Fine particulate matter (PM2.5) pollution, dominated by secondary inorganic aerosols (SIA), remains a critical environmental issue in China's Yangtze River Delta. In this study, we utilized hourly high-resolution measurements of water-soluble ions and precursor gases collected in suburban Nanjing from January to March 2021. By coupling these observations with the ISORROPIA-II and WRF-Chem models, we elucidated how aerosol liquid water content (ALWC) and pH govern SIA formation in ammonia (NH3)-rich environments, and further established quantitative policy thresholds for emission mitigation. Observations revealed that SIA accounted for nearly half (49.55%) of the PM2.5 mass (mean: 34.4 μg/m3), with nitrate being the dominant species. Continuous ammonia-excess conditions provided sufficient NH3 to generate ammonium (NH4+) for complete anion neutralization, driving continuous SIA accumulation. Mechanistically, rising ALWC significantly enhanced aqueous-phase oxidation and promoted the partitioning of nitrate and ammonium into the particle phase. Meanwhile, aerosol pH strictly regulated both the gas-particle partitioning equilibrium of semi-volatile species and the sulfate production pathways, with transition metal ion (TMI)-catalyzed oxidation acting as the dominant pathway. Thermodynamic sensitivity analysis indicated that local conditions were strictly total nitrate (TNO3)-limited. Simulations from both the ISORROPIA-II and WRF-Chem models revealed that due to the strong buffering effect of the substantial gaseous NH3 pool, PM2.5 mass responds minimally to moderate NH3 reductions, requiring emission cuts of over 60% to drive significant PM2.5 mitigation. In contrast, reducing nitric acid (HNO3) alone yielded a mitigation efficiency comparable to joint HNO3 and NH3 controls. Therefore, mitigating PM2.5 pollution in such NH3-rich regions requires prioritizing nitrogen oxide (NOx) emission controls, supplemented by ammonia regulations tailored to local aerosol thermodynamics.

Nitrogen dioxide (NO2) drives ozone and secondary aerosol formation and harms human health. Chongqing, a mountainous megacity of 32 million people, lacks a fine-scale satellite assessment of its NO2 evolution. We analyzed tropospheric NO2 vertical column density (VCD) over Chongqing for 2019–2024. The analysis used Sentinel-5P TROPOMI observations. We computed monthly, seasonal, and annual composites at 5.5 km resolution. Trends were quantified with the Theil–Sen slope and, at the pixel level, the Seasonal Mann–Kendall (SMK) test applied to the full 72-month series. A MODIS land-cover mask separated urban built-up from non-urban pixels. NO2 concentrated in the central districts and along the Yangtze valley. The core exceeded the mountainous counties by a factor of 3 to 4. TROPOMI resolved the Wanzhou and Yongchuan–Jiangjin hotspots as separate features. The record was divided into three phases. The 2020 lockdown produced the minimum, 31% below the prior February. Rebound emissions produced the 2021 maximum of 5.6 × 1015 molecules cm−2 under near-normal dispersion conditions, with ERA5 (the European Centre of Medium-range Weather Forecasts Reanalysis v.5) showing the January 2021 boundary layer 4.3% deeper than its climatological norm. Thereafter the regional mean stabilized: the area-weighted SMK slope was +0.042 × 1015 molecules cm−2 yr−1 and not significant (p = 0.14), because emission controls in the core and rising county emissions canceled in the average. Trends diverged sharply in space. The nine core districts declined (median urban Sen slope −0.11 × 1015 molecules cm−2 yr−1), whereas 41% of peripheral pixels rose significantly (p < 0.05). The urban-to-rural ratio narrowed from 3.0 in 2019 to 2.3 in 2024 (annual means). This convergence was robust to the built-up threshold (30–50%). Industrial relocation and county urbanization explain the peripheral rise. The results support extending vehicle and industrial emission standards from the core to the receiving counties.

This study analyzes the spatial and temporal distribution characteristics of pollutants and the influence of meteorological factors using data from 13 cities in Jiangsu Province from 2014 to 2022. The results showed that, from 2014 to 2022, the average concentrations of PM2.5, PM10, SO2, and CO in Jiangsu were high in the north and low in the south, while the NO2 concentration was low in the north and high in the south, all of which decreased over time. O3 concentration was higher on the eastern coast and increased with the year. PM2.5 pollution days in northern Jiangsu were higher in autumn and winter. O3 pollution days in southern Jiangsu were higher in spring, summer, and autumn. There was a significant positive correlation between O3 and temperature in spring and autumn, and it was weaker in summer. Relative humidity (RH) in winter was positively correlated with PM2.5 and RH showed a significant negative correlation with PM10 in spring, summer, and autumn. The scavenging effect of precipitation on PM10 concentration was the most pronounced, followed by PM2.5. Precipitation has the weakest scavenging effect on CO, only reducing its concentration by an average of 13%. Precipitation also exhibits a significant scavenging effect on O3. The decrease in O3 was the smallest on heavy rain days (14.7%) and the largest on severe, torrential rain days (25.9%).

To evaluate the effect of China’s National Action Plan on Air Pollution (NAPAP), we assessed the health benefits of PM2.5 remediation under the NAPAP from 2013 to 2017 in the Beijing-Tianjin-Hebei (BTH) area using a relative risk model with real PM2.5 monitoring data and recent statistical research data. The results revealed that the PM2.5 concentration in the BTH area decreased by 36 µg m−3 (34.0

To gain detailed insight into the gaseous sources of PM2.5, three kinds of positive matrix factorization were developed and applied to hourly elemental and gaseous data (PMF-GAS). According to the results of PMF-GAS1, which relied on gaseous markers to enhance source discrimination, crustal dust, vehicular exhaust, coal combustion, sulfate and nitrate (CD1, VE1, CC1, SUL1 and NIT1) directly contributed 20%, 17%, 15%, 34% and 14% to the PM2.5, respectively. Using PMF-GAS2, which summed species found in PM2.5, and their corresponding precursors to estimate the overall influence of primary sources, the total contribution from CD2, VE2 and CC2 to PM2.5 was quantified as 30%, 29% and 41%, respectively. Finally, PMF-GAS3 quantified the contribution of oxidation (OXI3; 27%) based on the relationships between the species and their precursors. NH4+ was found mostly in CD2 and CD3 but also in SUL1 and NIT1, implying that crustal dust can provide alkaline conditions for the formation of ammonium salts. High correlations were found between corresponding source contributions, but CD1 showed relatively weak links with CD2 and CD3 due to NH4+ being present in different factors. A fully populated map of classical bootstrap (BS) runs implies the high stability of these PMF-GAS results.

Since the distinct thermostability difference of sulfate ammonium and nitrate ammonium aerosols, their distributions, evolutions and sources could be unpredictable on a long-range transport condition. Here, we highlighted the 3-D structures and sources of SO42-, NO3- and NH4+ (SNA) during two cold front episodes in east China. Cold fronts effectively uplift and transport PM2.5 and its precursors from upstream sources to the Yangtze River Delta (YRD). Specifically, in the YRD, surface SO42- is mostly imported from the upstreams, accounting for similar to 48%, significantly higher than the contribution from the YRD itself (similar to 29%). In contrast, NH4NO3 is thermally unstable and more easily lost in the warmer and lower boundary layer (BL) ahead of cold front. Consequently, only 20% of the total NO3- originates from upstreams, while the YRD contributes 28%. In the upper BL, the contribution of SO42- from upstreams remain high (similar to 49%), with only 18% originating from the YRD. However, due to the intense thermostability of NH4NO3 in colder and wetter air, the YRD's contribution to NO3- is 27%, and upstreams contribute 20%. The physical processes exert relatively consistent effects on variations of PM2.5 and SNA concentrations. The aerosol chemical process (AERO) of (NH4)2SO4 consistently contributes positively throughout the entire BL. Conversely, the temperature-sensitive NH4NO3 undergoes repeated dissociation/condensation and deposition, causing positive AERO contributions in upper BL and negative contributions in lower BL. Results indicate that one difference in physicochemical property of species could induce their distinct distributions and sources in large scale, and should be considered in regional air pollution control. Long-range transport of PM2.5 by cold frontal passage is an important haze formation mechanism. Previous field and modeling studies have revealed that the vertical distribution of particle sulfate and particle nitrate concentrations varied significantly. However, few studies have explored the 3-D structures and sources of particle sulfate and nitrate under a long-range transport conditions. In this study, we used combined observations and model simulations during cold front events to address the unrevealed inconsistent 3-D structures and sources of sulfate and nitrate resulting from temperature stability differences. Cold front episodes redistribute SNA and precursors in three dimensions, driven by drastic meteorology changes and long range transport. Consequently, the distributions, variations and sources of SNA may exhibit complexity and unpredictablility during long-range transport. Specificlly, (NH4)2SO4 is mostly imported from the upstream in the whole boundary layer (BL), but NH4NO3 is dominant by local source. Moreover, uplifting by cold front, temperature-sensitive NH4NO3 form in the upper BL and dissociation in the lower BL, whereas (NH4)2SO4 forms uniformly across the whole BL. These findings suggest that one difference in physicochemical property of species can induce distinct distributions and sources in large scale, highlighting the importance of considering such differences in regional air pollution control. Uplifted by cold fronts, the temperature-sensitive NH4NO3 forms in the upper BL and dissociates in the lower BL (NH4)2SO4 forms in the whole BL because it is highly thermally stable and impervious to dissociation The differences in thermostability and lifetime result in local sources being dominant for NH4NO3, while upstream sources dominate for (NH4)2SO4

The chemical composition and optical properties of particulate matter (PM) were characterized in an urban-industrial area of Nanjing, China, in January 2015, when heavily polluted periods frequently occurred. Only 30

Atmospheric ice nucleation particles (INPs) play a crucial role in influencing cloud formation and microphysical properties, which in turn impact precipitation and Earth’s radiation budget. However, the influence of anthropogenic activities on the properties and concentrations of INPs remains an area of significant uncertainty. This study investigated the physical and chemical characteristics of atmospheric ice nucleation particles in Huangshan, China during the May Day labor holiday period (spanning 8 days, from April 27th to May 5th). INP concentrations were measured at temperatures from −17 °C to −26 °C and relative humidities (RHw) from 95% to 101%. Average INP concentrations reached 13.7 L−1 at −26 °C and 101% RH, 137 times higher than at −17 °C and 95% RH. INP concentrations showed exponential increases with decreasing temperature and exponential increases with increasing RH. Concentration fluctuations were observed over time, with a peak of ~30 L−1 (t = −26 °C, RHw = 101%) around the start and end of the holiday period. Aerosol number concentrations were monitored simultaneously. The peak in aerosols larger than 0.5 μm aligned with the peak in INP concentrations, suggesting a link between aerosol levels and INPs. Chemical composition analysis using SEM–EDX revealed the distinct elemental makeup of INPs based on the activation temperature. INPs active at warmer temperatures contained N, Na, and Cl, indicating possible biomass and sea salt origins, while those active at colder temperatures contained crustal elements like Al and Ca.

In this study, the aerosol size distributions, cloud condensation nuclei (CCN) number concentration (NCCN), single-particle chemical composition and meteorological data were collected from May 12 to June 8, 2017, at the summit of Mt. Tai. The effects of new particle formation (NPF) events and aerosol chemical components on CCN at Mt. Tai were analyzed in detail. The results showed that, NPF events significantly enhanced the CCN population, and the enhancement effect increased with increasing supersaturation (SS) value at Mt.Tai. NCCN at SS ranging from 0.1 to 0.9 % on NPF days was 10.9 %, 36.5 %, 44.6 %, 53.5 % and 51.5 % higher than that on nonNPF days from 10:00-13:00 as NPF events progressed. The effect of chemical components on CCN activation under the influence of NPF events was greater than that in the absence of NPF events. The correlation coefficients of EC-Nitrate particles (EC-Sulfate particles) and CCN at all SS levels on NPF days were 1.31-1.59 times (1.17-1.35 times) higher than those on non-NPF days. Nitrate particles promoted CCN activation but sulfate particles inhibited activation at Mt. Tai. There are differences or even opposite effects of the same group of particles on CCN activation under the influence of NPF events in different air masses. EC-Sulfate particles inhibited CCN activation at all SS levels for type I but weakly promoted activation at lower SS ranging from 0.1 to 0.3 % and weakly inhibited it at higher 0.9 % SS for type II. OCEC particles significantly inhibited CCN activation for type II, and this effect decreased with increasing SS. OCEC particles only weakly inhibited activation at SS ranging from 0.5 to 0.7 % for type I. OCEC particles only weakly inhibited this process at 0.1 % SS, while they very weakly promoted activation for SS > 0.1 %. This reveals that the CCN activity is not only related to the chemical composition of the particles, but the mixing state also has an important effect on the CCN activity.

The Southern Ocean (SO) and Antarctica play important roles in the global climate. The new particle formation (NPF) alters the availability of cloud condensation nuclei (CCN), leading to impacts on the cloud reflectance and global radiative budget. In this review, we introduce the common instruments for measuring particle number concentration (PNC) and particle number size distribution (PNSD). Based on the observations over the Antarctic and some Antarctic research stations, we explored spatial and temporal characteristics of PNCs and PNSDs. From the SO to the interior of the Antarctic, the total PNCs show a decreasing trend, and the total PNCs present an obvious seasonal cycle, with the low concentration in winter (June–August) and the high concentration in summer (December–February). By summarizing the research progress over the SO and Antarctica, we discuss possible precursors of the NPF: sulfuric acid (H2SO4, SA), methanesulfonic acid (CH3S(O)2OH, MSA), dimethyl sulfide ((CH3)2S, DMS), iodic acid (HIO3, IA), iodous acid (HIO2), ammonia (NH3), dimethylamine ((CH3)2NH, DMA), highly oxygenated organic molecules (HOMs) and other organics with low vapor pressure. We also explore several possible nucleation mechanisms: ion-induced nucleation of H2SO4 and NH3, H2SO4-amines, H2SO4-DMA-H2O, H2SO4-MSA-DMA, IA-MSA, IA-DMA, heterogeneous IA-organics nucleation mechanisms and environmental conditions required for the NPF. NPF is one of the main sources of CCN in the remote marine boundary layer, such as the SO and Antarctica. Thus, we discuss the contribution of NPF to CCN and the indirect impacts of NPF on climate. Through this review, we could better understand the PNC and NPF over the SO and Antarctica and their impacts on the global climate.

As one of the important sources of aerosols, new particle formation events can affect the spatiotemporal dis-tribution of CCN. To analyze the characteristics of new particle formation (NPF) events and their effects on cloud condensation nuclei (CCN) during the summer at Mt.Tian, the data of aerosol size distribution and CCN number concentrations were measured using an aerosol wide-range particle size spectrometer and a cloud condensation nuclei counter from August 4 to 25, 2019, and combined with meteorological data and polycyclic aromatic hydrocarbons (PAHs) data. NPF events at Mt.Tian occurred seven days during the observation period, accounting for 32% of the observation days, and usually occurred at 13:00 and ended at 17:00 (Beijing Time, same below). NPF events particularly influenced the diurnal variations of aerosol number concentrations in different modes. The number concentrations of nucleation and Aitken modes increased rapidly while the accumulation mode increased slowly during 13:00 and 17:00 on NPF days. The peak particle number concentrations in the nucle-ation, Aitken and accumulation modes on NPF days were 5360.1 cm-3, 7185.6 cm-3 and 839.3 cm -3, respec-tively, which were 3.3, 1.8 and 1.7 times higher than those on non-NPF days during 13:00 and 17:00. The meteorological conditions of temperature higher than 20 degrees C, air pressure lower than 806 hPa, relative humidity (RH) lower than 40% and wind speed higher than 2.2 m s- 1 are favorable for the occurrence of NPF events. The NPF events at Mt.Tian can impact the mass concentration of PAHs. More Fluoride (FL) and Phenanthrene (PHE) were generated on NPF days. The mass concentrations of FL and PHE on NPF days were 0.002 & PLUSMN; 0.003 ng m- 3 and 0.020 & PLUSMN; 0.010 ng m- 3, which were 243.54% and 28.44% higher than those on non-NPF days, respectively. NPF events were conducive to increased CCN concentration at Mt.Tian. After the NPF events, the mean number concentrations of CCN at each supersaturation (SS) on NPF days was about 20%-50% higher than on non-NPF days. The contribution of NPF events to the CCN number concentrations was 35.75%, 28.56%, 44.15%, 42.11% and 29.12% at 0.1%, 0.2%, 0.4%, 0.6% and 0.8% SS, respectively.

Mixed-phase clouds are the main source of precipitation over the mainland China. Atmospheric ice nucleating particle (INP) is one of the most important preconditions for ice formation, and is vital in controlling the microphysics and optical properties in mixed-phase clouds. In this study, the concentration of INP was measured in different seasons in Tian Shan Mountains, which is the largest mountain system in central Aisa. The results show that the INP concentration was an order of magnitude higher than that measured 20 years ago. The surface active site density (ns) was higher than in other areas, while the INP concentration was similar. The observed INP concentration in summer was higher than that in winter. A good correlation was found between the INP con-centration and the number concentration of aerosol particles with a size >1.0 mu m. And the correlation with aerosol surface concentration is slightly higher than number concentration. Several parameterizations of INPs are compared based on the measurements, and the analysis indicate that the parametrizations with supersaturation considered are more consistent with the observation.

In this study, the water-soluble inorganic ions (WSIIs) composition of fine particulate matter (PM2.5) was measured in the northern Nanjing city from 2015 to 2021. NH4+, NO3− and SO42− concentrations dominated in total WSIIs (Na+, NH4+, K+, Mg2+, Ca2+, Cl−, NO3− and SO42−), accounting for 87.8%. The nitrate with highest average concentration among all ions was 11.0 μg·m−3. Total WSIIs concentrations were higher in winter and lower in summer, with the highest levels in December (45.6 μg·m−3) and the lowest levels in August (15.1 μg·m−3). NO3−/SO42− was higher than 1, indicating the important contribution of mobile sources. The aerosols exhibited a weak acidic by the molar ratio of water-soluble anions and cations. Positive matrix factorization (PMF) analysis results showed that secondary nitrate and sulfate were the major pollution sources in December 2016 and 2020. The contribution of secondary nitrate in 2020 increased by 47.6% compared to 2016, while that of secondary sulfate decreased by 42.4%. The potential source contribution results demonstrated that for secondary aerosol concentrations, the contribution of regional transport from north of Anhui increased, while the contribution of local emissions decreased. The results from this study could contribute to the better prevention and control of regional air pollution in the future.

为进一步提高雾中能见度的预报准确度,本文基于安徽黄山站 2008年 4～7月、2009年 5～8月、2011年 5～9月和湖北恩施山顶站 2009年 1～3月的雾微物理等观测资料,建立了新的雾中能见度诊断方案,并加以检验.首先,对已有的能见度诊断方案进行比较,验证了能见度方案同时包含数浓度和含水量的重要性.其次,在已有的方案中,能见度与微物理量之间函数关系式的系数往往取作常数,但研究发现这些系数与微物理量本身紧密相关.先利用黄山 2008年一半的雾观测数据建立了拟合系数与数浓度之间的关系,改进了能见度的诊断方案.然后把黄山 2008年另一半、2009、2011年和恩施 2009年的数据作为独立数据,对改进后新方案进行验证,结果均表明新方案能更好地计算能见度.

Ice-nucleating particles (INPs) are crucial for cloud freezing processes in the atmosphere. Given the limited knowledge about the vertical distribution of INPs and its relation to aerosols in China, we present two aircraft observations of INPs over the North China Plain on 23 October 2019 and 25 October 2019, before and after a cold front passage. We used a well-established method to identify the INPs on a silicon wafer and then performed single-particle chemical composition analysis using an environmental scanning electron microscope-energy dispersive spectrometer (ESEM-EDS). The INP concentrations range from 0.1 to 9.2 L−1 within activation temperatures from −20 to −29 °C. INPs are mostly concentrated within the boundary layer, and their concentration shows a decreasing trend with height (0.5~6 km) before the cold front passage. However, the highest INP concentration always appears at higher altitudes (4~5 km) after the cold front passage. The cold front passage also significantly weakens the correlations between the concentrations of INPs and aerosol particles at different sizes. The activated fraction (AF) of total aerosols increases from 10−6 to 10−4 with height from near ground to 6 km, reflecting a better nucleating capacity of the aerosols at higher altitudes. There is no obvious variation in AF after the cold front passage. Chemical analysis reveals that the INPs containing mineral dust components comprise the majority of total INPs during both flights. The proportion of pure mineral dust declines from 52.2% to 43.5% after the cold front passage while the proportion of mixed mineral dust increases from 23.9% to 45.7%, suggesting that an increased probability of aging or coating of INPs is introduced by the cold front during their long-distance transport. In addition, 88% of INPs have a diameter larger than 1 μm. This indicates that larger aerosols (>1 μm) are the major contributors to INPs at high altitudes despite their relatively low abundance. Our results demonstrate a significant impact of transport events on the sources and vertical distribution of INPs in the atmosphere.

Atmospheric polycyclic aromatic hydrocarbons (PAHs) are a type of organic pollutants that seriously endanger human health. Obtaining the diurnal variations of PAHs and clarifying their impact mechanisms are significant for the government to formulate targeted prevention and control measures. However, the influencing factors that dominate the diurnal variations of common PAHs are currently unclear. In order to solve this problem, 16 PAHs selected by the United States Environmental Protection Agency (EPA) as priority-controlled pollutants were simulated with high resolution. The simulation results were validated based on diurnal observations in the vertical direction. Although the model underestimated the particle-phase concentrations of most components, it captured their diurnal variations fairly well. In addition, we assessed the factors affecting the diurnal variations of PAHs with sensitivity tests, including chemical reactions and atmospheric diffusion. The results showed that the transforming ratios of PAHs by oxidants were higher during the day than that at night due to the dominant reactions with OH radical. Atmospheric dispersion affected the vertical distribution of PAHs, which resulted in higher day/night ratios at high altitudes than near the ground. We also compared the strength of atmospheric diffusion and chemical reaction on the diurnal trends of PAHs. Near the ground, atmospheric diffusion was the most dominant factor in determining their diurnal trends. At high altitudes, their diurnal trends were determined by a combination of atmospheric diffusion and chemical reactions. These findings can provide a comprehensive understanding of the diurnal variations of common PAHs, which are informative for the prevention and control of PAHs pollution.

The composition of marine aerosol is quite complex, and its sources are diverse. Across the East China Sea (ECS) and the Yellow Sea (YS), multi-dimensional analysis of marine aerosols was conducted. The characteristics of carbonaceous aerosols and gaseous pollutants were explored through in situ ship-based observation, MERRA-2 reanalysis datasets and TROPOMI data from Sentinel-5P satellite. Black carbon (BC)’s average concentration is 1.35 ± 0.78 μg/m3, with high-value BC observed during the cruise. Through HYSPLIT trajectory analysis, sources of BC were from the northern Eurasian continent, the Shandong Peninsula, the ECS and Northwest Pacific Ocean (NWPO). The transport of marine sources like ship emissions cannot be ignored. According to the absorption Angstrom exponent (AAE), BC originates from biomass burning (BB) in the shortwave band (~370 nm) and from fossil fuel combustion in the longwave band (~660 nm). Organic carbon (OC), sulfate (SO42−) and BC report higher Angstrom exponent (AE) while dust and sea salt reveal lower AE, which can be utilized to classify the aerosols as being fine- or coarse-mode, respectively. OC has the highest AE (ECS: 1.98, YS: 2.01), indicating that anthropogenic activities could be a significant source. The process of biomass burning aerosol (BBA) mixed with sea salt could contribute to the decline in BBA’s AE. Ship emissions may affect the distribution of tropospheric nitrogen dioxide (NO2) in the ECS, especially during the COVID-19 pandemic. Tropospheric NO2 over the YS has the highest value (up to 12 × 1015 molec/cm2). Stratospheric NO2 has a ladder-like distribution from north to south, and the variation gradient was lower than that in the troposphere. Carbon monoxide (CO) accumulates in the south and east of the ECS and the east of the YS, while the variation over the eastern YS is relatively frequent. Seas near the Korean Peninsula have extremely high CO concentration (up to 1.35 × 1017 molec/cm2).

Dilution ratios (DRs) and burning conditions obviously affect particle number size distributions (PNSD), chemical compositions, and mixing states. These impacts for domestic solid fuel burning were investigated. For honeycomb briquettes, total particle number emission factors (EFPN) under DR150 for flaming and smoldering were (7.1 +/- 0.8) x 10(15) and (19.6 +/- 5.9) x 10(16) particles kg(-1), respectively. Smoldering and flaming conditions promoted different emissions of organic species, mineral species, trace metals, and soot particles, impacting the following homogeneous nucleation or condensation and collision, which could explain their diversities in PNSD. The EFPN would be overestimated under DR150 and underestimated under DR100. Single particles were classified into carbonaceous particles, K-rich particles, Na-K particles, metal particles, and other particles. For coal burning, metal-containing particles dominated (9.5%-88.7%) the particles in the size range of 0.5-1.5 mu m, with 3.7%-90.3% of them containing iron (Fe). Here, 93.1% of Fe particles were already internally mixed with sulfate, and high DR150 would promote their mixing. For crop residue and wood flaming, the mixed elemental and organic carbon (ECOC) particles dominated (87.1%-95.2%), with 74.7% and 45.1% of them containing levoglucosan. The PNSDs and mixing states of chemical species are helpful to update the initial settings of corresponding modeling studies.

Thunderstorms can significantly influence the air composition via strong updraft and lightning nitrogen oxides (LNOx). In this study, the ozonesondes and TROPOMI (TROPOspheric Monitoring Instrument) nitrogen dioxide (NO2) observations for two cases are combined with a model to investigate the effects of typical strong convection on vertical redistribution of air pollutants in Nanjing, southeastern China. The ozonesonde observations show higher O-3 and water vapor mixing ratios in the upper troposphere (UT) after convection, indicating the strong updraft transporting lower-level air masses into the UT and the possible downward O-3-rich air near the top of UT over the convective period. During the whole convection life cycle, the UT O-3 production is driven by the chemistry (5-10 times the magnitude of dynamic contribution) and reduced by the LNOx (-40 %). Sensitivity tests demonstrate that neglecting LNOx in standard TROPOMI NO2 products causes over-estimated air mass factors over fresh lightning regions and the opposite for outflow and aged lightning areas. Therefore, a new high-resolution retrieval algorithm is applied to estimate the LNOx production efficiency. Our work shows the demand for high-resolution modeling and satellite observations on LNOx emissions of both active and dissipated convection, especially small-scale storms.

基于2015年1月1日—2021年2月10日南京市大气污染物监测数据,分析了南京市主要大气污染物时空分布特征与潜在源区贡献.结果表明:1)近6年南京市6种大气污染物(CO、NO2、SO2、O3、PM10和PM2.5)年均质量浓度分别为800、43.1、13.0、106.0、77.1和43.0μg·m-3;南京臭氧质量浓度均值高于中国典型城市(北京、上海、广州、成都、兰州和武汉),而PM2.5平均质量浓度最低.2)2015—2020年南京NO2、PM10和PM2.5超标天数呈减少趋势,平均降低率分别为29.1％、38.1％和28.1％,而臭氧超标天数呈增加趋势;臭氧季节变化表现出夏高冬低,其他5种污染物均呈现冬季高特征.3)冬季(特别是1月)南京PM2.5质量浓度均值最高,对该时间段南京细颗粒物进行潜在源分析,发现南京地区细颗粒物主要受周边工业污染物输送影响,安徽、江苏北部和山东为主要潜在源区.4)对比研究了2019、2020和2021年1—2月大气污染物情况,发现2020年南京大气污染物质量浓度最低,说明因新冠疫情采取的封控措施减少了人类活动,进而显著影响了环境空气质量.