Ions species size distribution in particulate matter associated with VOCs and meteorological conditions over an urban region

Variability and sources of non-methane hydrocarbons at a Mediterranean urban atmosphere: The role of biomass burning and traffic emissions

Levels and sources of non-Methane Hydrocarbons (NMHCs) were investigated at the urban background Thissio station, close to the historical center of Athens (Greece) from March 2016 to February 2017 (12 months), by means of an automated GC-FID. Alkanes dominated over aromatics and alkenes, with hourly mean levels ranging from detection limit up to 60 μg m^-3 for i-pentane and 90 μg m^-3 for toluene. Higher levels were recorded in the cold period relative to the warmer one. In addition, NMHCs seasonal diurnal cycles were characterized by a bimodal pattern, following the trend of tracers of anthropogenic sources. The Positive Matrix Factorization (PMF) was used for the allocation of NMHC to their sources. Five factors were identified and quantified, with traffic-related sources being the main one contributing up to 60% to total NMHCs, while biomass burning contributes up to 19%. A supplementary PMF assimilation was applied on a seasonal basis further including α-pinene, C6-C16 alkanes and aromatics. This PMF resulted to a seven-factor solution that allowed the examination of two additional sources, in addition to five already identified, highlighting the main contribution of anthropogenic sources (70%) to α-pinene.

Chemical characterization, sources and potential health risk of PM2.5 and PM1 pollution across the Greater Athens Area

With the principal aim to assess the typical Mediterranean profile of the PM_2.5 and PM₁ pollution, three intensive monitoring campaigns took place simultaneously within different types of environment across an urban location of the basin. Focusing on the PM components with numerous anthropogenic sources and increased potential health risk, the samples were chemically analyzed for 20 p.m.-bound Polycyclic Aromatic Hydrocarbons (PAHs). Carbonaceous and ionic constituents were quantified as well. In order to uncover the spatiotemporal variation of the PM profile the key sources were identified, the seasonal effects and the role of the prevailing mesoscale atmospheric circulation were evaluated and most importantly the potential health risk was estimated. In general, the pollution status of the basin was the result of a complex interaction between the local and external input with Particulate Organic Matter (POM) and Secondary Inorganic Aerosols (SIA) being the main aerosols' components. PM₁ was a better indicator of the anthropogenic emissions while according to the results of factor analysis the co-existence of various combustion sources was determinant. Chemically, the maxima of the ΣPAHs, the differentiation of their structure in accordance with their molecular weight and the distribution of the individual compounds confirmed the significance of the emission sources. Similarly, the estimated carcinogenicity/mutagenicity was emission-dependent with the maximum contribution coming from B[a]P, IndP, B[ghi]Per, B[e]P and B[b]F. Seasonally, the highest potential health risk of the PAHs' mixture was recorded during the cold season while meteorologically, it was mostly associated with the south flow.

Levels, Sources and Health Risk of PM2.5 and PM1-Bound PAHs across the Greater Athens Area: The Role of the Type of Environment and the Meteorology

Fine particulate matter (PM) has significant impacts on public health. Among its various chemical components, Polycyclic Aromatic Hydrocarbons (PAHs) are of particular importance since they contribute to a large extent or even enhance its toxic potency. Despite the verified importance of the fine PM pollution for the Greater Athens Area (GAA), information on its composition with respect to the hydrocarbons is extremely scarce. This study aims to uncover the occurrence of the PM2.5 and PM1-bound PAHs across the GAA investigating the impact of the sources and meteorology on the configuration of their profile and potential health risk. The fieldwork took place at three different locations during two different mesoscale wind regimes. Using the Diagnostic PAHs’ Ratio method, the sources were identified while for the quantification of the emissions from the traffic and central heating sectors, the FEI-GREGAA emission inventory was taken into consideration. The potential health risk was estimated calculating the toxic/mutagenic equivalency factors. The peaks for both the PM mass and the PAHs were attributed to the intensity of the emissions. On the other hand, the carcinogenic/mutagenic risk was mainly influenced by the varying characteristics of traffic and especially for the background atmosphere, from the arriving air masses from longer scale distances.

The traffic signature on the vertical PM profile: Environmental and health risks within an urban roadside environment

In an attempt to investigate the traffic-impacted vertical aerosols profile and its relationship with potential carcinogenicity and/or mutagenicity, samples of different sized airborne particles were collected in parallel at the 1st and 5th floor of a 19 m high building located next to one of the busiest roads of Athens. The maximum daily concentrations were 65.9, 42.5 and 38.5 μg/m³, for PM₁₀, PM_2.5 and PM₁, respectively. The vertical concentration ratio decreased with increasing height verifying the role of the characteristics of the area (1st/5th floor: 1.21, 1.13, 1.09 for PM₁₀, PM_2.5 and PM₁, respectively). Chemically, strengthening the previous hypothesis, the collected particles were mainly carbonaceous (68%-93%) with the maximum budget of the polyaromatic hydrocarbons being recorded near the surface (1st/5th floor: 1.84, 1.07, 1.15 for PM₁₀, PM_2.5 and PM₁, respectively). The detected PM-bound PAHs along with the elements as well as the carbonaceous and ionic constituents were used in a source apportionment study. Exhaust and non-exhaust emissions, a mixed source of biomass burning and high temperature combustion processes (natural gas, gasoline/diesel engines), sea salt, secondary and soil particles were identified as the major contributing sources to the PM pollution of the investigated area. With respect to the health hazards, the calculation of the Benzo[a]Pyrene toxicity equivalency factors underlined the importance of the height of residence in buildings for the level of the exposure (1st/5th floor: B[a]P_TEQ: 1.82, 1.12, 1.10, B[a]P_MEQ: 1.85, 1.13, 1.09 for PM₁₀, PM_2.5 and PM₁, respectively). Finally, despite its verified significance as a surrogate compound for the mixture of the hydrocarbons (its contribution up to 72%, 79% on the level of the 1st and 5th floor, respectively), the importance of the incorporation of PAH species in addition to B[a]P when assessing PAH toxicity was clearly documented.

Spatial-seasonal characteristics and critical impact factors of PM2.5 concentration in the Beijing-Tianjin-Hebei urban agglomeration

As China's political and economic centre, the Beijing-Tianjin-Hebei (BTH) urban agglomeration experiences serious environmental challenges on particulate matter (PM) concentration, which results in fundamental or irreparable damages in various socioeconomic aspects. This study investigates the seasonal and spatial distribution characteristics of PM2.5 concentration in the BTH urban agglomeration and their critical impact factors. Spatial interpolation are used to analyse the real-time monitoring of PM2.5 data in BTH from December 2013 to May 2017, and partial least squares regression is applied to investigate the latest data of potential polluting variables in 2015. Several important findings are obtained: (1) Notable differences exist amongst PM2.5 concentrations in different seasons; January (133.10 mg/m3) and December (120.19 mg/m3) are the most polluted months, whereas July (38.76 mg/m3) and August (41.31 mg/m3) are the least polluted months. PM2.5 concentration shows a periodic U-shaped variation pattern with high pollution levels in autumn and winter and low levels in spring and summer. (2) In terms of spatial distribution characteristics, the most highly polluted areas are located south and east of the BTH urban agglomeration, and PM2.5 concentration is significantly low in the north. (3) Empirical results demonstrate that the deterioration of PM2.5 concentration in 2015 is closely related to a set of critical impact factors, including population density, urbanisation rate, road freight volume, secondary industry gross domestic product, overall energy consumption and industrial pollutants, such as steel production and volume of sulphur dioxide emission, which are ranked in terms of their contributing powers. The findings provide a basis for the causes and conditions of PM2.5 pollution in the BTH regions. Viable policy recommendations are provided for effective air pollution treatment.

Sources of atmospheric aerosol from long-term measurements (5 years) of chemical composition in Athens, Greece

To identify the sources of aerosols in Greater Athens Area (GAA), a total of 1510 daily samples of fine (PM 2.5) and coarse (PM 10-2,5) aerosols were collected at a suburban site (Penteli), during a five year period (May 2008-April 2013) corresponding to the period before and during the financial crisis. In addition, aerosol sampling was also conducted in parallel at an urban site (Thissio), during specific, short-term campaigns during all seasons. In all these samples mass and chemical composition measurements were performed, the latest only at the fine fraction. Particulate organic matter (POM) and ionic masses (IM) are the main contributors of aerosol mass, equally contributing by accounting for about 24% of the fine aerosol mass. In the IM, nss-SO4(-2) is the prevailing specie followed by NO3(-) and NH4(+) and shows a decreasing trend during the 2008-2013 period similar to that observed for PM masses. The contribution of water in fine aerosol is equally significant (21 ± 2%), while during dust transport, the contribution of dust increases from 7 ± 2% to 31 ± 9%. Source apportionment (PCA and PMF) and mass closure exercises identified the presence of six sources of fine aerosols: secondary photochemistry, primary combustion, soil, biomass burning, sea salt and traffic. Finally, from winter 2012 to winter 2013 the contribution of POM to the urban aerosol mass is increased by almost 30%, reflecting the impact of wood combustion (dominant fuel for domestic heating) to air quality in Athens, which massively started in winter 2013.

Seasonal and diurnal variation in particulate matter (PM10 and PM2.5) at an urban site of Beijing: analyses from a 9-year study

Air pollution has become a top environmental concern in China. In the present study, 9 years of PM10 and PM2.5 data from an urban monitoring station in Beijing was analyzed relative to other gaseous pollutants and several meteorological parameters. The levels and characteristics of particulate matters as well as the sources and factors affecting them were provided in the present study. During the 9-year observation period, PM10 and PM2.5 showed high levels, with annual mean values of 138.5 ± 92.9 and 72.3 ± 54.4 μg/m(3), respectively. Slight decreasing trends of annual mean PM10 and PM2.5 were observed; autumn was the main season that contributed to the decrease in annual mean PM10 and PM2.5. Higher values for both PM fractions were generally observed in the spring and summer months, respectively, whereas lower values were found in the summer and spring months, respectively. Pronounced diurnal variations were found for PM10 and PM2.5, which both displayed a bimodal pattern with peaks between 7:00 and 8:00 a.m. as well as 7:00 and 11:00 p.m.; a minimum generally appeared at approximately noon. The seasonal and diurnal variations in particulate concentration are mostly dominated by the seasonal and diurnal variability of boundary layer and source emissions. A principal components analysis revealed that both the traffic-related emissions and combustion sources were major contributions to the particles; their contributions ranged between 35.5-75.1%. Furthermore, a directional analysis shows a stronger association between particles and the southerly winds, the PM derived from sources south of Beijing, most likely secondary PM, significantly affects concentrations at the sampling site. To improve air quality in Beijing, mitigation measures including phasing out high energy-consuming industries and prioritize the use of clean energy sources should be designed to reduce emissions from both local and regional sources.

Assessment of PM₂.₅ and PM₁ chemical profile in a multiple-impacted Mediterranean urban area: origin, sources and meteorological dependence

Airborne particulate matter in the PM2.5 and PM1 size ranges has been sampled at three sites within the Mediterranean urban area of the Athens Basin, representing background, roadside-industrialized and coastal background locations. With the principal aim to identify the sources and discriminate the contribution of the regional input versus the local one, simultaneous chemical characterization with respect to carbonaceous and ionic species was also carried out on the collected samples. In general, the average recorded values were within the Mediterranean concentration range. The constant prevalence of the ionic mass (52%-79%) over one of the carbonaceous, being combined with the occurrence of its maximum rates at the coastal background environment (74%-79% and 73%-77% for PM2.5 and PM1, respectively) leads to the hypothesis that the fine PM pollution in the basin, especially for the remote locations, is evidently governed by the external intrusion. Even at the polluted atmosphere of the roadside-industrialized environment, the PM mass was regionally originated, with the corresponding input reaching up to 87% (northward flow). Applying factor analysis on the PM2.5 database it came obvious that the sources which were responsible for the configured PM burden were not fully differentiated not only between the different types of environment but also between the exceedances and the clean air events. The contribution of the secondary, marine and combustion processes was constant at all the stations of the network, while a continuous input of crustal particles characterized both the roadside-industrialized and the coastal atmosphere. Finally, the episodic values show a general common signal of secondary mixed ΡΜ emissions, high influence of both regional and local pollution spikes, confirming the earlier findings for the significance of transportation.

Particulate matter pollution over a Mediterranean urban area

The main purpose of this study is to investigate the aerosols' (PM10, PM2.5, and PM1) spatial and temporal distribution in different types of environment in a Mediterranean urban region, the Greater Athens Area based on data from a sampling campaign that took place during the cold and warm period of 2008. The influence of the atmospheric circulation patterns, the possible local transport mechanisms, as well as the differentiation of the PM behaviour from that of the inorganic pollutants (NOx, O3), are analysed and discussed. Furthermore, the Comprehensive Air Quality Model with extensions (CAMx) was applied for selected sampling dates and its results were evaluated against measurements in order to interpret qualitatively the configured picture of the air pollution above the GAA. Analysis of the measurement data show that local sources such as traffic and industry dominate over the prevailing PM loads, especially at the 'hot spot' areas. Moreover, the synoptic circulation patterns associated with calm conditions and southerly flows lead to high particulate pollution levels that also affect the urban background stations. Saharan dust outbreaks appeared to increase the particles' diameter as well as the number of E.U. limit value exceedances within the stations of our network. Without any dependence on the characteristics of the investigated atmosphere, PM1 always constituted the greatest part of the PM2.5 mass while PM10, especially during the Saharan dust episodes, was mainly constituted by the coarse fraction. The numerical modelling approach of the geographical distribution of PM10, PM2.5, NOx and O3 justified the design of the sampling campaign, indicating the need for the systematic and parallel monitoring and modelling of the pollutants' dispersion in order to understand the particulate pollution problem in the GAA and to aid to the formulation of pollution control strategies.

Carbonaceous and ionic compositional patterns of fine particles over an urban Mediterranean area

A carefully designed experimental study based on the monitoring of fine airborne particles, was carried out at three different locations (suburban background, traffic-industrial, coastal background) of an urban Mediterranean area, the Athens Basin. Understanding of the PM(2.5) and PM(1) nature has an important policy implication. In total, five hundred and nineteen samples were chemically analyzed with respect to carbonaceous (organic/elemental carbon) and ionic (NH(4)(+), K(+), Mg(2+), Ca(2+), NO(3)(-), Cl(-), SO(4)(2-)) species. The dataset consists one of the very few in the Mediterranean which simultaneously deals with the carbonaceous and ionic components of fine aerosol fractions, especially for PM(1). Daily PM(2.5) averages often exceeded the E.U. limit values, with their mass being mainly composed of PM(1). The most important constituents of secondary particles were SO(4)(2-) and organic carbon, with both accounting for 56.4%-64.3% and 60.5%-62.3% of the total PM(2.5) and PM(1) mass, respectively. Regional sources, marine/crustal elements, combustion sources and traffic were indicated by factor analysis as the greatest contributors to the mass of both PM(2.5) and PM(1) fractions, accounting for 85.3% and 83.6%, respectively of the total variance in the system. It is worthy to note, the key role of the prevailing atmospheric conditions to the configuration of the obtained picture of the particulate pollution.

The role of meteorology on different sized aerosol fractions (PM₁₀, PM₂.₅, PM₂.₅-₁₀)

The scope of the present study is to assess the influence of meteorology on different diameter particles (PM(10), PM(2.5), PM(2.5-10)) during a 53 months long experimental campaign at an urban Mediterranean area. Except for the investigation of the wind, temperature and relative humidity role, day by day synoptic conditions were classified over the Attica peninsula in order to explore as well, the role of the synoptic scale atmospheric circulation. The strong dependence of the aerosols character on their various sources, not only explain the different diameter particles behavior and their differentiation with the inorganic pollutants but also highlights the need for an effective emission policy. High PM(10) and PM(2.5-10) concentrations found to be closely related to the southwesterly regime, suggesting long range transport from the 'polluted' south sector while the general prevalence of the secondary particles generation revealed the health hazard. PM(2.5) showed a weaker correlation than the bigger particles with both the circulation patterns and the parameters' fluctuations. Temporal pollutants variations were clearly governed by the emissions patterns while the low wind speed was not necessarily a good indicator of high concentration levels. Finally it was found that only during the open/close anticyclonic days and the southwesterly wind regime the morning levels were continuously higher than those of the night.

Particulate matter levels in a suburban Mediterranean area: analysis of a 53-month long experimental campaign

Parallel measurements of ambient particulate matter mass in terms of PM(10), PM(2.5) and PM(2.5-10), conducted during a 53 months long experiment, between 2003 and 2008. The data constituting one of the longest simultaneous comparative data sets for the three PM fractions in Europe, collected at a suburban area of Athens, Aghia Paraskevi. Total means of mass concentrations for PM(10), PM(2.5) and PM(2.5-10) were in the order of 34.8, 18.0 and 23.8 microg/m(3), respectively. Seasonal variability of PM levels governed by the fact that the specific site is dominated by secondary aerosol emissions with the concentrations presenting a shift to the warm period. During the whole sampling period PM(10) were mainly composed of PM(2.5) while particles with the bigger diameter proved to be strongly correlated in all the cases. It would be interesting to mention that all the three aerosol fractions did not present any association with the inorganic pollutants. Stagnant conditions as well as the wind direction proved to be key mechanisms for the configuration of the air quality patterns. Saronic Gulf sea-breeze development enhanced the aerosol transportation from the industrialized greater area of Piraeus and the polluted center of the city, to the Northern suburbs.