Ambient particle characteristics by single particle aerosol mass spectrometry at a coastal site in Hong Kong: a case study affected by the sea-land breeze

The sea-land breeze (SLB) circulation plays a vital role in the transport of atmospheric pollutants in coastal cities. In this study, a single particle aerosol mass spectrometer (SPAMS) and combined bulk aerosol instruments were deployed to investigate the ambient particle characteristic at a suburban coastal site in Hong Kong from February 22 to March 10, 2013. Significant SLB circulations were captured from March 6-10, 2013, during the campaign. During the SLB periods, air quality worsened, with PM_2.5 concentrations reaching a peak of 55.6 μg m^-3 and an average value of 42.8 ± 4.5 μg m^-3. A total of 235,894 particles were measured during the SLB stage. Eight major sources were identified by investigating the mixing states of the total particles, including the coal-burning related particles (48.1%), biomass burning particles (6.7%), vehicle emission-related particles (16.4%), sea salt (9.2%), ship emission particles (2.7%), dust/steeling industries (3.7%), waste incineration (6.3%), and road dust (3.9%). It was noteworthy that the PM_2.5 concentrations and particle numbers increased sharply during the transition of land wind to the sea breeze. Meanwhile, the continental sourced pollutants recirculated back to land resulting in a cumulative increase in pollutants. Both individual and bulk measurements support the above results, with high contributions from coal burning, biomass burning, bulk K⁺, and NO₃ ^-, which were probably from the regional transportation from the nearby area. In contrast, the ship and vehicle emissions increased during the SLB period, with a high sulfate concentration partially originating from the ship emission. In this study, field evidence of continental-source pollutants backflow to land with the evolution of sea breeze was observed and helped our current understanding of the effect of SLB on air quality in the coastal city.

Unraveling the sources of atmospheric organic aerosols over the Arabian Sea: Insights from the stable carbon and nitrogen isotopic composition

The isotopic composition of stable carbon (δ¹³C) and nitrogen (δ¹⁵N) in marine aerosols influenced by the continental outflows are useful proxies for understanding the aging and secondary formation processes. Every winter, the haze pollutants transported from South Asia significantly affect the chemical composition of marine atmospheric boundary layer of the Arabian Sea. Here, we assessed the δ¹³C of total carbon (TC) and δ¹⁵N of total nitrogen (TN) in marine aerosols collected over the Arabian Sea during a winter cruise (6-24 December 2018). TC (2.1-13.4 μg m^-3) is strongly correlated with TN (0.9-5.0 μg m^-3), likely because of their common source-emissions, biomass burning and fossil-fuel combustion in the Indo-Gangetic Plain and South Asia (corroborated by backward-air mass trajectories and satellite fire counts). Besides, the linear relationship between the mass ratios of water-soluble organic carbon (WSOC) to TC (0.04-0.65) and δ¹³C_TC (-25.1‰ to -22.9‰) underscores the importance of aging process. This means oxidation of organic aerosols during transport not only influences the WSOC levels but also affects their δ¹³C_TC. Likewise, the prevalent inverse linear relationship between the equivalent mass ratio of (NH₄⁺/non-sea-salt- or nss-SO₄^2-) and δ¹⁵N_TN (+15.3‰ to +25.1‰) emphasizes the overall significance of neutralization reactions between major acidic ([nss-SO₄^2-] ≫ [NO₃^-]) and alkaline species (NH₄⁺) in aerosols. Higher δ¹⁵N_TN values in winter than the spring inter-monsoon clearly emphasizes the significance of the anthropogenic combustion sources (i.e., biomass burning) in the South Asian outflow. A comparison of δ¹³C_TC and δ¹⁵N_TN with the source emissions revealed that crop-residue burning emissions followed by the coal fired power plants mostly dictate the atmospheric abundance of organic aerosols in the wider South Asian outflow.

Carbonaceous aerosols and their light absorption properties over the Bay of Bengal during continental outflow

The marine atmosphere of the Bay of Bengal (BoB) is prone to get impacted by anthropogenic aerosols from the Indo-Gangetic Plain (IGP) and Southeast Asia (SEA), particularly during the northeast monsoon (NEM). In this study, we quantify and characterize carbonaceous aerosols and their absorption properties collected in two cruise campaigns onboard ORV Sindhu Sadhana during the continental outflow period over the BoB. Aerosol samples were classified based on the air mass back trajectory analyses, wherein samples were impacted by the continental air parcel (CAP), marine air parcel (MAP), and mix of both (CAP + MAP). Significant variability in the PM₁₀ mass concentration (in μg m^-3) is found with a maximum value for MAP samples (75.5 ± 36.4) followed by CAP + MAP (58.5 ± 27.3) and CAP (58.5 ± 27.3). The OC/EC ratio (>2) and diagnostic tracers i.e. nss-K⁺/EC (0.2-0.96) and nss-K⁺/OC (0.11-1.32) along with the absorption angstrom exponent (AAE: 4.31-6.02) and MODIS (Moderate Resolution Imaging Spectroradiometer) derived fire counts suggest the dominance of biomass burning emission sources. A positive correlation between OC and EC (i.e. r = 0.86, 0.70, and 0.42 for CAP, MAP, and CAP + MAP, respectively) further confirmed the similar emission sources of carbonaceous species. Similarly, a significant correlation between estimated secondary organic carbon (SOC) and water-soluble organic carbon (WSOC; r = 0.99, 0.96, and 0.97 for CAP, MAP, and CAP + MAP, respectively) indicate their similar chemical nature as well as dominant contribution of SOC to WSOC. The absorption coefficient (b_abs-365) and mass absorption efficiency (MAE_BrC-365) of the soluble fraction were estimated at 365 nm wherein, b_abs-365 showed a linear relationship with WSOC and nss-K⁺, signifying the contribution of water soluble brown carbon from biomass burning emissions. The estimated MAE_BrC-365 (0.30-0.93 m² g^-1), during this study, was consistent with the earlier observations over the BoB, particularly during the continental outflow season.

Distribution and gas-particle partitioning of polycyclic aromatic hydrocarbons over the East China Sea and Yellow Sea in spring: Role of atmospheric transport transition

To elucidate the variations in the East Asian monsoon system during seasonal changes and their impacts on continental outflow of polycyclic aromatic hydrocarbons (PAHs), sixteen integrated air samples were collected during a research cruise covering the Yellow Sea (YS) and East China Sea (ECS) in mid-spring of 2017. The concentrations of total suspended particle (TSP), aerosol-phase PAH fractions, ratios of organic to elemental carbon (OC/EC) and gas-particle partitioning of atmospheric PAHs exhibited clear regional differences associated with variations in the monsoon regime. The total concentrations of 16 USEPA priority PAHs (Σ₁₆PAHs) varied from 3.11 to 13.4 ng/m³ throughout the cruise, with medium-to-high molecular weight (MW) PAHs more enriched over the YS and north ECS than the south ECS. Together with the relatively low gaseous PAH fraction over the YS and north ECS (78 ± 4%) relative to the south ECS (95 ± 13%), this result indicates the pattern of regional atmospheric transport. The ratio of organic to elemental carbon varied significantly between the south ECS (lower than 4) and the YS and north ECS (greater than 4), indicating contributions from vehicle emissions and coal combustion or biomass burning, respectively, following different atmospheric input pathways of carbonaceous aerosols, as supported by backward trajectory analysis. Considering the gas-particle partitioning of PAHs, soot adsorption was the main partitioning mechanism in the study region; while high-MW PAHs in the YS and north ECS were influenced by both absorption and adsorption. The K_oa absorption model provided better predictions for high-MW PAHs when continental air masses prevailed, despite underestimating the partition coefficients (k_p) of low-MW PAHs. Meanwhile, predicted k_p for medium MW PAHs was better estimated over the YS and ECS when K_sa was included.

Characterization and source apportionment of single particles from metalworking activities

Industrial metalworking facilities emit a variety of air toxics including volatile organic compounds, polycyclic aromatic hydrocarbons (PAHs) and heavy metals. In order to investigate these emissions, a 1-month multi-instrument field campaign was undertaken at an industrial site in Grande-Synthe, Dunkirk (France), in May and June 2012. One of the main objectives of the study was to provide new information on the chemical composition of particulate matter with aerodynamic diameters smaller than 2.5 μm (PM_2.5) in the vicinity of metalworking facilities. An aerosol time-of-flight mass spectrometer (ATOFMS) was deployed to provide size-resolved chemical mixing state measurements of ambient single particles at high temporal resolution. This mixing state information was then used to apportion PM_2.5 to local metalworking facilities influencing the receptor site. Periods when the site was influenced by metalworking sources were characterised by a pronounced increase in particles containing toxic metals (manganese, iron, lead) and polycyclic aromatic hydrocarbons (PAHs) with a variety of chemical mixing states. The association of specific particle classes with a nearby ferromanganese alloy manufacturing plant was confirmed through comparison with previous analysis of raw materials (ores) and chimney filter particle samples collected at the facility. Particles associated with emissions from a nearby steelworks were also identified. The contribution of local metalworking activities to PM_2.5 at the receptor site for the period when the ATOFMS was deployed ranged from 1 to 65% with an average contribution of 17%, while the remaining mass was attributed to other local and regional sources. These findings demonstrate the impact of metalworking facilities on air quality downwind and provide useful single particle signatures for future source apportionment studies in communities impacted by metalworking emissions.

Using Mie Scattering to Determine the Wavelength-Dependent Refractive Index of Polystyrene Beads with Changing Temperature

Polystyrene beads are often used as test particles in aerosol science. Here, a contact-less technique is reported for determining the refractive index of a solid aerosol particle as a function of wavelength and temperature (20-234 °C) simultaneously. Polystyrene beads with a diameter of 2 μm were optically trapped in air in the central orifice of a ceramic heating element, and Mie spectroscopy was used to determine the radius and refractive index (to precisions of 0.8 nm and 0.0014) of eight beads as a function of heating and cooling. Refractive index, n, as a function of wavelength, λ (0.480-0.650 μm), and temperature, T, in centigrade, was found to be n = 1.5753 - (1.7336 × 10^-4)T + (9.733 × 10^-3)λ^-2 in the temperature range 20 < T < 100 °C and n = 1.5877 - (2.9739 × 10^-4)T + (9.733 × 10^-3)λ^-2 in the temperature range 100 < T < 234 °C. The technique represents a step change in measuring the refractive index of materials across an extended range of temperature and wavelength in an absolute manner and with high precision.

Evidence for brown carbon absorption over the Bay of Bengal during the southwest monsoon season: a possible oceanic source

The near UV-visible light-absorbing organic carbon (OC) of ambient aerosols, referred to here as brown carbon (BrC), significantly influences the atmospheric radiative forcing on both regional and global scales. Here, we documented BrC absorption in the aqueous and methanol extracts of marine aerosols collected over the Bay of Bengal (BoB: September-October 2017) and a city, Visakhapatnam (May-June 2018), in southern India during the southwest monsoon (i.e., a transition period with weak continental impact). The absorption spectra of BrC over the BoB showed several peaks around 300-400 nm and differ from those observed over Visakhapatnam. The absorption coefficient of BrC over the BoB, unlike Visakhapatnam data, does not seem to covary with other chemical proxies of biomass burning (non-sea-salt or nss-K+) and coal combustion (nss-SO42-) in the continental outflows, suggesting a different source of BrC over the BoB. Besides, we observed higher proportions of water-insoluble organic carbon (WIOC/OC: 0.89 ± 0.02) and significant enrichment of Mg2+ over Na+ (i.e., relative to seawater) in BoB aerosols. This result and the backward air mass trajectories both hinted their major source of OC from marine-derived organic matter. In contrast, the absorption spectra of BrC over Visakhapatnam are like those from biomass burning emissions in the Indo-Gangetic Plain. This observation is further supported by the satellite-based fire counts and backward air mass trajectories. Therefore, our study underscores the BrC aerosols from the oceanic sources and southern India, hitherto unknown, and can improve our understanding of the regional climate effects of carbonaceous aerosols if included in models.

Diesel Soot and Amine-Containing Organic Sulfate Aerosols in an Arctic Oil Field

The rapid decrease in Arctic sea ice is motivating development and increasing oil and gas extraction activities. However, few observations of these local Arctic emissions exist, limiting the understanding of impacts on atmospheric composition and climate. To address this knowledge gap, the chemical composition of atmospheric aerosols was measured within the North Slope of Alaska oil fields during August and September 2016 using an aerosol time-of-flight mass spectrometer (ATOFMS) and a time-of-flight aerosol chemical speciation monitor (ToF-ACSM). Plumes from oil and gas extraction activities were characterized by soot internally mixed with sulfate (matching diesel soot) and organic carbon particles containing aminium sulfate salts. Sea spray aerosol at the coastal site was frequently internally mixed with sulfate and nitrate, from multiphase chemical processing from elevated NO_x and SO₂ within the oil field. Background (nonplume) air masses were characterized by aged combustion aerosol. No periods of "clean" (nonpolluted) Arctic air were observed. The composition of the nonrefractory aerosol measured with the ACSM was similar during plume and background periods and was consistent with the mass concentrations of nonrefractory particles measured by ATOFMS. Two ultrafine aerosol growth events were observed during oil field background periods and were correlated with fine mode amine-containing particles.

Brown carbon in the continental outflow to the North Indian Ocean

In this paper, we synthesize the size distribution and optical properties of the atmospheric water-soluble fraction of light-absorbing organic carbon (brown carbon; BrC) in the continental outflow from the Indo-Gangetic Plain (IGP) in South Asia to the North Indian Ocean. A comparison of the mass absorption coefficient of water-soluble BrC (babs-WSBrC-365nm) in PM2.5 with that in PM10 sampled over the Bay of Bengal reveals the dominance of BrC in fine mode. Furthermore, the babs-BrC-365nm shows a significant linear relationship with mass concentrations of airborne particulate matter, water-soluble organic carbon and non-sea-salt-K+ in the continental outflow from the IGP. This observation emphasizes the ubiquitous nature and significant contribution of water-soluble BrC from biomass burning emissions (BBEs). Comparing the absorption properties from this study with global datasets, it is discernible that BBEs dominate BrC absorption. Furthermore, the imaginary refractive index of water-soluble BrC (kWSBrC-365nm) in marine aerosols sampled over the North Indian Ocean during November is significantly higher than during December to January. Thus, significant temporal variability is associated with crop-residue burning emissions in the IGP on the composition of BrC over the North Indian Ocean. Our estimates show that the babs-WSBrC-365nm and kWSBrC-365nm from post-harvest crop-residue burning emissions in the IGP are much higher than the BBEs from the southeastern United States and Amazonian forest fires. Another major finding of this study is the lack of significant relationship between kWSBrC-365nm and the mass ratio of elemental carbon to particulate organic matter, as previously suggested by chamber experiments to model varying BrC absorption properties in ambient aerosols. Therefore, considerable spatio-temporal variability prevails among emission sources (wood burning vs. crop-residue burning), which needs to be considered when assessing the regional radiative forcing of BrC relative to major absorbing elemental carbon.

Real time analysis of lead-containing atmospheric particles in Guangzhou during wintertime using single particle aerosol mass spectrometry

The toxic effects of lead on human health and the environment have long been a focus of research. To explore sources of lead in Guangzhou, China, we investigated atmospheric lead-containing particles (LCPs) during wintertime using a single particle aerosol mass spectrometer (SPAMS). Based on mass spectral features, LCPs were classified into eight major particle types, including Pb-Cl and Pb-Cl-Li (coal combustion and waste incineration), Pb-Cl-EC and Pb-Cl-OC (diesel trucks and coal combustion), Pb-Cl-Fe (iron and steel industry), Pb-Cl-AlSi (dust), Pb-Sec (secondary formation), and Pb-Cl-Zn (industrial process); these sources (in parentheses) were identified by comparing atmospheric LCP mass spectra with authentic Pb emission source mass spectra. Sampling periods with LCP number fractions (NFs) more than three times the average LCP NF (APF = 4.35%) and below the APF were defined as high LCP NF periods (HLFPs: H1, H3, and H5) and low LCP NF APF periods (LLFPs: L2 and L4), respectively. Diurnal patterns and high Pb-Sec content during LLFPs indicate that photochemical activity and heterogeneous reactions may have controlled Pb-Sec particle formation. The inverse Pb-Cl and Pb-Sec particle diurnal trends during LLFPs suggest the replacement of Cl by sulfate and nitrate. On average over the five periods, ~ 76% of the LCPs likely arose from coal combustion and/or waste incineration, which were dominant sources during all five periods, followed by diesel trucks during LLFPs and iron- and steel-related sources during HLFPs; HLFP LCPs arose mainly from primary emissions. These results can be used to more efficiently control Pb emission sources and prevent harm to human and environmental health from Pb toxicity.

Impact of marine and continental sources on aerosol characteristics using an on-board SPAMS over southeast sea, China

The chemical composition of atmospheric aerosols was characterized using an on-board single particle aerosol mass spectrometer (SPAMS) over the Southeast China Sea. High-time-resolution observation of marine aerosols was carried out to clarify the source of aerosols and the interaction of marine and continental aerosols. Atmospheric aerosols were determined by the interaction of continental and marine sources over coastal area. Aerosols from continental sources flux into sea surfaces through deposition or diffusion, which results in the rapid decrease of continental aerosols. Five main subtypes of carbonaceous particles are identified as C_Al-Si, C_V-Ni, C_S, C_K, and C_secondary to clarify the impact of marine and continental sources on atmospheric aerosols. High fraction of C_Al-Si and C_secondary is present over XA (Xiamen anchorage), accounting for 23.8% and 18.6% of total carbonaceous particles. Contrarily, the relative percentage of C_S increases as the distance from land to sea increases. The influence of continental aerosols declines, while the contribution of marine aerosols increases as the distance from land to sea increases. Air masses in XA, LSA (land to sea area), SLA (sea to land area), and SA (sea area) were all from ocean during the observation period, resulting in low relative fraction of continental aerosols in SLA, SA, and LSA. High-time-resolution measurement is useful to understand aerosol source types and the impact of marine and continental sources on marine atmosphere aerosols.

Mass spectra features of biomass burning boiler and coal burning boiler emitted particles by single particle aerosol mass spectrometer

In this study, single particle mass spectra signatures of both coal burning boiler and biomass burning boiler emitted particles were studied. Particle samples were suspended in clean Resuspension Chamber, and analyzed by ELPI and SPAMS simultaneously. The size distribution of BBB (biomass burning boiler sample) and CBB (coal burning boiler sample) are different, as BBB peaks at smaller size, and CBB peaks at larger size. Mass spectra signatures of two samples were studied by analyzing the average mass spectrum of each particle cluster extracted by ART-2a in different size ranges. In conclusion, BBB sample mostly consists of OC and EC containing particles, and a small fraction of K-rich particles in the size range of 0.2-0.5μm. In 0.5-1.0μm, BBB sample consists of EC, OC, K-rich and Al_Silicate containing particles; CBB sample consists of EC, ECOC containing particles, while Al_Silicate (including Al_Ca_Ti_Silicate, Al_Ti_Silicate, Al_Silicate) containing particles got higher fractions as size increase. The similarity of single particle mass spectrum signatures between two samples were studied by analyzing the dot product, results indicated that part of the single particle mass spectra of two samples in the same size range are similar, which bring challenge to the future source apportionment activity by using single particle aerosol mass spectrometer. Results of this study will provide physicochemical information of important sources which contribute to particle pollution, and will support source apportionment activities.

Chemical Constituents of Carbonaceous and Nitrogen Aerosols over Thumba Region, Trivandrum, India

Aerosol filter samples collected at a tropical coastal site Thumba over Indian region were analysed for water-soluble ions, total carbon and nitrogen, organic carbon (OC), elemental carbon (EC), and water-soluble organic carbon/nitrogen and their sources for different seasons of the year. For the entire study period, the order of abundance of ions showed the dominance of secondary ions, such as SO₄^2-, NO₃^-, and NH₄⁺. On average, Mg²⁺ (56%), K⁺ (11%), SO₄^2- (8.8%), and Ca²⁺ (8.1%) contributions were from maritime influence. There was significant chloride depletion due to enhanced levels of inorganic acids, such as SO₄^2- and NO₃^-. Total carbon contributed 21% of the aerosol total suspended particulate matter in which 85% is organic carbon. Primary combustion-generated carbonaceous aerosols contributed 41% of aerosol mass for the entire study period. High average ratios of OC/EC (5.5 ± 1.8) and WSOC/OC (0.38 ± 0.11) suggest that organic aerosols are predominantly comprised of secondary species. In our samples, major fraction (89 ± 9%) was found to be inorganic nitrate in total nitrogen (TN). Good correlations (R ² ≥ 0.82) were observed between TN with NO₃^- plus NH₄⁺, indicating that nitrate and ammonium ions account for a significant portion of TN. The temporal variations in the specific carbonaceous aerosols and air mass trajectories demonstrated that several pollutants and/or their precursor compounds are likely transported from north western India and the oceanic regions.

Source characterization of urban particles from meat smoking activities in Chongqing, China using single particle aerosol mass spectrometry

A Single Particle Aerosol Mass Spectrometer (SPAMS) was deployed in the urban area of Chongqing to characterize the particles present during a severe particulate pollution event that occurred in winter 2014-2015. The measurements were made at a time when residents engaged in traditional outdoor meat smoking activities to preserve meat before the Chinese Spring Festival. The measurement period was predominantly characterized by stagnant weather conditions, highly elevated levels of PM_2.5, and low visibility. Eleven major single particle types were identified, with over 92.5% of the particles attributed to biomass burning emissions. Most of the particle types showed appreciable signs of aging in the stagnant air conditions. To simulate the meat smoking activities, a series of controlled smoldering experiments was conducted using freshly cut pine and cypress branches, both with and without wood logs. SPAMS data obtained from these experiments revealed a number of biomass burning particle types, including an elemental and organic carbon (ECOC) type that proved to be the most suitable marker for meat smoking activities. The traditional activity of making preserved meat in southwestern China is shown here to be a major source of particulate pollution. Improved measures to reduce emissions from the smoking of meat should be introduced to improve air quality in regions where smoking meat activity prevails.

Single particle mass spectral signatures from vehicle exhaust particles and the source apportionment of on-line PM2.5 by single particle aerosol mass spectrometry

In order to accurately apportion the many distinct types of individual particles observed, it is necessary to characterize fingerprints of individual particles emitted directly from known sources. In this study, single particle mass spectral signatures from vehicle exhaust particles in a tunnel were performed. These data were used to evaluate particle signatures in a real-world PM_2.5 apportionment study. The dominant chemical type originating from average positive and negative mass spectra for vehicle exhaust particles are EC species. Four distinct particle types describe the majority of particles emitted by vehicle exhaust particles in this tunnel. Each particle class is labeled according to the most significant chemical features in both average positive and negative mass spectral signatures, including ECOC, NaK, Metal and PAHs species. A single particle aerosol mass spectrometry (SPAMS) was also employed during the winter of 2013 in Guangzhou to determine both the size and chemical composition of individual atmospheric particles, with vacuum aerodynamic diameter (d_va) in the size range of 0.2-2μm. A total of 487,570 particles were chemically analyzed with positive and negative ion mass spectra and a large set of single particle mass spectra was collected and analyzed in order to identify the speciation. According to the typical tracer ions from different source types and classification by the ART-2a algorithm which uses source fingerprints for apportioning ambient particles, the major sources of single particles were simulated. Coal combustion, vehicle exhaust, and secondary ion were the most abundant particle sources, contributing 28.5%, 17.8%, and 18.2%, respectively. The fraction with vehicle exhaust species particles decreased slightly with particle size in the condensation mode particles.

Classification and Identification of Plant Fibrous Material with Different Species Using near Infrared Technique-A New Way to Approach Determining Biomass Properties Accurately within Different Species

Plant fibrous material is a good resource in textile and other industries. Normally, several kinds of plant fibrous materials used in one process are needed to be identified and characterized in advance. It is easy to identify them when they are in raw condition. However, most of the materials are semi products which are ground, rotted or pre-hydrolyzed. To classify these samples which include different species with high accuracy is a big challenge. In this research, both qualitative and quantitative analysis methods were chosen to classify six different species of samples, including softwood, hardwood, bast, and aquatic plant. Soft Independent Modeling of Class Analogy (SIMCA) and partial least squares (PLS) were used. The algorithm to classify different species of samples using PLS was created independently in this research. Results found that the six species can be successfully classified using SIMCA and PLS methods, and these two methods show similar results. The identification rates of kenaf, ramie and pine are 100%, and the identification rates of lotus, eucalyptus and tallow are higher than 94%. It is also found that spectra loadings can help pick up best wavenumber ranges for constructing the NIR model. Inter material distance can show how close between two species. Scores graph is helpful to choose the principal components numbers during the model construction.

Effect of typhoon on atmospheric aerosol particle pollutants accumulation over Xiamen, China

Great influence of typhoon on air quality has been confirmed, however, rare data especially high time resolved aerosol particle data could be used to establish the behavior of typhoon on air pollution. A single particle aerosol spectrometer (SPAMS) was employed to characterize the particles with particle number count in high time resolution for two typhoons of Soulik (2013) and Soudelor (2015) with similar tracks. Three periods with five events were classified during the whole observation time, including pre - typhoon (event 1 and event 2), typhoon (event 3 and event 4) and post - typhoon (event 5) based on the meteorological parameters and particle pollutant properties. First pollutant group appeared during pre-typhoon (event 2) with high relative contributions of V - Ni rich particles. Pollution from the ship emissions and accumulated by local processes with stagnant meteorological atmosphere dominated the formation of the pollutant group before typhoon. The second pollutant group was present during typhoon (event 3), while typhoon began to change the local wind direction and increase wind speed. Particle number count reached up to the maximum value. High relative contributions of V - Ni rich and dust particles with low value of NO3(-)/SO4(2-) was observed during this period, indicating that the pollutant group was governed by the combined effect of local pollutant emissions and long-term transports. The analysis of this study sheds a deep insight into understand the relationship between the air pollution and typhoon.

Real time analysis of lead-containing atmospheric particles in Beijing during springtime by single particle aerosol mass spectrometry

Using a single particle aerosol mass spectrometer (SPAMS), the chemical composition and size distributions of lead (Pb)-containing particles with diameter from 0.1 μm to 2.0 μm in Beijing were analyzed in the spring of 2011 during clear, hazy, and dusty days. Based on mass spectral features of particles, cluster analysis was applied to Pb-containing particles, and six major classes were acquired consisting of K-rich, carboneous, Fe-rich, dust, Pb-rich, and Cl-rich particles. Pb-containing particles accounted for 4.2-5.3%, 21.8-22.7%, and 3.2% of total particle number during clear, hazy and dusty days, respectively. K-rich particles are a major contribution to Pb-containing particles, varying from 30.8% to 82.1% of total number of Pb-containing particles, lowest during dusty days and highest during hazy days. The results reflect that the chemical composition and amount of Pb-containing particles has been affected by meteorological conditions as well as the emissions of natural and anthropogenic sources. K-rich particles and carbonaceous particles could be mainly assigned to the emissions of coal combustion. Other classes of Pb-containing particles may be associated with metallurgical processes, coal combustion, dust, and waste incineration etc. In addition, Pb-containing particles during dusty days were first time studied by SPAMS. This method could provide a powerful tool for monitoring and controlling of Pb pollution in real time.

Fine Iron Aerosols Are Internally Mixed with Nitrate in the Urban European Atmosphere

Atmospheric iron aerosol is a bioavailable essential nutrient playing a role in oceanic productivity. Using aerosol time-of-flight mass spectrometry (ATOFMS), the particle size (0.3-1.5 μm), chemical composition and mixing state of Fe-containing particles collected at two European urban sites (London and Barcelona) were characterized. Out of the six particle types accounting for the entire Fe-aerosol population, that arising from long-range transport (LRT) of fine Fe-containing particles (Fe-LRT, 54-82% across the two sites) was predominant. This particle type was found to be internally mixed with nitrate and not with sulfate, and likely mostly associated with urban traffic activities. This is in profound contrast with previous studies carried out in Asia, where the majority of iron-containing particles are mixed with sulfate and are of coal combustion origin. Other minor fine iron aerosol sources included mineral dust (8-11%), traffic brake wear material (1-17%), shipping/oil (1-6%), biomass combustion (4-13%) and vegetative debris (1-3%). Overall, relative to anthropogenic Asian Fe-sulfate dust, anthropogenic European dust internally mixed with additional key nutrients such as nitrate is likely to play a different role in ocean global biogeochemical cycles.

Local and regional components of aerosol in a heavily trafficked street canyon in central London derived from PMF and cluster analysis of single-particle ATOFMS spectra

Positive matrix factorization (PMF) has been applied to single particle ATOFMS spectra collected on a six lane heavily trafficked road in central London (Marylebone Road), which well represents an urban street canyon. PMF analysis successfully extracted 11 factors from mass spectra of about 700,000 particles as a complement to information on particle types (from K-means cluster analysis). The factors were associated with specific sources and represent the contribution of different traffic related components (i.e., lubricating oils, fresh elemental carbon, organonitrogen and aromatic compounds), secondary aerosol locally produced (i.e., nitrate, oxidized organic aerosol and oxidized organonitrogen compounds), urban background together with regional transport (aged elemental carbon and ammonium) and fresh sea spray. An important result from this study is the evidence that rapid chemical processes occur in the street canyon with production of secondary particles from road traffic emissions. These locally generated particles, together with aging processes, dramatically affected aerosol composition producing internally mixed particles. These processes may become important with stagnant air conditions and in countries where gasoline vehicles are predominant and need to be considered when quantifying the impact of traffic emissions.

PM₂.₅., EC and OC in atmospheric outflow from the Indo-Gangetic Plain: temporal variability and aerosol organic carbon-to-organic mass conversion factor

Temporal variability (November'09-March'10) in the mass concentrations of PM2.5, mineral dust, organic carbon and elemental carbon (OC and EC), water-soluble organic carbon (WSOC) and inorganic species (WSIS) has been studied in the atmospheric outflow to the Bay of Bengal from a sampling site [Kharagpur: 22.02°N, 87.11°E] in the Indo-Gangetic Plain (IGP). Based on diagnostic ratios of carbonaceous species [OC/EC ≈ 7.0 ± 2.2, WSOC/OC ≈ 0.52 ± 0.16, and K(+)/EC≈0.48±0.17], we document dominant impact from biomass burning emissions (wood-fuel and post-harvest agricultural-waste burning) in the IGP-outflow. Relatively high concentration of sulphate (SO4(2-) ≈ 6.9-25.3 μg m(-3); SO4(2-)/ΣWSIS=45-77%) and characteristic ratios of nss-SO4(2-)/EC (3.9 ± 2.1) and nss-SO4(2-)/OC (0.61 ± 0.46) provide information on absorption/scattering properties of aerosols. Based on quantitative assessment of individual components of PM2.5, we document aerosol organic carbon-to-organic mass (OC to OM) conversion factor centring at 1.5 ± 0.2 (range: 1.3-2.7) in the atmospheric outflow from IGP. The aerosol composition over the Bay of Bengal shows striking similarity with the diagnostic ratios documented for the IGP-outflow. Relatively high conversion factor for assessing the mass of organic aerosols over the Bay of Bengal (1.1-3.7) provides evidence for their oxidation during long-range atmospheric transport.

Source and mixing state of iron-containing particles in Shanghai by individual particle analysis

Bioavailable iron (Fe) is an essential nutrient that can control oceanic productivity, thereby impacting the global carbon budget and climate. Therefore it is of vital importance to identify chemical species and mixing state of Fe-containing particles in the air, which are demonstrated to pose substantial impact on bioavailability of Fe. Using a single particle aerosol mass spectrometer (SPAMS), ~2,000,000 individual particles with mass spectra were collected in Shanghai for nearly 22d during the winter of 2011. Number fraction of Fe-containing particles (NfFe) varied in a wide range (<1-15%) throughout the measurement. Fe-containing particles were mainly clustered into four chemical groups, comprising of Fe-rich, K-rich, Dust and V-containing particle types. Analysis of mass spectra and mixing state suggests that Fe-containing particles correspond to various sources in Shanghai, especially anthropogenic sources iron/steel industrial activities, and fly ashes from both biomass burning and coal combustion, accounting for ~55% and ~18%, respectively. However, invasion of dust from northern desert areas is suspected to be more responsible for the spikes of NfFe (>10%), when Dust particle type contributed to >50% of Fe-containing particles. It is also revealed that Fe-containing particles were internally mixed with secondary species (e.g., sulfate and nitrate). Anthropogenic K-rich and Fe-rich particles tended to associate with both sulfate and nitrate, and thus might lead to more fraction of soluble Fe, compared to Dust particles. These results imply that atmospheric processing of Fe-containing particles from various sources might vary and thus would change the bioavailability of atmospheric Fe.

Air quality impact and physicochemical aging of biomass burning aerosols during the 2007 San Diego wildfires

Intense wildfires burning >360000 acres in San Diego during October, 2007 provided a unique opportunity to study the impact of wildfires on local air quality and biomass burning aerosol (BBA) aging. The size-resolved mixing state of individual particles was measured in real-time with an aerosol time-of-flight mass spectrometer (ATOFMS) for 10 days after the fires commenced. Particle concentrations were high county-wide due to the wildfires; 84% of 120-400 nm particles by number were identified as BBA, with particles <400 nm contributing to mass concentrations dangerous to public health, up to 148 μg/m(3). Evidence of potassium salts heterogeneously reacting with inorganic acids was observed with continuous high temporal resolution for the first time. Ten distinct chemical types shown as BBA factors were identified through positive matrix factorization coupled to single particle analysis, including particles comprised of potassium chloride and organic nitrogen during the beginning of the wildfires, ammonium nitrate and amines after an increase of relative humidity, and sulfate dominated when the air mass back trajectories passed through the Los Angeles port region. Understanding BBA aging processes and quantifying the size-resolved mass and number concentrations are important in determining the overall impact of wildfires on air quality, health, and climate.

Analysis of atmospheric aerosols

Aerosols represent an important component of the Earth's atmosphere. Because aerosols are composed of solid and liquid particles of varying chemical complexity, size, and phase, large challenges exist in understanding how they impact climate, health, and the chemistry of the atmosphere. Only through the integration of field, laboratory, and modeling analysis can we begin to unravel the roles atmospheric aerosols play in these global processes. In this article, we provide a brief review of the current state of the science in the analysis of atmospheric aerosols and some important challenges that need to be overcome before they can become fully integrated. It is clear that only when these areas are effectively bridged can we fully understand the impact that atmospheric aerosols have on our environment and the Earth's system at the level of scientific certainty necessary to design and implement sound environmental policies.

Emission factors and real-time optical properties of particles emitted from traditional wood burning cookstoves

It is estimated that the combustion of biofuel generates 20% of all carbonaceous aerosols, yet these particles are studied less than those of other common sources. We designed and built a portable battery-operated emission-sampling cart to measure the real-time optical properties and other emission characteristics of biofuel cookstoves. In a field study in Honduras, we measured emission factors averaging 8.5 g/kg, higher than those found in previous laboratory studies. Strong flaming events emitted very dark particles with the optical properties of black particles. The elemental carbon to total carbon ratios ranged from 0.07 to 0.64, confirming that high elemental carbon fractions can be emitted from biofuel combustion and may not be used to distinguish fossil-fuel from biofuel sources when cooking is the dominant usage. Absorption Angstrom exponents, representing the dependence of absorption on wavelength, ranged from 1 (black) to 5 (yellow). Strongly absorbing particles with absorption inversely dependent on wavelength were emitted separately from particles with weak absorption and strong wavelength dependence; the latter probably contained conjugated aromatic compounds. Because combustion occurs in distinct phases, different types of carbonaceous aerosols from biofuel combustion are externally mixed at emission and may have different atmospheric fates.

Single particle characterization of ultrafine and accumulation mode particles from heavy duty diesel vehicles using aerosol time-of-flight mass spectrometry

The aerodynamic size and chemical composition of individual ultrafine and accumulation mode particle emissions (Da = 50-300 nm) were characterized to determine mass spectral signatures for heavy duty diesel vehicle (HDDV) emissions that can be used for atmospheric source apportionment. As part of this study, six in-use HDDVs were operated on a chassis dynamometer using the heavy heavy-duty diesel truck (HHDDT) five-cycle driving schedule under different simulated weight loads. The exhaust emissions were passed through a dilution/residence system to simulate atmospheric dilution conditions, after which an ultrafine aerosol time-of-flight mass spectrometer (UF-ATOFMS) was used to sample and characterize the HDDV exhaust particles in real-time. This represents the first study where refractory species including elemental carbon and metals are characterized directly in HDDV emissions using on-line mass spectrometry. The top three particle classes observed with the UF-ATOFMS comprise 91% of the total particles sampled and show signatures indicative of a combination of elemental carbon (EC) and engine lubricating oil. In addition to the vehicle make/year, the effects of driving cycle and simulated weight load on exhaust particle size and composition were investigated.

A single-particle characterization of a mobile Versatile Aerosol Concentration Enrichment System for exposure studies

BACKGROUND

An Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) was used to investigate the size and chemical composition of fine concentrated ambient particles (CAPs) in the size range 0.2-2.6 microm produced by a Versatile Aerosol Concentration Enrichment System (VACES) contained within the Mobile Ambient Particle Concentrator Exposure Laboratory (MAPCEL). The data were collected during a study of human exposure to CAPs, in Edinburgh (UK), in February-March 2004. The air flow prior to, and post, concentration in the VACES was sampled in turn into the ATOFMS, which provides simultaneous size and positive and negative mass spectral data on individual fine particles.

RESULTS

The particle size distribution was unaltered by the concentrator over the size range 0.2-2.6 microm, with an average enrichment factor during this study of approximately 5 (after dilution of the final air stream). The mass spectra from single particles were objectively grouped into 20 clusters using the multivariate K-means algorithm and then further grouped manually, according to similarity in composition and time sequence, into 8 main clusters. The particle ensemble was dominated by pure and reacted sea salt and other coarse inorganic dusts (as a consequence of the prevailing maritime-source climatology during the study), with relatively minor contributions from carbonaceous and secondary material. Very minor variations in particle composition were noted pre- and post-particle concentration, but overall there was no evidence of any significant change in particle composition.

CONCLUSION

These results confirm, via single particle analysis, the preservation of the size distribution and chemical composition of fine ambient PM in the size range 0.2-2.6 microm after passage through the VACES concentration instrumentation.

Determination of single particle mass spectral signatures from light-duty vehicle emissions

In this study, 28 light-duty gasoline vehicles (LDV) were operated on a chassis dynamometer at the California Air Resources Board Haagen-Smit Facility in El Monte, CA. The mass spectra of individual particles emitted from these vehicles were measured using aerosol time-of-flight mass spectrometry (ATOFMS). A primary goal of this study involves determining representative size-resolved single particle mass spectral signatures that can be used in future ambient particulate matter source apportionment studies. Different cycles were used to simulate urban driving conditions including the federal testing procedure (FTP), unified cycle (UC), and the correction cycle (CC). The vehicles were selected to span a range of catalytic converter (three-way, oxidation, and no catalysts) and engine technologies (vehicles models from 1953 to 2003). Exhaust particles were sampled directly from a dilution and residence chamber system using particle sizing instruments and an ATOFMS equipped with an aerodynamic lens (UF-ATOFMS) analyzing particles between 50 and 300 nm. On the basis of chemical composition, 10 unique chemical types describe the majority of the particles with distinct size and temporal characteristics. In the ultrafine size range (between 50 and 100 nm), three elemental carbon (EC) particle types dominated, all showing distinct EC signatures combined with Ca, phosphate, sulfate, and a lower abundance of organic carbon (OC). The relative fraction of EC particle types decreased as particle size increased with OC particles becoming more prevalent above 100 nm. Depending on the vehicle and cycle, several distinct OC particle types produced distinct ion patterns, including substituted aromatic compounds and polycyclic aromatic hydrocarbons (PAH), coupled with other chemical species including ammonium, EC, nitrate, sulfate, phosphate, V, and Ca. The most likely source of the Ca and phosphate in the particles is attributed to the lubricating oil. Significant variability was observed in the chemical composition of particles emitted within the different car categories as well as for the same car operating under different driving conditions. Two-minute temporal resolution measurements provide information on the chemical classes as they evolved during the FTP cycle. The first two minutes of the cold start produced more than 5 times the number of particles than any other portion of the cycle, with one class of ultrafine particles (EC coupled with Ca, OC, and phosphate) preferentially produced. By number, the three EC with Ca classes (which also contained OC, phosphate, and sulfate) were the most abundant classes produced by the nonsmoking vehicles. The smoker category produced the highest number of particles, with the dominant classes being OC comprised of substituted monoaromatic compounds and PAHs, coupled with Ca and phosphate, thus suggesting used lubricating oil was associated with many of these particles. These studies show, by number, EC particles dominate gasoline emissions in the ultrafine size range particularlyforthe lowest emitting newer vehicles, suggesting the EC signature alone cannot be used as a unique tracer for diesels. This represents the first report of high time- and size-resolved chemical composition data showing the mixing state of nonrefractory elements in particles such as EC for vehicle emissions during dynamometer source testing.