spectrometry and its application to atmospheric and soil samples

http://www.atmos-meas-tech-discuss.net/4/4539/2011/amtd-4-4539-2011.htmlInternational audienceThe determination of atmospheric concentrations of levoglucosan and its two isomers, unambiguous tracers of biomass burning emissions, became even more important with the development of wood as renewable energy for domestic heating. Many researches demonstrated the increase during recent years of atmospheric particulate matter load due to domestic biomass combustion in developed countries. Analysis of biomass burning tracers is traditionally performed with Gas Chromatography-Mass Spectrometry (GC-MS) technique after derivatization and requires an organic solvent extraction. A simpler and faster technique using Liquid Chromatography - Electrospray Ionisation - tandem Mass Spectrometry (LC-ESI-MS/MS) was optimized for the analysis of levoglucosan, mannosan and galactosan isomers after an aqueous extraction. This technique allows a good separation between the three compounds in a very reduced time (runtime ~5 min). LOD and LOQ of this method are 30 μg l−1 and 100 μg l−1 respectively, allowing the use of filters from low-volume sampler (as commonly used in routine campaigns). A comparison of simultaneous levoglucosan measurements by GC-MS and LC-ESI-MS/MS for about 50 samples coming from different types of sampling sites and seasons was realized and shows very good agreement between the two methods. Therefore LC-ESI-MS/MS method can be used as an alternative to GC-MS particularly for measurement campaigns in routine where analysis time is important and detection limit is reduced. This paper shows that this method is also applicable to other environmental sample types like soil

Formation of highly oxygenated organic molecules from aromatic compounds

Anthropogenic volatile organic compounds (AV-OCs) often dominate the urban atmosphere and consist to a large degree of aromatic hydrocarbons (ArHCs), such as benzene, toluene, xylenes, and trimethylbenzenes, e.g., from the handling and combustion of fuels. These compounds are important precursors for the formation of secondary organic aerosol. Here we show that the oxidation of aromatics with OH leads to a subsequent autoxidation chain reaction forming highly oxygenated molecules (HOMs) with an O:C ratio of up to 1.09. This is exemplified for five single-ring ArHCs (benzene, toluene, o-/m-/p-xylene, mesitylene (1,3,5-trimethylbenzene) and ethylbenzene), as well as two conjugated polycyclic ArHCs (naphthalene and biphenyl). We report the elemental composition of the HOMs and show the differences in the oxidation patterns of these ArHCs. A potential pathway for the formation of these HOMs from aromatics is presented and discussed. We hypothesize that AV-OCs may contribute substantially to new particle formation events that have been detected in urban areas.Peer reviewe

Secondary organic aerosol formation from smoldering and flaming combustion of biomass: a box model parametrization based on volatility basis set

International audienceResidential wood combustion remains one of the most important sources of primary organic aerosols (POA) and secondary organic aerosol (SOA) precursors during winter. The overwhelming majority of these precursors have not been traditionally considered in regional models, and only recently were lignin pyrolysis products and polycyclic aro-matics identified as the principal SOA precursors from flam-ing wood combustion. The SOA yields of these components in the complex matrix of biomass smoke remain unknown and may not be inferred from smog chamber data based on single-compound systems. Here, we studied the ageing of emissions from flaming and smoldering-dominated wood fires in three different residential stoves, across a wide range of ageing temperatures (− 10, 2 and 15 • C) and emission loads. Organic gases (OGs) acting as SOA precursors were monitored by a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS), while the evolution of the aerosol properties during ageing in the smog chamber was monitored by a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). We developed a novel box model based on the volatility basis set (VBS) to determine the volatility distributions of the oxidation products from different precursor classes found in the emissions, grouped according to their emission pathways and SOA production rates. We show for the first time that SOA yields in complex emissions are consistent with those reported in literature from single-compound systems. We identify the main SOA precursors in both flaming and smoldering wood combustion emissions at different temperatures. While single-ring and polycyclic aromatics are significant precursors in flam-ing emissions, furans generated from cellulose pyrolysis appear to be important for SOA production in the case of smoldering fires. This is especially the case at high loads and low temperatures, given the higher volatility of furan oxidation products predicted by the model. We show that the oxidation products of oxygenated aromatics from lignin pyrolysis are expected to dominate SOA formation, independent of the combustion or ageing conditions, and therefore can be used as promising markers to trace ageing of biomass smoke in the field. The model framework developed herein may be gener-alizable for other complex emission sources, allowing determination of the contributions of different precursor classes to SOA, at a level of complexity suitable for implementation in regional air quality models

Study The Overprescription Of Proton Pump Inhibitors And Their Relation With Recurrent Community Aquired Infections In Outpatient Refilled Prescriptions Of Chronic Diseases Patients

Background: proton pump inhibitors are widely used worldwide and studies have demonstrated that the use of PPIs to be associated with various diseases such as several types of infection. Study objectives: to explore the effect of using PPIs on patients through studying some inflammatory biomarkers including WBC, neutrophil count, ESR, CRP, and IL-6. Methods and subjects: a retrospective study design was followed to collect data from study participants. The study included 62 patients receiving PPIs and 60 persons without being prescribed for PPIs. A working sheet was created for each patient and included the following information: age, WBC, neutrophil count, ESR, CRP, and IL-6. Data analysis was carried out using SPSS version 20. The relationship between variables was tested using independent T test. Significance was considered at alpha level < 0.05. Study findings: age was not varied significantly between study group and control group. All inflammatory biomarkers under study were significantly elevated in study group compared with control group. Conclusions: the findings of the present study showed that the use of PPIs was associated significantly with increased inflammatory biomarkers. We think that health settings should pay much attention to the role of pharmacists and pharmacy doctors to increase the awareness about the use of PPIs

Indoor terpene emissions from cooking with herbs and pepper and their secondary organic aerosol production potential

Cooking is widely recognized as an important source of indoor and outdoor particle and volatile organic compound emissions with potential deleterious effects on human health. Nevertheless, cooking emissions remain poorly characterized. Here the effect of herbs and pepper on cooking emissions was investigated for the first time to the best of our knowledge using state of the art mass spectrometric analysis of particle and gas-phase composition. Further, the secondary organic aerosol production potential of the gas-phase emissions was determined by smog chamber aging experiments. The emissions of frying meat with herbs and pepper include large amounts of mono-, sesqui- and diterpenes as well as various terpenoids and p-cymene. The average total terpene emission rate from the use of herbs and pepper during cooking is estimated to be 46 ± 5 gg-1 Herbs min-1. These compounds are highly reactive in the atmosphere and lead to significant amounts of secondary organic aerosol upon aging. In summary we demonstrate that cooking with condiments can constitute an important yet overlooked source of terpenes in indoor air

Effects of aerosol size and coating thickness on the molecular detection using extractive electrospray ionization

Extractive electrospray ionization (EESI) has been a well-known technique for high-throughput online molecular characterization of chemical reaction products and intermediates, detection of native biomolecules, in vivo metabolomics, and environmental monitoring with negligible thermal and ionization-induced fragmentation for over two decades. However, the EESI extraction mechanism remains uncertain. Prior studies disagree on whether particles between 20 and 400nm diameter are fully extracted or if the extraction is limited to the surface layer. Here, we examined the analyte extraction mechanism by assessing the influence of particle size and coating thickness on the detection of the molecules therein. We find that particles are extracted fully: organics-coated NH4NO3 particles with a fixed core volume (156 and 226nm in diameter without coating) showed constant EESI signals for NH4NO3 independent of the shell coating thickness, while the signals of the secondary organic molecules comprising the shell varied proportionally to the shell volume. We also found that the EESI sensitivity exhibited a strong size dependence, with an increase in sensitivity by 1-3 orders of magnitude as particle size decreased from 300 to 30nm. This dependence varied with the electrospray (ES) droplet size, the particle size and the residence time for coagulation in the EESI inlet, suggesting that the EESI sensitivity was influenced by the coagulation coefficient between particles and ES droplets. Overall, our results indicate that, in the EESI, particles are fully extracted by the ES droplets regardless of the chemical composition, when they are collected by the ES droplets. However, their coalescence is not complete and depends strongly on their size. This size dependence is especially relevant when EESI is used to probe size-varying particles as is the case in aerosol formation and growth studies with size ranges below 100nm. © 2021 The Author(s)

Secondary organic aerosol formation from gasoline vehicle emissions in a new mobile environmental reaction chamber

We present a new mobile environmental reaction chamber for the simulation of the atmospheric aging of different emissions sources without limitation from the instruments or facilities available at any single site. Photochemistry is simulated using a set of 40 UV lights (total power 4 KW). Characterisation of the emission spectrum of these lights shows that atmospheric aging of emissions may be simulated over a range of temperatures (-7 to 25°C). A photolysis rate of NO2, JNO2, of (8.0±0.7)×10-3 s-1 was determined at 25°C. We demonstrate the utility of this new system by presenting results on the aging (OH=12×106 cm-3h) of emissions from a modern (Euro 5) gasoline car operated during a driving cycle (New European Driving Cycle, NEDC) on a chassis dynamometer in a vehicle test cell. Emissions from the entire NEDC were sampled and aged in the chamber. A thorough investigation of the composition of the gas phase emissions suggests that the observed SOA is from previously unconsidered precursors and processes. This large enhancement in PM mass from gasoline vehicle aerosol emissions due to SOA formation, if it occurs across a wider range of gasoline vehicles, would have significant implications for our understanding of the contribution of on-road gasoline vehicles to ambient aerosols.JRC.F.8-Sustainable Transpor