Soil Dust Aerosols Research Articles

Observationally constrained regional variations of shortwave absorption by iron oxides emphasize the cooling effect of dust

Abstract. The composition of soil dust aerosols derives from the mineral abundances in the parent soils that vary across dust source regions. Nonetheless, Earth system models (ESMs) have traditionally represented mineral dust as a globally homogeneous species. The growing interest in modeling dust mineralogy, facilitated by the recognized sensitivity of the dust climate impacts to composition, has motivated state-of-the-art ESMs to incorporate the mineral speciation of dust along with its effect upon the dust direct radiative effect (DRE). In this work, we enable the NASA Goddard Institute for Space Studies ModelE2.1 to calculate the shortwave (SW) DRE accounting for the regionally varying soil mineralogy. Mineral–radiation interaction at solar wavelengths is calculated according to two alternative coupling schemes: (1) external mixing of three mineral components that are optically distinguished, one of which contains embedded iron oxides; (2) a single internal mixture of all dust minerals with a dynamic fraction of iron oxides that varies regionally and temporally. We link dust absorption to the fractional mass of iron oxides based on recent chamber measurements using natural dust aerosol samples. We show that coupled mineralogy overall enhances the scattering by dust, and thus the global cooling, compared to our control run with globally uniform composition. According to the external mixing scheme, the SW DRE at the top of atmosphere (TOA) changes from −0.25 to -0.30Wm-2, corresponding to a change in the net DRE, including the longwave effect, from −0.08 to -0.12Wm-2. The cooling increase is accentuated when the internal mixing scheme is configured: the SW DRE at the TOA becomes -0.34Wm-2 with a net DRE of -0.15Wm-2. The varying composition modifies the regional distribution of single scattering albedo (SSA), whose variations in specific regions can be remarkable (above 0.03) and significantly modify the regional SW DRE. Evaluation against the AErosol RObotic NETwork (AERONET) shows that explicit representation of soil mineralogy and its regional variations reduces the low bias of model dust SSA while improving the range of variability across stations and calendar months. Despite these improvements, the moderate spatiotemporal correlation with AERONET reveals remaining modeling challenges and the need for more accurate measurements of mineral fractions in soils.

Identification of potential source regions and long-range transport routes/channels of marine PM2.5 at remote sites in East Asia

Long-range transport (LRT) of air masses in East Asia and their impacts on marine PM2.5 were explored. Situated in the leeward region of East Asia, Taiwan Island marked by its elevated Central Mountain Range (CMR) separates air masses into two distinct air currents. This study aims to investigate the transport of PM2.5 from the north to the leeward region. Six transport routes (A-F) were identified and further classified them into three main channels (i.e. East, West, and South Channels) based on their transport routes and potential sources. Green Island (Site GR) and Hengchun Peninsula (Site HC) exhibited similarities in their transport routes, with Central China, North China, and Korean Peninsula being the major source regions of PM2.5, particularly during the Asian Northeastern Monsoons (ANMs). Dongsha Island (Site DS) was influenced by both Central China and coastal regions of East China, indicating Asian continental outflow (ACO) as the major source of PM2.5. The positive matrix factorization (PMF) analysis of PM2.5 resolved that soil dust, sea salts, biomass burning, ship emissions, and secondary aerosols were the major sources. Northerly Channels (i.e. East and West Channels) were primarily influenced by ship emissions and secondary aerosols, while South Channel was dominated by oceanic spray and soil dust. The results of W-PSCF and W-CWT analysis indicated that three remote sites experienced significant contributions from Central China in the highest PM2.5 concentration range (75–100%). In contrast, PM2.5 in the 0–25% and 25–50% ranges primarily originated from the open seas, with ship emissions being the prominent source. It suggested that northern regions with heavy industrialization and urbanization have impacts on high PM2.5 concentrations, while open seas are the main sources of low PM2.5 concentrations.

Modeling dust mineralogical composition: sensitivity to soil mineralogy atlases and their expected climate impacts

Abstract. Soil dust aerosols are a key component of the climate system, as they interact with short- and long-wave radiation, alter cloud formation processes, affect atmospheric chemistry and play a role in biogeochemical cycles by providing nutrient inputs such as iron and phosphorus. The influence of dust on these processes depends on its physicochemical properties, which, far from being homogeneous, are shaped by its regionally varying mineral composition. The relative amount of minerals in dust depends on the source region and shows a large geographical variability. However, many state-of-the-art Earth system models (ESMs), upon which climate analyses and projections rely, still consider dust mineralogy to be invariant. The explicit representation of minerals in ESMs is more hindered by our limited knowledge of the global soil composition along with the resulting size-resolved airborne mineralogy than by computational constraints. In this work we introduce an explicit mineralogy representation within the state-of-the-art Multiscale Online Nonhydrostatic AtmospheRe CHemistry (MONARCH) model. We review and compare two existing soil mineralogy datasets, which remain a source of uncertainty for dust mineralogy modeling and provide an evaluation of multiannual simulations against available mineralogy observations. Soil mineralogy datasets are based on measurements performed after wet sieving, which breaks the aggregates found in the parent soil. Our model predicts the emitted particle size distribution (PSD) in terms of its constituent minerals based on brittle fragmentation theory (BFT), which reconstructs the emitted mineral aggregates destroyed by wet sieving. Our simulations broadly reproduce the most abundant mineral fractions independently of the soil composition data used. Feldspars and calcite are highly sensitive to the soil mineralogy map, mainly due to the different assumptions made in each soil dataset to extrapolate a handful of soil measurements to arid and semi-arid regions worldwide. For the least abundant or more difficult-to-determine minerals, such as iron oxides, uncertainties in soil mineralogy yield differences in annual mean aerosol mass fractions of up to ∼ 100 %. Although BFT restores coarse aggregates including phyllosilicates that usually break during soil analysis, we still identify an overestimation of coarse quartz mass fractions (above 2 µm in diameter). In a dedicated experiment, we estimate the fraction of dust with undetermined composition as given by a soil map, which makes up ∼ 10 % of the emitted dust mass at the global scale and can be regionally larger. Changes in the underlying soil mineralogy impact our estimates of climate-relevant variables, particularly affecting the regional variability of the single-scattering albedo at solar wavelengths or the total iron deposited over oceans. All in all, this assessment represents a baseline for future model experiments including new mineralogical maps constrained by high-quality spaceborne hyperspectral measurements, such as those arising from the NASA Earth Surface Mineral Dust Source Investigation (EMIT) mission.

Different Reactivity of Birnessite and Cryptomelane toward Isoprene: Effect of Structure, Morphology, and Exposed Faces

This study investigates the adsorption and oxidation of isoprene, the most abundant biogenic volatile organic compound, on two common Mn(IV) (hydr)oxides in Earth’s surface environment, birnessite and cryptomelane. Both minerals show high adsorption capability toward isoprene under increasing environmental temperature and low relative humidity, whereas the adsorbed isoprene on birnessite is oxidized into carboxylate species, mainly formate. For both Mn(IV) (hydr)oxides, the adsorption of isoprene not only reduces Mn4+ to Mn3+ but also gives rise to the slight distortion of the crystal structure. Compared to cryptomelane, birnessite exhibits better adsorption and oxidation capability of isoprene, which is improved by the decrease in crystallinity. This is attributed to the high density of oxygen anions on the (001) surface, owing to the participation of lattice oxygen, electrophilic adsorbed oxygen, and hydroxyl groups in the oxidation of isoprene. For cryptomelane, the particles with short and thick nanorods show higher adsorption capacity but lower oxidizability than those with long and sharp nanorods, as the (001) surface of cryptomelane prefers to adsorb isoprene and Mn4+ in long sharp nanorods and accept more electrons from isoprene. Based on the experimental results, we propose that Mn(IV) (hydr)oxide in soil dust aerosols is an important regulator of atmospheric isoprene, which enhances the bioavailability of both isoprene and Mn(IV) (hydr)oxides.

A New Chemistry-Climate Model GRIMs-CCM: Model Evaluation of Interactive Chemistry-Meteorology Simulations

We describe a new chemistry-climate model, Global/Regional Integrated Model system Chemistry Climate Model (GRIMs-CCM), developed by coupling the chemistry modules of the GEOS-Chem chemical transport model to the GRIMs general circulation model. The GRIMs-CCM is driven by meteorological variables simulated by the GRIMs and uses simulated gas and aerosol concentrations to calculate the radiative transfer equations at each time step. The model is evaluated by comparing ozone and aerosol concentrations with respective observations from the surface networks and the satellite datasets. It is found that the GRIMs-CCM successfully reproduces the observed spatial distributions of annual-mean aerosol optical depth and captures the seasonal and latitudinal variations of total column ozone. The evaluation of simulated aerosols in surface air against the observations reveals that the model reproduces the observed temporal and spatial variations but shows biases in soil dust aerosols. We also estimate the climatic impact of aerosols by conducting two sets of 10-year simulations for the preindustrial and present conditions. The GRIMs-CCM shows the aerosol radiative forcing of − 0.30 W m−2 from the preindustrial to present-day climates, comparable to the values from other climate model intercomparison projects. These results suggest that the GRIMs-CCM is suitable for studying chemistry-climate interactions and their changes over time.

Sources of airborne particulate matter-bound metals and spatial-seasonal variability of health risk potentials in four large cities, South Korea

Fifteen airborne particulate matter-bound metals were analyzed at 14 sites in four large cities (Seoul, Incheon, Busan, Daegu) in South Korea, between August 2013 and June 2017. Among the seven sources resolved by positive matrix factorization, soil dust and marine aerosol accounted for the largest and second largest portions in the three cities; however, in Seoul, soil dust and traffic occupied the largest and the second largest, respectively. Non-carcinogenic risk assessed by inhalation of eight metals (Cd, Co, Ni, Pb, As, Al, Mn, and V) was greater than the hazard index (HI) of 1 at four sites located at or near the industrial complexes. Cumulative incremental lifetime cancer risk (ILCR) due to exposure to five metals (Cd, Co, Ni, Pb, and As) exceeded the 10−6 cancer benchmark at 14 sites and 10−5 at six sites, which includes four sites with HI greater than 1. The largest contributor to ILCR was coal combustion in Seoul, Incheon, and Daegu, and industry sources in Busan. Moreover, industry sources were the largest contributors to non-carcinogenic risk in Seoul, Busan, and Daegu, and soil dust was in Incheon. Incheon had the highest HI in spring because of the higher contribution of soil dust sources than in other seasons. The higher ILCR in Incheon in spring and winter and higher ILCR and HI in Daegu in autumn were mainly due to the influence of industry or coal combustion sources. Statistically significant differences in the ILCR and HI values among the sampling sites in Busan and Daegu resulted from the higher contribution of industry sources at a certain site in the respective city.

Soil dust aerosol in the atmosphere: sources, quantities, properties (overview)

Dust is a major component of atmospheric aerosols – 75% of the global aerosol load. Natural and anthropogenic sources are listed, as well as dust research methods. According to different estimates, the average mineral dust load in the atmosphere ranges from 20 to 33 Tg, and the annual dust emission is 1 200–5 900 Tg/year. Reports from the Intergovernmental Panel on Climate Change (IPCC) inform about the total direct radiative forcing of dust ranging from -0.56 to +0.1 W/m2, with little scientific understanding of the processes leading to this result. The particle size, including soil aerosol, is divided into fine (<5 μm), medium (5–10(20) μm) and coarse (>20 μm) dust. Fine dust cools the global climate due to dispersion of solar radiation, while coarse dust (greater than 5 μm) warms the climate by absorbing solar and thermal radiation. However, the coarse dust (above 20 μm) remains poorly investigated, with very little data on its content and emission. Recent studies suggest that coarse dust (17 Tg), missed by the global models, contributes on average 0.15 W/m2 (0.10 to 0.24 W/m2) to atmospheric heating and also affects the global distribution of clouds and precipitation. In addition, soil dust is characterised by a complex and diverse particle shape and structure, heterogeneous mineralogical and chemical composition; due to its dispersion ability and large surface area dust reacts with other types of aerosols, resulting in the formation of different films on the particle surface or internal mixing. All this significantly changes the optical properties of mineral dust and complicates the development of models for its investigation.

Real-time source apportionment of fine particle inorganic and organic constituents at an urban site in Delhi city: An IoT-based approach

An Internet of things (IoT) based real-time source apportionment methodology of PM2.5 aerosol was developed and demonstrated for an urban site in Delhi city, India. A dashboard was designed and developed to display in real-time the data from low-cost PM sensors, PM2.5 chemical speciation monitors data, and source apportionment results using a chemical mass balance (CMB) algorithm performed on an IoT platform. Ten source profiles were used in CMB modeling for the urban site of Delhi. Major contributing source categories were identified as biomass burning, soil dust, vehicle, coal combustion, waste burning, industries, and secondary aerosol. Biomass burning and secondary aerosol was a significant contributor in autumn and winter (23–30%), while soil dust exhibited highs during summer. The vehicle sources remained consistent over the year with an ∼8–12% contribution. Similarly, consistent seasonal contributions of waste burning, and industries were observed. Coal combustion was found to be a substantial contributor in Delhi during the monsoon and summer; primarily from regional power plants outside the Delhi region, and/or from smaller-scale industrial outfits in the vicinity of the Delhi region. Hourly resolved sources of fine particles were displayed in real-time on a customized dashboard. This is the first such demonstration of an IoT-based real-time source apportionment in India (and in many parts of the world). The approach developed could be a resource to identify and control emissions from local and regional sources in real-time, and actions to curtail air quality and health detriment in a scientifically sound manner.

Aerosol characteristics over the Tibetan Plateau simulated with a coupled aerosol–climate model (FGOALS-f3-L) 耦合气溶胶气候模式FGOALS-f3-L模拟青藏高原地区气溶胶特性

This study presents the simulated aerosol spatiotemporal characteristics over the Tibetan Plateau (TP) with a newly developed coupled aerosol–climate model (FGOALS-f3-L). The aerosol properties are simulated over the TP for the period 2002–11. The results indicate that soil dust, sulfate, and carbonaceous aerosols (black carbon (BC), organic carbon (OC) and BC/OC) account for 53.6%, 32.2%, and 14.2% of the total aerosol mass over the TP, respectively. The simulated aerosol surface mass concentrations and aerosol optical depths (AODs) are evaluated with ground-based and satellite observations, respectively. Underestimations of the aerosol surface mass concentration are found at the Lhasa site, especially for BC and OC. The spatial distribution and interannual variation of AOD are consistent with MODIS observations, with the RMSE of 0.081 and bias of 0.036. Due to the uncertainty of the parameterization of dust emissions, the model's performance in summer and autumn is much better than that in spring.摘要基于新耦合气溶胶气候模式FGOALS-f3-L模拟分析了2002–2011年青藏高原地区气溶胶时空分布特征.结果表明:青藏高原地区, 沙尘,硫酸盐,碳质气溶胶 (包括黑碳,有机碳和混合碳) 地表质量浓度分别占比为53.6%, 32.2%, 14.2%;在拉萨站点, 模拟的气溶胶地表质量浓度被低估, 尤其是黑碳和有机碳气溶胶;模拟的气溶胶光学厚度 (AOD) 时空分布与卫星观测结果较为一致, 均方根误差和偏差分别为0.081和0.036;由于模式中沙尘排放参数化的不确定性, 模式对AOD的模拟效果在夏季和秋季优于春季

Trace metal composition of rainwater and aerosol from Kolkata, a megacity in eastern India

India is one of the world's wettest countries receiving over 1000 mm of rainfall annually and also one of the countries experiencing regular floods and droughts. This study quantifies elemental composition of rainwater and aerosol collected simultaneously during 2019 monsoon season from Kolkata, a megacity in Eastern India marred by air pollution to understand sources and estimate wet deposition flux. Elemental composition (Na, Ca, Mg, Al, Fe, Mn, V, Cr, Ni, Cu, Zn, Cd, Pb) of rainwater was measured in ICP MS along with pH, conductivity, chloride (Cl−), nitrate (NO3−) and sulphate (SO42−) ions. Trace metal composition of PM10 collected in between rain events were also analysed to understand anthropogenic sources and atmospheric leaching of metals. Crustal enrichment factors (EFs) identified anthropogenic sources for Ni, Cu, Zn, Pb and Cd in PM10. Principal component analysis (PCA) identified three anthropogenic sources, industrial emission, traffic emission and waste incineration in addition to the natural background from the crustal dust for the aerosol metals. Majority of rainwater samples had almost neutral pH (average 6.81 ± 0.74, 1SD), with a range of 5.4 to 8.0. In rainwater, Na and Cl− had marine origin and majority of SO42− had non-marine sources. Cu, Zn, Cd, V, Cr and Pb concentrations of rainwater follow the trend in PM10 most likely because part of the metals are derived from aerosol leaching. The EFs indicated that all the metals except Fe had anthropogenic origin in rainwater. The wet deposition fluxes were in the order of Ca > Na > Mg > Al > Zn > Fe > Mn > Cu > Ni > Pb > Cr > V > Cd. Overall, the results show significant influence of anthropogenic sources on rainwater chemistry in addition to natural soil dust and marine aerosols. In spite of anthropogenic influence, the trace metal and anion concentrations in rainwater are well within the limits prescribed by World Health Organization (WHO), European Union (EU), USA and Indian Drinking Water Standards.

Chemical Characteristics and Identification of PM10 Sources in Two Lima Districts, Peru

This study evaluates the concentration of PM10 and PM2.5 and identification of source in the districts of San Juan de Lurigancho and Puente Piedra (PPD) in Lima-Peru. The samples were collected from April to May 2017 by the National Meteorology and Hydrology Service of Peru (Senamhi). The concentration of PM10 and PM2.5, measured by gravimetric techniques, exceeded the international (WHO) and national standards; with maximum values for PM10 and PM2.5 of 160 and 121.56 µg/ m3 in PPD and 295.06 and 154.58 µg/ m3 in SJL. Identification of sources by the Positive Matrix Factorization Model (PMF 5.0) and Principal Component Analysis (ACP), showed similar sources for both districts. In SJL, the combination of vehicular traffic and resuspension of soil dust, marine aerosol and iron and steel industry was determined, while in PPD the resuspension of soil dust, vehicular source, industrial activity and marine aerosol.

Investigating size-segregated sources of elemental composition of particulate matter in the South China Sea during the 2011 <i>Vasco</i> cruise

Abstract. The South China Sea (SCS) is a receptor of numerous natural and anthropogenic aerosol species from throughout greater Asia. A combination of several developing countries, archipelagic and peninsular terrain, a strong Asian monsoon climate, and a host of multi-scale meteorological phenomena make the SCS one of the most complex aerosol–meteorological systems in the world. However, aside from the well-known biomass burning emissions from Indonesia and Borneo, the current understanding of aerosol sources is limited, especially in remote marine environments. In September 2011, a 2-week research cruise was conducted near Palawan, Philippines, to sample the remote SCS environment. Size-segregated aerosol data were collected using a Davis Rotating Uniform size-cut Monitor (DRUM) sampler and analyzed for concentrations of 28 elements measured via X-ray fluorescence (XRF). Positive matrix factorization (PMF) was performed separately on the coarse, fine, and ultrafine size ranges to determine possible sources and their contributions to the total elemental particulate matter mass. The PMF analysis resolved six sources across the three size ranges: biomass burning, oil combustion, soil dust, a crustal–marine mixed source, sea spray, and fly ash. Additionally, size distribution plots, time series plots, back trajectories and satellite data were used in interpreting factors. The multi-technique source apportionment revealed the presence of biogenic sources such as soil dust, sea spray, and a crustal–marine mixed source. Anthropogenic sources were also identified: biomass burning, oil combustion, and fly ash. Mass size distributions showed elevated aerosol concentrations towards the end of the sampling period, which coincided with a shift of air mass back trajectories to southern Kalimantan. Covariance between coarse-mode soil dust and fine-mode biomass burning aerosols were observed. Agreement between the PMF and the linear regression analyses indicates that the PMF solution is robust. While biomass burning is indeed a key source of aerosol, this study shows the presence of other important sources in the SCS. Identifying these sources is not only key for characterizing the chemical profile of the SCS but, by improving our picture of aerosol sources in the region, also a step forward in developing our understanding of aerosol–meteorology feedbacks in this complex environment.

Classroom indoor PM2.5 sources and exposures in inner-city schools

Children spend over 6 h a day in schools and have higher asthma morbidity from school environmental exposures. The present study aims to determine indoor and outdoor possible sources affecting indoor PM2.5 in classrooms. Weeklong indoor PM2.5 samples were collected from 32 inner-city schools from a Northeastern U.S. community during three seasons (fall, winter and spring) during the years 2009 to 2013. Concurrently, daily outdoor PM2.5 samples were taken at a central monitoring site located at a median distance of 4974 m (range 1065–11,592 m) from the schools. Classroom indoor concentrations of PM2.5 (an average of 5.2 μg/m3) were lower than outdoors (an average of 6.5 μg/m3), and these averages were in the lower range compared to the findings in other schools' studies. The USEPA PMF model was applied to the PM2.5 components measured simultaneously from classroom indoor and outdoor to estimate the source apportionment. The major sources (contributions) identified across all seasons of indoor PM2.5 were secondary pollution (41%) and motor vehicles (17%), followed by Calcium (Ca)-rich particles (12%), biomass burning (15%), soil dust (6%), and marine aerosols (4%). Likewise, the major sources of outdoor PM2.5 across all seasons were secondary pollution (41%) and motor vehicles (26%), followed by biomass burning (17%), soil dust (7%), road dust (3%), and marine aerosols (1%). Secondary pollution was the greatest contributor to indoor and outdoor PM2.5 over all three seasons, with the highest contribution during spring with 53% to indoor PM2.5 and 45% to outdoor PM2.5. Lower contributions of this source during fall and winter are most likely attributed to less infiltration indoors. In contrast, the indoor contribution of motor vehicles source was highest in the fall (29%) and winter (25%), which was presumably categorized by a local source. From the relationship between indoor-to-outdoor sulfur ratios and each source contribution, we also estimated the local and regional influence on indoor PM2.5 concentration. Overall, the observed differences to indoor PM2.5 are related to seasonality, and the distinct characteristics and behavior of each classroom/school.

Interannual Variation of Metal Elements and Water-Soluble Ions in PM2.5 During Wintertime in Xinxiang and Their Source Apportionment

To study the interannual variations of chemical composition and source apportionment, a field campaign was carried out to collect the PM2.5 temperance sample during the winter of 2015 and the winter of 2016 in Xinxiang urban areas. PM2.5 mass concentration, metal elements, and the water-soluble ions were determined and meteorological factors were recorded simultaneously. The results showed that the daily mean concentrations of PM2.5 indicated serious pollution with values of 226 μg·m-3 and 224 μg·m-3 in 2015 and 2016, respectively. The Cd and Pb elements in PM2.5 were significantly enriched, with EF more than 1000. However, compared with 2015, the enrichment effect of most metal elements showed a trend of decrease in 2016. The water-soluble ions were mainly composed of SO42-, NO3-, and NH4+. The results showed a trade-off effect between metal elements and water-soluble ions in the two study periods. The results of PCA and PMF analyses show that there were four main emission sources in Xinxiang city in winter, namely dust, secondary source, industrial source, and fossil fuel combustion source. Moreover, the main sources of PM2.5 was the mixed source of soil and building dust and secondary aerosol pollution, with contributions of 37.46% and 34.94% in the winters of 2015 and 2016, respectively.

Investigation of Aerosol Properties and Structures in Two Representative Meteorological Situations over the Vipava Valley Using Polarization Raman LiDAR

Vipava valley in Slovenia is a representative hot-spot for complex mixtures of different aerosol types of both anthropogenic and natural origin. Aerosol loading distributions and optical properties were investigated using a two-wavelength polarization Raman LiDAR, which provided extinction coefficient, backscatter coefficient, depolarization ratio, backscatter Ångström exponent and LiDAR ratio profiles. Two different representative meteorological situations were investigated to explore the possibility of identifying aerosol types present in the valley. In the first case, we investigated the effect of strong downslope (Bora) wind on aerosol structures and characteristics. In addition to observing Kelvin–Helmholtz instability above the valley, at the height of the adjacent mountain ridge, we found new evidence for Bora-induced processes which inject soil dust aerosols into the free troposphere up to twice the height of the planetary boundary layer (PBL). In the second case, we investigated aerosol properties and distributions in stable weather conditions. From the observed stratified vertical aerosol structure and specific optical properties of different layers we identified predominant aerosol types in these layers.

Chemical Characterization and Source Apportionment of PM2.5 in a Nonattainment Rocky Mountain Valley.

Severe air pollution has significant adverse health effects and poses a threat to public health in many communities, including nonattainment areas in the Unites States. To develop effective control strategies to reduce air pollution with minimum economic cost, one of the biggest challenges is to quantify the contributions from different sources. By combining chemical analyses, Positive Matrix Factorization modeling, and emission inventory development, this study identified primary and secondary sources of particulate matter with a diameter of <2.5 μm (PM) in a nonattainment Rocky Mountain valley (i.e., West Silver Valley [WSV]) in Idaho. The results show that biomass burning is the dominant source and contributes ∼84% of the PM concentration in the valley. The study also identified influences on the WSV PM concentrations from traffic (7.4%), soil dust (3.4%), and secondary aerosols (4.8%). The results of this paper represent the first report on the chemical composition and source apportionment of PM in mountain valleys of northern Idaho and have been used to develop effective strategies to reduce the PM concentrations in the WSV. Moreover, this study provides detailed equations and methods in PM speciation, accounting for artifacts of the chemical analysis, Positive Matrix Factorization modeling, and emission inventory development, which can be used for source apportionment of severe air pollution in other regions.

Chemical Characteristics and Source Apportionment of PM2.5 and Long-Range Transport from Northeast Asia Continent to Niigata in Eastern Japan

Seasonal intensive sampling was undertaken for two weeks during each of four seasons from May 2015 to February 2017 at Niigata-Maki station in Niigata, eastern Japan. Daily mean concentrations of PM2.5 ranged from 4.2 µg m–3 to 33.4 µg m–3 during the observation period, which were lower than Japanese Environmental Quality Standard for PM2.5 (35 µg m–3). The higher concentrations of SO42−, NH4+ and OC were observed in spring and summer, which may result from photochemical activity and secondary OC production. The major chemical components of PM2.5 at Niigata-Maki site were SO42−, NO3−, NH4+, OCM, EC and crustal elements. Compared with data at other urban sites, a lower concentration of EC and NO3− and higher OC/EC ratio were observed at Niigata-Maki site, which may result from no significant stationary source and low vehicular traffic in the rural site. PM2.5 source apportionment was characterized by positive matrix factorization (PMF) analysis, and the results inferred four major sources: sea salt (10.2%), biomass combustion (18.9%), soil dust (13.2%) and secondary aerosol (44.4%). The potential source contribution function (PSCF) analysis suggested that the major sources of secondary aerosol and sea salts were domestic in southwest Japan and the Sea of Japan, whereas the sources of biomass combustion and soil dust in specific seasons were long range transportation from the Northeast Asian continent (NEA). Comparing with previous studies in western Japan, this study showed a large domestic contribution of southwest Japan for secondary aerosol, while a larger contribution of the NEA was observed in the previous studies. Significant contribution of biomass combustion from northeast China in autumn, and local area in Niigata and southwest Japan in the other seasons was uniquely observed in this study.

Ice nucleation activity of agricultural soil dust aerosols from Mongolia, Argentina, and Germany

AbstractSoil dust particles emitted from agricultural areas contain considerable mass fractions of organic material. Also, soil dust particles may act as carriers for potentially ice‐active biological particles. In this work, we present ice nucleation experiments conducted in the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) cloud chamber. We investigated the ice nucleation efficiency of four types of soil dust from different regions of the world. The results are expressed as ice nucleation active surface site (INAS) densities and presented for the immersion freezing and the deposition nucleation mode. For immersion freezing occurring at 254 K, samples from Argentina, China, and Germany show ice nucleation efficiencies which are by a factor of 10 higher than desert dusts. On average, the difference in ice nucleation efficiencies between agricultural and desert dusts becomes significantly smaller at temperatures below 247 K. In the deposition mode the soil dusts showed higher ice nucleation activity than Arizona Test Dust over a temperature range between 232 and 248 K and humidities RHice up to 125%. INAS densities varied between 109 and 1011 m−2 for these thermodynamic conditions. For one soil dust sample (Argentinian Soil), the effect of treatments with heat was investigated. Heat treatments (383 K) did not affect the ice nucleation efficiency observed at 249 K. This finding presumably excludes proteinaceous ice‐nucleating entities as the only source of the increased ice nucleation efficiency.

Chemical characterization and source apportionment of PM2.5 in a semi-arid and petrochemical-industrialized city, Northwest China

Daily PM2.5 samples were collected in 2014 at a suburban petrochemical industrial site and a downtown site in Lanzhou city, Northwest China. Major chemical components in PM2.5, including water-soluble ions, metal elements, and organic and elemental carbon (OC and EC) were determined. The chemical mass closure method and the ISORROPIA II thermodynamic equilibrium model were used to reconstruct PM2.5 mass and quantify the combinations of NH4+, SO42− and NO3− to PM2.5. Positive matrix factorization (PMF) model was employed to apportion potential sources of PM2.5. The annual average PM2.5 concentration was 93.7±49.6μgm−3 at the suburban petrochemical industrial site and 88.9±52.0μgm−3 at the urban site, with the highest seasonal average in winter and the lowest in summer at both sites. Mineral dust was identified as the highest contributor to PM2.5 in spring, while water-soluble inorganic ions and carbonaceous aerosols were the dominant chemical components in other seasons. The correlation relationships between OC and EC and between K+ and EC suggested that coal combustion and vehicle exhaust were the major sources of carbonaceous aerosols in Lanzhou. Six major sources were identified by the PMF model. Coal combustion, soil dust, traffic emissions, and secondary inorganic aerosols were the dominant contributors, together accounting for 82% of PM2.5 mass.

Size-distribution of airborne polycyclic aromatic hydrocarbons and other organic source markers in the surroundings of a cement plant powered with alternative fuels

The distributions of polycyclic aromatic hydrocarbons (PAHs) and molecular tracer organic compounds for biomass combustion, traffic emissions, soil dust, and secondary aerosol processing have been studied in three fractions of ambient air particulate matter (PM10, 2.5, and 1) collected in the vicinity of a cement plant. PAH concentrations were used to estimate the carcinogenic risks in humans. Combustion related compounds, including PAHs, and those from secondary aerosol processing, predominated in the finest (PM<1) fraction, while saccharides related to organic soil dust predominated in the coarse fraction (2.5<PM<10). The molecular markers of biomass combustion were found in high concentrations, indicating the influence of biomass burning on PM. Most predominant PAHs were five and six rings species, related to a PAH profile characteristic of urban-industrial environments. The concentrations of benzo[a]pyrene varied between 0.2 and 1.0ng/m3, which is close but lower than the annual limit value of 1ng/m3 established by law. Exposure and inhalation carcinogenic risks from total PAHs were below the EPA threshold of acceptable risk (1·10−6).