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Ambient ammonia (NH3) measurements were performed with a mobile platform in three European cities: Zurich (Switzerland), Tartu (Estonia) and Tallinn (Estonia) deploying an NH3 analyzer based on cavity ring-down spectroscopy. A heated inlet line along with an auxiliary flow was used to minimize NH3 adsorption onto the inlet walls. In addition, a detailed characterization of the response and recovery times of the measurement system was used to deconvolve the true NH3 signal from the remaining adsorption-induced hysteresis. Parallel measurements with an aerosol mass spectrometer were used to correct the observed NH3 for the contribution of ammonium nitrate, which completely evaporated in the heated line at the chosen temperature, in contrast to ammonium sulfate. In this way a quantitative measurement of ambient gaseous NH3 was achieved with sufficient time resolution to enable measurement of NH3 point sources with a mobile sampling platform. The NH3 analyzer and the aerosol mass spectrometer were complemented by an aethalometer and various gas-phase analyzers to enable a complete characterization of the sources of air pollution, including the spatial distributions and the regional background concentrations and urban increments of all measured components. Although at all three locations similar increment levels of organic aerosols were attributed to biomass burning and traffic, traffic emissions clearly dominated the city enhancements of NH3, equivalent black carbon (eBC) and carbon dioxide (CO2). Urban increments of 3.4, 1.8 and 3.0 ppb of NH3 were measured in the traffic areas in Zurich, Tartu and Tallinn, respectively, representing an enhancement of 36.6, 38.3 and 93.8% over the average background concentrations. Measurements in areas strongly influenced by traffic emissions (including tunnel drives) were used to estimate emission factors (EF) for the traffic-related pollutants. The obtained median EFs range between 136.8-415.1 mg kg−1 fuel for NH3, 157.1–734.8 mg kg−1 fuel for eBC and 39.9–324.3 mg kg−1 fuel for HOA. Significant differences were found between the EFs of certain components in the three cities, which were partially linked to an older vehicle fleet in Estonia compared to Switzerland. Using the determined EFs we show that traffic can fully explain the NH3 enhancements in the three cities and also presents a non-negligible fraction of the background concentrations, which are mostly related to agricultural activities. Moreover, the estimated total contribution of traffic to NH3 at all three locations is in good agreement with the available emission inventories.

This study presents the first multi-site evolution analysis of fine Organic Aerosols (OA) and inorganics in the Delhi megacity (National Capital Region (NCR)) using high-resolution-particle time of flight (HR-PToF) size distribution obtained from Aerodyne HR-ToF-AMS. It provides a comprehensive view of the atmospheric dynamic processes responsible for the aerosol size and composition transformation. The measurements were performed at two different sampling sites (1) Indian Institute of Technology, Delhi (IITD), and (2) Manav Rachna International University, Faridabad (MRIU) during a late winter period (February to March 2018). Among organics, primary OA (POA) showed particle growth, whereas it was absent in secondary OA proxies. IITD was observed to have a distinct growth pattern as compared to MRIU because of high vehicular density and heterogeneity, and the presence of growth-promoting factors such as acidity and RH conditions. IITD aerosols were observed to be more acidic (ANR∼ 0.75) compared to MRIU (ANR∼1) and showed a distinct diurnal bin-wise increase during the photochemically active period (PAP). Such high acidic conditions are responsible for promoting acid-catalyzed SOA productions over the broader size bins, especially during the PAPs. Primary OA (POA) such as HOA and BBOA proxies show a diurnal growth from ∼440 to 970 nm and from ∼370 to 550 nm, at IITD and from ∼270 to 400 nm and ∼430–470 nm, at MRIU respectively. Further, OA families (amines and hydrocarbons), and inorganics such as chloride and nitrate also showed distinct concurrent diurnal growth patterns at IITD (from an MMDs of ∼380–520 nm to 650–960 nm). We have also observed a positive correlation between OA and inorganics growth and the mass fraction (MF = SOA/OA) of SOA at both sites of NCR. For 0.1 (MF) increase in SOA, the sizes of HOA, chloride, primary CH family and amines (CHN family), and secondary amines (CHON family) are increased by ∼93, 80, 64, 66, and 47 nm at IITD and ∼14, 35, 8, 11, and 16 nm at MRIU respectively. The concurrent growth of these species with the increase in the SOA concentration indicates the existence of a similar size evolution mechanism at both NCR sites, further promoting the formation of internally mixed aerosols during some phase of their evolution. This suggests that condensation is significantly governing the growth mechanism in NCR. Our study indicates the inclusion of such dynamic growth patterns arising from local prevailing conditions into the models for a better understanding of atmospheric aerosol evolution and estimation of fine particulate matter budget.

To reduce the influence of biomass burning on air quality, consumers are encouraged to replace their old woodstove with new and cleaner appliances. While their primary emissions have been extensively investigated, the impact of atmospheric aging on these emissions, including secondary organic aerosol (SOA) formation, remains unknown. Here, using an atmospheric smog chamber, we aim at understanding the chemical nature and quantify the emission factors of the primary organic aerosols (POA) from three types of appliances for residential heating, and to assess the influence of aging thereon. Two, old and modern, logwood stoves and one pellet burner were operated under typical conditions. Emissions from an entire burning cycle (past the start-up operation) were injected, including the smoldering and flaming phases, resulting in highly variable emission factors. The stoves emitted a significant fraction of POA (up to 80%) and black carbon. After ageing, the total mass concentration of organic aerosol (OA) increased on average by a factor of 5. For the pellet stove, flaming conditions were maintained throughout the combustion. The aerosol was dominated by black carbon (over 90% of the primary emission) and amounted to the same quantity of primary aerosol emitted by the old logwood stove. However, after ageing, the OA mass was increased by a factor of 1.7 only, thus rendering OA emissions by the pellet stove almost negligible compared to the other two stoves tested. Therefore, the pellet stove was the most reliable and least polluting appliance out of the three stoves tested. The spectral signatures of the POA and aged emissions by a High Resolution – Time of Flight – Aerosol Mass Spectrometer (Electron Ionization (EI) at 70 eV) were also investigated. The m/z 44 (CO2+) and high molecular weight fragments (m/z 115 (C9H7+), 137 (C8H9O2+), 167 (C9H11O3+) and 181 (C9H9O4+, C14H13+)) correlate with the modified combustion efficiency (MCE) allowing us to discriminate further between emissions generated from smoldering vs flaming conditions.

We report highly time-resolved estimates of airborne bacteria-like particle concentrations in ambient aerosol using an Aerodyne aerosol mass spectrometer (AMS). AMS measurements with a newly developed PM 2.5 and the standard (PM 1 ) aerodynamic lens were performed at an urban background site (Zurich) and at a rural site (Payerne) in Switzerland. Positive matrix factorization using the multilinear engine (ME-2) implementation was used to estimate the contribution of bacteria-like particles to non-refractory organic aerosol. The success of the method was evaluated by a size-resolved analysis of the organic mass and the analysis of single particle mass spectra, which were detected with a light scattering system integrated into the AMS. Use of the PM 2.5 aerodynamic lens increased measured bacteria-like concentrations, supporting the analysis method. However, at all sites, the low concentrations of this component suggest that airborne bacteria constitute a minor fraction of non-refractory PM 2.5 organic aerosol mass. Estimated average mass concentrations were below 0.1 μg/m 3 and relative contributions were lower than 2% at both sites. During rainfall periods, concentrations of the bacteria-like component increased considerably reaching a short-time maximum of approximately 2 μg/m 3 at the Payerne site in summer.

This study examines the light absorption characteristics of fine atmospheric particulates using the co-located real-time measurements of chemical and optical aerosol characteristics at a site located in Delhi during winter. The contribution of absorption by black carbon and brown carbon (BC and BrC) to the total absorption (babs) is computed using the absorption Angstrom exponent (AAE) method. The period average contribution of BrC absorption (babs_BrC) to babs is found to be highest at 370 nm (23%) that decreased exponentially with increasing wavelengths, i.e.,18, 12, 10, and 4% at 470, 520, 590, and 660 nm, respectively. The absorption spectrum of BrC is used to study the bulk composition of BrC, which indicates that primary BrC was dominant during morning and night time, whereas secondary BrC was significant during the rest of the time. Further, organic aerosols (OA) were divided into different factors using positive-matrix factorization (PMF) analysis, and the mass absorption efficiency (Eabs) of each factor was assessed through multivariate linear regression of babs_BrC with OA factors. The biomass burning OA (BBOA) exhibited the highest Eabs at 370 nm (0.86 m2 g−1), followed by semi-volatile oxygenated OA (SVOOA; 0.67 m2 g−1) and hydrocarbon-like OA (HOA; 0.42 m2 g−1). Further, although the composition of OA was dominated by LVOOA (32%) and BBOA (32%), followed by SVOOA (22%), and HOA (14%), their contribution to bBrC followed different order due to differences in their mass absorption efficiencies. The BBOA contributed almost half (48%) of babs_BrC followed by SVOOA (26%), and HOA (10%). This study provides quantitative information on the sources of BrC and their relative contribution to BrC absorption over a heavily polluted region, which is still lacking in the literature. These results have implications in understanding the source-specific BrC absorption.

We report ambient measurements using a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) on a mobile platform in the southeast Po Valley (Italy) in summer 2012. During the PEGASOS southbound campaign measurements of non-refractory aerosol were performed in urban and rural environments as well as near the coast of the Adriatic Sea. Organic source apportionment analysis of the aerosol mass spectrometer data was carried out using positive matrix factorization and multilinear engine (ME-2) receptor modelling. Five major organic aerosol components were identified: hydrocarbon-like organic aerosol (HOA), semi-volatile oxygenated organic aerosol (SVOOA), low volatility oxygenated organic aerosol (LVOOA), cooking organic aerosol (COA) and a regionally influenced highly oxygenated organic aerosol (HOOA). Essential changes in both aerosol composition and concentration were induced by the ventilation and recirculation of air masses in the East-West direction of the valley (land/sea breeze system) and via the Apennine mountain range (mountain/valley wind system). An urban increment of the non-refractory aerosol mass concentration in Bologna of about 1.6-2.3 ?g/m3 compared to the surrounding regions was quantified which can be explained by the sum of local contributions from cooking activities and from hydrocarbon-like aerosol related to traffic emissions. © 2015 Elsevier Ltd.

Observations from four periods (three late springs and one early summer) at temperate forest sites in western and eastern Canada offer the first estimation of how the concentrations of submicron forest organic aerosol mass (SFOM) from the oxidation of biogenic volatile organic compounds (BVOC) vary over the ambient temperature range of 7 °C to 34 °C. For the measurement conditions of clear skies, low oxides of nitrogen and within approximately one day of emissions, 50 estimates of SFOM concentrations show the concentrations increase exponentially with temperature. The model that is commonly used to define terpene emissions as a function of temperature is able to constrain the range of the SFOM values across the temperature range. The agreement of the observations and model is improved through the application of an increased yield of SFOM as the organic mass concentration increases with temperature that is based on results from chamber studies. The large range of SFOM concentrations at higher temperatures leaves open a number of questions, including the relative contributions of changing yield and of isoprene, that may be addressed by more ambient observations at higher temperatures.

Evolution of the cloud condensation nucleus (CCN) activity of 36 ± 4 nm diameter anthropogenic aerosol particles at a water supersaturation of 1.0 ± 0.1% is examined for particle nucleation and growth. During the early stages of one event, relatively few of the anthropogenic particles at 36 nm were CCN active and their growth rates by water condensation were delayed relative to ammonium sulphate particles. As the event progressed, the particle size distribution evolved to larger sizes and the relative numbers of particles at 36 nm that were CCN active increased until all the 36 nm particles were activating at the end of the event. Based on the chemistry of larger particles and the results from an aerosol chemical microphysics box model, the increase in CCN activity of the particles was most likely the result of the condensation of sulphate in this case. Despite the increased CCN activity, a delay was observed in the initial growth of these particles into cloud droplets, which persisted even when the aerosol was most CCN active later in the afternoon. Simulations show that the delay in water uptake is explained by a reduction of the mass accommodation coefficient assuming that the composition of the 36 nm particles is the same as the measured composition of the 60–100 nm particles.