Seasonal variation and size distributions of water-soluble inorganic ions and carbonaceous aerosols at a coastal site in Ningbo, China

Stark seasonal contrast of fine aerosol levels, composition, formation mechanism, and characteristics in a polluted megacity

In this study, we investigated the temporal variation of organic and inorganic aerosol with its optical properties in Mumbai (India), an urban coastal region. Mean PM2.5 concentrations during the sampling period were 175 μg/m3 (winter) and 90 μg/m3 (summer). During winter, the average concentrations of organic (OC), elemental (EC), and water-soluble organic carbon (WSOC) were three times higher than in summer. Secondary organic carbon (SOC) contribution in OC was higher in summer (78%) than in winter (53%), and strong solar radiation in summer likely caused this outcome. Aerosols were slightly acidic in both seasons, with an average pH of 5.7 (winter) and 6.0 (summer). A correlation was observed between SOC and the acidity of particles in summer (R2 = 0.6), indicating some amount of acid-catalysed SOC formation. In both seasons, the sulphate oxidation ratio (SOR) was higher than the nitrate oxidation ratio (NOR), which may reflect a preference for SO2 oxidation over NO2 or the difference in partitioning ammonium nitrate into ammonium sulphate under high RH. The dominant mechanism of SOC formation (gas vs aqueous phase oxidation) also showed seasonal variation. In winter, a relatively steep reduced major axis (RMA) slope of O3/CO suggests gas phase oxidation was the dominant mechanism of SOC production. Winter has more BrC fraction than summer, indicating higher absorbing aerosols, though the efficiency of absorbing the light was higher in summer. To assess the radiative forcing of PM2.5 on a local scale, an effective carbon ratio (ECR) was computed. The findings pointed to a local radiative heating impact caused by PM2.5. The spectral slope ratio and MAE at 250 to 300 nm ratio (E2/E3) revealed a higher abundance of high molecular weight species in WSOC during summer than in winter.

Size Distributions and Health Risks of Particulate Polycyclic Aromatic Hydrocarbons in the Atmosphere at Coastal Areas in Ningbo, China

Most current research focusing on the health risk assessments of particulate polycyclic aromatic hydrocarbons (PAHs) have not analyzed the size distributions and human respiratory deposition rates. In the present study, size-separated particulate matter (PM) was collected in the coastal area of Ningbo using an Anderson eight-stage air sampler over a 1-year period (2014-2015). The 16 US Environmental Protection Agency priority PAHs associated with PM were pretreated with rapid solvent extraction and analyzed by gas chromatography-mass spectrometry. The respiratory exposure assessment was determined using the multiple-path particle dosimetry (MPPD) model. The results show that all PAHs exhibited bimodal distribution with one mode peak in accumulation mode (0.43-0.65 µm) and another mode peak in coarse mode (4.7-5.8 µm). In addition, a low coefficient of divergence of PAHs between PM2.1 and PM2.1-10 indicated a high spatial heterogeneity in source factor contribution and formation mechanism. The deposition fluxes (tracheobronchial + pulmonary) of PM were highest for children in the size range of 3.3 µm < particle diameter (Dp) < 9 µm, while for males and females the highest fluxes occurred in the size range of 1.1 µm < Dp < 2.1 µm. The depositions of coarse PM in children were significantly higher than those in adults. The benzo[a]pyrene equivalent (BaPeq) depositions of dibenz[a,h]anthracene ranged from 1.4e-04 to 0.015 ng h-1, which were highest among the PAHs. The PAHs on particles with Dp >4.7 µm contributed approximately three times more to children than to males and females. Therefore, the toxicity of coarse PM to children needed attention. The incremental lifetime cancer risks (ILCR) for children, males, and females were estimated to be 2.92 × 10-7, 1.82 × 10-7, and 2.38 × 10-7, respectively, which were below the cancer risk guideline value (10-6). These ILCR values were much lower than the risks calculated without considering particle size distributions and respiratory depositions. The combination of the size-segregated sampling technique and the MPPD model can effectively avoid the overestimation of human respiratory exposure. Environ Toxicol Chem 2024;43:1364-1377. © 2024 SETAC.

Characterization of water-soluble ions in PM10 over an industrial area in northern Colombia: Temporal variations and correlation with satellite data

This study was designed to assess the concentrations of nine water-soluble ions in PM10 mass at two sites of an open-pit coal mine and to analyze the correlation and variation of the spatial distribution of sulfate ions with the PM10 sulfate aerosol optical depth at 550 nm (suaod550) in two (North and South) stations of the study area. The daily average of PM10 concentrations ranged from 20.48 to 53.10 μg/m3 and thus did not exceed the daily average maximum permissible level of PM10 (100 μg/m3) established in the Colombia standard at any station. The concentrations of nine water-soluble ions in PM10 (Cl-, NO3-, PO43-, SO42- Na+, NH4+, K+, Mg2+, and Ca2+) were determined. The ions under analysis, SO42-, Na+, and NH4+ had the highest concentrations. Combined, they accounted for 75% of the mass of water-soluble ions in a total of 210 samples. The SO42- concentrations in PM10 significantly correlated with suaod550 (r ranging from 0.57 to 0.66), emphasizing the strong effect of suaod550 from Venezuela (Lake Maracaibo) on central and northern Colombia. These results demonstrate that the effects of local sulfate emissions near monitoring sites can be predicted and assessed using satellite data.

Sampling efficiency of a polyurethane foam air sampler: Effect of temperature

Effective monitoring of atmospheric concentrations is vital for assessing the Stockholm Convention's effectiveness on persistent organic pollutants (POPs). This task, particularly challenging in polar regions due to low air concentrations and temperature fluctuations, requires robust sampling techniques. Furthermore, the influence of temperature on the sampling efficiency of polyurethane foam discs remains unclear. Here we employ a flow-through sampling (FTS) column coupled with an active pump to collect air samples at varying temperatures. We delved into breakthrough profiles of key pollutants, such as polycyclic aromatic hydrocarbons (PAHs), polychlorobiphenyls (PCBs), and organochlorine pesticides (OCPs), and examined the temperature-dependent behaviors of the theoretical plate number (N) and breakthrough volume (VB) using frontal chromatography theory. Our findings reveal a significant relationship between temperature dependence coefficients (KTN, KTV) and compound volatility, with decreasing values as volatility increases. While distinct trends are noted for PAHs, PCBs, and OCPs in KTN, KTV values exhibit similar patterns across all chemicals. Moreover, we establish a binary linear correlation between log (VB/m3), 1/(T/K), and N, simplifying breakthrough level estimation by enabling easy conversion between N and VB. Finally, an empirical linear solvation energy relationship incorporating a temperature term is developed, yielding satisfactory results for N at various temperatures. This approach holds the potential to rectify temperature-related effects and loss rates in historical data from long-term monitoring networks, benefiting polar and remote regions.

Water-soluble inorganic ions (WSIs) in the aerosols from Central Asia via transboundary transport measured in Jimunai in 2020

Air pollution is a global issue that often transcends national borders, leading to disputes over environmental concerns and climate-mitigation responsibilities. Between March and July 2020, we collected aerosol samples in Jimunai, a town in western China neighboring Kazakhstan, to assess transboundary air pollution in the region. Our analysis focused on major water-soluble inorganic ions (WSIs), with Ca2+ and SO42- accounting for almost 60% of the total ion loading. The ratio of cations to anions was greater than one (1.33 ± 0.27), indicating alkaline aerosols during the sampling period. Our results suggest that the pollutants measured were primarily sourced from Kazakhstan, as demonstrated by local meteorological data, air-mass trajectory analysis, and pollutant emission inventories in Kazakhstan. Correlation and primary component analysis indicated that NH4+ played an important role in neutralizing NO3- and SO42-, while Cl- was significantly depleted by the probable reaction HNO3↑ + NaCl = HCl↑ + NaNO3. These findings highlight the need for continued monitoring and regulation of air pollution sources in the region to address transboundary air pollution.

Roles of ambient temperature and relative humidity on the relationship between fine particulate matter and gaseous pollutants in the largest industrial city of Ulsan, South Korea

Although meteorological conditions play a significant role in air pollution, research on their effects on the relationship between air pollutants is limited. In this study, trends of six criteria air pollutants were investigated from 15 air quality monitoring stations (AQMSs) in Ulsan, a multi-industrial city in South Korea, during 2015-2019. Unlike CO and O3, SO2, NO2, PM10, and PM2.5 showed statistically significant decreasing trends over the period. The companion relationship between PM2.5 and gaseous pollutants was evaluated by their correlations [R (PM2.5-GPs)]. R (PM2.5-NO2) was relatively high at almost all AQMSs, whereas high R (PM2.5-SO2) was observed near the petrochemical industrial complex, suggesting a great influence of local emissions (vehicles and industries). R (PM2.5-CO) and the standardized regression coefficients of CO obtained from the multiple linear regression model were the highest, indicating that combustion processes may significantly contribute to PM2.5. The effect of temperature (T) was more apparent on R (PM2.5-GPs) than that of relative humidity, with significant values under T > 15 °C. Moreover, R (PM2.5-O3) was positive at the T range of 12-18 °C, suggesting that reducing GPs emitted by industrial facilities during May-June may control PM2.5 and O3 in Ulsan. The methodology demonstrated in this study can be further used for a better understanding of the influences of environmental factors on the secondary PM2.5 formation from gaseous precursors and the R (PM2.5-O3).

Pollution levels and health risk assessment of potentially toxic metals of size-segregated particulate matter in rural residential areas of high lung cancer incidence in Fuyuan, China

The highest incidence and mortality rate of lung cancer in rural area of Fuyuan has been a research hotspot, and the pathogenesis is still unclear. Therefore, atmospheric particulate matters (APMs) samples were collected between 18 February and 01 March 2017, exploring water-soluble potentially toxic metals (WSPTMs) and water-soluble inorganic ionic species (WSIIs) levels, size distribution, sources, acidity and alkalinity, and potential carcinogenic and non-carcinogenic risks, hoping to provide scientific basic data to solve this problem. In our study, the average ratio of nitrate ion (NO₃^-)/sulfate ion (SO₄^2-) within PM_1.1, PM_1.1-2.0, PM_2.0-3.3, PM_3.3-7.0, and PM_>7.0 were 0.22, 0.18, 0.15, 0.34 and 0.36, respectively, that revealed that combustion sources contributed to PM were more significant. The anions in equilibrium (ANE) / cations in equilibrium (CAE) < 1 for all samples within PM_1.1, PM_2.0-3.3, PM_3.3-7.0 indicate that the APMs were alkaline, but PM_1.1-2.0 particulate matter shows weak acidity. SO₄^2- prefers to combine with NH₄⁺ to form (NH₄)₂SO₄, which hinders the formation of NH₄NO₃, the remaining SO₄^2- and NO₃^- to neutralize the K⁺, KNO₃ was formed at all particulate, however, K₂SO₄ can only be formed in PM_<3.3. Arsenic (As) and Selenium (Se) were identified as the most enriched WSPTMs in all PM sizes, predominantly from anthropogenic emissions, were suggested that coal combustion is a significant source of PM-bound WSPTMs. Total WSPTMs exhibited high total carcinogenic risks (TCR) values (9.98 × 10^-6, 1.06 × 10^-5, and 1.19 × 10^-5 for girls, boys and adults, respectively) in the smaller particles (< 1.1 μm). Se was considered as the major contributor (63.60%) to carcinogenic risk (CR) in PM_2.0 and had an inverse relationship with PM size that should be of prime concern.

Characteristics and sources of carbonaceous aerosols in a semi-arid city: Quantifying anthropogenic and meteorological impacts

Carbonaceous aerosols have great adverse impacts on air quality, human health, and climate. However, there is a limited understanding of carbonaceous aerosols in semi-arid areas. The correlation between carbonaceous aerosols and control measures is still unclear owing to the insufficient information regarding meteorological contribution. To reveal the complex relationship between control measures and carbonaceous aerosols, offline and online observations of carbonaceous aerosols were conducted from October 8, 2019 to October 7, 2020 in Hohhot, a semi-arid city. The characteristics and sources of carbonaceous aerosols and impacts of anthropogenic emissions and meteorological conditions were studied. The annual mean concentrations (± standard deviation) of fine particulate matter (PM_2.5), organic carbon (OC), and elemental carbon (EC) were 42.81 (±40.13), 7.57 (±6.43), and 2.25 (±1.39) μg m^-3, respectively. The highest PM_2.5 and carbonaceous aerosol concentrations were observed in winter, whereas the lowest was observed in summer. The result indicated that coal combustion for heating had a critical role in air quality degradation in Hohhot. A boost regression tree model was applied to quantify the impacts of anthropogenic emissions and meteorological conditions on carbonaceous aerosols. The results suggested that the anthropogenic contributions of PM_2.5, OC, and EC during the COVID-19 lockdown period were 53.0, 15.0, and 2.36 μg m^-3, respectively, while the meteorological contributions were 5.38, 2.49, and -0.62 μg m^-3, respectively. Secondary formation caused by unfavorable meteorological conditions offset the emission reduction during the COVID-19 lockdown period. Coal combustion (46.4% for OC and 35.4% for EC) and vehicular emissions (32.0% for OC and 50.4% for EC) were the predominant contributors of carbonaceous aerosols. The result indicated that Hohhot must regulate coal use and vehicle emissions to reduce carbonaceous aerosol pollution. This study provides new insights and a comprehensive understanding of the complex relationships between control strategies, meteorological conditions, and air quality.

Heterogeneous changes of chemical compositions, sources and health risks of PM2.5 with the "Clean Heating" policy at urban/suburban/industrial sites

China has enacted the "Clean Heating" (CH) policy in north China. The domain-specific impacts on PM2.5 constituents and sources in small cities are still lacking, which obstruct the further policy optimization. Here, we performed an intensive observation covering the heating period (HP) and pre-heating period (PHP) in winter of 2017 at urban (UR), industrial (IS), and suburban (SUR) sites in one of the "2 + 26" cities. The mean PM2.5 concentrations at UR and IS decreased by 15.2 % and 4.6 %, while increased by 9.8 % at SUR in the HP compared with the PHP, indicating the heterogeneous responses. The lowest contribution percentages of coal combustion (14.6 %) and industrial emissions (17.1 %) to PM2.5 at UR in the HP implied the CH policy played more effective role. The most increase in NO3-/SO42- ratio by 26.8 % and the highest NO3- concentration at UR in the HP were linked mainly with the thermal-NOx emitted from natural gas (NG) burning in view of NOx emission reductions from other sources. The highest concentrations of OC, SO42-, K+, and Cl-, and contribution percentages of biomass burning (20.0 %) and coal combustion (24.8 %) to PM2.5 at SUR in the HP evidenced the enhanced usage of biomass/coal. Coal banning in the HP at IS and UR led to the obvious decreases in OC, SO42-, As, and Sb. Secondary nitrate became the largest PM2.5 source at IS and UR in the HP. Coal banning, emission control on large-size enterprises and ignored control on small-size enterprises efficiently modified the concentrations and health risks of heavy metals. The lowest carcinogenic risks moved from SUR in the PHP to UR in the HP. The policies on de-NOx of NG-burning related enterprises, reduction of biomass/coal usage in suburban area, and strict regulation of small-size enterprises were urgently need to further improve the air quality.

Variations in the concentration, source activity, and atmospheric processing of PM2.5-associated water-soluble ionic species over Jammu, India

Concentrations, sources, and atmospheric processing of water-soluble ionic species associated with PM_2.5 collected from 2015 to 2017 were studied in Jammu, an urban location in the North-Western Himalayan Region (NWHR). Being ecologically sensitive and sparsely studied for dynamics in PM_2.5 and associated WSIS, the present study is important for developing robust air pollution abatement strategies for the air-shed of NWHR. Twenty-four hourly PM_2.5 samples were collected on weekly basis at a receptor site and analyzed for WSIS using ion chromatography system. On annual basis, total sum of WSIS (ΣWSIS) contributed about 28.5% of PM_2.5, where the contribution of sulfate-nitrate-ammonium, a proxy for secondary inorganic aerosols (SIA), was found to be 18.7% of PM_2.5. The ΣWSIS and PM_2.5 concentration showed a seasonal cycle with the maximum concentration during winters and the minimum in summers. Mass fraction of ΣWSIS in PM_2.5 showed an anti-phase seasonal pattern indicating more source activity during summers. Season-wise, dominant WSIS constituting PM_2.5 were NO₃^-, SO₄^2-, NH₄⁺, and K⁺ during winters; whereas summer was marked with dominant contributions from SO₄^2-, NH₄⁺, Ca²⁺, and K⁺. Seasonal variability exhibited among SIA constituents underscored the crucial role of air temperature and relative humidity regime. It was observed that nss-K⁺ + NH₄⁺ were sufficient to neutralize most of the acidic species arising from precursor gases (NO_x and SO_x). Using principal component analysis, five major sources and processes, viz. (a) biomass burning activities, (b) secondary inorganic aerosol formation, (c) input from re-suspended dust, (d) transported dust, and (e) fertilizer residue, were identified for the emissions of PM_2.5-associated WSIS over Jammu. In future studies, impacts of dry and/or wet deposition of aerosol-associated WSIS on the crop productivity in the region should be studied.

Size-segregated physicochemical properties of inhalable particulate matter in a tunnel-ventilated layer house in China

This study investigated the physicochemical properties of the particles in a typical commercial laying hen barn in Southeast China. Mass concentrations and size distributions of the particulate matter (PM) and the key components (incl. organic carbon (OC), element carbon (EC), and the water-soluble inorganic ions (WSIIs)) were analyzed. The result shows that the mass concentrations of PM accumulated along with the airflow inside the house, with the total mass of the sampling particles increasing from 843.66 ± 160.74 μg/m³ at the center of the house to 1264.93 ± 285.70 μg/m³ at the place close to exhaust fans. The particles with the aerodynamic equivalent diameter, Dp > 9 μm, coarse particles (2.1 μm < Dp ≤ 9 μm), fine particles (Dp ≤ 2.1 μm) accounted for around 50%, 40%, and 10% of the total mass of the sampling particles, respectively. Mass closure analysis shows secondary inorganic ions (NH₄⁺, SO₄^2- and NO₃^-) were abundant in the fine-mode fraction and OC accounted for more than 40% of the coarse particles. Size distribution analysis shows that the three secondary inorganic ions were bimodally distributed, and the rest tested components were unimodally distributed. The ratios of OC/EC in fine particles were smaller than those in the coarse particles. The equivalent concentration of WSIIs indicated that fine particles were slightly acidic, and the large size particles were slightly alkaline. Knowledge gained from this study will lead to a better understanding of physicochemical properties, sources, and formation of PM.

Spatiotemporal Variation and Influencing Factors of TSP and Anions in Coastal Atmosphere of Zhanjiang City, China

Water-soluble anions and suspended fine particles have negative impacts on ecosystems and human health, which is a current research hotspot. In this study, coastal suburb, coastal urban area, coastal tourist area, and coastal industrial area were explored to study the spatiotemporal variation and influencing factors of water-soluble anions and total suspended particles (TSP) in Zhanjiang atmosphere. In addition, on-site monitoring, laboratory testing, and analysis were used to identify the difference of each pollutant component at the sampling stations. The results showed that the average concentrations of Cl⁻, NO₃⁻, SO₄²⁻, PO₄³⁻, and TSP were 29.8 μg/m³, 19.6 μg/m³, 45.6 μg/m³, 13.5 μg/m³, and 0.28 mg/m³, respectively. The concentration of Cl⁻, NO₃⁻, PO₄³⁻, and atmospheric TSP were the highest in coastal urban area, while the concentration of SO₄²⁻ was the highest in coastal industrial area. Moreover, there were significantly seasonal differences in the concentration of various pollutants (p < 0.05). Cl⁻ and SO₄²⁻ were high in summer, and NO₃⁻ and TSP were high in winter. Cl⁻, SO₄²⁻, PO₄³⁻, and TSP had significant correlations with meteorological elements (temperature, relative humidity, atmospheric pressure, and wind speed). Besides, the results showed the areas with the most serious air pollution were coastal urban area and coastal industrial area. Moreover, the exhaust emissions from vehicles, urban enterprise emissions, and seawater evaporation were responsible for the serious air pollution in coastal urban area. It provided baseline information for the coastal atmospheric environment quality in Zhanjiang coastal city, which was critical to the mitigation strategies for the emission sources of air pollutants in the future.

The impact of ammonium on the distillation of organic carbon in PM2.5

Thermal desorption coupled with different detectors is an important analysis method for ambient carbonaceous aerosols. However, it is unclear how the compounds coexisting in both the gas and particle phases affect carbonaceous aerosol concentrations and measurements during thermal desorption. We observed matrix effects leading to a redistribution of different OC fractions (OC1 to OC4) during the thermal desorption process. These factors led to the formation of OC with low volatility (OC4), mainly from high-volatility OC (OC1 and OC2). Laboratory studies further indicated that ammonium promotes such matrix effects by transforming OC in the particle phase. Therefore, in addition to providing insights into the chemical evolution of OC during haze events, we argue that thermal-desorption-based OC measurements should be used with caution, which is an important step towards a more accurate measurement of OC in the ambient atmosphere.

Seasonal variation and size distribution of inorganic and carbonaceous components, source identification of size-fractioned urban air particles in Kuala Lumpur, Malaysia

This study aims to determine the inorganic and carbonaceous components depending on the seasonal variation and size distribution of urban air particles in Kuala Lumpur. Different fractions of particulate matter (PM) were measured using a Nanosampler from 17 February 2017 until 27 November 2017. The water-soluble inorganic ions (WSIIs) and carbonaceous components in all samples were analysed using ion chromatography and carbon analyser thermal/optical reflectance, respectively. Total PM concentration reached its peak during the southwest (SW) season (70.99 ± 6.04 μg/m³), and the greatest accumulation were observed at PM_0.5-1.0 (22%-30%, 9.55 ± 1.03 μg/m³) and PM_2.5-10 (22%-25%, 10.34 ± 0.81 μg/m³). SO₄^2-, NO₃^- and NH₄⁺ were major contributors of WSIIs, and their formation was favoured mainly during SW season (80.5% of total ions). PM_0.5-1.0 and PM_2.5-10 exhibited the highest percentage of WSII size distribution, accounted for 28.4% and 13.5% of the total mass, respectively. The average contribution of carbonaceous species (OC + EC) to total carbonaceous concentrations were higher in PM_0.5-1.0 (35.2%) and PM_2.5-10 (26.6%). Ultrafine particles (PM_<0.1) consistently indicated that the sources were from vehicle emission while the SW season was constantly dominated by biomass burning sources. Using the positive matrix factorization (PMF) model, secondary inorganic aerosol and biomass burning (30.3%) was known as a significant source of overall PM. As a conclusion, ratio and source apportionment indicate the mixture of biomass burning, secondary inorganic aerosols and motor vehicle contributed to the size-segregated PM and seasonal variation of inorganic and carbonaceous components of urban air particles.

Size distributions and dry deposition fluxes of water-soluble inorganic nitrogen in atmospheric aerosols in Xiamen Bay, China

Size-segregated aerosol particles were collected using a high volume MOUDI sampler at a coastal urban site in Xiamen Bay, China, from March 2018 to June 2020 to examine the seasonal characteristics of aerosol and water-soluble inorganic ions (WSIIs) and the dry deposition of nitrogen species. During the study period, the annual average concentrations of PM₁, PM_2.5, PM₁₀, and TSP were 14.8 ± 5.6, 21.1 ± 9.0, 35.4 ± 14.2 μg m^-3, and 45.2 ± 21.3 μg m^-3, respectively. The seasonal variations of aerosol concentrations were impacted by the monsoon with the lowest value in summer and the higher values in other seasons. For WSIIs, the annual average concentrations were 6.3 ± 3.3, 2.1 ± 1.2, 3.3 ± 1.5, and 1.6 ± 0.8 μg m^-3 in PM₁, PM_1-2.5, PM_2.5-10, and PM_>10, respectively. In addition, pronounced seasonal variations of WSIIs in PM₁ and PM_1-2.5 were observed, with the highest concentration in spring-winter and the lowest in summer. The size distribution showed that SO₄ ^2-, NH₄ ⁺ and K⁺ were consistently present in the submicron particles while Ca²⁺, Mg²⁺, Na⁺ and Cl^- mainly accumulated in the size range of 2.5-10 μm, reflecting their different dominant sources. In spring, fall and winter, a bimodal distribution of NO₃ ^- was observed with one peak at 2.5-10 μm and another peak at 0.44-1 μm. In summer, however, the fine mode peak disappeared, likely due to the unfavorable conditions for the formation of NH₄NO₃. For NH₄ ⁺ and SO₄ ^2-, their dominant peak at 0.25-0.44 μm in summer and fall shifted to 0.44-1 μm in spring and winter. Although the concentration of NO₃-N was lower than NH₄-N, the dry deposition flux of NO₃-N (35.77 ± 24.49 μmol N m^-2 d^-1) was much higher than that of NH₄-N (10.95 ± 11.89 μmol N m^-2 d^-1), mainly due to the larger deposition velocities of NO₃-N. The contribution of sea-salt particles to the total particulate inorganic N deposition was estimated to be 23.9-52.8%. Dry deposition of particulate inorganic N accounted for 0.95% of other terrestrial N influxes. The annual total N deposition can create a new productivity of 3.55 mgC m^-2 d^-1, accounting for 1.3-4.7% of the primary productivity in Xiamen Bay. In light of these results, atmospheric N deposition could have a significant influence on biogeochemistry cycle of nutrients with respect to projected increase of anthropogenic emissions from mobile sources in coastal region.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10874-021-09427-8.

Mass Concentration, Chemical Composition, and Source Characteristics of PM2.5 in a Plateau Slope City in Southwest China

In order to investigate the seasonal variations in the chemical characteristics of PM2.5 at the plateau slope of a mountain city in southwest China, 178 PM2.5 filters (89 quartz and 89 Teflon samples for PM2.5) were collected to sample the urban air of Wenshan in spring and autumn 2016 at three sites. The mass concentrations, water-soluble inorganic ions, organic and inorganic carbon concentrations, and inorganic elements constituting PM2.5 were determined, principal component analysis was used to identify potential sources of PM2.5, and the backward trajectory model was used to calculate the contribution of the long-distance transmission of air particles to the Wenshan area. The average concentration of PM2.5 in spring and autumn was 44.85 ± 10.99 μg/m3. Secondary inorganic aerosols contributed 21.82% and 16.50% of the total PM2.5 in spring and autumn, respectively. The daily mean value of OC/EC indicated that the measured SOC content was generated by the photochemical processes active during the sampling days. However, elements from anthropogenic sources (Ti, Si, Ca, Fe, Al, K, Mg, Na, Sb, Zn, P, Pb, Mn, As and Cu) accounted for 99.38% and 99.24% of the total inorganic elements in spring and autumn, respectively. Finally, source apportionment showed that SIA, dust, industry, biomass burning, motor vehicle emissions and copper smelting emissions constituted the major components in Wenshan. This study is the first to investigate the chemical characterizations and sources of PM2.5 in Wenshan, and it provides effective support for local governments formulating air pollution control policies.

Study on the Characteristics of Size-Segregated Particulate Water-Soluble Inorganic Ions and Potentially Toxic Metals during Wintertime in a High Population Residential Area in Beijing, China

Airborne particulate matter (PM) pollution often occurs in the wintertime in northern China, posing a potential threat to human health. To date, there are limited studies about the metals and inorganic ions to link source apportionments and health risk assessments in the different size-segregated PM samples. In this study, our samples were collected by a high-volume air sampler from 26 December 2018 to 11 January 2019 in a high population residential area (Beijing). Water-soluble inorganic ions, metal elements in the different size-segregated PM samples were determined for health risk assessments by inhalation of PM. During the sampling period in Beijing, the average concentrations of PM1.1 and PM1.1–2.0 were 39.67 ± 10.66 μg m−3 and 32.25 ± 6.78 μg m−3. Distinct distribution profiles characterized the different elements. The markers of coal combustion Pb, As, and Se had >52% of their mass concentration in PM1.1. The average mass ratios of (NO3− + NO2−)/SO42−, Cl−/Na+, Cl−/K+, and Cl−/(NO3− + NO2−) were 1.68, 6.58, 6.18, and 0.57, which showed that coal combustion and vehicle emissions were the main anthropogenic sources of PM in Beijing in winter. PM1.1 was the major contributor of Pb, Cd, and As for carcinogenic risks (CR) and hazard quotient (HQ). It was indicated that PM1.1 is more harmful than coarse PM. The toxic elements of Cr (VI) (1.12 × 10−6), V (0.69 × 10−6), and As (0.41 × 10−6) caused higher CR for children than Ni, Cd, Co, and Pb. Meanwhile, Pb (35.30 × 10−6) and Ni (21.07 × 10−6) caused higher CR for adults than As, Cr (VI), V, Co, and Cd, especially PM1.1. This study provides detailed composition data and the first report on human health in a high population residential area in Beijing.

Atmospheric Behaviour of Polycyclic and Nitro-Polycyclic Aromatic Hydrocarbons and Water-Soluble Inorganic Ions in Winter in Kirishima, a Typical Japanese Commercial City

Kirishima is a typical Japanese commercial city, famous for frequent volcanic activity. This is the first study to determine the characteristics of PM2.5-bound polycyclic and nitro-polycyclic aromatic hydrocarbons (PAHs and NPAHs) and water-soluble inorganic ions (WSIIs) in this city. In this study, the non-volcanic eruption period was taken as the target and daily PM2.5 samples were collected from 24 November to 21 December 2016. The daily concentrations in PM2.5 of ƩPAHs, ƩNPAHs, and ƩWSIIs ranged from 0.36 to 2.90 ng/m3, 2.12 to 22.3 pg/m3, and 1.96 to 11.4 μg/m3, respectively. Through the results of the diagnostic ratio analyses of the PAHs, NPAHs, and WSIIs and the backward trajectory analysis of the air masses arriving in Kirishima, the emission sources of PAHs, NPAHs, and WSIIs in PM2.5 in Kirishima were influenced by the coal burning that came from the East Asian continent, although there was no influence from volcanic emission sources during the sampling period. The total benzo[a]pyrene (BaP)-equivalent concentration was lower than many other cities but the health risks in Kirishima were nonetheless notable. These findings are very important for future research on PM samples during the inactive Asian monsoon and volcanic eruption periods, to further understand the characteristics of air pollutants in Kirishima, and to contribute to the improvement in health of residents and a reduction in the atmospheric circulation of air pollutants in East Asia.

Atmospheric fine particles in a typical coastal port of Yangtze River Delta

In recent decades, coastal ports have experienced rapid development and become an important economic and ecological hub in China. Atmospheric particle is a research hotspot in atmospheric environmental sciences in inland regions. However, few studies on the atmospheric particle were conducted in coastal port areas in China, which indeed suffers atmospheric particle pollution. Lack of the physicochemical characteristics of fine particles serves as an obstacle toward the accurate control for air pollution in the coastal port area in China. Here, a field observation was conducted in an important coastal port city in Yangtze River Delta from March 6 to March 19, 2019. The average PM_2.5 concentration was 63.7 ± 27.8 μg/m³ and NO₃^-, SO₄^2-, NH₄⁺, and organic matter accounted for ~60% of PM_2.5. Fe was the most abundant trace metal element and V as the ship emission indicator was detected. Transmission electron microscopy images showed that SK-rich, soot, Fe, SK-soot and SK-Fe were the major individual particles in the coastal port. V and soluble Fe were detected in sulfate coating of SK-Fe particles. We found that anthropogenic emissions, marine sea salt, and secondary atmosphere process were the major sources of fine particles. Backward trajectory analysis indicated that the dominant air masses were marine air mass, inland air mass from northern Zhejiang and inland-marine mixed air mass from Shandong and Shanghai during the sampling period. The findings can help us better understand the physicochemical properties of atmospheric fine particles in the coastal port of Eastern China.

Comparative Analysis of PM2.5-Bound Polycyclic Aromatic Hydrocarbons (PAHs), Nitro-PAHs (NPAHs), and Water-Soluble Inorganic Ions (WSIIs) at Two Background Sites in Japan

Daily PM2.5 (particulate matter with aerodynamic diameter ≤2.5 μm) samples were simultaneously collected at two background sites (Wajima Air Monitoring Station (WAMS) and Fukue-Jima Atmosphere and Aerosol Monitoring Station (FAMS)) in Japan in the East Asian winter and summer monsoon periods of 2017 and 2019, to compare the characteristics of air pollutants among different regions and to determine the possible variation during the long-range transport process. Polycyclic aromatic hydrocarbons (PAHs), nitro-PAHs (NPAHs), and water-soluble inorganic ions (WSIIs) were analyzed. Despite the PM2.5 concentrations at FAMS (8.90-78.5 µg/m3) being higher than those at WAMS (2.33-21.2 µg/m3) in the winter monsoon period, the average concentrations of ∑PAHs, ∑NPAHs, and ∑WSIIs were similar between the two sites. Diagnostic ratios indicated PAHs mainly originated from traffic emissions and mostly aged, whereas NPAHs were mostly secondarily formed during long-range transport. WSIIs at WAMS were mainly formed via the combustion process and secondary reactions, whereas those at FAMS mainly originated from sea salt and dust. Backward trajectories revealed the air masses could not only come from Asian continental coastal regions but also distant landlocked areas in the winter monsoon period, whereas most came from the ocean in the summer monsoon period. These findings can provide basic data for the establishment of prediction models of transboundary air pollutants in East Asia.

Water-soluble ionic species in atmospheric aerosols over Dhauladhar region of North-Western Himalaya

Water-soluble ionic species (WSIS) have been used as potential markers for different source(s) and underlining process(es) emitting and transforming atmospheric aerosols. PM₁₀ aerosol sampling was performed once in a week for a complete one year, at a mid-altitude urban and a low-altitude rural location simultaneously in the Dhauladhar region of the North-Western Himalaya. Aerosol samples were analysed for major WSIS (anions: F^-, Cl^-, NO₃^-, PO₄^3- and SO₄^2-; cations: Na⁺, NH₄⁺, K⁺, Ca²⁺ and Mg²⁺) using the ion chromatography system. Results showed that WSIS constitutes around 15% of PM₁₀ aerosol load in the region. SO₄^2- contributes the maximum (~ 50%) followed by NO₃^- (~ 12.5%) and NH₄⁺ (~ 12.5%) to the total concentration of WSIS analysed. During all the seasons, average concentrations of PM₁₀ and associated WSIS were observed to be higher over the rural location in comparison to the urban location. The total concentration of WSIS was found to be maximum during the winter season. Principal component analysis performed on the WSIS concentration dataset revealed four major sources of PM₁₀-associated WSIS viz. re-suspension of soil or local sediments; conversion of pollutant gases (SO_x, NO_x and NH₃) to particles, i.e., secondary inorganic aerosol formation; evaporative loss or re-suspension of inorganic (NPK) fertilizers' residues and biomass/crop-residue burning emissions in the Dhauladhar region of the North-Western Himalaya.

Aerosol-associated non-polar organic compounds (NPOCs) at Jammu, India, in the North-Western Himalayan Region: seasonal variations in sources and processes

Fine particulate (PM_2.5) bound non-polar organic compounds (NPOCs) and associated diagnostic parameters were studied at Jammu, an urban location in the foothills of North-Western Himalayan Region. PM_2.5 was collected daily (24 h, once a week) over a year to assess monthly and seasonal variations in NPOC concentration and their source(s) activity. Samples were analyzed on thermal desorption-gas chromatography mass spectrometry to identify and quantify source-specific organic markers. Homologous series of n-alkanes, polycyclic aromatic hydrocarbons (PAHs), isoprenoid hydrocarbons and nicotine were investigated to understand the sources of aerosols in the region. The annual mean concentration of PM_2.5 during the sampling period was found higher than the permissible limit of India's National Ambient Air Quality Standards (NAAQS) and World Health Organisation (WHO) guidelines. The rise of concentration for PM_2.5 and associated NPOCs in summer season was attributed to enhanced emission. The n-alkane-based diagnostic parameters indicated mixed contributions of NPOCs from anthropogenic sources like fossil fuel-related combustion with significant inputs from biogenic emission. Moreover, high influence of petrogenic contribution was observed in summer (monsoon) months. The quantifiable amounts of isoprenoid hydrocarbons further confirmed this observation. Total PAH concentration also followed an increasing trend from March to June, and June onwards a sharp decrease was observed. The higher concentration of environmental tobacco smoke marker nicotine in winter months was plausibly due to lower air temperature and conditions unfavourable to photo-degradation. A clear dominance of low molecular weight PAHs was noticed with rare presence of toxic PAHs in the ambient atmosphere of Jammu. PAH-based diagnostic parameters suggested substantial contribution from low temperature pyrolysis processes like biomass/crop-residue burning, wood and coal fire in the region. Specific wood burning markers further confirmed this observation.

Assessments of Water-Soluble Inorganic Ions and Heavy Metals in Atmospheric Dustfall and Topsoil in Lanzhou, China

The chemical features of atmospheric dustfall and topsoil in the same region could reflect the processes of the migration, transport, and diffusion of pollutants in the atmospheric-soil system. Samples of atmospheric dustfall and topsoil were collected in Lanzhou City. The contents and correlation of water-soluble inorganic ions (WSIIs) and heavy metals in dustfall and topsoil were analyzed, the sources of heavy metals and WSIIs in dustfall were distinguished, and the potential ecological risks of heavy metals in dustfall and topsoil were evaluated. The highest contents of WSIIs are SO₄²⁻ (18,594 mg·kg⁻¹) and Ca²⁺ (10,070 mg·kg⁻¹) in dustfall, and for SO₄²⁻ (8271 mg·kg⁻¹) and Na⁺ (1994 mg·kg⁻¹) in topsoil. The concentrations of heavy metals (Pb, Cu, Zn, Cr, Cd, and Ni) in dustfall are considerably higher than those in topsoil. Combustion of biomass and coal, transportation and industrial activities are the major anthropogenic sources of WSIIs and heavy metals in Lanzhou. Pollution of heavy metals except Cr and Ni in dustfall, and Cu, Cr, and Ni in topsoil was up to different degrees, where the pollution of Cd was serious. The risk of Cd in dustfall is high while moderate in topsoil. This research could offer a reference for the atmospheric particle pollution prevention and control in Lanzhou.

The characteristics and mixing states of PM2.5 during a winter dust storm in Ningbo of the Yangtze River Delta, China

Dust particulates play an essential role for the nucleation, hygroscopicity and also contribute to aerosol mass. We investigated the chemical composition, size distribution and mixing states of PM_2.5 using a single-particle aerosol mass spectrometer (SPAMS), Monitor for AeRosols and Gases (MARGA), and off-line membrane sampling from 2018.1.24 to 2018.2.20 at a coastal supersite in Ningbo, a port city in Yangtze River Delta, China. During the study campaign, the eastern part of China had experienced a wide range of cooling, sandstorm, and snowfall processes. The entire sampling campaign was categorized into five sub-periods based on the levels of PM_2.5 and the ratios of PM_2.5/PM₁₀, namely clean (T1), heavy pollution (T2), light pollution (T3), dust (sandstorm) (T4) and cleaning pollution (T5) period. After comparing the average mass spectrum for each period, it shows that the primary ions, such as Ca²⁺and SiO₃^-, rarely coexist with each other within a single particle, but secondary ions generally coexist with these primary ions. Furthermore, the coexistence of each two different ions within a particle does not show distinct variation for the whole study periods. All these suggest that the absorption and partitioning of gaseous contaminants into the surface of primary aerosol through heterogeneous reactions are the major pathways of aging and growth of aerosol; and the merging of particles through collisions usually is insignificant. Although the absolute concentrations of nitrate and sulfate all increased with the PM_2.5 concentrations, the relative equivalent concentrations of NO₃^- and SO₄^2- displayed opposite trends; the relative contribution of sulfate decreased and that of nitrate increased as the increase of pollution. During the dust period, the relative equivalent concentrations of calcium and/or potassium ions in PM_2.5 are significantly higher. This study provided deep insights about the mixing states and characteristics of particulate after long-range transport and a visualization tool for aerosol study.

Characteristics and temporal variations of organic and elemental carbon aerosols in PM1 in Changchun, Northeast China

The present study offers the first evaluation of organic and elemental carbon (OC and EC) of submicron (PM₁) fraction in Changchun (Northeast China) during a year-long sampling period (October 24, 2016 to October 23, 2017). More than 288 PM₁ (particulate matter with an aerodynamic diameter of less than 1 μm) samples were collected. The PM₁ concentrations ranged from 3.78 to 451.08 μg·m^-3, with an average of 57.73 μg·m^-3, which was 1.65 times higher than the Chinese National Standard II. Following the concept of the well-known IMPROVE algorithm, OC and EC values were obtained. The OC values ranged from 1.18 to 82.54 μg∙m^-3, and the EC values were from 0.30 to 14.19 μg∙m^-3. Total carbon (TC = EC + OC) constituted 9.11-40.35% of the total PM₁ mass, and OC dominated over EC. The average OC/EC ratio was 4.78, which implied a low percentage for vehicles and a high contribution of coal and biomass consumption to PM₁. Among OC, the annual primary organic carbon (POC) value was 7.69 μg∙m^-3, accounting for 63% of the OC, while secondary organic carbon (SOC) contributed 37% with 4.12 μg∙m^-3. Among EC, CHAR (EC1) dominated over SOOT (EC2 + EC3), and the CHAR/SOOR ratio ranged from 2.91 to 28.55. The results of the OC and EC values as well as the OC/EC and CHAR/SOOT ratios suggest that possible sources of PM₁ include vehicles, coal burning, cooking, and biomass burning.

Seasonal Control of Water-Soluble Inorganic Ions in PM2.5 from Nanning, a Subtropical Monsoon Climate City in Southwestern China

In this study, we measured the daily water-soluble inorganic ions (WSIIs) concentration (including SO42−, NO3−, NH4+, Ca2+, K+, Cl−, Na+, Mg2+, and F−) of PM2.5 (particulate matter with a diameter smaller than 2.5 μm) throughout the year in Nanning (a typical subtropical monsoon climate city in southwestern China) to explore the influence of seasonal climate change on the properties of PM2.5 pollution. This suggested that SO42−, NO3−, and NH4+ were the main component of WSIIs in Nanning. Secondary inorganic ions from fossil fuel combustion, agricultural activities, and automobile emissions were the main contributors to PM2.5, contributing more than 60% to PM2.5. Compared with the wet season, the contributions of different sources increased in the dry season (including pollution days); of these sources, automobile emissions and coal combustion emissions increased the most (about nine times and seven times, respectively). Seasonal weather and climate change affected the concentration level of WSIIs. During the wet season, higher temperatures and abundant rainfalls contributed to the volatilization and removal of WSIIs in PM2.5, while in the dry season and on pollution days, lower temperatures and less precipitation, higher emissions, and poor diffusion conditions contributed to the accumulation of WSIIs in PM2.5. NH4HSO4, (NH4)2SO4 and NH4NO3 were the main chemical forms of secondary inorganic ions. Sufficient NH3, intense solar radiation, and moist particulate matter surface promoted the formation of secondary inorganic ions. The higher temperature contributed to the volatilization of secondary inorganic ions.

A combined chemical/size fractionation approach to study winter/summer variations, ageing and source strength of atmospheric particles

We studied the size distribution of ions (Cl^-, NO₃^-, SO₄⁼, Na⁺, NH₄⁺, K⁺, Mg⁺⁺, Ca⁺⁺) and elements (As, Ba, Cd, Co, Cs, Cu, Fe, Li, Mn, Ni, Pb, Rb, Sb, Se, Sn, Sr, Ti, Tl, V, Zn) during the winter and summer seasons of seven consecutive years (2008-2014) in an area of the Po Valley (Northern Italy) characterised by industrial, agricultural and urban settings. The study included the collection and analysis of 41 series of size-segregated samples (MOUDI sampler, 10 stages, cut sizes from 0.18 to 18 μm). Ions were analysed by ion chromatography; elemental analysis was carried out by ICP-MS, by applying a chemical fractionation method able to increase the selectivity of PM source tracers. Our results indicate that important winter/summer variations occurred in both the concentration and size distribution of most PM components. These variations were explained in terms of variations in the strength of the prevailing sources of each component. The contribution of biomass burning for domestic heating was highlighted by the well-known tracer K⁺ but also by the soluble fraction of Rb, Cs and Li. Biomass burning contribution to atmospheric PM was mostly contained in the fine fraction, with a broad size-distribution from 0.18 to 1.8 μm. This source also appreciably increased the concentration of other elements in fine PM (As, Cd, Co, Mn, Pb, Sb, Sn). A few PM components (tracers of sea-spray, brake lining and some industries) did not show marked seasonal variations in concentration and size distribution. However, during winter, for brake lining and industry tracers we observed an upward shift in the dimension of fine particles and a downward shift in the dimension of coarse particles, due to the ageing of the air masses.

Spatial Distributions and Sources of Inorganic Chlorine in PM2.5 across China in Winter

Chlorine is an important atmospheric photochemical oxidant, but few studies have focused on atmospheric chlorine. In this study, PM2.5 samples were collected from urban and rural sites across China in January 2018, and concentrations of Cl− and other water-soluble ions in PM2.5 were analyzed. The size-segregated aerosol Cl− data measured across Chinese cities by other studies were compiled for comparison. The observed data demonstrated that the Cl− concentrations of PM2.5 in northern cities (5.0 ± 3.7 µg/m3) were higher than those in central (1.9 ± 1.2 µg/m3) and southern cities (0.84 ± 0.54 µg/m3), suggesting substantial chlorine emissions in northern cities during winter. The concentrations of Cl− in aerosol were significantly higher in urban regions (0.11–26.7 µg/m3) compared to than in rural regions (0.03–0.61 µg/m3) across China during winter, implying strong anthropogenic chlorine emission in cities. Based on the mole ratios of Cl−/Na+, Cl−/K+ and Cl−/ SO 4 2 − and the PMF model, Cl− in northern and central cities was mainly sourced from the coal combustion and biomass burning, but in southern cities, Cl− in PM2.5 was mainly affected by the equilibrium between gas-phase HCl and particulate Cl−. The size-segregated statistical data demonstrated that particulate Cl− had a bimodal pattern, and more Cl− was distributed in the fine model than that in the coarse mode in winter, with the opposite pattern was observed in summer. This may be attributed to both sources of atmospheric Cl− and Cl− involved in chemical processes. This study reports the concentrations of aerosol Cl− on a national scale, and provides important information for modeling the global atmospheric reactive chlorine distribution and the effects of chlorine on atmospheric photochemistry.