Atmospheric Environment: X最新文献

In this study, we evaluate the relative redox activity of various water-soluble organic aerosol (WSOA) sources in Delhi's winter PM_2.5, focusing on their capacity to generate reactive oxygen species (ROS). Using offline-aerosol mass spectrometry (AMS) and positive matrix factorization (PMF), we identified two oxidized factors—more oxidized oxygenated organic aerosol (MO-OOA) and less oxidized oxygenated organic aerosol (LO-OOA)—and three primary factors, namely nitrogen-enriched hydrocarbon-like organic aerosol (NHOA), biomass-burning organic aerosol (BBOA), and solid-fuel combustion organic aerosol (SFC-OA). The ROS-generating capability of PM_2.5 was assessed using a real-time oxidative potential (OP) measurement system based on the dithiothreitol (DTT) assay. We employed multivariate linear regression technique (MLR) to explore the association between the DTT activity of water-soluble PM_2.5 and these identified factors. We found BBOA, SFCOA, and MO-OOA significantly contributed to volume-normalized OP, with intrinsic water-soluble activities of 39 ± 11, 106 ± 31 and 160 ± 43 pmol/min/μg, respectively. MO-OOA, primarily from non-fossil precursors, serves as a proxy for aged biomass burning, which intensifies during winter and significantly influences the DTT activity. Additionally, OP is significantly influenced by WSOA derived from local incomplete solid fuel combustion sources, including coal and wood burning for household cooking and heating, burning of leaves, biodegradable waste, and garbage along the roadside. Interestingly, water-soluble metals (Mn, Cu, and Fe) showed no discernible contribution to the OP. These findings highlight the need for targeted mitigation strategies addressing local combustion processes and unregulated biomass burning to effectively reduce PM health exposure in Delhi.

This study investigates the impact of black carbon (BC) emissions on monsoon rainfall patterns across the Indian subcontinent. The results show that BC exerts localized warming effects, providing valuable insights into the mechanisms influencing the rainfall distribution across the Indian landmass. The study analyzes the vertical profile of mean tropospheric temperature differences between two sets of simulations: (i) with default BC emissions (WBC) and (ii) with BC emissions reduced by 99% (WoBC), conducted for JJAS, 2017, focusing on the region along the eastern coast. The analysis of the tropospheric temperature variations over the eastern coast reveals significant rainfall differences, primarily attributed to the intensification of convective rainfall. The results indicate that WoBC simulation leads to abnormal cooling in the lower troposphere and warming in the mid-upper troposphere, plausibly linked to the release of latent heat from the enhanced convective activity observed over the region. These alterations in the tropospheric temperature profile correspond remarkably well with the changes in the spatial distribution of rainfall over this area, providing valuable insights into the intricate dynamics of the climate system over this region.

Volatile Organic Compounds (VOCs) serve as precursors for tropospheric ozone (O₃) and Secondary Organic Aerosol (SOA) formation. The formation of O₃ and SOA are the indicators of the oxidative capacity specific to a given chemical environment. The current study investigates the oxidative capacity of the relatively less explored tropical rural atmosphere. This study is accomplished by measuring the concentrations of various VOCs and combining them with OH loss rates to estimate the potentials for O₃ and SOA formation (OFP and SOAP, respectively). Continuous diel VOC measurement data from Gadanki (13.5°N, 79.2°E), Peninsular India, encompassing four distinct seasons and comprising over 4000 samples, have been utilized to estimate OFP and SOAP and their variations across different seasons. Additionally, efforts have been made to comprehend the contribution of different VOC sources to O₃ and SOA formation. The results indicate that, 1, 3, 6-trimethyl benzene (20.09 %) among the VOCs and aromatics (44.37%) among the VOC groups exhibit the highest OFP at the observational site. Among seasons, the post-monsoon period exhibits the highest OFP (31.94%). The increased presence of biogenic VOCs, such as ethylene, propylene, and 1-butene during monsoon, likely due to the increased vegetation cover can be attributed for the elevated OFP. Similarly, n-dodecane (43.22%) and the VOC group of alkanes (50.79%) show the highest SOAP. The summer season has the highest SOAP (29.7%), owing to the enhanced concentrations and photochemistry initiated by OH radicals. Within the PMF-modelled sources, biomass-burning VOCs make a substantial contribution to both OFP and SOAP, distinguishing the rural atmosphere from its urban counterpart, where traffic emissions predominantly influence OFP and SOAP.

This study investigates the effects of significant activity changes on air pollutant concentrations across the three European cities Hamburg, Liège, and Marseille and focuses on the effects of COVID-19 lockdown measures as a case study for such significant activity changes. To identify such effects, this study utilizes urban-scale chemistry transport modeling, embedded in regional-scale Chemistry Transport simulations. The outcomes underscore the significance of considering local conditions and emissions sources, as variations between urban and regional simulations demonstrate. Notably, lockdown regulations yield the most substantial impact in Marseille due to its dense road traffic and port area, with Liège following suit, primarily influenced by regional air quality alterations. Conversely, Hamburg exhibits lower mean changes, attributed to its widespread urban structure. Analysis of modeled exceedances of limit values reveals significant reductions, particularly in areas of urban and road land use. These findings contribute valuable insights into the efficacy of significant activity changes, such as lockdown measures, in mitigating air pollution, underlining the importance of tailored strategies for emission reduction in urban environments.

Neighborhood-scale air pollution hotspots have recently been identified through detailed field campaigns, including the 100x100 Black Carbon Experiment which took place in West Oakland, CA, in 2017. Here, high-resolution nested atmospheric simulations are used together with a Bayesian inversion framework to estimate source apportionment at the hyper-local scale for a neighborhood in West Oakland. Forward simulations are performed with the Weather Research and Forecasting (WRF) model using 6 grid nests from 11.25 km to 2 m horizontal resolution. On the finest grid, building geometries are resolved using the immersed boundary method. Seven point sources and four line sources at known locations are included in the forward simulation for two 1-h periods during the 2017 field campaign. Data from 12 black carbon sensors are used to perform source inversion using a Markov Chain Monte Carlo approach, which provides a probability distribution for each of the 11 source strengths. From this, a most-likely plume can be created using the peaks of the distributions, and source apportionment can be estimated for each sensor. In addition, a composite plume can be constructed to indicate 90% confidence that concentrations are above or below a specified value. With this probabilistic analysis, it is possible to determine that more than half of the neighborhood has black carbon concentrations of higher than 0.4 μg/m³, with some areas higher than 3 μg/m³ during the time periods studied.

Transportation is a major sector of anthropogenic emissions in urban areas and deteriorates air quality. The surface and vertical observational data were combined with the model results to reveal its impact on the horizontal and vertical variations of pollutants during the COVID-19 lockdown period. The evident reductions in ambient PM_2.5 (∼30%) and NO₂ (∼50%) concentrations but a ∼25% increase in O₃ concentration were observed at the transportation sites. On the vertical scale, a uniform decrease of ∼28% in PM_2.5 concentrations was observed within 600 m. However, the vertical profiles of NO₂ and O₃ exhibited increasing vertical variation rates with concentrations varying significantly within 400 m. Meanwhile, O_x shared a similar pattern of vertical profile with O₃, with a uniform increase (∼5%) within 600 m in the urban area. The WRF-CMAQ model reproduced the variations, and revealed that the reduction of transportation emissions was the key factor contributing to the increase of urban O₃ and O_x due to the weakened NO titration effect. The simulated vertical profile of NO₂ was featured by a decreasing curve, while that of O₃ exhibited the opposite trend. We find that the transportation emissions impact vertical concentrations of NO₂ and O₃ within at most 400 m. The process analysis revealed that the vertical transport and horizontal transport from bay areas contributed to O₃ in the urban area, while chemical processes mainly consumed it. The reduction in transportation emissions weakened the consumption and resulted in O₃ accumulation during rush hours and at night. The variation of planetary boundary layer height also favored the rise of urban O₃ by promoting vertical transport at daytime and trapping it at night. The reduction in NO_x emissions from the transportation enhanced O₃ pollution, suggesting that collaborative reductions in VOCs from multiple sectors should be conducted. This study also indicated that regional collaborations in emission reductions were necessary for comprehensive air pollution prevention.

India is experiencing a rapid urban growth in recent decades modifying the regional air quality around urban agglomerations. Hyderabad, the capital city of Telangana state in India, has been experiencing significant urbanization of about 17 % growth in urban agglomeration over the past two decades. We investigated the long-term pollution characteristics along with the meteorology in and around Hyderabad (300 km × 300 km) using satellite-based remote sensing, and reanalysis data. Columnar aerosol loading was highest during the Spring while the positive trend was more during the Winter. The northeastern and southeastern parts of the study domain experienced higher aerosol loading. A significant increasing linear trend in AOD and PM_2.5 is observed over the urban region as well as the northern and eastern parts. The NO₂ and SO₂ columnar concentrations showed considerable enhancement over the northeast sub-region where numerous thermal power plants are located, and over the urban centre. The SO₂ concentration and SSA values were higher during the Autumn, while the NO₂ values peaked along with lower SSA values during the Spring. The observed spatio-temporal features in air pollutants are further investigated using rainfall information, transport pathways, vegetation index, and fire events. Higher surface temperature and the polluted northeasterlies caused the comparative enhancement of NO₂ concentration during Spring. The investigation on the NDVI and the fire events in different sub-regions points to the possibility of enhanced human settlement, and thereby the associated anthropogenic activities are notable over the West and South parts of Hyderabad. However, the presence of thermal power plants in the northeast and natural gas plants along the coast act as persistent regional sources for aerosols and pollutant gases irrespective of the wet removal.

The observational characterization of anthropogenic methane (CH₄) emissions in the Eastern Mediterranean and Middle East (EMME) region, known for its significant oil and gas (OG) production, remains limited. Light alkanes, such as ethane (C₂H₆), are co-emitted with CH₄ by OG activities and are promising tracers for identifying the CH₄ emissions from this sector at the wider regional scale. In this study, in-situ measurements of CH₄ and alkanes (C2–C8 were collected during a field campaign at a regional background site (Cape Greco, Cyprus). A mobile laboratory housed the instrumentation at the south-eastern edge of the island between December 2021 and February 2022. This specific location and time of year were selected to capture air masses originating from distant southern and eastern regions, primarily impacted by sources from the Middle East. Based on these observations we 1) evaluate the significance of long-range transported versus local sources in Cyprus, 2) identify and document regional anthropogenic CH₄ sources with the help of the concomitant alkane measurements, and 3) assess the accuracy of the EDGAR sectoral emission inventory over the EMME region. The highest alkane mixing ratios observed were associated with the Middle Eastern OG CH₄ signal. Surprisingly, the Middle Eastern emissions of CH₄ were found to be heavily influenced by the breeding and waste management sectors. By investigating the measured CH₄ mixing ratios together with an atmospheric dispersion model (FLEXPART), we derive a comprehensive characterization of the pollution sources at a regional scale over the Eastern Mediterranean region. Our results indicate that CH₄ emissions from the Middle Eastern OG sector are likely underestimated by ca. 69 %. These findings underscore the efficacy of using experimental observations of alkanes for CH₄ source identification at receptor sites. This tracer approach would also benefit from a substantial revision of light hydrocarbon emission inventories.

In this paper we set up a modeling chain to study the impact of different urban planning scenarios on air quality and ultimately the exposure of the population. The analysis relates to the intensity of the polluting activities associated with each scenario, as well as their environmental and health impact. The implementation of a 2030 prospective scenario on Ile-de-France allows us to assess the magnitude of the leverage effect of the actions recommended in the regional master plan. The objective is to quantify the importance of emission reductions, but also the gain in terms of exposure to pollutants, which can be obtained when we transcribe into the model the implementation of regulatory texts on the metropolis of Greater Paris. The results allow us to debate the paradox between reducing emissions and increasing the exposure created by situations of high urban densification.