Physicochemical properties of aerosol were investigated by analyzing the inorganic water soluble content in PM2.5 samples collected in the eastern part of the Po Valley (Italy). In this area the EU ...limits for many air pollutants are frequently exceeded as a consequence of local sources and regional-scale transport of secondary inorganic aerosol precursors. Nine PM2.5-bound major inorganic ions (F−, Cl−, NO3−, SO42−, Na+, NH4+, K+, Mg2+, Ca2+) were monitored over one year in three sites categorized as semi-rural background, urban background and industrial. The acidic properties of the PM2.5 were studied by applying the recently developed E-AIM thermodynamic model 4 (Extended Aerosol Thermodynamics Model). The experimental data were also examined in relation to the levels of gaseous precursors of secondary inorganic aerosol (SO2, NOx, NO, NO2) and on the basis of some environmental conditions having an effect on the secondary aerosols generation processes. A chemometric procedure using cluster analysis on experimental NH4+/SO42− molar ratio and NO3− concentration has been applied to determine the conditions needed for ammonium nitrate formation in different chemical environments. Finally, some considerations on the secondary inorganic aerosol formation and the most relevant weather conditions concerning the sulfate-nitrate-ammonium system were also discussed. The obtained results and discussion can help in understanding the secondary aerosol formation dynamics in the Po Valley, which is one of the most critical regions for air pollution in southern Europe.
The major sources of fine particulate matter (PM2.5) in New York City (NYC) were apportioned by applying positive matrix factorization (PMF) to two different sets of particle characteristics: mass ...concentrations using chemical speciation data and particle number concentrations (PNC) using number size distribution, continuously monitored gases, and PM2.5 data. Post-processing was applied to the PMF results to: (i) match with meteorological data, (ii) use wind data to detect the likely locations of the local sources, and (iii) use concentration weighted trajectory models to assess the strength of potential regional/transboundary sources. Nine sources of PM2.5 mass were apportioned and identified as: secondary ammonium sulfate, secondary ammonium nitrate, road traffic exhaust, crustal dust, fresh sea-salt, aged sea-salt, biomass burning, residual oil/domestic heating and zinc. The sources of PNC were investigated using hourly average number concentrations in six size bins, gaseous air pollutants, mass concentrations of PM2.5, particulate sulfate, OC, and EC. These data were divided into 3 periods indicative of different seasonal conditions. Five sources were resolved for each period: secondary particles, road traffic, NYC background pollution (traffic and oil heating largely in Manhattan), nucleation and O3-rich aerosol. Although traffic does not account for large amounts of PM2.5 mass, it was the main source of particles advected from heavily trafficked zones. The use of residual oil had limited impacts on PM2.5 mass but dominates PNC in cold periods.
•Major sources of PM2.5 mass and particle number concentrations are apportioned in NYC.•Nine sources resolved over PM mass; 5 for particle number concentration.•Temporal patterns, weather, wind data and regional transport used for interpretation.•Relationships between results on PM mass and number concentrations investigated.•Air quality status and atmospheric processes over the NYC area are discussed.
A year-long sampling campaign of major air pollutants and submicron particle number size distributions was conducted at two sites taken as representative of city-wide air quality in New York City and ...Long Island, respectively. A number of species were quantified with hourly time resolution, including particle number concentrations in 6 size ranges (20–30 nm, 30–50 nm, 50–70 nm, 70–100 nm, 100–200 nm, and >200 nm), nitrogen oxides, sulfur dioxide, ozone, carbon monoxide, methane, non-methane hydrocarbons, PM2.5 mass concentration and some PM major components (sulfate, organic and elemental carbon). Hourly concentrations of primary and secondary organic carbon were estimated using the EC tracer method. Data were matched with weather parameters and air parcel back-trajectories. A series of tools were thus applied to: (i) study the seasonal, weekly, diurnal cycles of pollutants; (ii) investigate the relationships amongst pollutants through correlation and lagged correlation analyses; (iii) depict the role of atmospheric photochemical processes; (iv) examine the location of the potential sources by mean of conditional bivariate probability function analysis and (v) investigate the role of regional transport of air masses to the concentrations of analyzed species. Results indicate that concentrations of NOx, SO2, CO, non-methane hydrocarbons, primary OC and EC are predominantly determined by local sources, but are also affected by regional transports of polluted air masses. On the contrary, the transport of continental polluted air masses has a main effect in raising the concentrations of secondary PM2.5 (sulfate and secondary organic carbon). By providing direct information on the concentrations and trends of key pollutants and submicron particle number concentrations, this study finally enables some general considerations about air quality status and atmospheric processes over the New York City metropolitan area.
•One-year air quality data measured hourly at 2 urban sites in NYC and Long Island.•Particle number resolved over 6 bins, gases, PM2.5 mass, EC/OC and sulfate measured.•Primary and secondary organic carbon are estimated using the EC tracer method.•Seasonal, weekly, diurnal cycles and relationships with weather are investigated.•Location of the potential sources and role of regional transport are discussed.
This study reports the results of an experimental research project carried out in Bologna, a midsize town in central Po valley, with the aim at characterizing local aerosol chemistry and tracking the ...main source emissions of airborne particulate matter. Chemical speciation based upon ions, trace elements, and carbonaceous matter is discussed on the basis of seasonal variation and enrichment factors. For the first time, source apportionment was achieved at this location using two widely used receptor models (principal component analysis/multi-linear regression analysis (PCA/MLRA) and positive matrix factorization (PMF)). Four main aerosol sources were identified by PCA/MLRA and interpreted as: resuspended particulate and a pseudo-marine factor (winter street management), both related to the coarse fraction, plus mixed combustions and secondary aerosol largely associated to traffic and long-lived species typical of the fine fraction. The PMF model resolved six main aerosol sources, interpreted as: mineral dust, road dust, traffic, secondary aerosol, biomass burning and again a pseudo-marine factor. Source apportionment results from both models are in good agreement providing a 30 and a 33 % by weight respectively for PCA-MLRA and PMF for the coarse fraction and 70 % (PCA-MLRA) and 67 % (PMF) for the fine fraction. The episodic influence of Saharan dust transport on PM₁₀ exceedances in Bologna was identified and discussed in term of meteorological framework, composition, and quantitative contribution.
The international airport of Heathrow is a major source of nitrogen oxides, but its contribution to the levels of sub-micrometre particles is unknown and is the objective of this study. Two sampling ...campaigns were carried out during warm and cold seasons at a site close to the airfield (1.2 km). Size spectra were largely dominated by ultrafine particles: nucleation particles ( < 30 nm) were found to be ∼ 10 times higher than those commonly measured in urban background environments of London. Five clusters and six factors were identified by applying k means cluster analysis and positive matrix factorisation (PMF), respectively, to particle number size distributions; their interpretation was based on their modal structures, wind directionality, diurnal patterns, road and airport traffic volumes, and on the relationship with weather and other air pollutants. Airport emissions, fresh and aged road traffic, urban accumulation mode, and two secondary sources were then identified and apportioned. The fingerprint of Heathrow has a characteristic modal structure peaking at < 20 nm and accounts for 30–35 % of total particles in both the seasons. Other main contributors are fresh (24–36 %) and aged (16–21 %) road traffic emissions and urban accumulation from London (around 10 %). Secondary sources accounted for less than 6 % in number concentrations but for more than 50 % in volume concentration. The analysis of a strong regional nucleation event showed that both the cluster categorisation and PMF contributions were affected during the first 6 h of the event. In 2016, the UK government provisionally approved the construction of a third runway; therefore the direct and indirect impact of Heathrow on local air quality is expected to increase unless mitigation strategies are applied successfully.
Primary emissions from wood and pellet stoves were aged in an atmospheric simulation chamber under daytime and nighttime conditions. The aerosol was analyzed with online aerosol mass spectrometry and ...offline Fourier transform infrared spectroscopy (FTIR). Measurements using the two techniques agreed reasonably well in terms of the organic aerosol (OA) mass concentration, OA:OC trends, and concentrations of biomass burning markers – lignin-like compounds and anhydrosugars. Based on aerosol mass spectrometry, around 15 % of the primary organic aerosol (POA) mass underwent some form of transformation during daytime oxidation conditions after 6–10 h of atmospheric exposure. A lesser extent of transformation was observed during the nighttime oxidation. The decay of certain semi-volatile (e.g., levoglucosan) and less volatile (e.g., lignin-like) POA components was substantial during aging, highlighting the role of heterogeneous reactions and gas–particle partitioning. Lignin-like compounds were observed to degrade under both daytime and nighttime conditions, whereas anhydrosugars degraded only under daytime conditions. Among the marker mass fragments of primary biomass burning OA (bbPOA), heavy ones (higher m/z) were relatively more stable during aging. The biomass burning secondary OA (bbSOA) became more oxidized with continued aging and resembled that of aged atmospheric organic aerosols. The bbSOA formed during daytime oxidation was dominated by acids. Organonitrates were an important product of nighttime reactions in both humid and dry conditions. Our results underline the importance of changes to both the primary and secondary biomass burning aerosols during their atmospheric aging. Heavier fragments from aerosol mass spectrometry seldom used in atmospheric chemistry can be used as more stable tracers of bbPOA and, in combination with the established levoglucosan marker, can provide an indication of the extent of bbPOA aging.
A detailed comparison was made of two bathymetric charts of the Lagoon of Venice (LV) from 1970 and 2000, in tandem with a comparison of sediment grain size data. Analysis of the data revealed marked ...changes in both morphology and sedimentation, with more than 50% of the 400 km
2 assessed in this study 15–20 cm shallower in 1970 than in 2000. The four sub-basins into which the LV is subdivided saw different patterns of change.
The Northern basin A was identified as “
pristine”, i.e. still in quasi-natural condition, with slight clay enrichment and a small degree of deepening (4–5 cm), essentially due to sea level rise (SLR).
The bathymetry and sedimentology of the northern-central sub-basin B (identified as “
urban”) and the southern-central basin C (identified as “
open”) were affected by infill activities and excavation of industrial navigation channels in the 1970s, causing the loss of ~
60 km
2 of mudflats, and creating an “open” lagoon.
The southernmost basin D (identified as “
exploited-subsiding”) of the LV was found to be relatively unchanged and still in semi-natural condition.
Comparison of sediment types showed depletion of fine-grained fractions (<
22 μm) in all sub-basins except the northernmost one. Consequent enrichment in sand (>
63 μm) was recorded, except in the southern-central sub-basin C where medium and coarse sand fractions declined.
The results suggest that climate-related SLR accounts for a small fraction of bathymetric change, whilst variations in hydrodynamics (currents and wind patterns) and sediment supply are likely causal factors for the different evolution of the four sub-basins.
Definition of the attributes of each sub-basin provided data that was essential not only for the LV but also for predicting the fate of transitional environments facing both anthropic (fishing, navigation, land use changes) as well as natural (SLR, eustatism) forcing factors.
In this study, the performance of two types of source apportionment models was evaluated by assessing the results provided by 40 different groups in the framework of an intercomparison organised by ...FAIRMODE WG3 (Forum for air quality modelling in Europe, Working Group 3). The evaluation was based on two performance indicators: z-scores and the root mean square error weighted by the reference uncertainty (RMSEu), with pre-established acceptability criteria. By involving models based on completely different and independent input data, such as receptor models (RMs) and chemical transport models (CTMs), the intercomparison provided a unique opportunity for their cross-validation. In addition, comparing the CTM chemical profiles with those measured directly at the source contributed to corroborate the consistency of the tested model results. The most commonly used RM was the US EPA- PMF version 5. RMs showed very good performance for the overall dataset (91% of z-scores accepted) while more difficulties were observed with the source contribution time series (72% of RMSEu accepted). Industrial activities proved to be the most difficult sources to be quantified by RMs, with high variability in the estimated contributions. In the CTMs, the sum of computed source contributions was lower than the measured gravimetric PM10 mass concentrations. The performance tests pointed out the differences between the two CTM approaches used for source apportionment in this study: brute force (or emission reduction impact) and tagged species methods. The sources meeting the z-score and RMSEu acceptability criteria tests were 50% and 86%, respectively. The CTM source contributions to PM10 were in the majority of cases lower than the RM averages for the corresponding source. The CTMs and RMs source contributions for the overall dataset were more comparable (83% of the z-scores accepted) than their time series (successful RMSEu in the range 25% - 34%). The comparability between CTMs and RMs varied depending on the source: traffic/exhaust and industry were the source categories with the best results in the RMSEu tests while the most critical ones were soil dust and road dust. The differences between RMs and CTMs source reconstructions confirmed the importance of cross validating the results of these two families of models.
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•Receptor models (RMs) and chemical transport models (CTMs) were tested jointly.•Unprecedented database with 49 independent source apportionment results.•Differences between brute force and tagged species CTM approaches were observed.•CTMs tend to have lower source contributions or impacts than RMs.•The study provides the basis for the joint application of RMs and CTMs.
The atmosphere in Venice, like in other European cities, is influenced by complex PM sub(1) sub(0) multi-emission sources with a net tendency to exceed the limits fixed by the directive 99/30/EC. ...This study investigated the composition of an ensemble of similar industrial sources, the Murano Glassmaking Factories (MGFs), and their influence on the Venice air quality, using a modelling approach, statistical analysis and geochemical considerations. Preliminary modelling simulations were conducted to select three sampling sites along the way of preferential transport of pollutants from source between February and April 2003. Subsequently, a sampling campaign was carried out in the same period of simulations. Concentrations of PM sub(1) sub(0), eight major elements (Al, Ti, Ca, Mg, Na, K, Fe, Mn), 20 minor and trace elements (Li, V, Cr, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Ru, Rh, Cd, Sb, Ba, Ce, Pt, Pb) and four PAHs (BaA, BbF, BkF, BaP) were quantified. The analytical results were statistically processed for exploring the relationships between inorganic elements and organic compounds, and results were interpreted using geochemical considerations. Results show a MGF component of PM sub(1) sub(0) characterised by two different fingerprints: the first linked to glass raw material composition and the second mainly related to glass additives. Particularly, Cd, Se, As and Li preserve their ratios in all study area, and are interpreted as principal components of the MGF emissions. Other fingerprints can be traced to urban sources from the Venetian mainland.
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