Environmental science: atmospheres最新文献

High incidences of crop residue burning (CRB) in Punjab and Haryana during October–November is one of the major causes of elevated PM_2.5 in Delhi National Capital Region (NCR). An estimation of precise contribution of CRB emissions to PM_2.5 levels in Delhi-NCR is hindered by uncertainties in meteorology, atmospheric chemistry and emissions, and lack of quality observations. We use continuous in situ observations of PM_2.5 from a wide area network of 30 stations during 16 October to 30 November (peak CRB season) of 2022, 2023 and 2024 under Aakash project. The WRF-Chem model is used for simulation of chemical compositions of the atmosphere over the northwest India region. We have incorporated five distinct CRB emission scenarios in addition to commonly used industrial and biological emissions for the simulations. Scenarios with and without CRB emissions from different regions were compared to assess their impacts on PM_2.5. The average CRB emission impact on PM_2.5 concentrations in Delhi-NCR during CRB season are estimated at 18%, 16% and 9% in 2022, 2023 and 2024, respectively. The low impact of CRB on PM_2.5 in 2024 could arise from a shift in CRB time to evening, which was not captured by existing emission inventories due to absence of satellite overpass in late evening. A shift to late evening CRB leads to very strong nighttime build-up of PM_2.5 due to emissions when the boundary layer is shallow. Inclusion of appropriate diurnal and synoptic variability in CRB emissions is important for simulating observed PM_2.5 levels and evaluation human health exposures.

The semiconductor-based Figaro Taguchi Gas Sensor (TGS) is sensitive to reducing gases, including methane. TGS methane response can be characterised by using the ratio between resistance in the presence of methane mole fraction ([CH₄]) enhancements and a reference resistance, representative of sampling under the same environmental conditions and with the same background gas composition, but at a reference [CH₄] level. Effects of environmental variables, including water mole fraction ([H₂O]), are expected to cancel in this resistance ratio, allowing for independent [CH₄] characterisation. This work seeks to examine the cause of changes in [CH₄] resistance ratio characterisation over time, including the hypothesis that resistance ratios are independent of [H₂O]. Precise gas blends were sampled under controlled conditions during sensor characterisation in synthetic air (SCS) tests, which showed [H₂O] to influence resistance ratio methane characterisation, although this effect's importance depends on the reference gas. Three SCS tests were also performed with gaps of 137 days followed by 295 days, all under similar environmental conditions and gas blends. [CH₄] resistance ratio response changed significantly during the first time gap, suggesting that something inherently changed sensor behaviour, but negligibly during the second time gap, suggesting that natural ageing is not otherwise a key driver of sensor behaviour. Additional SCS tests showed persistent changes in [CH₄] resistance ratio response following hydrogen sulphide exposure; this may have caused a change between controlled SCS tests conducted 137 days apart, although other atmospheric species may also have been responsible. This is an important consideration for laboratory testing and final sensor application. Meanwhile, power loss and sampling dry air negligibly affected a different TGS. In addition, a total of 147 successful sensor characterisation in ambient air (SCA) tests occurred irregularly over approximately 25 months, where small amounts of gas with a high [CH₄] were blended with ambient outdoor air. SCA tests showed a weaker correlation between time and [CH₄] response when restricted to the period covering the second (295-day) time window between the similar SCS tests. A residual observed SCA testing correlation with time could be attributed to changes in [H₂O] over time, supporting SCS testing conclusions.

Exposure to indoor air pollutants is one of the most significant environmental and health risks people face, especially since they spend most of their time indoors. Therefore, evaluating indoor air pollution levels and comfort parameters is essential for achieving sustainable indoor air quality (IAQ). The main objective of this study was to identify patterns of indoor air pollution in two buildings with different characteristics located on a university campus in northeastern Mexico. We measured the concentration of particulate matter in fractions of 1.0 μm (PM₁), 2.5 μm (PM_2.5), and 10 μm (PM₁₀), as well as carbon dioxide (CO₂), carbon monoxide (CO), and ozone (O₃), along with the temperature and relative humidity in each microenvironment during the working hours of spring, summer, and autumn. Next, unsupervised machine learning was employed to identify behavioral patterns of air pollutants within the microenvironments. The K-means clustering algorithm was used to identify homogeneous microenvironments within the study area. We performed three clustering analyses per building: (1) considering all the variables in the dataset, (2)selecting the significant variables through principal component analysis (PCA), and (3) examining two time ranges within the working day. The robustness of the proposed approach was evaluated through a comparative analysis of the K-means, DBScan, and hierarchical algorithms, assessing their performance using the Davies–Bouldin index and Silhouette score metrics. Furthermore, the stability of the clusters over time intervals was assessed using the adjusted Rand index. Cluster analysis enabled us to identify microenvironments with maximum similarity and those that change groups, as their behavior depends on the time range. Consequently, grouping microenvironments into homogeneous IAQ classes is effective in accurately identifying spaces based on patterns related to their contamination levels and guiding actions to reduce pollution levels by zone or building.

Nanoplastics—originating from the fragmentation of macro- and micro plastic debris or direct industrial sources—have recently been recognized as an emerging class of marine pollutants with persistent oceanic presence. These tiny colloidal particles can potentially accumulate near the ocean surface owing to their buoyant and hydrophobic nature, positioning themselves within the sea surface microlayer (SSML), a biologically active interfacial zone enriched in lipids, proteins, and polysaccharides that shapes the chemical composition of sea spray aerosols (SSAs) generated during wave breaking events. In this study, we investigated the interfacial interactions between aged (mimicking solar UV wavelengths) polystyrene nanoplastics and a marine-representative lipid, palmitic acid (a dominant fatty acid in the ocean SSML and a known SSA constituent), using a combination of surface pressure-area isotherms, Brewster angle microscopy (BAM), and infrared reflection–absorption spectroscopy (IRRAS). The results demonstrate that nanoplastics dispersed in a seawater-proxy subphase solution significantly disrupts the structural integrity and morphology of palmitic acid films by altering intermolecular cohesion. Additionally, spectroscopic evidence suggests that these disruptions are predominantly mediated by cation–driven interactions at the carboxylate headgroup region, while the lipid hydrophobic core conserves its packing orientation. Such findings indicate that nanoplastics incorporated into SSAs can modify the surface organic film morphology during their atmospheric flight time, potentially altering aerosol mechanical stability, hygroscopicity, and cloud condensation nuclei (CCN) activity—processes that ultimately influence aerosol–cloud interactions and climate-relevant mechanisms.

Given that biomass-burning aerosol emissions have a direct radiative effect on the atmosphere, it is important to understand the chemistry that occurs within wildfire smoke that may change aerosol particle optical properties. To investigate night-time aging chemistry, this laboratory study explores the kinetics of the reaction between gas-phase nitrate radicals (NO₃) and vanillic acid (VA), a functionalized phenol. As breakdown products of lignin, phenolic compounds are the commonly observed components of biomass burning smoke. They are also present in urban air pollution, formed by the oxidation of aromatic precursors. The study was conducted in an aerosol flow tube with a residence time of 15 minutes, where roughly 1.6 pptv of NO₃ was formed by the reaction of NO₂ (21 ppbv) and O₃ (230 ppbv), and VA/ammonium sulfate (AS) solutions were atomized to form particles in the accumulation mode size range. The reaction was monitored by an aerosol mass spectrometer (AMS), which measured nitrated aerosol products, and by a 5-wavelength aethalometer, which observed the optical absorption of aerosol particles. The observed gas-surface kinetics are consistent with a NO₃ reactive uptake coefficient to form a nitrated product of 0.30 ± 0.39 and 0.19 ± 0.12 at respectively RH = 25% ± 5% and 55% ± 5% at 296 K. The aerosol particles became highly absorbing during the reaction in the near ultraviolet (375 nm) and visible (470, 528, and 625 nm) regions. While this change in absorptivity presumably arises via the nitration of the aromatic ring, the reaction drives stronger particle absorption, which extends much more deeply into the visible part of the spectrum than is characteristic of (mono) nitrovanillic acid (NVA), indicative of the formation of complex reaction products. These results demonstrate that night-time atmospheric aging of phenol-containing wildfire smoke and urban particulates will occur rapidly and significantly darken the particles throughout the visible part of the spectrum.

The acidity of cloud droplets can vary with size due to differences in aerosol composition and cloud chemistry and differential soluble gas uptake. Chemical transport models (CTMs) often assume that all droplets have the same composition and therefore acidity. In this work, we use the PMCAMx CTM to simulate size-resolved cloud and fog droplet acidity over the US during a winter and a summer month as a function of altitude. Small droplets are assumed to form on the activated particles smaller than 2.5 μm and have an average diameter of 20 μm, whereas large droplets form on the coarse particles and have an average diameter of 30 μm. Our simulations show that large droplets are often more alkaline than small (up to 100% lower H⁺ concentrations) especially in regions influenced by dust. In areas with more acidic conditions, the difference in H⁺ concentrations between small and large droplets is smaller. The pH of droplets either decreases or increases with altitude, depending on the composition of the aerosol on which the droplets were formed. Comparison of the bulk and two-section size-resolved approaches indicates that current differences in aqueous-phase sulfate concentrations over the US are generally low and usually less than 20% at approximately 10 min intervals (the most frequent difference ranges from zero to 5%). Based on our results, bulk calculations can simulate current aerosol composition and droplet pH over the US with small discrepancies. This is due to reduced SO₂ emissions causing SO₂ levels in clouds to often fall below those of H₂O₂. Under these conditions the importance of the pH-dependent ozone sulfate production pathway is diminished. These findings are specific to the US and may not apply to regions with higher SO₂ emissions.

A Wideband Integrated Bioaerosol Sensor (WIBS) was used in conjunction with chemical tracer analysis for the first time during the 2022–2023 grass pollen season in Melbourne, Australia. WIBS detected continuous levels of bioaerosol throughout the campaign. From 18th November to 7th December 2022, fluorescent particles accounted for an average of 10% of total particles in number, corresponding to an estimated 0.18 μg m⁻³ PM_2.5 (14%) and 0.49 μg m⁻³ PM₁₀ (25%). Using mannitol as a chemical tracer, fungal spores were estimated to contribute to an average of 2% of PM_2.5 and 9% of PM₁₀ mass. Analysis of fructose in PM_2.5 as a marker for sub-pollen particles (SPPs) showed elevated concentrations during periods of hot and dry weather. There was negligible fructose observed with rain, suggesting that SPP production is not limited to water absorption processes or high relative humidity in Melbourne. Estimates of SPP mass via fructose corresponded to the equivalent of 1.1 m⁻³ intact pollen grains on average, 2% of the total pollen concentration, 7% of PM_2.5 fluorescent particle mass, and 1% of PM_2.5 mass. New hourly measured grass pollen data confirmed the timing and magnitude of grass pollen emissions in the Victorian Grass Pollen Emission Model (VGPEM) and captured the strong diurnal variation. Five grass pollen rupturing mechanisms using different meteorological drivers were tested against the WIBS and fructose measurements. Whilst the WIBS and model were not well correlated, likely due to the complex mixture of bioaerosols and low relative abundance of SPPs, the mechanical wind speed rupturing mechanism represented the fructose time series well. Conceptually, this suggests that mechanical rupturing describes SPP formation during hot and dry conditions in Melbourne. Long-term measurements in Melbourne will improve SPP formation process forecasting.

Accounting for nearly 5% of the global gross domestic product, the construction industry significantly contributes to environmental pollution, emitting a broad range of hazardous pollutants, including particulate matter (PM₁₀, PM_2.5), carbon monoxide (CO), nitrogen oxides (NO_x), volatile organic compounds (VOCs), benzene and polycyclic aromatic hydrocarbons (PAHs). Individuals spend approximately 90% of their time indoors, where the air quality is heavily influenced by construction and demolition (C&D) activities that are carried out within or adjacent to residences. Despite regulatory interventions in the early 21st century emphasizing the importance of indoor air quality (IAQ), the contribution of C&D activities to indoor pollution remains largely underexplored, particularly to seasonal variations, extended renovation periods, and the release of case-specific pollutants. This review bridges knowledge gaps by examining the correlation between construction activities, pollutant emissions, health risks, and the efficacy of existing regulations. Key investigations include the impact of infrastructural inefficiencies and improper ventilation on IAQ, seasonal pollutant variations, and the disproportionate exposure risks faced by vulnerable populations, such as women and workers. The literature suggests that prolonged exposure prompts sick-building syndrome and ailments such as compromised immunity, bronchial allergy, asthma, and lung cancer. A survey-based data collection and analysis were conducted to gather and refine residents' practical insights across India, contributing to the development of an IAQ index. This tailored index, ranging from 22 to 100, is designed for indoor environments, incorporating building-specific and occupancy-related factors. In the long term, the index can provide actionable insights for administrators and communities to mitigate IAQ risks effectively, promoting healthier indoor environments by providing a quantitative measure of the health risks associated with exposure to poor indoor air quality in the absence of a pollutant dataset. The study enables individual households to take measures to retrofit indoor spaces by upgrading to better-quality materials or modifying the design of the building to reduce health risks and improve air exchange.

Airborne cloud water measurements are examined in this study, with a focus on pH and interrelationships with influential species for three regions: the Northwest Atlantic (winter and summer 2020–2022), the West Pacific (summer 2019), and the Northeast Pacific (summers between 2011 and 2019). Northwest Atlantic results are categorized into three ways: data closer to the U.S. east coast for (i) winter, (ii) summer, and (iii) summertime measurements over Bermuda. The median pHs are as follows: Northwest Atlantic winter/summer = 4.83/4.96, Bermuda = 4.74, West Pacific = 5.17, and Northeast Pacific = 4.40. The regions exhibit median pH values of ∼4–6 across various altitude bins reaching as high as 6.8 km, with the overall minimum and maximum values being 2.92 and 7.58, respectively (both for the Northeast Pacific). Principal component analysis of species to predict pH shows that the most influential principal component is anthropogenic in nature. Machine leaning modeling suggests that the most effective combination of species to predict pH includes some subset of oxalate, non-sea salt Ca²⁺, NO₃⁻, non-sea salt SO₄²⁻, and methanesulfonate. These results demonstrate that cloud water acidity is relatively well constrained between a pH of 4 and 5.5 and that anthropogenic activities impact regional cloud water pH in the areas examined, with dust offsetting acidity at times.

Marine Cloud Brightening (MCB) is a proposed solar radiation management technique whereby the albedo of low-lying clouds is artificially enhanced by the addition of Cloud Condensation Nuclei (CCN). It is generally accepted that these would be produced by atomisation of seawater to produce droplets which form appropriately sized artificial sea spray aerosol (SSA). Despite extensive theoretical consideration of the MCB concept, progress in understanding how perturbations to complex cloud microphysical processes would evolve has been hampered by the technical inability to produce the very large numbers of SSA required. To facilitate the first phase of outdoor experimentation a single MCB station should be capable of producing around 10¹⁵ per s CCN. Effervescent nozzle technology has been posited as potentially capable of meeting these requirements. Here we describe an effervescent nozzle design that produces ∼1.73 × 10¹² per s SSA, with ∼71% of aerosols within a 30 to 1000 nm range (considered likely CCN), using ∼512 W of energy per nozzle. Producing 10¹⁵ CCN using this design would then require 814 nozzles and around 417 kW of energy, a demand that can be practically met on a research vessel. The nozzle described here is therefore sufficiently practical to facilitate outdoor in situ experimentation of MCB, enabling a new generation of perturbation experiments that directly probe cloud microphysical and radiative responses to aerosol.