查看更多>>摘要：Tire wear particles (TWPs) generated from vehicular sources significantly contribute to urban air pollution and pose risks to human health. To investigate the emission behavior of TWPs, chassis dynamometer driving tests were conducted on different-mileage vehicles. The results revealed that tire wear mileage increase led to decreased particle number emission for 10-500 nm TWPs and a gradual increase in particle mass emission. The long-mileage tires result in the formation of lumpy particles with fibrous structures. Tires with varying mileage produce lumpy particles and agglomerated irregular particles. Characteristic elements from the tire material are uniformly distributed on the lumpy particles. The agglomerated irregular particles mainly contain C and O and are not uniformly distributed with other characteristic elements. In addition, tire surface material from shortmilage vehicles reduces more mass than long-milage vehicles under low thermogravimetric analysis temperatures. The lost material is mainly oxidized to CO2 gas. Wear over long mileages can lead to changes in the organic substances of tire surface material. The discussion of mileage impact provides data to support the assessment and control of particle emissions over the full life cycle of tires.
查看更多>>摘要：Elucidating the effects of anthropogenic pollutants on the formation mechanism of secondary organic aerosol (SOA) is crucial for the improvement of atmospheric models toward the development of effective control strategies. It is extremely challenging to precisely clarify the impacts of concentrations of anthropogenic pollutants on the molecular compositions and particle number/mass concentrations of SOA under complicated conditions. Here, we report a series of the studies on the effects of anthropogenic pollutants (NO2 and SO2) on the photo-oxidation of a representative monoterpene, O3-carene, by using the scanning mobility particle sizer spectrometer, recently-developed vacuum ultraviolet free electron laser (VUV-FEL) photoionization aerosol mass spectrometry, and quantum chemical calculations. The results indicated that with the increase of NO2 concentration, the SOA yields increased under low-NO2 conditions but decreased under high-NO2 conditions. The OH radical was found to be the primary oxidant under low-NO2 conditions, whereas O3 became the dominant oxidant under high-NO2 conditions. SO2 substantially enhanced the formation of highly oxidized molecules via the acid-catalyzed pathway. A series of new compounds (i.e., organic peroxides, organic nitrates, and organosulfates) were observed and their formation mechanisms were proposed. The present findings highlight the critical role of anthropogenic pollutants in the photooxidation of monoterpene under low and high pollution environments and also open new avenues toward systematic studies of a broader class of volatile organic compounds.
查看更多>>摘要：Biomass burning (BB) has a major impact on air quality and population health, with the brown carbon (BrC) of special concern as an important source of pollution and absorbing incoming radiation. The impact of BB was quantified in an urban area of Moscow, the northern gas-fuel heated European megacity, during warm and cold seasons. Real-time measurements of aerosol optical properties were performed by an aethalometer. Heating and non-heating periods are marked by Absorption Angstrom exponent (AAE) equal 1.1 and 1.2, spring agricultural and summer wildfires by 1.3 and 1.4, respectively. Light absorption babs of 10 f 9 Mm-1 at 880 nm and 29 f 27 Mm-1 at 370 nm was independent on heating activity. No significant seasonal difference was revealed by mass absorption coefficient for black carbon (BC) of 13.5 m2 g-1 and BrC of 0.9 m2 g-1. BC contribution to total absorption dominated in all wavelength ranges and seasons. During heating period, BrC contribution to total absorption at 370 nm (%babsBrC) was 16 f 21 %, lower than in other European and Asian megacities where populations widely burn biomass and coal. It was 24 f 31 % in spring due to agricultural fire impact and increased BB activity because of the population migration out of the city during the May holiday. Ryazan wildfire plumes affected Moscow, with babs(880) and babs(370) increase 1.7 and 2.4 times, respectively, with a high % babsBrC of 37 +/- 59 %, and strong BrC absorption capacity in both day and nighttime. The relative absorption forcing of BrC compared to BC was estimated to range between 36.2 +/- 1.1 % and 29.8 +/- 2.7 % in ultraviolet and visible radiation range, respectively. Backward trajectory cluster and concentration weighted trajectory analyses revealed the regional origin of BB sources, coinciding with areas of observed wildfires. Collocated 12 h sampling and chemical composition analyses of BB tracers (levoglucosan and K+) identified the emission sources by significant correlations with BrC absorption. Four factors of BrC apportionment were identified via positive matrix factorization, showing contributions from fossil fuel combustion and secondary organic (82 %), and BB (18 %). As a result, regional population activity and spring and summer wildfires highlighted the uniqueness of Moscow as the northern gas-fuel heated megacity for BB impact studies in Europe and Asia.
查看更多>>摘要：Vertical mixing of pollutants and secondary inorganic aerosol formations over Beijing, China are investigated based on an unique observational platform on the roof of a high building (528 m above ground) and stations near ground. The contrary trends in diurnal variations of pollutants (SO2, NOx etc.) between the 528 m layer and near ground confirm that pollutants are well mixed in the daytime, but strongly suppressed at night due to the decoupling of the residual layer (RL) and nocturnal stable boundary layer (SBL). The decoupling also results in differences of aerosol formations between the two layers due to the differences in gaseous precursors, atmospheric oxidation capacity, and meteorological variables. Observations indicate that sulfate formation is more efficient near ground than in the 528 m layer due to higher relative humidity (RH) near ground, while nocturnal nitrate formation is more efficient in the 528 m layer due to higher O3 in this layer. The formed nitrate in the RL is downwards transported to ground in next morning, highlighting the potential importance of vertical pollutants mixing and residual layer chemistry in air quality near ground.
查看更多>>摘要：To characterize the distribution characteristics of PM2.5 pollution within a small scale within the city, PM2.5 concentration estimation data with high spatial resolution is required. However, the existing PM2.5 data mostly have a resolution of more than 1 km, and the spatial scale is relatively coarse, which makes it difficult to meet the actual needs of fine pollution monitoring and governance in cities. To address this limitation, this study based on the deep neural network (DNN) model, used multi-source auxiliary data such as the top atmospheric reflectance (TOAR) data and meteorological data of the Gaofen-1 (GF-1) satellite to achieve near-ground PM2.5 concentration retrieval with a spatial resolution of 30 m in the Beijing-Tianjin-Hebei (BTH) region. The model's performance was evaluated by a cross-validation (CV) method based on samples and sites. The results showed that the sample-based R2 was 0.912 with an RMSE of 10.326 mu g/m3, while the site-based R2 was 0.780 with an RMSE of 16.375 mu g/m3. The high-resolution PM2.5 data retrieved in this study can reveal the spatial differences in pollution at the urban block and even building scale. Combined with the analysis of a typical pollution event, the practical application potential of this high-resolution data in identifying local pollution sources and analyzing pollution changes within the city was verified. This study provides a new technical path for high-resolution PM2.5 retrieval and provides important data support for refined urban air quality monitoring and scientific governance.
查看更多>>摘要：Long-term monitoring of atmospheric aerosols is essential for understanding the interaction between natural processes and anthropogenic activities. This study analyzes a 20-year (2002-2022) dataset of water-soluble ions (WSIs) in aerosols collected at Urumqi Glacier No. 1 (UG1) in the eastern Tianshan Mountains, China. Significant increases in calcium ions (Ca2+) and aerosol pH were observed, indicating enhanced dust deposition and a shift toward an alkaline atmospheric environment. Mann-Kendall trend analysis revealed a notable annual increase in Ca2+ concentration (0.053 mu g m(-3), p < 0.001), with Ca2+ contributing up to 73 % of the total ion content during dust-heavy periods (2013-2015 and 2020-2022). Backward trajectory analysis and ion balance calculations identified Central Asian deserts as primary dust sources, while other WSIs (e.g., SO42-, NO3-, NH4+) reflect contributions from anthropogenic emissions. These findings highlight the growing influence of transboundary dust transport and its implications for air quality, glacier dynamics, and environmental changes in high-altitude regions.
NETL
NSTL
Elsevier