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Aerosols have been associated with large uncertainties in estimates of the radiation budget and cloud formation processes in the Arctic. This paper reports the results of a study of in situ measurements of hygroscopicity, fraction of volatile species, mixing state, and off-line morphological and elemental analysis of Aitken and accumulation mode particles in the Arctic (Ny-Ålesund, Svalbard) in May and September 2012. The accumulation mode particles were more abundant in May than in September. This difference was due to more air mass flow from lower latitude continental areas, weaker vertical mixing, and less wet scavenging in May than in September, which may have led to a higher amount of long-range transport aerosols entering the Arctic in the spring. The Aitken mode particles observed intermittently in May were produced by nucleation, absent significant external mixing, whereas the accumulation mode particles displayed significant external mixing. The occurrence of an external mixing state was observed more often in May than in September and more often in accumulation mode particles than in Aitken mode particles, and it was associated more with continental air masses (Siberian) than with other air masses. The external mixing of the accumulation mode particles in May may have been caused by multiple sources (i.e., long-range transport aerosols with aging and marine aerosols). These groups of externally mixed particles were subdivided into different mixing structures (internal mixtures of predominantly sulfates and volatile organics without nonvolatile species and internal mixtures of sulfates and nonvolatile components, such as sea salts, minerals, and soot). The variations in the mixing states and chemical species of the Arctic aerosols in terms of their sizes, air masses, and seasons suggest that the continuous size-dependent measurements observed in this study are useful for obtaining better estimates of the effects of these aerosols on climate change.

In this paper we derive typical emission factors for coarse particulate matter (PM(10)), oxides of nitrogen (NO(x)), black carbon (BC), and number particle size distributions based on a combination of measurements and air quality dispersion modeling. The advantage of this approach is that the emission factors represent integrated emissions from several vehicle types and different types of wood stoves. Normally it is very difficult to estimate the total emissions in cities on the basis of laboratory measurements on single vehicles or stoves because of the large variability in conditions. The measurements were made in Temuco, Chile, between April 18 and June 15, 2005 at two sites. The first one was located in a residential area relatively far from major roads. The second site was located in a busy street in downtown Temuco where wood consumption is low. The measurements support the assumption that the monitoring sites represent the impact of different emission sources, namely traffic and residential wood combustion (RWC). Fitting model results to the available measurements, emission factors were obtained for PM(10) (RWC = 2160 +/- 100 mg/kg; traffic = 610 +/- 51 mg/veh-km), NO(x) (RWC = 800 +/- 100 mg/kg; traffic = 4400 +/- 100 mg/veh-km), BC (RWC = 74 +/- 6 mg/kg; traffic = 60 +/- 3 mg/veh-km) and particle number (N) with size distribution between 25 and 600 nm (N(25-600)) (RWC = 8.9 +/- 1 x 10(14) pt/kg; traffic = 6.7 +/- 0.5 x 10(14) pt/veh-km). The obtained emission factors are comparable to results reported in the literature. The size distribution of the N emission factors for traffic was shown to be different than for RWC. The main difference is that although traffic emissions show a bimodal size distribution with a main mode below 30 nm and a secondary one around 100 nm, RWC emissions show the main mode slightly below 100 nm and a smaller nucleation mode below 50 nm.

We have evaluated the feasibility of using Empore solid-phase extraction (SPE) membranes as an alternative to conventional techniques for sampling fine airborne particulate matter (PM), including nanoparticles, utilizing a scanning mobility particle sizer (SMPS) and a condensation particle counter to evaluate their efficiency for trapping fine particles in the 10-800 nm size range. The results demonstrate that the membranes can efficiently trap these particles and can then be conveniently packed into an extraction cell and extracted under matrix solid-phase dispersion (MSPD) conditions. The potential utility of sampling PM using Empore membranes followed by dynamic subcritical water extraction (DSWE) for fast, efficient, class-selective extraction of polycyclic aromatic hydrocarbons (PAHs) associated with the particles, prior to changing the solvent and analysis by GC/MS, was then explored. The performance of the method was tested using National Institute of Standards and Technology (NIST)-certified "urban dust" reference material (SRM 1649a) and real samples collected at a site in central Rome with heavy road traffic. The method appears to provide comparable extraction efficiency to that of conventional techniques and with using GC/MS, detection limits ranged in the few picograms per cubic meter level. Sampling PM by Empore membranes may reduce the risks of losses of semivolatile compounds, while allowing relatively high sampling flow rates and safe sample storage. Moreover, the combination of MSPD with DSWE permits specific fractions of the PM components to be eluted, thereby generating clean extracts and reducing both analysis time and sample manipulation.

A set of aerosol measurements was conducted in the residential area of Forsdala in Lycksele, Northern Sweden, during winter 2005/2006. This article describes the temporal and diurnal variation of the aerosol physical properties (concentrations of PM10, PM1, light-absorbing carbon, and particle number, and number size distributions), and the relationship among aerosol concentrations and meteorological variables. A large day-to-day and hour-to-hour variability in aerosol concentrations was observed during the intensive study period. Evening aerosol concentrations were statistically significantly higher on weekends than on weekdays. On weekdays, particle size distribution and concentrations varied diurnally with small particles (diameter <30nm) associated mainly with morning motor vehicle emissions. The results suggest that a combination of emissions from residential wood combustion and traffic sources might explain the high evening concentrations of PM10, PM1, particle number, and light-absorbing carbon as well as large geometric mean diameters observed during weekdays and weekends. Strong correlations of PM10 and PM1 with particle size distributions are found in the diameter range 130–500nm and are remarkably high on weekend evenings when larger particles are sampled. The correlation between light-absorbing carbon mass concentration and particle size distribution is high regarding both particle number and mass for particle diameters >95nm. High aerosol concentrations were associated with low air temperatures and very stable atmospheric conditions close to the ground. [Copyright &y& Elsevier]

Carbonaceous aerosol particles were observed in a residential area with wood combustion during wintertime in Northern Sweden. Filter samples were analyzed for elemental carbon (EC) and organic carbon (OC) content by using a thermo-optical transmittance method. The light-absorbing carbon (LAC) content was determined by employing a commercial Aethalometer and a custom-built particle soot absorption photometer. Filter samples were used to convert the optical signals to LAC mass concentrations. Additional total PM10 mass concentrations and meteorological parameters were measured. The mean and standard deviation mass concentrations were 4.4±3.6μgm−3 for OC, and 1.4±1.2μgm−3 for EC. On average, EC accounted for 10.7% of the total PM10 and the contribution of OC to the total PM10 was 35.4%. Aethalometer and custom-built PSAP measurements were highly correlated (R 2=0.92). The hourly mean value of LAC mass concentration was 1.76μgm−3 (median 0.88μgm−3) for the winter 2005–2006. This study shows that the custom-built PSAP is a reliable alternative for the commercial Aethalometer with the advantage of being a low-cost instrument. [Copyright &y& Elsevier]

Two and a half years (June 2002 to September 2004) of air pollution and meteorological parameters in a street canyon in Stockholm were analyzed. A distinctive dependence of particle number concentration, normalized by , with ambient temperature was found. By comparison with , it is concluded that this variation is not related to variability in the emissions nor due to changes in atmospheric dilution. The observed ratio between total particle number and increases from ca. [] particles per picogram of [] at to [] [] at . The increase in particle number concentration with decreasing temperatures is different for different particle sizes. For particle sizes smaller than 40nm the variation is more pronounced while for particle sizes larger than 100nm the change is not statistically significant. This reflects the impact of temperature dependent processes that affect mainly particles smaller than 100nm in diameter. Modeling results indicate that condensation of volatile compounds onto pre-existing aerosols gives similar changes in the particle size distribution as those observed. Coagulation is shown to have only minor effects on the particle size distribution. Even though, with the present data set is not possible to quantify the impact of an increased nucleation rate with low temperatures, it was shown that nucleation mode particles are largely influenced by relative humidity with high concentrations during high relative humidity periods and therefore it is expected that for cold periods, when the relative humidity is higher, nucleation is enhanced by the water content of the air. [Copyright &y& Elsevier]

Aerosols have been associated with large uncertainties in estimates of the radiation budget and cloud formation processes in the Arctic. This paper reports the results of a study of in situ measurements of hygroscopicity, fraction of volatile species, mixing state, and off-line morphological and elemental analysis of Aitken and accumulation mode particles in the Arctic (Ny-Ålesund, Svalbard) in May and September 2012. The accumulation mode particles were more abundant in May than in September. This difference was due to more air mass flow from lower latitude continental areas, weaker vertical mixing, and less wet scavenging in May than in September, which may have led to a higher amount of long-range transport aerosols entering the Arctic in the spring. The Aitken mode particles observed intermittently in May were produced by nucleation, absent significant external mixing, whereas the accumulation mode particles displayed significant external mixing. The occurrence of an external mixing state was observed more often in May than in September and more often in accumulation mode particles than in Aitken mode particles, and it was associated more with continental air masses (Siberian) than with other air masses. The external mixing of the accumulation mode particles in May may have been caused by multiple sources (i.e., long-range transport aerosols with aging and marine aerosols). These groups of externally mixed particles were subdivided into different mixing structures (internal mixtures of predominantly sulfates and volatile organics without nonvolatile species and internal mixtures of sulfates and nonvolatile components, such as sea salts, minerals, and soot). The variations in the mixing states and chemical species of the Arctic aerosols in terms of their sizes, air masses, and seasons suggest that the continuous size-dependent measurements observed in this study are useful for obtaining better estimates of the effects of these aerosols on climate change. [ABSTRACT FROM AUTHOR]