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Abstract A methodology to detect the weekly cycle impact of the particulate matter (PM), and PM sources on the near surface temperature and wind speed is discussed in the paper. Chemically-speciated PM10 and PM2.5 samples are analyzed to detect the weekly cycle of both the PM mass concentrations and the PM sources identified by the Positive Matrix Factorization technique. The average percent departure (APD) of the PM mass concentration from the mean value calculated for each day of the week shows that a positive (higher values during midweek) and a negative (higher values during weekend) weekly cycle characterizes the PM10 and PM2.5 mass concentrations in Autumn-Winter (AW, September–February) and Spring-Summer (SS, March–August), respectively. The westerly transport of pollution seems to have a role on the negative PM weekly cycle found in SS. The analysis of the six identified aerosol sources indicates that in SS the mixed anthropogenic and the reacted dust sources likely impact the PM10 negative weekly cycle and that the mixed anthropogenic source likely impacts the PM2.5 negative weekly cycle. The mixed anthropogenic and soil dust sources likely affect in AW the positive weekly cycle of the PM10 mass concentration. Both sources in addition to the reacted dust source seem to affect the PM2.5 mass concentration in AW. The APD analysis of the temperature (T) and wind speed (WS) at the surface from measurements co-located in space and time with the PM ones reveals that the WS and T values are characterized by a negative weekly cycle in AW. Conversely, in SS, the WS-APD value decreases on Sunday and the T-APD values increase in the second half of the week. These last results likely give evidence of the PM impact on the near-surface temperature and wind speed at the study site. Graphical abstract Unlabelled Image Highlights • Weekly cycles of PM10 and PM2.5 mass concentrations and seasonal dependence • Weekly cycles of temperature and wind speed at the surface and seasonal dependence • Chemical speciation of PM10 and PM2.5 samples • Aerosol source identification by Positive Matrix Factorization • Aerosol source impact on the weekly cycles of PM10 and PM2.5 mass concentrations [ABSTRACT FROM AUTHOR]

Integrating nephelometer measurements have been combined with co-located in space and time PM10 and PM1 mass concentration measurements to highlight the benefits of integrating aerosol optical properties with the chemical speciation of PM1 and PM10 samples. Inorganic ions (SO 4 2− , NO 3 − , NH 4 + , Cl − , Na + , K + , Mg 2+ , and Ca 2+ ), metals (Fe, Al, Zn, Ti, Cu, V, Mn, and Cr), and the elemental and organic carbon (EC and OC, respectively) have been monitored to characterize the chemical composition of PM1 and PM10 samples, respectively. The scattering coefficient ( σ p ) at 450 nm, the scattering Ångström coefficient ( Å ) calculated at the 450–635 nm wavelength pair, and the scattering Ångström coefficient difference (∆ Å ) retrieved from nephelometer measurements have been used to characterize the optical properties of the particles at the surface. The frequency distribution of the Å daily means during the one-year monitoring campaign, performed at a southeastern Italian site, has allowed identifying three main Å variability ranges: Å  ≤ 0.8, 0.8 <  Å  ≤ 1.2, and Å  > 1.2. We found that σ p and ∆ Å mean values and the mean chemical composition of the PM1 and PM10 samples varied with the Å variability range. σ p and ∆ Å reached the highest (149 Mm −1 ) and the smallest (0.16) mean value, respectively, on the days characterized by Å  > 1.2. EC, SO 4 2− , and NH 4 + mean mass percentages also reached the highest mean value on the Å  > 1.2 days, representing on average 8.4, 9.8, and 4.2%, respectively, of the sampled PM10 mass and 12.4, 10.6, and 7.7%, respectively, of the PM1 mass. Conversely, σ p and ∆ Å mean values were equal to 85 Mm −1 and 0.55, respectively, on the days characterized by Å  ≤ 0.8 and the EC, SO 4 2− , and NH 4 + mean mass percentages reached smaller values on the Å  ≤ 0.8 days, representing 4.5, 6.0, and 1.9% of the PM10 mass and 9.4, 7.3, and 5.8% of the PM1 mass, respectively. Primary and secondary OC (POC and SOC, respectively) contributions also varied with the Å variability range. POC and SOC mean mass percentages reached the highest and the smallest value, respectively, on the days characterized by Å  > 1.2. Conversely, POC and SOC mean mass percentages reached the smallest and the highest value, respectively, on the days characterized by Å  ≤ 0.8. It has also been shown that the PM, OC, OC + EC, POC, and SOC mass scattering cross sections varied significantly with the Å variability range, because of the Å dependence on aerosol sources and/or emission, transport, and transformation mechanisms. Therefore, it has been shown that Å daily mean values can represent a good tool to better differentiate the chemical speciation of size-fractioned PM samples. [ABSTRACT FROM AUTHOR]

Mass concentrations of PM2.5, mineral dust, organic carbon (OC) and elemental carbon (EC), water-soluble organic carbon (WSOC), sea salts and anthropogenic metals have been studied in a city-port of south Italy (Brindisi). This city is characterized by different emission sources (ship, vehicular traffic, biomass burning and industrial emissions) and it is an important port and industrial site of the Adriatic sea. Based on diagnostic ratios of carbonaceous species we assess the presence of biomass burning emissions (BBE), fossil fuel emissions (FFE) and ship emission (SE). Our proposed conversion factors from OC to OM are higher than those reported in the literature for urban site: the reason of this could be due to the existence of aged combustion aerosols during the sampling campaign (WSOC/OC = 0.6 ± 0.3). [ABSTRACT FROM AUTHOR]

This paper presents aerosol light absorption measurements using a seven channel Aethalometer (AE-42), recorded during September 2011–November 2012 over a tropical semi-arid site in Kadapa, India. The annual average black carbon (BC) mass concentration ([BC]) during the studied period was 2.20 ± 0.78 μg m − 3 which is in agreement when compared to other sites of similar environment. Strong seasonal variation was observed with high values during winter (2.87 ± 0.81 μg m − 3 ) and low in monsoon (1.30 ± 0.31 μg m − 3 ) season, which could be attributed to regional synoptic meteorology and long range transport. The two peaks in diurnal variations of [BC] were observed during morning between 06:00 and 08:00 h local time (LT) and in the evening around 19:00–21:00 h LT, with a minimum peak in the afternoon (~ 16:00 h LT) which is strongly correlated with the boundary layer dynamics, local and regional sources, and associated meteorology. The relationships between measured [BC] and the corresponding meteorological parameters for the studied region were also analysed. The estimated monthly mean spectral absorption coefficient values range from 0.56 to 1.15 with an average of 0.90, which suggests high BC/OC ratio and possible source of emission of aerosols is fossil fuel burning. Trajectory cluster analysis showed significant impact of long range transport of BC aerosols towards the observational site during the period of study. [ABSTRACT FROM AUTHOR]

Visibility, particulate matter (PM) mass concentration, and aerosol optical properties data from June 2009 to December 2011 were obtained at Shenyang in Northeast China. The characteristics and relationships between these parameters were statistically analyzed. The results demonstrate that the monthly averaged visibility over Shenyang was higher in spring and autumn but lower in summer and winter, and had an inverse trend to PM and aerosol optical depth (AOD). Higher AOD at 500 nm was found year by year, with the maximum value (1.31 ± 0.45) occurring in June 2011, and the minimum in June 2010 (0.72 ± 0.31). The mean value of the Ångström exponent underwent a notable reduction during the period of 2011, with values less than 1.0 from February to September. The single scattering albedo was consistently around 0.90 during 2009–2011, which was higher in summer but lower in winter. The higher absorption aerosol optical depth at 440 nm in 2011 indicates that there were more absorbing aerosol particles in this period compared with the corresponding absorption Ångström exponent in the same year (about 0.75). The direct radiative forcing at the bottom of the atmosphere increased to − 200 W/m 2 in 2011, compared with − 150 W/m 2 from June 2009 to December 2010, suggesting a stronger cooling effect of aerosols at the surface. The positive radiative forcing at the top of the atmosphere in November and December 2009 could have been due to snow cover, which has a large surface albedo that reflects shortwave radiation to the atmosphere. [ABSTRACT FROM AUTHOR]

Both PM 2.5 mass concentration and its chemical composition are a great concern to human health. In this study, the concentrations of PM 2.5 and their metallic elements were measured to identify the characteristics and to trace sources at two different functional areas, a residential and a cement industrial area. The average PM 2.5 concentrations were not significantly different between the two sites, but their chemical compositions were clearly different. Crustal elements in PM 2.5 were significantly higher in the residential area, while the concentrations of metals typically emitted from anthropogenic sources were generally higher in the cement industrial area. Crustal elements often increased during spring in the residential area due to the blustery weather with high wind speeds; however, most metallic elements were enhanced during winter in the cement industrial area. Principal component analysis was used to trace the sources. Soil re-suspension, traffic-related sources, and asphalt concrete production were identified as the main sources of PM 2.5 in the residential area, while the cement industry, Ni–Cr plating industry, and other industrial activities were identified in the cement industrial area. [ABSTRACT FROM AUTHOR]

The first simultaneous aethalometer and solar radiometer measurements of black carbon (BC) mass concentration (surface-level) and aerosol optical, microphysical and radiative parameters (columnar) have been made during 2005–2011 over two contrasting experimental sites, one representing background rural environment (Sinhagad) and the other surrounded by urban environment (Pune) in the south-west India. The long-term diurnal cycle of BC aerosols over both sites exhibited a strong peak during daytime and a weaker plateau around evening–midnight hours, implying the influence of anthropogenic emissions as well as changes in planetary boundary layer (PBL). The multi-year seasonal mean variation in BC concentration shows the highest during winter and lowest during monsoon seasons, which is found to be inversely related to the variations in single scattering albedo (SSA). Moreover, the BC variations were found to be strongly associated with greater values of Angstrom exponent ( α ), indicating that the observed BC involves abundance of fine-mode aerosol fraction. The higher concentrations of BC during winter and lower concentrations during pre-monsoon over both Pune and Sinhagad are noticed to be closely linked with aerosol optical depth, revealing significant contribution of BC to the composite aerosol over both the regions. The columnar AOD and Angstrom exponent also showed relatively greater optical depth and α values during winter as compared to pre-monsoon season over both sites. [ABSTRACT FROM AUTHOR]

An intensive sampling campaign was conducted in the autumn of 2012 to study the size distribution of inorganic ions and ion deposition at an offshore site of Yangtze River Delta region (YRD), China. Particles in <0.43, 0.43-0.65, 0.65-1.1, 1.1-2.1, 2.1-3.3, 3.3-4.7, 4.7-5.8, 5.8-9.0 and 9.0-10.0 µm were collected and analyzed by ion chromatography for NH4+, Na+, Mg2+, K+, Ca2+, F-, Cl-, NO3- and SO42-. The average mass concentrations in the nine particle sizes ranged from 13.1 to 38.7 µ g m-3, accounting for 5.5%-16.8% of the total mass. Concentrations exhibit bi-modal distribution, peaking at 0.65-1.1 µm and 3.3-4.7 µm. PM1.1, PM2.1 and PM2.1-10 account for 41%, 56% and 44% of PM10 implying the dominance of finer particles. Different ions hold different size distribution patterns. The concentrations of NO3-, SO42-, NH4+, K+ and Ca2+ exhibit the highest values when compared to literature values indicating the serious air pollution situation in YRD. A haze-precipitation-fog transition course is captured. The precipitation can decrease all the particles in the nine sizes by 20%-62% and the fog formation process can promote the particles' accumulation, with their mass concentrations increasing by 26%-232% except for those in 5.8-9.0 µm and 9.0-10 µm. Mass percentages of SO42-, NO3- and NH4+ exhibit decreases during precipitation and increases during fog formation course. The anion to cation ratios are lower than 1.0 indicating the anion deficiency and they exhibit significant negative relationship with the particle diameter. The Cl-dep (%) is higher for particles larger than 0.65 µm, increasing from 1.3% to 61% with size added. Sea salt only accounts for 0.12%-2.1% of PM10. The ratios of nss-SO42-/NO3- decrease with increasing particle size, from 1.68 to 0.69, and are well fit as linear form (r = -0.74, p = 0.02). It indicates that stationary sources make more contributions to smaller particles and vehicle emission is more important for larger particles. The dry deposition fluxes for F-, Cl-, NO3- and SO42- are 3.10, 0.59, 22.99 and 17.04 mg/(m²d). They exhibit multi-linear correlation with corresponding ion concentrations and the coefficients are higher for coarse particles. More researches are needed to obtain the distribution, transportation and deposition characteristic of ions at Chinese coastal area. [ABSTRACT FROM AUTHOR]