Environmental science: atmospheres最新文献

The influence of biomass burning (BB)-derived organic aerosol (OA) emissions on solar radiation via absorption and scattering is related to their physicochemical properties and can change upon atmospheric aging. We systematically examined the compositionally-resolved mass concentration and production of primary and secondary organic aerosol (POA and SOA, respectively) in the NC A&T University smog chamber facility. Mass spectral profiles of OA measured by the Aerosol Chemical Speciation Monitor (ACSM) revealed the influence of dark- and photo-aging, fuel type, and relative humidity. Unit mass resolution (UMR) mapping, the ratio of the fraction of the OA mass spectrum signal at m/z 55 and 57 (f ₅₅/f ₅₇) vs. the same fraction at m/z 60 (f ₆₀) was used to identify source-specific emission profiles. Furthermore, Positive Matrix Factorization (PMF) analysis was conducted using OA mass spectra, identifying four distinct factors: low-volatility oxygenated OA (LV-OOA), primary biomass-burning OA (BBOA), BB secondary OA (BBSOA), and semi-volatile oxygenated OA (SV-OOA). Data supports a robust four-factor solution, providing insights into the chemical transformations under different experimental conditions, including dark- and photo-aged, humidified, and dark oxidation with NO₃ radicals. This work presents the first such laboratory study of African-derived BBOA particles, addressing a gap in global atmospheric chemistry research.

Industries, governments, and regulators need trustworthy emissions data to enable them to make informed decisions regarding methane abatement strategy and policies. There are many differing data reporting metrics, as well as a diverse range of both emission sources and methods for monitoring emissions. Different data structures and terminologies can be used to describe similar objects, activities, or characteristics associated with methane monitoring. There is no currently accepted definition of what constitutes a methane monitoring method. Since there is no common basis to describe this information, confusion concerning language, definitions, and terminology can arise which can undermine confidence in data. This paper describes a framework, based on a set of taxonomies and a common lexicon, which aims to address these issues by providing a common structure in which data requirements, emission sources and monitoring methods can be described. The principles of metrology and quality assurance are embedded into this framework along with a means to define the temporal and spatial scales of the reporting and monitoring. It is envisaged that this framework will be developed into a standard to help facilitate more reliable transfer of information between stakeholders internationally. Usage examples for this framework include: to aid the development of test standards (between test laboratories, site operators, and standards bodies); to help ensure the most cost-effective monitoring methods are deployed for a specific purpose; to help identify technological and methodological gaps between what monitoring is needed and what is available, or to help drive more focused innovation in this field.

The reaction of gas-phase SO₂ with unsaturated carbon–carbon double bonds forms organosulfates at the surface of the aerosol. Previous studies have focused on the reaction products and not the fate of organic films in the atmosphere. Neutron reflectometry was used to study the interaction of gas-phase SO₂ at the air–water interface with organic material extracted from atmospheric particulate matter and pure proxy chemicals to determine whether the reaction of organic films with SO₂ removes the film and if a product film is formed. Films formed from atmospheric aerosol collected in urban and woodland environments typically produced a layer of approximately 0.6 nm thickness, whereas a thick (>40 nm) film was formed by the woodsmoke sample. Fitting of this thicker woodsmoke film suggested a three-layered structure at the interface that has been interpreted to be consistent with a surfactant-rich layer next to the air–water interface, a mid-layer rich in polyaromatic hydrocarbons (PAH), and topped with a more aliphatic region. The multilayer structure of atmospheric extracted material at the air–water interface is potentially an exciting result that requires further study. Gas-phase SO₂ was confirmed to react with pure insoluble surfactant molecules at the air–water interface that contained carbon–carbon double bonds (oleic acid) and did not react with a similar saturated surfactant (stearic acid). No reaction was observed during the interaction of SO₂ and atmospheric material extracted from urban and woodland environments, and no material appeared to be removed from the interface; however, films made from woodsmoke-extracted material did appear to be altered by SO₂ but there was no significant loss of material. In addition, the gas-phase ozone mixing ratios in the neutron blockhouse, which have historically been of some concern for reactions with organics, were found to be of the order 15 ppb, with no evidence of additional production in the neutron beam-path. Owing to a lack of substantial removal of material from real atmospheric extracted films, SO₂ is not considered atmospherically significant for the removal of organic films from the air–water interface.

Nitrate ion-based chemical ionization mass spectrometry (NO₃ ^--CIMS) is widely used for detection of highly oxygenated organic molecules (HOMs). HOMs are known to participate in molecular clustering and new particle formation and growth, and hence understanding the formation pathways and amounts of these compounds in the atmosphere is essential. However, the absence of analytical standards prevents robust quantification of HOM concentrations. In addition, nitrate-based ionization is usually very selective towards the most oxygenated molecules and blind to less oxygenated compounds hindering the investigation of molecular formation pathways. Here, we explore varying concentrations of nitric acid reagent gas in the sheath flow of a chemical ionization inlet as a method for detecting a wider range of oxidation products in laboratory-simulated oxidation of benzene and naphthalene. When the concentration of reagent nitric acid is reduced, we observe an increase in signals of many oxidation products for both precursors suggesting that they are not detected at the collision limit. The sensitivity of naphthalene oxidation products is enhanced to a larger extent than that of benzene products. This enhancement in sensitivity has a negative relationship with molecular oxygen content, the oxygen-to-carbon ratio, the oxidation state of carbon, and lowered volatility. In addition, the sensitivity enhancement is lower for species that contain more exchangeable H-atoms, particularly for accretion products. While more experimental investigations are needed for providing the relationship between enhancement ratios and instrumental sensitivities, we suggest this method as a tool for routine check of collision-limited sensitivities and enhanced detection of lower-oxygenated species.

Semivolatile organic compounds (SVOCs) in exhaust gas, though not directly regulated by emission standards, play a crucial role in assessing both conventional and alternative fuels. Our aim is to compare the differences in and toxicological effects of SVOC exhaust emissions from conventional and alternative fuels under sub-freezing conditions. High levels of NO_x, CO₂ and PAHs in SVOCs were observed in DI-E2 (EN590 winter-grade diesel), with E10 (gasoline with 10% ethanol) exhibiting higher CO₂ and PAH levels compared to E85 (high-blend ethanol with an 83/17% ethanol–gasoline ratio). SVOCs from DI-E6 (EN590 diesel) demonstrated significant cytotoxicity, while E10 resulted in higher inflammatory mediators and genotoxicity. Our findings show that SVOC composition and toxicity in exhaust gas differ based on the fuel type. Despite new emissions regulations reducing diesel vehicle emissions, SVOC toxicity remains unchanged. Toxicity from SVOCs in compressed natural gas and ethanol/gasoline vehicles is notable, with gasoline exhaust showing high inflammatory and genotoxic potential.

The influence of a prolonged Saharan Dust event across Europe and specifically in Munich (Germany) in March 2022 was detected and analyzed in detail. The event arose from a sequence of Saharan Dust incursions intertwined with a stagnation in the regional circulation leading to the persistence of a mineral dust plume for several weeks over the region. Trace element and meteorological data were collected. Enrichment factors, size distribution analyses, and multivariate techniques such as Varimax and Self-Organizing Maps (SOM) were applied to highlight the influence of Saharan Dusts and to evaluate the pollution sources in Munich municipality. The overall results revealed how the Munich airshed was clearly affected by long-distance mineral dusts from the North African desert, that increased the concentrations of natural (e.g. Al, Mg, Ca) and anthropogenic (e.g. Sb, Mo, Pb) elements based on the different paths followed by the dusts. Moreover, the chemometric analyses revealed a range of well-defined local anthropogenic emission sources including road traffic, energy production by coal combustion (S and Se), traffic (Cu, Sb), and waste incineration (Zn).

The contributions of meteorology and emissions to air pollutant trends are critical for air quality management, but they have not been fully analyzed, especially in the background area of northern China. Here, we used a machine learning technique to quantify the impacts of meteorological conditions and emissions on PM_2.5, NO₂, SO₂, O₃, and CO pollution during 2013–2021 and evaluated their contributions to Clean Air Action policies. The annual effect of the meteorology on PM_2.5, NO₂, SO₂, and CO levels was dominated by the meteorological conditions during the cold season, while that of the O₃ level largely depended on the meteorological conditions during the warm season. Meteorology-driven anomalies contributed −14.8 to 10.3%, −8.5 to 7.3%, −11 to 7.1%, −7.9 to 6.0%, and −7.4 to 7.3% to the annual mean concentrations of PM_2.5, NO₂, SO₂, O₃, and CO during the study period, respectively. The Clean Air Actions have led to a major improvement in the air quality at regional scale, with the reduction of 1.7 μg m⁻³ year⁻¹, 0.2 μg m⁻³ year⁻¹, 1.5 μg m⁻³ year⁻¹, 0.7 μg m⁻³ year⁻¹, and 0.03 mg m⁻³ year⁻¹ for PM_2.5, NO₂, SO₂, O₃, and CO at background area, respectively, after meteorological correction. Although emissions dominated the long-term variations in pollutants, the meteorological conditions obviously played a positive role during the action periods for pollutants except for O₃. Considering the notable effects of the meteorological conditions on air pollution and the interreaction between pollutants, a more comprehensive control strategy should be considered on a broader regional scale.

Ice nucleating particles (INPs) play a crucial role in freezing water droplets by acting as heterogeneous ice nuclei, influencing cloud phase state and climate dynamics. INPs from marine aerosol particles are particularly relevant. Saturated fatty alcohols and acids have been identified in sea spray aerosols (SSA). In this study, we employ a micro-Raman spectrometer integrated with an environmental cell to control relative humidity and temperature and measure the ice nucleation activity of individual lipid particles, including fatty alcohols and fatty acids of varying chain lengths. For fatty acids, we observe little IN activity for these lipid particles as they freeze close to the temperature found for homogeneous freezing. For fatty alcohols, we demonstrate that freezing temperatures depend on the carbon chain length, with longer chains leading to warmer ice nucleating temperatures. Although this result qualitatively agrees with existing literature, we observe that the ice nucleating temperatures of these lipid particles differ from the freezing temperatures measured for fatty alcohol monolayers at the air/water interface for large water droplets. To better understand these differences, we further investigate the effects of droplet size as well as phase state by theoretically determining the wet viscosity on freezing. Our results, taken together, suggest that for fatty alcohol particles, freezing occurs at the lipid particle/water interface. Overall, our findings highlight the influence of lipid chain length, droplet size, and phase state on ice nucleation for lipid particles.

The use of low-cost sensors (LCS) for the evaluation of the ambient pollution by particulate matter (PM) has grown and become significant for the scientific community in the past few years. However promising this novel technology is, the characterization of their limitations is still not satisfactory. Reports in the scientific literature rely on calibration, which implies the physical (or geographical) co-location of the LCS with reference in situ (or remote, e.g. onboard satellite platforms) instrumentation. However, calibration is not always feasible, and even when feasible, the validity of the developed relationship, even in similar settings, is subject to large uncertainties. In the present work, the performance of a popular LCS for PM, the Plantower PMS5003, is investigated. The LCS performs particle counts, which is the physical quantity that is input to the black-box model of the manufacturer to compute the ambient PM mass, which is output to the operator. The particle counts of LCS Plantower PMS5003 units were compared to those of the co-located research-grade Grimm EDM-164 monitor. The results show that humidity possibly has a reduced influence on the performance, but the performance can better be constrained, however spanning more than one order of magnitude in terms of agreement ratio, by functions of the actual particle count itself. In view of these results, further development in the field of LCS for PM monitoring should focus on improvements of the physical design of the devices, in order to enhance the sizing of the particles. The use of the actual Plantower PMS5003 models should be limited to the monitoring of PM mass in the smaller size bins.