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

Hepatitis C Infection Patterns at a Tertiary Care Center in New York: A Cross-Sectional Study.

Introduction In the United States, 2.7 to 3.9 million patients are infected with the hepatitis C virus (HCV) with 3,500 new cases reported yearly. According to the Centers for Disease Control and Prevention, HCV was the underlying or contributing cause of death of 19,659 patients in 2014. These facts underscore the need for a better understanding of the scope of this disease. Our epidemiologic study aimed at analyzing the pattern of occurrence of HCV infection at Staten Island University Hospital (SIUH) by evaluating the characteristics of newly infected patients with hepatitis C in 2014. The identified features served to better distinguish the targets for preventive health care in our particular population. Methodology A cross-sectional study of all newly diagnosed patients with HCV infections in the year 2014 presenting to SIUH was conducted using International Classification of Disease-9 codes (ICD-9) for hepatitis C. We included all patients with a positive HCV antibody confirmed by polymerase chain reaction testing. Patients were divided into groups according to age to simulate the age groups in the 2013 - 2014 Hepatitis B and C Annual Report of the New York City (NYC) Department of Health and Mental Hygiene published in 2016 (abbreviated to 2014 NYCDOH Report, hereafter). Gender and HCV genotypes were also collected. We compared disease frequency between age groups, gender, and genotype with the results of the 2014 NYCDOH Report. Results A total of 378 newly diagnosed HCV cases were identified; 60.05% were men, and 39.95% were women. The rate of infection with genotype 1a was the highest (36. 5%) followed by 1b (25.9%). In women, genotype 1b was predominant (13.76%) versus genotype 1a as the most common in men. The mean age was 54 years for men and 57 years for women. Most cases fell into the 60 to 69-year age group (32.28%), followed by the 50 to 59-year age group (31.48%). More so, all patients 80 years and older were exclusively women. Conclusions We found most new HCV infections at SIUH were diagnosed in patients aged 60 to 69 years, and the 2014 NYC DOH Report indicates most new HCV infections occur in patients aged 40 to 59 years. Also, all HCV infections detected in patients older than 80 years of age were found in women. These findings provide a better understanding of the patient demographics for appropriate HCV screening policies. Increased awareness and strict adherence to screening policies in baby boomers and high-risk populations are paramount in order to diagnose HCV infection early, offer therapy, and prevent HCV-related mortality and morbidity

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

Modeling the effect of reduced traffic due to COVID-19 measures on air quality using a chemical transport model : Impacts on the Po Valley and the Swiss Plateau regions

Publisher Copyright: © 2021 The Author(s).The spread of COVID-19 has posed serious challenges for the global communities. To reduce the circulation of the infection, governmental bodies have imposed different lockdown measures at various levels of complexity and duration. As a result, a substantial reduction in mobility might have important, yet unknown, implications for air quality. In this study, we applied the Comprehensive Air quality Model with eXtensions (CAMx) to investigate potential changes in air quality and its chemical composition over northern Italy and Switzerland during periods when lockdown measures were enforced. Our results indicated that lockdown measures reduced nitrogen dioxide (NO2) air concentrations by up to 46% and 25% in the Po Valley and Swiss Plateau regions, respectively, whereas fine particulate matter (PM2.5) air concentrations were reduced only by up to 10% and 6%. This highlights the importance of other emission categories other than traffic for the total PM2.5 levels. The analysis of the PM2.5 components indicated that elemental carbon (EC) and particulate nitrate (NO3 -) were the species most affected by the lockdown measures, whereas a mild increase in the secondary organic aerosol (SOA) concentrations occurred in the Po Valley, and specifically over the metropolitan area of Milan. Our results indicated that an increase in the oxidation capacity of the atmosphere, i.e. in the cOH and cNO3 radicals, was mainly responsible for the mild increase in SOA concentrations.Peer reviewe

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

Structures and reactivity of peroxy radicals and dimeric products revealed by online tandem mass spectrometry

Organic peroxy radicals (RO2) play a pivotal role in the degradation of hydrocarbons. The autoxidation of atmospheric RO2 radicals produces highly oxygenated organic molecules (HOMs), including low-volatility ROOR dimers formed by bimolecular RO2 + RO2 reactions. HOMs can initiate and greatly contribute to the formation and growth of atmospheric particles. As a result, HOMs have far-reaching health and climate implications. Nevertheless, the structures and formation mechanism of RO2 radicals and HOMs remain elusive. Here, we present the in-situ characterization of RO2 and dimer structure in the gas-phase, using online tandem mass spectrometry analyses. In this study, we constrain the structures and formation pathway of several HOM-RO2 radicals and dimers produced from monoterpene ozonolysis, a prominent atmospheric oxidation process. In addition to providing insights into atmospheric HOM chemistry, this study debuts online tandem MS analyses as a unique approach for the chemical characterization of reactive compounds, e.g., organic radicals.Peer reviewe