Search

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. [ABSTRACT FROM AUTHOR]

High temperature and pressure during lightning can quickly trigger multiple chemical reactions in the air, resulting in considerable impacts on aerosols, atmospheric chemistry, and air quality. Here, new particle formation (NPF) events motivated by lightning flashes were captured during an observation at Mt. Tai in summer 2017 for the first time. Numerous ultrafine particles were formed during the lightning events, leading to increases in nucleation and Aitken mode aerosols by 18.9 and 5.6 times, respectively. The formation rate (FR) and growth rate (GR) during lightning‐generated NPF were 67.1 cm−3·s−1 and 20.1 nm·h−1, which were 61 and 1.7 times higher than the averaged daytime NPF. Moreover, chemical composition of aerosols was strongly influenced by lightning NOx. Nitrate aerosol (NO2− and NO3−) signals intensified significantly (by 11.9% and 12.4%, respectively) during the lightning‐generated NPF, which contrasted with the sulfate aerosols measured in previous studies (non‐lightning NPF). Meanwhile, lightning contributed noticeably to surface NO2 concentrations. Accompanying the uplifting airflows before rainfall, surface air pollutants (SO2, NH3, and NOx, etc.) can be transported above the top of the planet boundary layer, which plays an important role in NPF. The NPF in the hot lightning channels resulted from pollution NOx and lightning NOx, with the latter dominating. Finally, lightning‐generated pollutants, including NOx and aerosols, were delivered down to the surface with descending airflows. Plain Language Summary: High temperature and pressure during lightning can quickly trigger multiple chemical reactions in the air, resulting in considerable impacts on the chemical composition of aerosols, atmospheric chemistry, and air quality. To date, new particle formation (NPF) events during lightning have rarely been observed. Here, NPF events motivated by lightning flashes were captured during an observation at Mt. Tai in summer 2017 for the first time. Accompanying the uplifting airflows before rainfall, surface air pollutants can be transported above the top of the planet boundary layer, which plays an important role in NPF. The NPF in the hot lightning channels resulted from pollution NOx and lightning NOx, with the latter dominating. Moreover, chemical composition of aerosols was strongly influenced by lightning NOx during the lightning‐generated NPF. Finally, lightning‐generated pollutants, including NOx and aerosols, were delivered down to the surface with descending airflows. Key Points: Lightning caused increases in nucleation and Aitken mode aerosols by 18.9 and 5.6 times, respectivelyFormation rate and growth rate during lightning‐generated new particle formation (NPF) were 61 and 1.7 times higher than the daytime NPF, respectivelyNitrate aerosol signals (NO3− and NO2−) intensified significantly during lightning‐generated NPF, which contrasted with the sulfate aerosols [ABSTRACT FROM AUTHOR]

Aerosol pH is a useful diagnostic of aerosol chemistry for formation of secondary aerosol and has been hypothesized to be a key factor in specific chemical reaction routes producing sulfate and nitrate. In this study, we measured hourly concentrations of water‐soluble ions in particulate matter with an aerodynamic diameter less than 2.5 μm, along with gaseous pollutants in Tianjin, China, from 4 to 31 January 2015. The following source contributions to water‐soluble ions were estimated by positive matrix factorization: secondary sulfate (13%), secondary nitrate (44%), coal (14%), vehicle (16%), and dust (13%). ISORROPIA‐II was used to investigate the complex relationships among aerosol pH, ammonia, and secondary aerosol formation. The estimated hourly aerosol pH varied from −0.3 to 7.7, with an average of 4.9 (±0.78); the median value was 4.89, and the interquartile range was 0.72. During less polluted conditions, aerosol pH ranged from less than 0 to about 7; during heavily polluted conditions, pH was close to 5 (3.9–7.9) despite large amounts of sulfate. Sufficient ammonia/ammonium was present to balance high sulfate and nitrate formation. NH4+/NH3 (g) helped stabilize pH while nonvolatile cations contributed less to decreasing aerosol acidity. High acidy (pH < 3), light pollution (total water soluble ions < 30 μg/m3), and low water content (less than 5 μg/m3) were more correlated with higher rates of sulfate formation than nitrate formation in the winter. Plain Language Summary: Megacities in China and elsewhere experience very smoggy days that get continuously worse during haze episodes. The high levels of smog are created both from directly emitted particles and the formation of more particulate matter from gas‐phase reactions. Scientists are not able to fully explain how so much smog is formed so rapidly during intense haze periods. Ammonia was found to stabilize the acidity of the aerosols, but the aerosols remained acidic with pH of around 4. Here detailed hourly measurements of many species are used to elucidate the importance of ammonia, which can potentially neutralize acidic gases and aqueous particles. Key Points: NH4+/NH3 and pH had a more nonlinear relationship during highly polluted periods, compared to less polluted periodsNH4+/NH3 (g) was important for stabilizing pH during the heavily polluted periodsSOR was higher than NOR under conditions with high acidity, light pollution, and low water content in the winter [ABSTRACT FROM AUTHOR]

As the largest independent east–west-trending mountain in the world, Mt. Tianshan exerts crucial impacts on climate and pollutant distributions in central Asia. Here, the vertical structures of meteorological elements and black carbon (BC) were first derived at Mt. Tianshan using an unmanned aerial vehicle system (UAVS). Vertical changes in meteorological elements can directly affect the structure of the planet boundary layer (PBL). As such, the influences of topography and meteorological elements' vertical structure on aerosol distributions were explored from observations and model simulations. The mass concentrations of BC changed slightly with the increasing height below 2300 m above sea level (a.s.l.), which significantly increased with the height between 2300–3500 m a.s.l. and contrarily decreased with ascending altitude higher than 3500 m. Topography and mountain–valley winds were found to play important roles in the distributions of aerosols and BC. The prevailing valley winds in the daytime were conducive to pollutant transport from surrounding cities to Mt. Tianshan, where the aerosol number concentration and BC mass concentration increased rapidly, whereas the opposite transport pattern dominated during nighttime. [ABSTRACT FROM AUTHOR]

The aerosol size distribution and cloud condensation nuclei (CCN) number concentration were measured using a wide-range particle spectrometer (WPS) and a cloud condensation nuclei counter (CCNC) on Mt. Tian from 31 July to 9 September, 2019. Combined with meteorological data, distribution characteristics of aerosol size and CCN and their influencing factors were analyzed. The results indicated that the mean aerosol number concentration was 5475.6 ± 5636.5 cm−3. The mean CCN concentrations were 183.7 ± 114.5 cm−3, 729.8 ± 376.1 cm−3, 1630.5 ± 980.5 cm−3, 2162.5 ± 1345.3 cm−3, and 2575.7 ± 1632.9 cm−3 at supersaturation levels of 0.1%, 0.2%, 0.4%, 0.6%, and 0.8%, respectively. The aerosol number size distribution is unimodal, and the dominant particle size is 30–60 nm. Affected by the height of the boundary layer and the valley wind, the diurnal variation in aerosol number concentration shows a unimodal distribution with a peak at 17:00, and the CCN number concentration showed a bimodal distribution with peaks at 18:00 and 21:00. The particle size distribution and supersaturation have a major impact on the activation of the aerosol into CCN. At 0.1% supersaturation (S), the 300–500 nm particles are most likely to activate to CCN. Particles of 100–300 nm are most easily activated at 0.2% (S), while particles of 60–80 nm are most likely activated at high supersaturation (≥0.4%). The concentrations of aerosol and CCN are higher in the northerly wind. Ambient relative humidity (RH) has little relationship with the aerosol activation under high supersaturation. According to N = CSk fitting the CCN spectrum, C = 3297 and k = 0.90 on Mt. Tian, characteristic of the clean continental type. [ABSTRACT FROM AUTHOR]

Particle size distribution, water soluble ions, and black carbon (BC) concentration in a long-term haze-fog episode were measured using a wide-range particle spectrometer (WPS), a monitor for aerosols and gases (MARGA), and an aethalometer (AE33) in Nanjing from 16 to 27 November, 2018. The observation included five processes of clean, mist, mix, haze, and fog. Combined with meteorological elements, the HYSPLIT model, and the IMPROVE model, we analyzed the particle size distribution, chemical composition, and optical properties of aerosols in different processes. The particle number size distribution (PNSD) in five processes differed: It was bimodal in mist and fog and unimodal in clean, mix, and haze. The particle surface area size distribution (PSSD) in different processes showed a bimodal distribution, and the second peak of the mix and fog processes shifted to a larger particle size at 480 nm. The dominant air masses in five processes differed and primarily originated in the northeast direction in the clean process and the southeast direction in the haze process. In the mist, mix, and fog processes local air masses dominated. NO3− was the primary component of water soluble ions, with the lowest proportion of 45.6% in the clean process and the highest proportion of 53.0% in the mix process. The ratio of NH4+ in the different processes was stable at approximately 23%. The ratio of SO42− in the clean process was 26.2%, and the ratio of other processes was approximately 20%. The average concentration of BC in the fog processes was 10,119 ng·m−3, which was 3.55, 1.80, 1.60, and 1.46 times that in the processes of clean, mist, mix, and haze, respectively. In the different processes, BC was primarily based on liquid fuel combustion. NO3−, SO42−, and BC were the main contributors to the atmospheric extinction coefficient and contributed more than 90% in different processes. NO3− contributed 398.43 Mm−1 in the mix process, and SO42− and BC contributed 167.90 Mm−1 and 101.19 Mm−1, respectively, during the fog process. [ABSTRACT FROM AUTHOR]

The size-resolved chemical composition and mixing state of single particles were observed by using single particle aerosol mass spectrometry (SPAMS) from May 12 to June 8, 2017. A total of 979,899 particles were successfully ionized to identify 6 main particle groups including carbon-rich particles (47.66%), K-rich particles (28.78%), heavy-metal particles (10.12%), sodium particles (8.86%), dust particles (3.89%), and ammonium particles (0.67%). The wind direction and speed had large impacts on the proportion of carbonaceous aerosol particles and had little influence on heavy-metal particles. The relative humidity (RH) had great impacts on the chemical components of aerosol particles. The proportion of secondary particles increased, while the primary particles diminished as RH increased. The proportion of carbon-rich particles decreased with increasing particle size. However, the size distributions varied significantly for different types of carbonaceous particles. Sodium particles and heavy-metal particles were mainly concentrated at sizes larger than 1 μm. K-rich particles had a maximum proportion at 0.5–1.0 μm. The number fraction of ammonium particles predominated chiefly at 0.6–2.0 μm. It has been found that aerosol particles, mainly from burning processes, were mixed with 36 [C 3 ]+ to different degrees at Mt. Tai. A high proportion of ammonium particles were mixed with organics and elemental carbon (OCEC), elemental carbon-sulfate (EC-sulfate), and elemental carbon-secondary (EC-secondary) particles, while few of these particles were mixed with EC-nitrate particles, which indicated that the ammonia in the air was inclined to combine with organic species and sulfate. A higher proportion of atmospheric particles mixed with nitrate were observed compared to those mixed with sulfate. Image 1 • SPAMS was used for the first time to observe at Mt. Tai. • The proportion of primary/secondary particles diminished/increased as RH increased. • Higher proportions of particles mixed with nitrate than with sulfate. [ABSTRACT FROM AUTHOR]

As one of the important sources of aerosols, new particle formation events can affect the spatiotemporal distribution 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 nucleation, Aitken and accumulation modes on NPF days were 5360.1 cm−3, 7185.6 cm−3 and 839.3 cm−3, respectively, 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 °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 ± 0.003 ng m−3 and 0.020 ± 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. • Favorable meteorological conditions for NPF events at Mt.Tian were analyzed. • NPF events significantly affect the mass concentrations of FL and PHE compared with other PAHs. • The NPF events enhanced CCN population significantly at Mt.Tian. [ABSTRACT FROM AUTHOR]

Abstract New particle formation (NPF) and growth is an important phenomenon in terms of the global particle number concentrations. However, our knowledge about NPF events at the top of the boundary layer is particularly weak in heavily polluted conditions. In this study, the aerosol size distributions, black carbon (BC), chemical components of single particles, particulate matter (PM 2.5 and PM 10) and meteorological data were collected from May 12 to June 8, 2017 at the summit of Mt. Tai by using a wide-range particle spectrometer (WPS), Aethalometer (AE-33), a single particle aerosol mass spectrometer (SPAMS), a β-ray continuous ambient particulate monitor and an automatic weather station. Twelve new particle growth (NPG) events occurred during the observation period, accounting for 46.2% of the total observation days. The average relative humidity (RH) was 52% on NPF days and was 11.5% lower than the value on non-NPG days. The average temperature and wind speed were 18 °C and 5.3 m s−1 on NPG days, respectively, which were 12.2% and 18.9% higher than those on non-NPG days. The PM 2.5 concentration differed slightly on NPG and non-NPG days. However, the concentrations of PM 10 and BC were relatively high on NPG days, with average values of 88.0 μg m−3 and 1849.9 ng m−3, respectively, which were 1.2 and 1.3 times higher than those on non-NPG days. The NPG events had major influences on the size distributions of aerosol number concentration at 10–60 nm and surface area concentrations at 100–300 nm. During the NPG events, the average formation rate (FR), growth rate (GR), condensational sink (CS), vapor source rate (Q) and condensing vapor concentration (C) were calculated to be 1.30 cm−3 s−1, 14.54 nm h−1, 3.21 × 10−2 s−1, 7.34 × 106 cm−3 s−1 and 19.92 × 107 cm−3, respectively. The NPG events were influenced mostly by foreign transport processes and less impacted by local surrounding pollutants. The meteorological factors varied with different types of NPG events. The chemical components varied greatly during different types of NPG events. Sulfate had a small influence on three types of NPG events. Nitrate and ammonium had comparatively great impacts on local and southerly transport NPG events. The organic matters contributed more significantly to the northerly transport NPG events. Highlights • The characteristics of NPG events are examined at summit of Mt. Tai. • The concentrations of PM 10 and BC were relatively high on NPG days. • NPG impacted on spectral distributions of N at 10–60 nm and S at 100–300 nm. • Nitrate and ammonium (organic) had great impacts on local and southerly transport (northerly transport) NPG. [ABSTRACT FROM AUTHOR]