Urban aerosol size distributions over the Mediterranean city of Barcelona, NE Spain

Differential mobility particle sizer (DMPS) aerosol concentrations (N<sub>13-800</sub>) were collected over a one-year-period (2004) at an urban background site in Barcelona, North-Eastern Spain. Quantitative contributions to particle number concentrations of the nucleation (33–39%), Aitken (39–49%) and accumulation mode (18–22%) were estimated. We examined the source and time variability of atmospheric aerosol particles by using both K-means clustering and Positive Matrix Factorization (PMF) analysis. Performing clustering analysis on hourly size distributions, nine K-means DMPS clusters were identified and, by directional association, diurnal variation and relationship to meteorological and pollution variables, four typical aerosol size distribution scenarios were identified: traffic (69% of the time), dilution (15% of the time), summer background conditions (4% of the time) and regional pollution (12% of the time). According to the results of PMF, vehicle exhausts are estimated to contribute at least to 62–66% of the total particle number concentration, with a slightly higher proportion distributed towards the nucleation mode (34%) relative to the Aitken mode (28–32%). Photochemically induced nucleation particles make only a small contribution to the total particle number concentration (2–3% of the total), although only particles larger than 13 nm were considered in this study. Overall the combination of the two statistical methods is successful at separating components and quantifying relative contributions to the particle number population

Characterization of distinct Arctic Aerosol Accumulation Modes and their Sources

10 pages, 4 figures, 1 table, supplementary data https://doi.org/10.1016/j.atmosenv.2018.03.060In this work we use cluster analysis of long term particle size distribution data to expand an array of different shorter term atmospheric measurements, thereby gaining insights into longer term patterns and properties of Arctic aerosol. Measurements of aerosol number size distributions (9–915 nm) were conducted at Villum Research Station (VRS), Station Nord in North Greenland during a 5 year record (2012–2016). Alongside this, measurements of aerosol composition, meteorological parameters, gaseous compounds and cloud condensation nuclei (CCN) activity were performed during different shorter occasions. K-means clustering analysis of particle number size distributions on daily basis identified several clusters. Clusters of accumulation mode aerosols (main size modes > 100 nm) accounted for 56% of the total aerosol during the sampling period (89–91% during February–April, 1–3% during June–August). By association to chemical composition, cloud condensation nuclei properties, and meteorological variables, three typical accumulation mode aerosol clusters were identified: Haze (32% of the time), Bimodal (14%) and Aged (6%). In brief: (1) Haze accumulation mode aerosol shows a single mode at 150 nm, peaking in February–April, with highest loadings of sulfate and black carbon concentrations. (2) Accumulation mode Bimodal aerosol shows two modes, at 38 nm and 150 nm, peaking in June–August, with the highest ratio of organics to sulfate concentrations. (3) Aged accumulation mode aerosol shows a single mode at 213 nm, peaking in September–October and is associated with cloudy and humid weather conditions during autumn. The three aerosol clusters were considered alongside CCN concentrations. We suggest that organic compounds, that are likely marine biogenic in nature, greatly influence the Bimodal cluster and contribute significantly to its CCN activity. This stresses the importance of better characterizing the marine ecosystem and the aerosol-mediated climate effects in the ArcticThe study was supported by the Spanish Ministry of Economy through project BIO-NUC (CGL2013-49020-R) and the Ramon y Cajal fellowship (RYC-2012-11922), and by the EU though the FP7-PEOPLE-2013-IOF programme (Project number 624680, MANU – Marine Aerosol NUcleations). The National Centre for Atmospheric Science NCAS Birmingham group is funded by the UK Natural Environment Research Council. [...] This work was financially supported by the Danish Environmental Protection Agency with means from the MIKA/DANCEA funds for Environmental Support to the Arctic Region, which is part of the Danish contribution to “Arctic Monitoring and Assessment Program” (AMAP) and the Danish research project “Short lived Climate Forcers” (SLCF), and the Danish Council for Independent Research (project NUMEN, DFF-FTP-4005-00485B). The findings and conclusions presented here do not necessarily reflect the views of the Agency. This work was also supported by the Nordic Centre of Excellence (NCoE) Cryosphere-Atmosphere Interactions in a Changing Arctic Climate (CRAICC). The Villum Foundation is acknowledged for funding the construction of Villum Research Station, Station NordPeer Reviewe

Sources and contributions of wood smoke during winter in London: Assessing local and regional influences

Determining the contribution of wood smoke to air pollution in large cities such as London is becoming increasingly important due to the changing nature of domestic heating in urban areas. During winter, biomass burning emissions have been identified as a major cause of exceedances of European air quality limits. The aim of this work was to quantify the contribution of biomass burning in London to concentrations of PM2:5 and determine whether local emissions or regional contributions were the main source of biomass smoke. To achieve this, a number of biomass burning chemical tracers were analysed at a site within central London and two sites in surrounding rural areas. Concentrations of levoglucosan, elemental carbon (EC), organic carbon (OC) and KC were generally well correlated across the three sites. At all the sites, biomass burning was found to be a source of OC and EC, with the largest contribution of EC from traffic emissions, while for OC the dominant fraction included contributions from secondary organic aerosols, primary biogenic and cooking sources. Source apportionment of the EC and OC was found to give reasonable estimation of the total carbon from non-fossil and fossil fuel sources based upon comparison with estimates derived from 14C analysis. Aethalometer-derived black carbon data were also apportioned into the contributions frombiomass burning and traffic and showed trends similar to those observed for EC. Mean wood smoke mass at the sites was estimated to range from 0.78 to 1.0 μgm-3 during the campaign in January–February 2012. Measurements on a 160m tower in London suggested a similar ratio of brown to black carbon (reflecting wood burning and traffic respectively) in regional and London air. Peaks in the levoglucosan and KC concentrations were observed to coincide with low ambient temperature, consistent with domestic heating as a major contributing local source in London. Overall, the source of biomass smoke in London was concluded to be a background regional source overlaid by contributions from local domestic burning emissions. This could have implications when considering future emission control strategies during winter and may be the focus of future work in order to better determine the contributing local sources

Sea Ice Microbiota in the Antarctic Peninsula Modulates Cloud-Relevant Sea Spray Aerosol Production

Este artículo contiene 21 páginas, 8 figuras.Sea spray aerosol (SSA) formation plays a major role in the climate system. The Antarctic Peninsula (AP) is affected by the greatest warming occurring in the Southern Ocean; changes in cryospheric and biological processes are being observed. Whilst there is some evidence that organic material produced by ice algae and/or phytoplankton in the high Arctic contributes to SSA, less is known about Antarctic Sea ice (sympagic) regions. To gain insight into the influence of Antarctic Sea ice biology and biogeochemistry on atmospheric aerosol, we report simultaneous water-air measurements made by means of in situ aerosol chamber experiments. For the first time, we present a methodology showing that the controlled plunging jet aerosol chamber settings do not cause major cell disruption on the studied sea ice ecosystems. Larger sea ice phytoplankton cells (>20 μm; mainly diatoms) tend to sediment at the bottomof the chamber (during the 24h experiment) and likely have a minor role on SSA production. When comparing four chamber experiments - we find that the two producing more SSA are the ones with highest abundance of nanophytoplankton cells (<20 μm; mainly nanoflagellates) as well as viruses. Our marine biogeochemical data show two broad groups of dissolved organic carbon: one rich in carbohydrates and proteic material and one rich in humic-like substances; the latter enhancing SSA production. This work provides unique insights into sea ice productivity that modulates SSA production, with potentially significant climate impacts. Further studies of these types are advised in order to see how microbiology impacts the biogeochemical cycling of elements and how aerosols are formed and processed in cold regions.The study was further supported by the Spanish Ministry of Economy through project PI-ICE (no. CTM 2017–89117-R) and the Ramon y Cajal fellowship (no. RYC-2012-11922). This work acknowledges the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S). The National Centre for Atmospheric Science (NCAS) Birmingham group is funded by the UK Natural Environment Research Council. DOC was analyzed by Mara Abad (ICM-CSIC) and the POC was analyzed at the IIM-CSIC (Vigo).Peer reviewe

A new methodology to assess the performance and uncertainty of source apportionment models II: The results of two European intercomparison exercises

The performance and the uncertainty of receptor models (RMs) were assessed in intercomparison exercises employing real-world and synthetic input datasets. To that end, the results obtained by different practitioners using ten different RMs were compared with a reference. In order to explain the differences in the performances and uncertainties of the different approaches, the apportioned mass, the number of sources, the chemical profiles, the contribution-to-species and the time trends of the sources were all evaluated using the methodology described in Belis et al. (2015). In this study, 87% of the 344 source contribution estimates (SCEs) reported by participants in 47 different source apportionment model results met the 50% standard uncertainty quality objective established for the performance test. In addition, 68% of the SCE uncertainties reported in the results were coherent with the analytical uncertainties in the input data. The most used models, EPA-PMF v.3, PMF2 and EPA-CMB 8.2, presented quite satisfactory performances in the estimation of SCEs while unconstrained models, that do not account for the uncertainty in the input data (e.g. APCS and FA-MLRA), showed below average performance. Sources with well-defined chemical profiles and seasonal time trends, that make appreciable contributions (>10%), were those better quantified by the models while those with contributions to the PM mass close to 1% represented a challenge. The results of the assessment indicate that RMs are capable of estimating the contribution of the major pollution source categories over a given time window with a level of accuracy that is in line with the needs of air quality management

Intercomparison and evaluation of global aerosol microphysical properties among AeroCom models of a range of complexity

Many of the next generation of global climate models will include aerosol schemes which explicitly simulate the microphysical processes that determine the particle size distribution. These models enable aerosol optical properties and cloud condensation nuclei (CCN) concentrations to be determined by fundamental aerosol processes, which should lead to a more physically based simulation of aerosol direct and indirect radiative forcings. This study examines the global variation in particle size distribution simulated by 12 global aerosol microphysics models to quantify model diversity and to identify any common biases against observations. Evaluation against size distribution measurements from a new European network of aerosol supersites shows that the mean model agrees quite well with the observations at many sites on the annual mean, but there are some seasonal biases common to many sites. In particular, at many of these European sites, the accumulation mode number concentration is biased low during winter and Aitken mode concentrations tend to be overestimated in winter and underestimated in summer. At high northern latitudes, the models strongly underpredict Aitken and accumulation particle concentrations compared to the measurements, consistent with previous studies that have highlighted the poor performance of global aerosol models in the Arctic. In the marine boundary layer, the models capture the observed meridional variation in the size distribution, which is dominated by the Aitken mode at high latitudes, with an increasing concentration of accumulation particles with decreasing latitude. Considering vertical profiles, the models reproduce the observed peak in total particle concentrations in the upper troposphere due to new particle formation, although modelled peak concentrations tend to be biased high over Europe. Overall, the multi-model-mean data set simulates the global variation of the particle size distribution with a good degree of skill, suggesting that most of the individual global aerosol microphysics models are performing well, although the large model diversity indicates that some models are in poor agreement with the observations. Further work is required to better constrain size-resolved primary and secondary particle number sources, and an improved understanding of nucleation and growth (e.g. the role of nitrate and secondary organics) will improve the fidelity of simulated particle size distributions

Variations in tropospheric submicron particle size distributions across the European continent 2008-2009

Beddows, D. C. S. ... et. al.-- 22 pages, 11 figures, 1 table, supplementary material related to this article is available online at http://www.atmos-chem-phys.net/14/4327/2014/acp-14-4327-2014-supplement.pdfClusteranalysis of particle number size distributions frombackground sites across Europeis presented. This generated a total of nine clusters of particle size distributions which could be further combined into two main groups, namely: a south-to-north category (four clusters) and a west-to-east category (five clusters). The first group was identified as most frequently being detected inside and around northern Germany and neighbouring countries, showing clear evidence of local afternoon nucleation and growth events that could be linked to movement of air masses from south to north arriving ultimately at the Arctic contributing to Arctic haze.The second group of particle size spectra proved to have narrower size distributions and collectively showed a dependence of modal diameter upon the longitude of the site (west to east) at which they were most frequently detected.These clusters indicated regional nucleation (at the coastal sites) growing to larger modes further inland. The apparent growth rate of the modal diameter was around 0.6-0.9 nm h-1. Four specific air mass back-trajectories were successively taken as case studies to examine in real time the evolution of aerosol size distributions across Europe. While aerosol growth processes can be observed as aerosol traverses Europe, the processes are often obscured by the addition of aerosol by emissions en route. This study revealed that some of the 24 stations exhibit more complex behaviour than others, especially when impacted by local sources or a variety of different air masses. Overall, the aerosol size distribution clustering analysis greatly simplifies the complex data set and allows a description of aerosol aging processes, which reflects the longer-term average development of particle number size distributions as air masses advect across Europe. © 2014 Author(s)The National Centre for Atmospheric Science is funded by the UK Natural Environment Research Council. This work was also supported by the European Union EUCAARI (Contract Ref. 036833) and EUSAAR (Contract Ref. 026140) research projectsPeer Reviewe

On the contribution of organics to the North East Atlantic aerosol number concentration

k-means statistical-cluster analysis of submicron aerosol size distributions is combined with coincident humidity tandem differential mobility analyser data, leading to five unique aerosol categories for hygroscopic growth factors (HGFs): low sea-salt background marine, high sea-salt background marine, coastal nucleation, open ocean nucleation and anthropogenically influenced scenarios. When considering only marine conditions, and generic aerosol species associated with this environment (e.g. non-sea-salt sulfate, sea-salt, partly soluble organic matter and water insoluble organic matter), the two-year annual average contribution to aerosol number concentration from the different generic species was made up as follows: 46% (30-54%) of partially modified ammonium sulfate particles; 23% (11-40%) of partially modified sea-salt; and the remaining 31% (25-35%) contribution attributed to two distinct organic species as evidenced by different, but low, HGFs. The analysis reveals that on annual timescales, ∿30% of the submicron marine aerosol number concentration is sourced from predominantly organic aerosol while 60% of the anthropogenic aerosol number is predominantly organic. Coastal nucleation events show the highest contribution of the lowest HGF mode (1.19), although this contribution is more likely to be influenced by inorganic iodine oxides. While organic mass internally mixed with inorganic salts will lower the activation potential of these mixed aerosol types, thereby potentially reducing the concentration of cloud condensation nuclei (CCN), pure organic water soluble particles are still likely to be activated into cloud droplets, thereby increasing the concentration of CCN. A combination of dynamics and aerosol concentrations will determine which effect will prevail under given conditions. © 2012 IOP Publishing Ltd

Urban aerosol size distributions over the Mediterranean city of Barcelona, NE Spain

Differential mobility particle sizer (DMPS) aerosol concentrations (N13-800) were collected over a one-year-period (2004) at an urban background site in Barcelona, North-Eastern Spain. Quantitative contributions to particle number concentrations of the nucleation (33-39%), Aitken (39-49%) and accumulation mode (18-22%) were estimated. We examined the source and time variability of atmospheric aerosol particles by using both K-means clustering and Positive Matrix Factorization (PMF) analysis. Performing clustering analysis on hourly size distributions, nine K-means DMPS clusters were identified and, by directional association, diurnal variation and relationship to meteorological and pollution variables, four typical aerosol size distribution scenarios were identified: traffic (69% of the time), dilution (15% of the time), summer background conditions (4% of the time) and regional pollution (12% of the time). According to the results of PMF, vehicle exhausts are estimated to contribute at least to 62-66% of the total particle number concentration, with a slightly higher proportion distributed towards the nucleation mode (34%) relative to the Aitken mode (28-32%). Photochemically induced nucleation particles make only a small contribution to the total particle number concentration (2-3% of the total), although only particles larger than 13 nm were considered in this study. Overall the combination of the two statistical methods is successful at separating components and quantifying relative contributions to the particle number population. © 2012 Author(s)