Secondary Inorganic Aerosols Research Articles

Observational insights into the environmental effect for secondary inorganic aerosol formation in the Northeast China: Influence of biomass burning

Secondary inorganic aerosols (SIA), as one of the main ubiquitous components of PM2.5, still have unclear impacts on their formation in the ambient environment, especially under extremely cold weather conditions. To explore the effects of open biomass burning (OBB) source emissions and meteorological factors on SIA formation, biomass burning tracer, i.e., levoglucosan (LG), was observed along with SIA were analyzed during the heating season at the Longfengshan (LFS) background of Northeast China. Based on the LG/OC ratio and fire hotspots, the entire sampling campaign was divided into OBB and non-open biomass burning (NBB) periods.It was found that OBB emissions had little effect on sulfate formation but a significant impact on nitrate formation. High relative humidity (RH) conditions played a crucial role in SIA formation, with both SO42−/EC and NO3−/EC increasing as RH elevated at temperatures below −10 °C. Furthermore, the temperature dependence of SO42−/EC and NO3−/EC indicated that temperature could enhance the activity of either aqueous-phase production or gas-phase reactions, subsequently promoting the formation of SO42− and NO3− in the ambient environment. Additionally, positive matrix factorization (PMF) analysis was used to scientifically separate the sources of ambient aerosols during OBB and NBB periods.

Spatial Distribution and Inter-City Transport of PM2.5 Concentrations from Vehicles in the Guanzhong Plain in Winter

Regional atmospheric environmental problems have become increasingly prominent due to continuous urbanization in China. In this study, the Weather Research and Forecasting (WRF) model coupled with the California Puff (CALPUFF) air quality model was applied to analyze the spatial distribution and inter-city transport of primary and secondary PM2.5 concentrations from vehicles in the Guanzhong Plain (GZP) in January 2019. The results show that the secondary PM2.5 concentration emitted by vehicles was more easily dispersed than primary PM2.5. The maximum hourly average concentrations of primary PM2.5, secondary inorganic aerosol (SIA), and secondary organic aerosol (SOA) were about 18, 9, and 2 µg/m3, respectively. Exhaust emission and secondary NO3− were the main contributors to the total PM2.5 concentration from vehicles, accounting for about 52% and 32%, respectively. The maximum contribution of vehicle emissions to the ambient PM2.5 concentration was about 19%. Inter-city transport contributed about 33% of the total PM2.5 concentration from vehicles in cities in the GZP on average. Among the PM2.5 components transported in each city, SIA was the most abundant, followed by primary PM2.5, and SOA was the least. These findings will provide valuable insights for mitigating the regional PM2.5 pollution caused by near-surface sources in urban agglomerations.

Different Response Mechanisms of N‐Bearing Components to Emission Reduction Across China During COVID‐19 Lockdown Period

AbstractThe response characteristics of secondary inorganic aerosols to COVID‐19 lockdown measures have been extensively reported, while spatial disparities of these response characteristics across China and key deriving mechanisms still remained poorly understood. In our study, a chemical transport model (GEOS‐Chem) was applied to simulate the national concentrations of four N‐bearing components during lockdown periods in 2020 and business‐as‐usual (BAU) period (the same period in 2019). Three distinct regional response mechanisms were distinguished across China. The increases of levels in the northern part of Beijing‐Tianjin‐Hebei (BTH) might be attributable to increased relative humidity (RH) and abundant ammonia (NH3) level (13.5 μg/m3). The dramatic decreases of secondary inorganic nitrogen in Southeast China were contributed by substantial emission reduction (−15.3%) and slightly favorable (pollutant removal) meteorological conditions (−4.36%). The consistent increases of levels, but decreased NH3 levels in tropical regions suggested extremely high RH (84%) and enhanced atmospheric oxidation capacity were dominant factors. The response mechanisms of secondary N‐bearing components showed the distinct characteristics between urban and rural regions, which might be closely associated with variations of emission reduction and meteorology during the COVID‐19 period. The natural experiment demonstrates priority control of NH3 emission might be the primary target for BTH, while the coordinated controls of VOCs and NOx emissions should be exerted in Southeast China especially the tropical regions.

Contribution of chemical composition to oxidative potential of atmospheric particles at a rural and an urban site in the Po Valley: Influence of high ammonia agriculture emissions

The present study investigates the chemical composition and oxidative potential (OP) of PM10 particles at two sites in the Po Valley (Norther Italy), with the aim of evidence the impact of high level of atmosphere ammonia (NH3). Field measurements were conducted in a rural location (Bertonico) close to farms strongly impacted by high ammonia emissions from agriculture and livestock husbandry. The urban site was in the metropolitan area of Milan. The NH3 concentrations observed at the rural site were about 5 times higher than those at the urban location, generating higher levels of secondary inorganic aerosol (ΣSIA) at Bertonico (16.6 ± 6.33 μg m−3) than at Milan 12.6 ± 4.93 μg m−3. The oxidative potential measured with the ascorbic acid assay (OPAAV) was almost triple in Milan than at Bertonico, namely 1.48 ± 1.08 nmol min−1 m−3 and 0.44 ± 0.23 nmol min−1 m−3, respectively, while the measured OPDTTV responses were similar at both sites, close to ∼ 0.5 ± 0.3 nmol min−1 m−3. These results suggested that the SIA components don't significantly contribute to the PM10 oxidative reactivity, although they account for most of the PM10 mass. Despite such an OP-inactivity, the SIA components resulted significantly correlated with both OPAAV and OPDTTV responses. This may be likely due to their inter-correlation with other redox-active components, such as the secondary organic species, which are synergically produced along with the SIA formation. In addition, an increase in the metals reactivity towards the OP assays, may be associated with the PM10 acidic environment produced by enhanced HNO3 and H2SO4 levels. Therefore, the contribution of the SIA to PM oxidative toxicity cannot be ignored in assessing health risk associated with PM exposure.

Characteristics and Cause of PM2.5 During Haze Pollution in Winter 2022 in Zhoukou, China

The characteristics and main factors of causes of haze in Zhoukou in January 2022 were analyzed. Six air pollutants, water-soluble ions, elements, OC, EC, and other parameters in fine particulate matter were monitored and analyzed using a set of online high-time-resolution instruments in an urban area. The results showed that the secondary inorganic aerosols(SNA), carbonaceous aerosols(CA, including organic carbon OC and inorganic carbon EC), and reconstructed crustal materials(CM, such as Al2O3, SiO2, CaO, and Fe2O3, etc.) were the three main components, accounting for 61.3%, 24.3%, and 9.72% in PM2.5, respectively. The concentrations of SNA, CA, CM, and SOA were increased, accompanied with higher AQI. The sulfur oxidation rate(SOR) and nitrogen oxidation rate(NOR) in January were 0.53 and 0.46, respectively. The growth rates[μg·(m3·h)] of sulfate and nitrate were 0.027(-5.89-9.47, range) and 0.051(-23.1-12.4), respectively. During the haze period, the growth rates of sulfate and nitrate were 0.13 μg·(m3·h)-1and 0.24 μg·(m3·h)-1, which were 4.8 and 4.7 times higher than the average value of January, respectively. Although the sulfur oxidation rate was greater than the nitrogen oxidation rate, the growth rate of nitrate was approximately 1.8 times that of sulfate owing to the difference in the concentration of gaseous precursors and the influence of relative humidity. The growth rates of nitrate in SNA were significantly higher than those of sulfate on heavily polluted days. The values of SOR, NOR, and concentrations of SNA and SOA during higher AQI and humidity periods were higher than those in lower AQI and humidity periods. The Ox(NO2+O3) decreased with the increase in relative humidity. The SOA was higher at nighttime, increasing faster with the humidity than that in daytime. Under the situation of lower temperature, higher humidity, and lower wind speed, the emission of gaseous precursors of SNA requires further attention in Zhoukou in winter. Advanced control strategies of emissions of SO2 and NO2, such as mobile sources and coal-burning sources, could reduce the peak of haze in winter efficiently.

Insight into Secondary Inorganic Aerosol (SIA) production enhanced by domestic ozone using a machine learning technique

Taiwan has prioritized management and air pollution control of ozone in the past decade. Atmospheric ozone reacts with gaseous precursors to produce secondary inorganic aerosols (SIAs), which worsen air quality to a great extent. The present study applied a bivariate polar plot, K-means clustering, and a nonlinear autoregressive network with exogenous input neural network (NARX-NN) to identify the sources of O3 and the formation mechanism of SIAs in an urban area, aiming to facilitate the development of exposure risk assessment methods and an O3 pollution early warning system for human health protection. Results show that the present NARX-NN model could be used to capture 72 h ahead of water-soluble inorganic salts (WIS) and O3 concentrations accurately with R2 of 0.71 for NO3-, 0.72 for SO42-, 0.80 for NH4+, and 0.79 for O3 concentrations. Based on the statistical and K-means clustering analysis, the domestic high O3 hours in a year (O3 concentrations>60 ppb) account for up to 76% and 99% of the total high O3 hours in northern and southern Taiwan, respectively. Under volatile organic compounds (VOCs)-limited regime, an increase in O3 concentrations by 57.4% was found to enhance heterogeneous oxidation reaction to produce SIAs by 48.0% of NO3- and 56.6% of SO42- under prevailing northeast monsoon during winter and spring seasons. It is evident that strict control measures are still necessary for local ozone sources to maintain air quality. The source tracing framework developed in the present study is applicable for policymakers to develop early warning systems and maintain air quality during the decision-making process.

Impact of mineral dust photocatalytic heterogeneous chemistry on the formation of the sulfate and nitrate: A modelling study over East Asia

Dust heterogeneous chemistry plays an important role in the atmosphere and has significant effects on climate and the environment. However, the traditional modelling method treats heterogeneous chemistry as pseudo-first-order reactions, which retains significant uncertainties, hindering the accurate prediction of secondary inorganic aerosols. In contrast, the actual dust heterogeneous chemistry involves complex multiphase reactions, including partition between gas- and dust-phase, and reactions on the dust surface. In this study, we implement a photocatalytic mechanism into the GEOS-Chem model and apply it to investigate the impact on atmospheric chemistry during a dust storm over East Asia during April 9–14th, 2018.With the photocatalytic heterogeneous chemistry (PHO), model simulation better reproduces observed sulfate and nitrate concentrations than those with the traditional pseudo-first-order mechanism (TDT) or without any dust heterogeneous chemistry at all (BASE). As validated against observations, normalized mean bias (NMB) in PHO reduces substantially compared to TDT, from −61.65% and 103.38% to −2.19% and 6.83% at Nanjing and Shanghai, respectively. The model also accurately simulates gaseous precursors such as SO2 and NO2, as evidenced by a decline in NMB from 103.38% to 81.80%–6.83% and 6.64% at the two sites, respectively. Furthermore, our analysis indicates that the larger dry deposition velocity of dust-phase sulfate and higher sulfate concentrations simulated by PHO jointly lead to a significant increase in SO4 dry deposition flux, demonstrating that the dust heterogeneous chemical process facilitates the removal of aerosol pollutants during dust events. These findings reinforce the need for enhancing the representation of dust heterogeneous chemistry in atmospheric models, underlining the criticality of this factor in accurate predictive modelling and environmental impact studies.

Evaluation of air quality changes in a Chinese megacity over a 15-year period (2006–2021) using PM2.5 receptor modelling

Air quality impairment has a massive impact on human health, with atmospheric particulate matter (PM) playing a major role. The People's Republic of China experienced a trend of increasing PM2.5 concentrations from 2000 to 2013. However, after the application of the Air Pollution Prevention and Control Action Plan and other related control measures, sharp decreases in air pollutant concentrations were particularly evident in the city of Wuhan (central China). This study analysed major changes in PM2.5 concentrations, composition and source apportionment (using receptor modelling) based on Wuhan's PM2.5 chemical speciation datasets from 2006 to 2007, 2019–2021 and contemporaneous gaseous pollutant values. Average SO2 concentrations decreased by 88%, from the first to the second period, mostly due to measures that reduced coal combustion. However, NO2 only declined by 25%, with policy measures likely being undermined by an increased number of vehicles. PM2.5 concentrations decreased by 65%, with the PM constituents each being affected differently. Coal combustion-related element concentrations, OC, SO42−, NH4+, EC, Cl−, Al, Ca, Cu, Fe, Co and NO3− decreased by 22–90%. Secondary inorganic aerosol (SIA) was initially dominated by (NH4)2SO4 (73%) in 2006, but later dominated by NH4NO3 (52%) in 2021. Receptor modelling identified major sources contributing to PM2.5: Mineral, road and desert dust (MRDD), Secondary sulphate (SECS), Secondary nitrate (SECN), Tungsten industry (W), Toxic Elements of Coal (TEC), Iron and Steel (IRONS), Coal Combustion (CC), Residential Heating (RH), Refinery (REF) and Traffic (TRF). In relative proportions, TEC (−83%), SECS (−64%) and SECN (−48%) reduced their contributions to PM2.5 whilst MRDD increased (+62.5%). Thus, the results indicate not only a drastic abatement of PM pollution in Wuhan but also a change in the sources of pollution, which requires further actions to reduce PM2.5 concentrations to health protective values. Secondary PM and fugitive emissions are key components to abate.

Source Apportionment of Atmospheric Aerosols in Kraków, Poland, before and during the COVID-19 Pandemic at a Traffic Monitoring Station

PM10 samples were collected at the Kraków air quality traffic monitoring station during two periods: February–May 2018 and February–June 2020. The PM10 concentrations dropped by 50% from 74 ± 29 µg/m3 to 37 ± 13 µg/m3 in 2018 and 2020, respectively. The elemental concentrations were determined by the energy-dispersive X-ray fluorescence (EDXRF) method, and the ion concentrations were determined by ion chromatography (IC). The concentration ratios in 2018 to 2020 were greater than 1.7 for the following elements: S, Cl, K, Zn, Br, and the ions SO42−, Na+, and NH4+. Similar concentrations were observed in 2018 and 2020 for the following chemical species: Ca, Ti, Mn, Ni, Rb, Sr, K+, Mg2+, Ca2+, and PO43−. The Cr concentration was higher in 2020 compared to 2018. Four source profiles were obtained from the PMF (Positive Matrix Factorization) modelling. The following sources were attributed to this: solid fuel combustion, secondary inorganic aerosols, traffic/industry/construction work, and soil. The contributions of solid fuel combustion and secondary inorganic aerosols (SIA) were significantly lower in February and March 2020 than in February and March 2018. The relative differences were in the range 70–98%. Traffic/industry/construction work contributions were 6% and 36% lower in March and May 2020 compared to the same months in 2018, respectively. Two factors affected the characteristics of PM10: one was the ban of using coal and wood for heating purposes introduced in Krakow in September 2019, observed mainly in February and March, and the COVID-19 pandemic that was observed mainly in April and May.

Exposure to air pollution and risk of respiratory tract infections in the adult Danish population—a nationwide study

ObjectivesThe association between air pollution and risk of respiratory tract infection (RTI) in adults needs to be clarified in settings with low to moderate levels of air pollution. We investigated this in the Danish population between 2004 and 2016. MethodsWe included 3 653 490 persons aged 18–64 years in a nested case-control study. Exposure was defined as the average daily concentration at the individual's residential address of CO, NOX, NO2, O3, SO2, NH3, PPM2.5, black carbon, organic carbon, mineral dust, sea salt, secondary inorganic aerosols, SO42-, NO3-, NH4+, secondary organic aerosols, PM2.5, and PM10 during a 3-month exposure window. RTIs were defined by hospitalization for RTIs. Incidence rate ratios (IRRs) and 95% CIs were estimated comparing highest with lowest decile of exposure using conditional logistic regression models. ResultsIn total, 188 439 incident cases of RTI were identified. Exposure to most air pollutants was positively associated with risk of RTI. For example, NO2 showed an IRR of 1.52 (CI: 1.48–1.55), and PM2.5 showed an IRR of 1.45 (CI: 1.40–1.50). In contrast, exposure to sea salt, PM10, NH3, and O3 was negatively associated with a risk of RTIs. DiscussionIn this nationwide study comprising adults, exposure to air pollution was associated with risk of RTIs and subgroups hereof. Sea salt, PM10, NH3, and O3 may be proxies for rural areas, as the levels of these species in Denmark are higher near the western coastlines and/or in rural areas with fewer combustion sources.

Significant Reductions in Secondary Aerosols after the Three-Year Action Plan in Beijing Summer.

Air quality in China has continuously improved during the Three-Year Action Plan (2018-2020); however, the changes in aerosol composition, properties, and sources in Beijing summer remain poorly understood. Here, we conducted real-time measurements of aerosol composition in five summers from 2018 to 2022 along with WRF-Community Multiscale Air Quality simulations to characterize the changes in aerosol chemistry and the roles of meteorology and emission reductions. Largely different from winter, secondary inorganic aerosol and photochemical-related secondary organic aerosol (SOA) showed significant decreases by 55-67% in summer, and the most decreases occurred in 2021. Comparatively, the decreases in the primary aerosol species and gaseous precursors were comparably small. While decreased atmospheric oxidation capacity as indicated by ozone changes played an important role in changing SOA composition, the large decrease in aerosol liquid water and small increase in particle acidity were critical for nitrate changes by decreasing gas-particle partitioning substantially (∼28%). Analysis of meteorological influences demonstrated clear and similar transitions in aerosol composition and formation mechanisms at a relative humidity of 50-60% in five summers. Model simulations revealed that emission controls played the decisive role in reducing sulfate, primary OA, and anthropogenic SOA during the Three-Year Action Plan, while meteorology affected more nitrate and biogenic SOA.

Moisture-induced secondary inorganic aerosol formation dominated the light absorption enhancement of refractory black carbon at an urban site in northwest China

Reducing the uncertainty in aerosol radiative forcing requires a comprehensive understanding of the factors affecting black carbon (BC) light absorption. In this study, the characteristics and influencing factors of light absorption enhancement (Eabs) of refractory BC (rBC) were investigated by conducting intensive measurements at an urban site in northwest China during the early summer of 2018. On average, the absorption of rBC was enhanced by 34% as a result of the internal mixing of rBC with other aerosol components. Secondary inorganic aerosols (SIAs) were found to have considerable effects on the Eabs of rBC. The Eabs showed a robust linear relationship with the bulk nitrate/rBC mass ratio in fine particles, with an increase of 3% per nitrate/rBC ratio unit. A notable increase in Eabs from dusk to the next morning was observed, in accordance with the diurnal variations in nitrate and sulfate, indicating the excellent contribution of non-photochemical formation of SIAs to Eabs. This fact was further supported by the positive correlation of the nitrate/rBC and sulfate/rBC ratios with relative humidity (RH) rather than photochemical indicators. This study indicates that the aqueous and/or heterogeneous formation of SIAs is likely the dominant aging pathway leading to the high Eabs of rBC.

Characteristics of secondary inorganic aerosols and contributions to PM2.5 pollution based on machine learning approach in Shandong Province

Primary emissions of particulate matter and gaseous pollutants, such as SO2 and NOx have decreased in China following the implementation of a series of policies by the Chinese government to address air pollution. However, controlling secondary inorganic aerosol pollution requires attention. This study examined the characteristics of the secondary conversion of nitrate (NO3−) and sulfate (SO42−) in three coastal cities of Shandong Province, namely Binzhou (BZ), Dongying (DY), and Weifang (WF), and an inland city, Jinan (JN), during December 2021. Furthermore, the Shapley Additive Explanation (SHAP), an interpretable attribution technique, was adopted to accurately calculate the contributions of secondary formations to PM2.5. The nitrogen oxidation rate exhibited a significant dependence on the concentration of O3. High humidity facilitates sulfur oxidation. Compared to BZ, DY, and WF, the secondary conversion of NO3− and SO42− was more intense in JN. The light-gradient boosting model outperformed the random forest and extreme-gradient boosting models, achieving a mean R2 value of 0.92. PM2.5 pollution events in BZ, DY, and WF were primarily attributable to biomass burning, whereas pollution in Jinan was contributed by the secondary formation of NO3− and vehicle emissions. Machine learning and the SHAP interpretable attribution technique offer a precise analysis of the causes of air pollution, showing high potential for addressing environmental concerns.

Ammonia Cycling and Emerging Inorganic Secondary Aerosols from Arable Agriculture

Air quality monitoring in Ireland is under the jurisdiction of the Environmental Protection Agency in compliance with the Gothenburg Protocol, EU/national legislation, and the National Clean Air Strategy. Secondary inorganic aerosols (SIAS) have been acknowledged as a key atmospheric pollutant, with serious public health impacts and no safe exposure threshold in place to date. Ammonia (NH3) emissions are linked to the secondary production of aerosols through atmospheric reactions occurring with acidic atmospheric components such as sulfuric, nitric, and hydrochloric acid. These reactions result in the formation of ammonium sulfate, ammonium nitrate and ammonium chloride, among others. Approximately 98% of NH3 emissions occurring in Ireland arise from agriculture, with minor contributions from transport and natural sources. A better understanding of NH3 emissions and SIA formation can be achieved through monitoring emissions at the source level. Additionally, mitigation strategies with a more thorough understanding of NH3 dynamics at the source level and consequential SIA formation allow for more efficient action. This project monitored ambient NH3 and SIA on two selected arable agricultural sites and a control site in a rural site close to Dublin on the east coast of Ireland to establish emission levels. Meteorological factors affecting emissions and SIA formation were also measured and cross-correlated to determine micro-meteorological effects. Monitoring at the agricultural sites observed ambient NH3 concentrations ranging from 0.52 µg m−3 to 1.70 µg m−3, with an average of 1.45 µg m−3. At the control site, ambient NH3 measured concentrations ranged from 0.05 µg m−3 to 1.76 µg m−3 with an average of 0.516 µg m−3. Aerosol NH4+ ranged from 0.03 µg m−3 to 1.05 µg m−3 with an average concentration of 0.27 µg m−3 at the agricultural site. The potential effects of meteorological conditions and the implications for the effects of these emissions are discussed, with recommendations to aid compliance with the National Emissions Ceiling and the National Clean Air Strategy (Directive 2001/81/EC).

Diurnal source apportionment of organic and inorganic atmospheric particulate matter at a high-altitude mountain site under summer conditions (Sierra Nevada; Spain)

High-altitude mountain areas are sentinel ecosystems for global environmental changes such as anthropogenic pollution. In this study, we report a source apportionment of particulate material with an aerodynamic diameter smaller than 10 μm (PM10) in a high-altitude site in southern Europe (Sierra Nevada Station; SNS (2500 m a.s.l.)) during summer 2021. The emission sources and atmospheric secondary processes that determine the composition of aerosol particles in Sierra Nevada National Park (Spain) are identified from the concentrations of organic carbon (OC), elemental carbon (EC), 12 major inorganic compounds, 18 trace elements and 44 organic molecular tracer compounds in PM10 filter samples collected during day- and nighttime. The multivariate analysis of the joint dataset resolved five main PM10 sources: 1) Saharan dust, 2) advection from the urbanized valley, 3) local combustion, 4) smoke from a fire-event, and 5) aerosol from regional recirculation with high contribution of particles from secondary inorganic and organic aerosol formation processes. PM sources were clearly associated with synoptic meteorological conditions, and day- and nighttime circulation patterns typical of mountainous areas. Although a local pollution source was identified, the contribution of this source to PM10, OC and EC was small. Our results evidence the strong influence of middle- and long-range transport of aerosols, mainly from anthropogenic origin, on the aerosol chemical composition at this remote site.

Variation of PM2.5 and PM10 in emissions and chemical compositions in different seasons from a manure-belt laying hen house

Particulate matter (PM) emissions from animal houses and the corresponding hazard have raised increasing attention during recent years. In this study, a large-scale manure-belt laying hen house located in Beijing, China was selected as the experimental site for the study of the emission rates (ER) and chemical compositions of PM2.5 and PM10 in 3 seasons, namely, summer, autumn, and winter, to investigate their possible influences on ambient air quality and human health. The results showed that the mean ER from the hen house in summer, autumn, and winter were 9.0 ± 1.7, 2.4 ± 0.7, and 1.9 ± 0.7 mg hen-1 d-1 for PM2.5 (P < 0.05), and 30.7 ± 1.1, 12.8 ± 1.5, and 10.9 ± 0.9 mg hen-1 d-1 for PM10 (P < 0.05), respectively. Moreover, large amounts of secondary inorganic aerosols (SIA) were observed inside the house in summer, accounting for 11.4 and 9.6% of indoor PM2.5 and PM10 mass, respectively, compared with the value of <1.4% in autumn and winter. Among the 31 detected elements in indoor PM, arsenic concentration exceeded the threshold set in legislation. Zn had a notably high concentration of 3,403 to 4,432 ng m-3 in indoor PM10, which was 28 to 71 times higher than that in ambient PM10. The findings suggest that the poultry-raising house emit PM2.5 and PM10 containing SIA and toxic heavy-metal elements such as As and Zn to the ambient with much more emissions in summer than in autumn and winter. Considering the increasing development of poultry-raising farming in China, the potential hazard derived from the exhaust of PM2.5 and PM10 should be focused on, especially during summer.

Outdoor PM2.5 and their water-soluble ions in the Northern part of the Persian Gulf

Background: The environmental conditions potentially predispose the northern part of the Persian Gulf to the occurrence of dust storms. Outdoor PM2.5 and their water-soluble ions in Bushehr port were studied from December 2016 to September 2017. Methods: A total of 46 outdoor PM2.5 samples were collected by high-volume air sampler and eight water-soluble ions, including Ca2+, Mg2+, Na+, K+, F- , Cl- , NO3 - , and SO4 2- in PM2.5 were also measured by ion chromatography (IC). Results: The 24-hour average concentration of PM2.5 was in the range of 22.09 to 292.45 µg/m3 . The mean concentration of water-soluble ions in PM2.5 was in the range of 0.10±0.14 to 6.76±4.63 µg/m3 . The major water-soluble ions were the secondary inorganic aerosols (SO4 2- and NO3 - ), which accounted for nearly 41% of total water-soluble ions in PM2.5. The total water-soluble ions level of PM2.5 in winter was higher than that in spring and summer. The positive matrix factorization (PMF) model showed that the source contributions of PM2.5 were in the order of dust (55.8%), sea salt (17.1%), secondary sulfate (11.8%), industries (7%), vehicular emission (4.7%), and secondary nitrate (3.7%). Conclusion: According to the results, dust and sea salt are the main sources of water-soluble ions in PM2.5 in Bushehr port, which should attract much attention.

Establishing an emission inventory for ammonia, a key driver of haze formation in the southern North China plain during the COVID-19 pandemic

Despite the significant reduction in atmospheric pollutant levels during the COVID-19 lockdown, the presence of haze in the North China Plain remained a frequent occurrence owing to the enhanced formation of secondary inorganic aerosols under ammonia-rich conditions. Quantifying the increase or decrease in atmospheric ammonia (NH3) emissions is a key step in exploring the causes of the COVID-19 haze. Historic activity levels of anthropogenic NH3 emissions were collected through various yearbooks and studies, an anthropogenic NH3 emission inventory for Henan Province for 2020 was established, and the variations in NH3 emissions from different sources between COVID-19 and non-COVID-19 years were investigated. The validity of the NH3 emission inventory was further evaluated through comparison with previous studies and uncertainty analysis from Monte Carlo simulations. Results showed that the total NH3 emissions gradually increased from north-west to south-east, totalling 751.80 kt in 2020. Compared to the non-COVID-19 year of 2019, the total NH3 emissions were reduced by approximately 4 %, with traffic sources, waste disposal and biomass burning serving as the sources with the top three largest reductions, approximately 33 %, 9.97 % and 6.19 %, respectively. Emissions from humans and fuel combustion slightly increased. Meanwhile, livestock waste emissions decreased by only 3.72 %, and other agricultural emissions experienced insignificant change. Non-agricultural sources were more severely influenced by the COVID-19 lockdown than agricultural sources; nevertheless, agricultural activities contributed 84.35 % of the total NH3 emissions in 2020. These results show that haze treatment should be focused on reducing NH3, particularly controlling agricultural NH3 emissions.

Quantifying the seasonal variations in and regional transport of PM2.5 in the Yangtze River Delta region, China: characteristics, sources, and health risks

Abstract. Given the increasing complexity of the chemical composition of PM2.5, identifying and quantitatively assessing the contributions of pollution sources has played an important role in formulating policies to control particle pollution. This study provides a comprehensive assessment between PM2.5 chemical characteristics, sources, and health risks based on sampling data conducted over 1 year (March 2018 to February 2019) in Nanjing. Results show that PM2.5 exhibits a distinct variation across different seasons, which is primarily driven by emissions, meteorological conditions, and the chemical conversion of gaseous pollutants. First, the chemical mass reconstruction shows that secondary inorganic aerosols (62.5 %) and carbonaceous aerosols (21.3 %) contributed most to the PM2.5 mass. The increasing oxidation rates of SO2 and NO2 from summer to winter indicate that the secondary transformation of gaseous pollutants is strongly positively correlated with relative humidity. Second, the positive matrix factorization (PMF) method shows that identified PM2.5 sources include secondary inorganic aerosol source (SIS, 42.5 %), coal combustion (CC, 22.4 %), industry source (IS, 17.3 %), vehicle emission (VE, 10.7 %), fugitive dust (FD, 5.8 %), and other sources (1.3 %). The Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model and the concentration-weighted trajectory (CWT) analysis are used to further explore different spatial distributions and regional transport of sources. The concentrations (10–11 µg m−3) of SIS and CC distribute in Nanjing and central China in winter. The concentrations (8–10 µg m−3) of IS and VE are potentially located north of Jiangsu, Anhui, and Jiangxi. Finally, the health risk assessment indicates that the carcinogenic and non-carcinogenic risks of toxic elements (Cr, As, Ni, Mn, V, and Pb) mainly come from IS, VE, and CC, which are within the tolerance or acceptable level. Although the main source of pollution in Nanjing is SIS at present, we should pay more attention to the health burden of vehicle emissions, coal combustion, and industrial processes.

Key factors for abating particulate matter in a highly industrialized area in N Spain: Fugitive emissions and secondary aerosol precursors

In highly industrialized areas, abating particulate matter (PM) is complex owing to the variety of emission sources with different chemical profiles that may mix in the atmosphere. Gijón—an industrial city in northern Spain—was selected as a case study to better understand the key emission sources and improve air quality in highly industrialized areas. Accordingly, the trends of various air quality indicators (PM10, PM2.5, SO2, NO2, and O3) during the past decade (2010–2019) were analyzed. Additionally, the inorganic and organic PM10 compositions were analyzed for source apportionment studies and to assess the impact of COVID-19 restrictions on PM10 levels.The results revealed that over the past decade, PM10 concentrations decreased, whereas PM2.5 concentrations dominated by secondary inorganic aerosols (SIA) remained relatively constant. Notably, during the COVID-19 lockdown, the PM10 concentration increased by 9.1%, primarily owing to an increase in regional SIA (>65%) due to specific meteorological conditions that favor the formation of secondary PM from gaseous precursors. Overall, eight key PM10 sources were identified: “industrial fugitive PM resuspension” (FPM, 28% of mean PM10 concentration), “aged sea spray” (SSp, 16%), “secondary nitrate” (SN, 15%), “local diffuse source” (LPM, 12%), “solid fuel combustion” (SFC, 7.8%), “biomass burning” (BB, 7.4%), “secondary sulphate” (SSu, 6.0%), and “sinter” (SIN, 4.5%). The PM10 concentration in Gijón is significantly influenced by the integrated steel industry (FPM, SFC, and SIN; 41% of PM10) and fugitive primary PM emissions were the main source (FPM and LPM; 40%). To reduce PM10 and PM2.5 concentrations, industrial fugitive emissions, which are currently poorly regulated, and SIA precursors must be abated.This study provides a methodological approach that combines trend analysis, chemical speciation, and source apportionment for assessing pollution abatement strategies in industrialized areas with a complex mix of emission sources.