Environmental science: atmospheres最新文献

The peroxycarboxylic nitric anhydrides (PANs; RC(O)O₂NO₂ with R ≠ H) are important trace gas constituents of the troposphere. One of the lesser studied molecules of the PAN family is peroxyacrylic nitric anhydride (APAN; CH₂CHC(O)O₂NO₂) which is found in elevated concentration in biomass burning (BB) plumes and downwind from petrochemical plants. In this work, we conducted laboratory and field experiments to constrain the thermal decomposition (TD) rates of APAN in the atmosphere. The TD of APAN was studied in laboratory experiments using a Pyrex reaction coil at temperatures between 295.2 K and 320.7 K as a function of flow rate (i.e., residence time). Gas streams containing APAN were generated from a diffusion source containing a synthetic sample stored in tridecane at water-ice temperature. Nitric oxide (NO) was added to this gas stream to prevent recombination of the TD products. Concentrations of APAN were monitored by gas chromatography with electron capture detection (PAN-GC). The TD rate constant is best described by 10^{(17.88±0.80)} e^{−(121.2±4.8) kJ mol−1/(RT)} s⁻¹, where R is the universal gas constant, and T is the temperature in kelvin. We report ambient air mixing ratios of peroxyacetic nitric anhydride (PAN), peroxypropionic nitric anhydride (PPN), and APAN measured by PAN-GC at the Calgary Central (Inglewood) air quality station from April 17 to May 31, 2023. From May 16 to May 21, the measurement location was blanketed by a BB plume as judged from co-located observations of fine particulate matter (PM_2.5) and carbon monoxide (CO). During this time, mixing ratios as high as 3.4 ppbv (PAN), 455 pptv (PPN), and 220 pptv (APAN) were observed. After sunset, mixing ratios of the PANs decreased with pseudo-first order kinetics, rationalized by a combination of dry deposition and loss by TD.

Tobacco curing poses serious environmental and health risks from elevated airborne pollutant emissions. This study aims to identify key air pollutants and associated behaviours during tobacco curing and storage operations, focusing on their impacts on air quality and potential health risks. This in situ analysis was conducted over 24 h at six tobacco curing houses (CHs) and three storage houses (SHs). Pollutant dynamics are influenced by ambient temperature and relative humidity, with higher temperatures and lower humidity amplifying emissions. Statistical analysis confirms that particulate matter (PM), total volatile organic compounds (TVOCs), HCHO, NO₂, O₃, CO, and SO₂ for both environments exceed WHO standard limits, and most pollutants follow flat distributions with occasional spikes. Indoor–outdoor ratio (I/O) analysis shows that outdoor pollution stems from biomass combustion, while indoor levels result from both outdoor diffusion and indoor emissions. Pearson's correlation, Principal Component Analysis (PCA), and cluster analysis reveal a strong correlation among TVOCs, HCHO, NO₂, and O₃, suggesting similar sources and behaviours. Air quality indices (AQIs) indicate severe degradation, with CHs reaching unhealthy and SHs reaching very unhealthy levels, primarily driven by PM, NO₂, and O₃. These pollutants pose significant threats to human health, particularly for children sleeping in SHs, with TVOCs, HCHO, NO₂, and PM primarily driving non-carcinogenic risks, and TVOCs are emerging as a major cancer risk. TVOCs, HCHO, and NO₂ also impair plant health. This research highlights severe air pollution and associated health hazards in tobacco curing and storage environments, guiding policies to reduce exposure and promote sustainable tobacco production practices.

Organic peroxy radicals (RO₂) are produced in the atmosphere by oxidation of volatile organic compounds (VOCs) and, in some cases, VOC photolysis. However, photolytic sources of RO₂ are often poorly understood, in part due to challenges in directly detecting RO₂ in both ambient and laboratory settings. We investigated Cl₂⁻ as a chemical ionization mass spectrometry reagent ion (Cl₂-CIMS) for measuring and speciating RO₂ in a laboratory setting. Cl₂-CIMS was more sensitive to the acetyl peroxy radical (CH₃C(O)O₂; 2.30 ± 0.04 ncps/ppt) than iodide CIMS (I-CIMS; 1.54 ± 0.03 ncps/ppt), but high backgrounds in our setup resulted in a slightly higher detection limit of 5 ppt (1 second integration) for Cl₂-CIMS than I-CIMS (2 ppt). We demonstrate the application of Cl₂-CIMS by quantifying the quantum yields of two radical products, CH₃C(O) and C₂H₅C(O), from methyl ethyl ketone photolysis at 254 nm. We identified O₂⁻ and Cl⁻ as possible secondary reagent ions that created unintended product ions in our experiments and thus could complicate the interpretation of Cl₂-CIMS mass spectra for complex atmospheric samples. While several strategies may minimize these effects, Cl₂-CIMS is suitable for measuring RO₂ in controlled laboratory experiments.

The gas-particle partitioning of low-volatility and semi-volatile organic compounds (L/S-VOCs) plays a dominant role in the formation of secondary organic aerosol, carrying implications for the health and climate effects of atmospheric particulate matter. Partitioning into aqueous particles and cloud droplets can also impact the fates of L/S-VOCs in the atmosphere. As the NH₃/NH₄⁺ conjugate pair begins to dominate the buffering capacity of the atmospheric aqueous phase, there is a growing need to consider how changing particle acidity may impact the phase distribution of different ionizable compounds. In this work, we use a partitioning space framework and graphical assessment method to predict the effects of varied pH and temperature on the partitioning behavior of 24 ionizable organic compounds, including carboxylic acids and amines. As pH increases from 2 to 6, amines exhibit significantly increased affinity for the gas phase, whereas a preference for the aqueous phase is generated among several weak acids that would otherwise have remained vapors. We find that temperature can have a strong influence on the partitioning of some compounds. However, temperature-dependence can vary widely between compounds, and our analysis was limited by a lack of enthalpy values, necessitating reliable thermodynamic data for a larger number of L/S-VOCs. We implement a new visualization to investigate the partitioning behavior of lesser-studied compounds under varied conditions, and through this approach we see that aerosol liquid water content can greatly impact pH-sensitivity in partitioning.

Underserved rural communities in northeastern North Carolina (NC), surrounding the Albemarle Sound, have faced degraded environmental quality from various sources of air and water pollution. However, access to local air quality data is regionally scarce due to a lack of state-run monitoring stations, which has motivated local community science efforts. In January 2022, we co-developed a community-led study to investigate the relationship between fine particulate matter (PM_2.5) and sources of regional air pollution, with a specific focus on previously identified emissions from cyanobacterial harmful algal blooms (CyanoHABs). Using low-cost PurpleAir air quality sensors to quantify PM_2.5 mass, satellite-derived indicators of CyanoHABs, and other publicly available atmospheric and meteorological data, we assessed environmental drivers of PM_2.5 mass in the airshed of the Albemarle Sound estuary during 2022–2023. We found that bias-corrected PurpleAir PM_2.5 mass concentrations aligned with composite data from the three nearest federal reference equivalent measurements within 1 μg m⁻³ on average, and that the temporal variation in PM_2.5 was most closely associated with changes in criteria air pollutants. Ultimately, satellite-based indicators of CyanoHABs (Microcystis spp. equivalent cell counts and bloom spatial extent) were not strongly associated with ambient/episodic increases in PurpleAir PM_2.5 mass during our study period. For the first time, we provide local PM_2.5 measurements to rural communities in northeastern NC with an assessment of environmental drivers of PM_2.5 pollution events. Additional compositional analyses of PM_2.5 are warranted to further inform respiratory risk assessments for this region of NC. Despite the lack of correlation between CyanoHABs and PM_2.5 observed, this work serves to inform future studies that seek to employ widely available and low-cost approaches to monitor both CyanoHAB aerosol emissions and general air quality in rural coastal regions at high spatial and temporal resolutions.

PAN (CH₃C(O)O₂NO₂) is often the most important chemical reservoir of reactive nitrogen compounds throughout the free- and upper troposphere and provides a means of transport of reactive nitrogen from source regions to more remote locations. Both PAN and PAA (peroxy acetic acid, CH₃C(O)OOH) are formed exclusively via reactions of the CH₃C(O)O₂ radical, with PAA favoured under low NO_X conditions. We present airborne measurements of PAN and PAA taken with a chemical-ionisation mass spectrometer on board the High Altitude-Long range (HALO) aircraft over the North and tropical Atlantic Ocean west of Africa in August–September 2018. Our observations showed that mixing ratios of PAN and PAA are enhanced in biomass-burning impacted air masses and we determined molar enhancement ratios for both trace gases relative to CO and CH₃CN. The PAA-to-PAN ratio was enhanced in biomass-burning impacted air masses compared to background air, which may reflect the continued photochemical formation of PAA in such plumes even after NO_X has been largely depleted. This was confirmed by the large ratio of PAN/(PAN + NO_X), which was on average ≈0.8 at 7–8 km altitude and approached unity in biomass burning impacted air masses. Although no measurements of total reactive nitrogen species (NO_y) or HNO₃ were available, a major fraction of NO_X was likely sequestered in the form of PAN in this region, especially in air masses that had been impacted by biomass burning.

This paper provides a chronological review of the governance history of solar radiation management (SRM), also called solar geoengineering, from 2006 to 2024. Often characterized as an ungoverned space, we argue that the governance landscape for SRM is actually quite rich, though activity is primarily in the Global North, where research and governance capacity is concentrated. We illuminate the many governance initiatives and mechanisms in this area, explaining each mechanism's significance, relevant politics, and intersections with questions of environmental justice. We then identify gaps, limitations, possible future developments, and key contestations, including as related to justice. Crucially, as the chronological review shows, historical developments have largely occurred within a handful of countries in the Global North, laying bare the need to strengthen ongoing efforts to capacitate climate vulnerable countries in the Global South so they can more effectively shape the trajectory of SRM governance. We conclude by offering suggestions for future governance development.

The kinetics of the reactions of mercurous bromide (HgBr) with NO₂ and O₂ have been studied using the pulsed laser photolysis – pulsed laser induced fluorescence technique in nitrogen, air and helium at room temperature and as a function of pressure. For reaction with NO₂, temporal profiles showed good pseudo-first order behavior and we see a three-body recombination and obtain rate coefficients of ∼1–7 × 10⁻¹¹ cm³ per molecules per s over the pressure range 50–700 Torr in nitrogen. As expected, He is a less efficient 3rd body and rates are somewhat slower. We monitored the presence of a reduction channel regenerating Hg(0) and saw no evidence for it occurring. We obtained temporal profiles of HgBr at pressures of up to 500 Torr of O₂ demonstrating that laser induced fluorescence has adequate sensitivity as a concentration diagnostic in laboratory studies. The temporal profiles showed no evidence for any reaction between HgBr and O₂ at room temperature.

Terpenoids, including isoprene and monoterpenes, are highly reactive volatile organic compounds (VOCs) that play an essential role in atmospheric chemistry, contributing to the formation of ozone and secondary organic aerosols (SOAs). While known for decades for their biogenic origin, their anthropogenic origin is now well established in urban areas worldwide. Nevertheless, there is still a lack of clarity regarding the relative significance of these emissions and their impact on secondary pollution at the urban scale where biogenic and anthropogenic emissions coexist. The objective of this study is to evaluate the role of anthropogenic terpenoids in secondary pollution over the megacity of Paris, a typical northern mid-latitude urban area, using a box model. The model employs the Master Chemical Mechanism (MCM v3.3.1) to describe the gaseous reactivity. A physico-chemical scenario was developed to reproduce a typical summertime environment built upon in situ observations collected during the EU-MEGAPOLI campaign in Paris. Emission ratios of anthropogenic VOCs over carbon monoxide were used to parametrize the primary emissions of more than 60 species (including anthropogenic terpenoids). The comparison between in situ observations and modelled trace gas concentrations demonstrated the model's capacity to reproduce the levels and their temporal variability. Two sensitivity tests were conducted to quantify the impact of terpenoid emissions on ozone formation and their potential to form SOA mass concentration according to two simulations modulating anthropogenic and biogenic emissions of terpenoids based on the uncertainties associated with their estimation. Ozone concentration slightly increases by 1 (±0.5)% when increasing anthropogenic terpenoid emissions and by 3 (±2)% when increasing biogenic terpenoid emissions; the increase of O₃ with increasing VOCs is consistent with the high-NO_x chemical regime. Looking at the potential terpenoid derived SOA production, isoprene and limonene dominate. The estimated total mass concentration of SOAs produced over a 24 h period is 0.53 μg m⁻³, with a maximum hourly produced mass concentration of 0.045 μg m⁻³ observed in the morning. This modelling study suggests that the production of SOAs through the oxidation of terpenoids emitted from anthropogenic sources is competitive with that derived from their biogenic sources and remains significant at night.

The emissions of nitrogen oxides (NO_x) from combustion have been regulated for several decades with substantial reductions in national totals being reported in high-income countries since the 1990s. Most technical regulation on emissions is sectoral, appliance specific, and uses metrics aligned to activity data, for example grams of NO_x per kilometre driven or grams per kilonewton thrust. It is not straightforward therefore to compare the relative stringency of emission regulation between sectors. Here we undertake a regulatory assessment placing all the key NO_x emitting sectors onto a common grams of NO_x per kilowatt hour (g_[NOx] kWh⁻¹) baseline, covering appliances as small as 1 kW to greater than 2 GW. This common scale facilitates meaningful regulatory comparisons and may help to inform future policy decisions. We find little regulatory consistency between sectors when viewed on a per kWh output basis, with non-road mobile machinery (NRMM), medium combustion plant (MCP), maritime and civil aviation having more permissive regulatory limits when compared to emissions from passenger cars and domestic boilers. This difference can be large for appliances with the same nominal power rating; for example, the allowable NO_x emissions for a backhoe loader are 4.3 times higher than those for a passenger car. Transparency in pollutant emissions varies considerably between sectors. Data from MCPs and the Industrial Emissions Directive (IED) are less accessible due to commercial sensitivities and the use of less definitively defined principles of ‘Best Available Techniques’. Whilst electrification is likely in the long-term to eliminate some NO_x sources, it is notable that this will be in sectors that currently have more stringent regulatory limits (e.g. road transport, domestic heating). More permissively regulated sectors such as NRMM, MCPs and aviation are likely to retain combustion systems and will continue to emit substantial NO_x unless the adoption of low carbon fuel is accompanied by revision of NO_x emission standards.