Chemical characterization and source apportionment of submicron aerosol particles with aerosol mass spectrometers

Fine particles affect climate change in complex ways that are not fully understood and were verified to be harmful to animal and human health. For these reasons information concerning their composition is important to understand their behaviour and to elaborate strategies to mitigate air pollution in urban environments. The overall objective of this study was to investigate in more detail chemical characteristics of ambient particulate matter (PM) and its sources. Studies made in laboratory and during field were used to study composition of fresh emissions, changes during aging, and finally composition of submicron PM (PM1) observed in ambient air. For that the field studies were performed at three different sites: rural, urban, and background urban with the HR-ToF-AMS and ACSM, instruments that measured only the non-refractory PM1 (NR-PM1). For this reason the new SP-AMS was further characterized in order to evaluate its feasi-bility to detect trace metals. The use of the positive matrix factorization (PMF) has shown useful in the identification of PM sources. Thus, the PMF was applied to the mass spectrometers datasets and 11 different components of the organic aerosol (OA) were identified, 6 types of oxygenated OAs (OOAs), one containing substantial organosulfate fragments from methanesulfonic acid (MSA), long-range transported biomass burning OA (LRT-BBOA), nitrogen-containing OA (NOA), local BBOA, coffee roastery OA (CROA), and hydrocarbon-like OA (HOA). The last three most likely represented the primary organic aerosol (POA), while the others represented the secondary OA (SOA). The OM was dominated by aerosol particles of secondary origin (65%). The investigation of different properties of the PM1 revealed more information about its composition and sources. A comparison of the AMS data with those from additional instrumentation indicated that most of the PM1 was non-refractory. The water-solubility of the OM indicated that the low-volatility OOA (LV-OOA) and the LRT-BBOA were the most water-soluble components. The SV-OOA presented clear semi-volatile character when investigated as a function of the local air temperature, decreasing in concentration with the air temperature increase. Concerning the aerosol neutralization, in most sites the results indicated enough ammonium to neutralize the major inorganic anions, except for Helsinki during wintertime when the aerosol particles were acidic most of the time. The size-resolved chemical composition was investigated in detail to different episodes and revealed internally and externally mixed aerosol particles in two different modes, an accumulation (~470 nm) and a lower mode (~130nm). The different modes were composed of different compounds and suggested a rather acidic lower mode mainly dominated by nitrate most likely from local traffic emissions. The laboratory experiments accomplished with the SP-AMS successfully confirmed the feasibility of detection of trace metals. 13 different metals were identified through the determination of isotopic patterns. Furthermore, the negative mass defect, typical from metals, was observed useful in their identification in the mass spectrum. The measurement of trace metals by the SP-AMS represents a step forward in the study of sources and might be extremely useful in the next source apportionment studies

Seasonal and diurnal changes in inorganic ions, carbonaceous matter and mass in ambient aerosol particles in an urban, background area

Concentration and composition of the fine particulate matter (PM) was measured using various online methods for 13 months in an urban, background area in Helsinki, Finland. Seasonal differences were found for ions and carbonaceous compounds. Biomass burning was found to increase inorganic ion and elemental carbon (EC) concentrations in winter, whereas organic carbon (OC) contribution was highest during summer due to secondary aerosol formation. Diurnal cycles, with maxima between 06:00 and 09:00, were recorded for EC and nitrate due to traffic emissions. In addition, the concentrations measured with the online and offline PM sampling devices were compared using regression analysis. In general, a good agreement (r(2) = 0.60-0.95) was found. During the year-long measurements, on average 65% of PM2.5 was identified by submicron chemical analyses (ions, OC, EC). As compared with filter measurements, the high resolution measurements provided important data on short pollution plumes and diurnal changes.Peer reviewe

Avaliação do comportamento das partículas inaláveis em área ocupada por atividade de mineração a céu aberto: um estudo de caso em Paracatu – MG / Assessment of the behavior of inhalable particles in area occupied by open pit mining activity: a case study in Paracatu – MG

O objetivo deste trabalho é verificar, por meio das partículas inaláveis com diâmetro menor que <10µm (MP10) medidas pelas estações de monitoramento da qualidade do ar localizadas no município de Paracatu – MG, o cumprimento dos padrões anuais e diários de qualidade previstos na legislação vigente no Brasil. Para tanto, foram analisadas as concentrações médias de MP10 obtidas no sítio da Fundação Estadual do Meio Ambiente (FEAM) para os anos de 2015, 2016 e 2017 nas 5 diferentes estações situadas entre o perímetro urbano e a área de mineração a céu aberto e comparadas com os padrões permitidos e previstos na legislação. Analisou-se também o comportamento sazonal desse parâmetro nesses locais e um estudo de caso nos dias que ultrapassaram os padrões diários de qualidade. Os resultados mostram que os valores médios, anuais e diários, de MP10, no período analisado, apresentaram poucas ultrapassagens do padrão primário de qualidade do ar nacional, entretanto, os valores apresentados demonstraram que a área se encontra em uma realidade totalmente distante das concentrações recomendadas pela Organização Mundial da Saúde (OMS). Em relação ao comportamento sazonal do MP10, esse mostrou estar relacionado com a concentração pluviométrica do município. Além disso, a maioria das estações apresentaram diferença a um nível de significância de 5%, fato que pode estar relacionado com a dispersão dos poluentes e as condições meteorológicas provenientes em cada ponto de monitoramento. Foi concluído que existe na área de estudo uma relação sazonal entre a pluviosidade e as concentrações de MP10. Além disso, a presença das atividades antrópicas provenientes no local pode estar influenciando pouco no parâmetro analisado, porém, diante dos valores recomendados pela OMS, o impacto da poluição atmosférica existe e deve ser monitorado pelos órgãos fiscalizadores ambientais. Por fim, vale frisar que este estudo é justificado devido à necessidade de se oferecer subsídios ao planejamento territorial do município de Paracatu – MG, porque nada se conhece, até o momento, sobre os resultados dos relatórios de monitoramento da poluição atmosférica ocasionada pela atividade de mineração a céu aberto localizada no limite do perímetro urbano desse. 

Avaliação da Dispersão de o3 Troposférico na RMSP Utilizando CIT e mm5

Avaliação da dispersão de O3 troposférico na RMSPutilizando CIT e MM

The variability of urban aerosol size distributions and optical properties in São Paulo – Brazil: new particle formation events occur at the site

Non peer reviewe

The Latin America Early Career Earth System Scientist Network (LAECESS): addressing present and future challenges of the upcoming generations of scientists in the region

Early career (EC) Earth system scientists in the Latin America and the Caribbean region (LAC) have been facing several issues, such as limited funding opportunities, substandard scientific facilities, lack of security of tenure, and unrepresented groups equality issues. On top of this, the worsening regional environmental and climatic crises call for the need for this new generation of scientists to help to tackle these crises by increasing public awareness and research. Realizing the need to converge and step up in making a collective action to be a part of the solution, the Latin America Early Career Earth System Scientist Network (LAECESS) was created in 2016. LAECESS’s primary goals are to promote regional networking, foster integrated and interdisciplinary science, organize soft skills courses and workshops, and empower Latin American EC researchers. This article is an initial step towards letting the global science community grasp the current situation and hear the early career LAC science community’s perspectives. The paper also presents a series of future steps needed for better scientific and social development in the LAC region

Disentangling vehicular emission impact on urban air pollution using ethanol as a tracer

The Sao Paulo Metropolitan Area is a unique case worldwide due to the extensive use of biofuel, particularly ethanol, by its large fleet of nearly 8 million cars. Based on source apportionment analysis of Organic Aerosols in downtown Sao Paulo, and using ethanol as tracer of passenger vehicles, we have identified primary emissions from light-duty-vehicles (LDV) and heavy-duty-vehicles (HDV), as well as secondary process component. Each of those factors mirror a relevant primary source or secondary process in this densely occupied area. Using those factors as predictors in a multiple linear regression analysis of a wide range of pollutants, we have quantified the role of primary LDV or HDV emissions, as well as atmospheric secondary processes, on air quality degradation. Results show a significant contribution of HDV emissions, despite contributing only about 5% of vehicles number in the region. The latter is responsible, for example, of 40% and 47% of benzene and black carbon atmospheric concentration, respectively. This work describes an innovative use of biofuel as a tracer of passenger vehicle emissions, allowing to better understand the role of vehicular sources on air quality degradation in one of most populated megacities worldwide

Chemical and physical characterization of traffic particles in four different highway environments in the Helsinki metropolitan area

Traffic-related pollution is a major concern in urban areas due to its deleterious effects on human health. The characteristics of the traffic emissions on four highway environments in the Helsinki metropolitan area were measured with a mobile laboratory, equipped with state-of-the-art instrumentation. Concentration gradients were observed for all traffic-related pollutants, particle number (CN), particulate mass (PM1), black carbon (BC), organics, and nitrogen oxides (NO and NO2). Flow dynamics in different environments appeared to be an important factor for the dilution of the pollutants. For example, the half-decay distances for the traffic-related CN concentrations varied from 8 to 83aEuro-m at different sites. The PM1 emissions from traffic mostly consisted of organics and BC. At the most open site, the ratio of organics to BC increased with distance to the highway, indicating condensation of volatile and semi-volatile organics on BC particles. These condensed organics were shown to be hydrocarbons as the fraction of hydrocarbon fragments in organics increased. Regarding the CN size distributions, particle growth during the dilution was not observed; however the mass size distributions measured with a soot particle aerosol mass spectrometer (SP-AMS), showed a visible shift of the mode, detected at aEuro-100aEuro-nm at the roadside, to a larger size when the distance to the roadside increased. The fleet average emission factors appeared to be lower for the CN and higher for the NO2 than ten years ago. The reason is likely to be the increased fraction of light-duty (LD) diesel vehicles in the past ten years. The fraction of heavy-duty (HD) traffic, although constituting less than 10aEuro-% of the total traffic flow, was found to have a large impact on the emissions.Peer reviewe

Elemental Mixing State of Aerosol Particles Collected in Central Amazonia during GoAmazon2014/15

Two complementary techniques, Scanning Transmission X-ray Microscopy/Near Edge Fine Structure spectroscopy (STXM/NEXAFS) and Scanning Electron Microscopy/Energy Dispersive X-ray spectroscopy (SEM/EDX), have been quantitatively combined to characterize individual atmospheric particles. This pair of techniques was applied to particle samples at three sampling sites (ATTO, ZF2, and T3) in the Amazon basin as part of the Observations and Modeling of the Green Ocean Amazon (GoAmazon2014/5) field campaign during the dry season of 2014. The combined data was subjected to k-means clustering using mass fractions of the following elements: C, N, O, Na, Mg, P, S, Cl, K, Ca, Mn, Fe, Ni, and Zn. Cluster analysis identified 12 particle types across different sampling sites and particle sizes. Samples from the remote Amazon Tall Tower Observatory (ATTO, also T0a) exhibited less cluster variety and fewer anthropogenic clusters than samples collected at the sites nearer to the Manaus metropolitan region, ZF2 (also T0t) or T3. Samples from the ZF2 site contained aged/anthropogenic clusters not readily explained by transport from ATTO or Manaus, possibly suggesting the effects of long range atmospheric transport or other local aerosol sources present during sampling. In addition, this data set allowed for recently established diversity parameters to be calculated. All sample periods had high mixing state indices (χ) that were \u3e0.8. Two individual particle diversity (Di) populations were observed, with particles \u3c0.5 µm having a Di of ~2.4 and \u3e0.5 µm particles having a Di of ~3.6, which likely correspond to fresh and aged aerosols, respectively. The diversity parameters determined by the quantitative method presented here will serve to aid in the accurate representation of aerosol mixing state, source apportionment, and aging in both less polluted and more developed environments in the Amazon Basin