{"title":"A pulsed laser photolysis – pulsed laser induced fluorescence study of the kinetics and mechanism of the reaction of HgBr with NO2 and O2†","authors":"Dieter Bauer, Deanna Donohoue and Anthony Hynes","doi":"10.1039/D4EA00148F","DOIUrl":"https://doi.org/10.1039/D4EA00148F","url":null,"abstract":"<p >The kinetics of the reactions of mercurous bromide (HgBr) with NO<small><sub>2</sub></small> and O<small><sub>2</sub></small> 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 NO<small><sub>2</sub></small>, temporal profiles showed good pseudo-first order behavior and we see a three-body recombination and obtain rate coefficients of ∼1–7 × 10<small><sup>−11</sup></small> cm<small><sup>3</sup></small> 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 O<small><sub>2</sub></small> 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 O<small><sub>2</sub></small> at room temperature.</p>","PeriodicalId":72942,"journal":{"name":"Environmental science: atmospheres","volume":" 5","pages":" 636-647"},"PeriodicalIF":2.8,"publicationDate":"2025-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.rsc.org/en/content/articlepdf/2025/ea/d4ea00148f?page=search","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143949407","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Farhat, L. Pailler, M. Camredon, A. Maison, K. Sartelet, L. Patryl, P. Armand, C. Afif, A. Borbon and L. Deguillaume
{"title":"Investigating the role of anthropogenic terpenoids in urban secondary pollution under summer conditions by a box modeling approach†","authors":"M. Farhat, L. Pailler, M. Camredon, A. Maison, K. Sartelet, L. Patryl, P. Armand, C. Afif, A. Borbon and L. Deguillaume","doi":"10.1039/D4EA00112E","DOIUrl":"https://doi.org/10.1039/D4EA00112E","url":null,"abstract":"<p >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 <em>in situ</em> 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 <em>in situ</em> 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 O<small><sub>3</sub></small> with increasing VOCs is consistent with the high-NO<small><sub><em>x</em></sub></small> 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<small><sup>−3</sup></small>, with a maximum hourly produced mass concentration of 0.045 μg m<small><sup>−3</sup></small> 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.</p>","PeriodicalId":72942,"journal":{"name":"Environmental science: atmospheres","volume":" 5","pages":" 574-590"},"PeriodicalIF":2.8,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.rsc.org/en/content/articlepdf/2025/ea/d4ea00112e?page=search","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143949384","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lucy J. Webster, Alastair C. Lewis and Sarah J. Moller
{"title":"Evaluating the variability and consistency of NOx emission regulation between sectors†","authors":"Lucy J. Webster, Alastair C. Lewis and Sarah J. Moller","doi":"10.1039/D4EA00149D","DOIUrl":"https://doi.org/10.1039/D4EA00149D","url":null,"abstract":"<p >The emissions of nitrogen oxides (NO<small><sub><em>x</em></sub></small>) 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<small><sub><em>x</em></sub></small> 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<small><sub><em>x</em></sub></small> emitting sectors onto a common grams of NO<small><sub><em>x</em></sub></small> per kilowatt hour (g<small><sub>[NO<small><sub><em>x</em></sub></small>]</sub></small> kWh<small><sup>−1</sup></small>) 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<small><sub><em>x</em></sub></small> 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<small><sub><em>x</em></sub></small> sources, it is notable that this will be in sectors that currently have more stringent regulatory limits (<em>e.g.</em> 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<small><sub><em>x</em></sub></small> unless the adoption of low carbon fuel is accompanied by revision of NO<small><sub><em>x</em></sub></small> emission standards.</p>","PeriodicalId":72942,"journal":{"name":"Environmental science: atmospheres","volume":" 5","pages":" 603-619"},"PeriodicalIF":2.8,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.rsc.org/en/content/articlepdf/2025/ea/d4ea00149d?page=search","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143949386","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yitong Zhai, Vasilios G. Samaras and S. Mani Sarathy
{"title":"Characterizing highly oxygenated organic molecules in limonene secondary organic aerosols: roles of temperature and relative humidity†","authors":"Yitong Zhai, Vasilios G. Samaras and S. Mani Sarathy","doi":"10.1039/D4EA00153B","DOIUrl":"https://doi.org/10.1039/D4EA00153B","url":null,"abstract":"<p >Highly oxygenated organic molecules (HOMs) are significant contributors to the formation of secondary organic aerosols (SOAs) and new particles in the atmosphere. The process of HOM formation <em>via</em> autoxidation is highly dependent on several factors, such as temperature, relative humidity (RH), and initial ozone concentration, among others. The current work investigates how temperature and RH affect the formation of HOMs in SOAs from limonene ozonolysis. Experiments were conducted in a laminar flow tube reactor under different experimental conditions (<em>T</em> = 5 °C and 25 °C; RH = 15% and 75%). A scanning mobility particle sizer was used to measure the concentration and size distribution of generated SOA particles. Fourier transform ion cyclotron resonance mass spectrometry was used to detect and characterize HOMs and SOAs. Experimental results show that lower temperatures (<em>i.e.</em>, <em>T</em> = 5 °C) and higher RH levels (<em>e.g.</em>, RH = 75%) promote the generation of HOMs and SOAs. Limonene-oxidation-derived HOMs exhibit a preference for stabilization under low-temperature and high-RH conditions. Within this context, semi-volatile, low-volatile, and extremely low-volatile organic compounds play a significant role. Our experimental findings indicate that the formation of C<small><sub>10</sub></small> compounds during limonene ozonolysis is strongly influenced by peroxy radical chemistry. Given that peroxy radicals are key intermediates in this process, their reactions—including autoxidation and bimolecular termination pathways—likely play a significant role in the formation and stabilization of HOMs in SOAs. The observed product distributions also suggest that these radicals contribute to the incorporation of multiple oxygen atoms, facilitating the formation of ELVOCs and LVOCs that ultimately drive particle-phase growth. The present work can improve our understanding of the generation of biogenic HOMs and SOAs at different temperatures and RH, which can be used in future exposure risk or climate models to provide more accurate air quality prediction and management.</p>","PeriodicalId":72942,"journal":{"name":"Environmental science: atmospheres","volume":" 4","pages":" 455-470"},"PeriodicalIF":2.8,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.rsc.org/en/content/articlepdf/2025/ea/d4ea00153b?page=search","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143809082","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
O. J. Nielsen, M. P. Sulbaek Andersen and J. Franklin
{"title":"Comment on “Assessing the atmospheric fate of trifluoroacetaldehyde (CF3CHO) and its potential as a new source of fluoroform (HFC-23) using the AtChem2 box model” by Pérez-Peña et al., Environ. Sci.: Atmos., 2023, 3, 1767–1777, DOI: 10.1039/D3EA00120B","authors":"O. J. Nielsen, M. P. Sulbaek Andersen and J. Franklin","doi":"10.1039/D4EA00123K","DOIUrl":"https://doi.org/10.1039/D4EA00123K","url":null,"abstract":"<p >Recently Pérez-Peña <em>et al.</em> published a paper in this journal on the potential atmospheric fate of trifluoroacetaldehyde (CF<small><sub>3</sub></small>CHO) as a source of CF<small><sub>3</sub></small>H (HFC-23). In their work they utilized both a box model and a global chemistry and transport model to evaluate the production of CF<small><sub>3</sub></small>H from the photolysis of CF<small><sub>3</sub></small>CHO, the latter generated from photochemical oxidation of HFO-1234ze (CF<small><sub>3</sub></small>CH<img>CHF). Certain chemical assumptions and simplifications were made. We believe the assumptions utilized by Pérez-Peña <em>et al.</em> misrepresent the environmental fate of CF<small><sub>3</sub></small>CHO. In the following, we present our comments on both the photolysis and the wet and dry deposition of CF<small><sub>3</sub></small>CHO. Furthermore, we contemplate the impact of the potential deposition of CF<small><sub>3</sub></small>CHO on the formation of trifluoroacetic acid (CF<small><sub>3</sub></small>COOH) during the environmental processing of CF<small><sub>3</sub></small>CHO.</p>","PeriodicalId":72942,"journal":{"name":"Environmental science: atmospheres","volume":" 4","pages":" 530-534"},"PeriodicalIF":2.8,"publicationDate":"2025-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.rsc.org/en/content/articlepdf/2025/ea/d4ea00123k?page=search","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143809086","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Maria Paula Pérez-Peña, Jenny A. Fisher, Christopher S. Hansen and Scott H. Kable
{"title":"Reply to the ‘Comment on “Assessing the atmospheric fate of trifluoroacetaldehyde (CF3CHO) and its potential as a new source of fluoroform (HFC-23) using the AtChem2 box model”’ by O. J. Nielsen, M. P. Sulbaek Andersen and J. Franklin, Environ. Sci.: Atmos., 2025, 5, DOI: 10.1039/D4EA00123K","authors":"Maria Paula Pérez-Peña, Jenny A. Fisher, Christopher S. Hansen and Scott H. Kable","doi":"10.1039/D4EA00154K","DOIUrl":"https://doi.org/10.1039/D4EA00154K","url":null,"abstract":"<p >In Pérez-Peña <em>et al.</em> (DOI: https://doi.org/10.1039/d3ea00120b), we used a suite of box model simulations to determine how trifluoroacetaldehyde (CF<small><sub>3</sub></small>CHO) produced from HFO-1234ze is lost in the atmosphere and how much fluoroform (CHF<small><sub>3</sub></small> or HFC-23) could potentially be produced as a result. For the first time in any modelling study, our simulations included both a minor CF<small><sub>3</sub></small>CHO photolytic loss channel leading to CHF<small><sub>3</sub></small> production and physical removal of CF<small><sub>3</sub></small>CHO <em>via</em> wet and dry deposition. In their comment, Sulbaek Andersen, Nielsen, and Franklin query the assumptions used to simulate these processes. Here, we show that the importance of the photolytic loss pathway remains a matter of community debate and that our results are relatively insensitive to assumptions underlying simulation of deposition. We reiterate the need for measurements of CF<small><sub>3</sub></small>CHO physical properties to reduce the uncertainties in these processes and pave the way for more sophisticated models.</p>","PeriodicalId":72942,"journal":{"name":"Environmental science: atmospheres","volume":" 4","pages":" 535-538"},"PeriodicalIF":2.8,"publicationDate":"2025-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.rsc.org/en/content/articlepdf/2025/ea/d4ea00154k?page=search","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143809087","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Siying Lu, Chiranjivi Bhattarai, Vera Samburova and Andrey Khlystov
{"title":"Particle size distributions of wildfire aerosols in the western USA†","authors":"Siying Lu, Chiranjivi Bhattarai, Vera Samburova and Andrey Khlystov","doi":"10.1039/D5EA00007F","DOIUrl":"10.1039/D5EA00007F","url":null,"abstract":"<p >Wildfires are a major source of aerosols during summer in the western United States. Aerosols emitted from wildfires could significantly affect air quality, human health, and the global climate. This study conducted a comparison of aerosol characteristics during wildfire smoke-influenced and non-smoke-influenced days. Ambient particle size distribution (PSD) data were collected in Reno, Nevada, between July 2017 and October 2020. During this period, the site was impacted by smoke from over a hundred wildfires burning in a wide range of ecosystems in the western United States located at different distances from the measurement site. The smoke-influenced days were identified using satellite images, a hazard mapping system, and wind back-trajectory. Positive matrix factorization (PMF) was applied to identify the main sources and their characteristics. The wildfire aerosols were observed to have a number mode diameter of 212 nm, which is significantly larger than aerosols on non-smoke-influenced days (61 nm). In addition to the increase in particle size, wildfires made a large contribution to PM<small><sub>2.5</sub></small> and CO concentrations. During fire-prone months (July, August, and September) from 2016 to 2021, 56% to 65% of PM<small><sub>2.5</sub></small> and 18% to 26% of CO concentrations could be attributed to wildfire emissions in the study area. On an annual basis, wildfire emissions were responsible for 35% to 47% of PM<small><sub>2.5</sub></small> concentrations and 5% to 12% of CO concentrations.</p>","PeriodicalId":72942,"journal":{"name":"Environmental science: atmospheres","volume":" 4","pages":" 502-516"},"PeriodicalIF":2.8,"publicationDate":"2025-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11917463/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143671766","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Colleen Marciel F. Rosales, Everlyn Gayle Tamayo, Dana Lightha Babela and Maria Preciosa Benjamin
{"title":"Indoor penetration of ambient particulate pollution in a hospital maternity ward in Manila, Philippines: perspectives towards holistic city-level air quality management†","authors":"Colleen Marciel F. Rosales, Everlyn Gayle Tamayo, Dana Lightha Babela and Maria Preciosa Benjamin","doi":"10.1039/D4EA00160E","DOIUrl":"https://doi.org/10.1039/D4EA00160E","url":null,"abstract":"<p >Several studies have analyzed and reported the relationship between particulate matter (PM) in the air and its adverse health effects, primarily on fetal development and subsequent early childhood. This study aims to understand how outdoor air made up of mainly PM, influences indoor air quality in a naturally ventilated maternity ward in an urban hospital setting. The data collection site in this study was the Dr Jose Fabella Memorial Hospital, a maternity hospital located in Manila, Philippines. Indoor and outdoor PM<small><sub>2.5</sub></small> levels from November 2021 to June 2022 were investigated. A strong positive correlation (<em>r</em><small><sup>2</sup></small> ranging from 0.78 to 0.98) was observed between the daily outdoor and indoor PM levels. While the median concentrations were above the World Health Organization (WHO) air quality guidelines, they were below the Philippine National Ambient Air Quality Guideline Values (NAAQGV) at the time of data collection. These results underscore the importance of updating guideline values. Indoor-to-outdoor diurnal ratios (<em>I</em>/<em>O</em>), ranging from 0.77 to 1.33, with peak times (indoor-source-dominated) between 12:00 and 13:00 and trough times (outdoor-source-dominated) between 04:00 and 05:00, offered insight into the times of the day dominated by indoor <em>versus</em> outdoor sources and highlighted the need for continuous air monitoring while providing additional protection in indoor spaces, such as clear indoor air quality guidelines combined with indoor ventilation and filtration requirements. These results highlight the need for a holistic air quality management approach which focuses concurrently on both ambient and indoor air quality in healthcare facilities. Naturally ventilated hospitals must be included as a priority monitoring site, as they are a critical in improving air quality in the context of public health protection.</p>","PeriodicalId":72942,"journal":{"name":"Environmental science: atmospheres","volume":" 5","pages":" 563-573"},"PeriodicalIF":2.8,"publicationDate":"2025-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.rsc.org/en/content/articlepdf/2025/ea/d4ea00160e?page=search","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143949383","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Patrick Attey-Yeboah, Christian Afful, Kelvin Yeboah, Carl H. Korkpoe, Eric S. Coker, R. Subramanian and A. Kofi Amegah
{"title":"Utility of low-cost sensor measurement for predicting ambient PM2.5 concentrations: evidence from a monitoring network in Accra, Ghana†","authors":"Patrick Attey-Yeboah, Christian Afful, Kelvin Yeboah, Carl H. Korkpoe, Eric S. Coker, R. Subramanian and A. Kofi Amegah","doi":"10.1039/D4EA00140K","DOIUrl":"https://doi.org/10.1039/D4EA00140K","url":null,"abstract":"<p >Ambient air pollution has been linked to several health endpoints. The WHO attributes 7 million deaths annually to air pollution with particulate matter (PM<small><sub>2.5</sub></small>) being the pollutant of critical importance due to its devastating health effects. Air quality monitoring is very limited in sub-Saharan African (SSA) countries and although satellite remote sensing has helped to bridge the huge air quality data gaps, these measurements have not been validated against ground-level measurements in these countries. We therefore evaluated the efficiency of low-cost sensors in estimating PM<small><sub>2.5</sub></small> concentrations in an African city through comparison of low-cost sensor data with satellite aerosol optical depth (AOD) data leveraging complex machine learning (ML) methods. Low-cost sensor data were collected from a monitoring network in Accra, Ghana, with AOD measurements extracted from the MODIS MCD19A2v061 dataset and processed using the MAIAC algorithm. Ordinary Least Squares regression, Random Forest, Extra Trees, Boosted Decision Trees and XGBoost were used to establish the relationship between AOD and low-cost sensor PM<small><sub>2.5</sub></small> measurements incorporating meteorological data. We observed significant positive relationships for two low-cost sensors deployed in the network (Clarity Node S and Airnote). The <em>R</em><small><sup>2</sup></small> values were, however, low, ranging from 0.18 to 0.27, with the corrected Airnote data recording the highest <em>R</em><small><sup>2</sup></small>. The ML models which integrated temperature and humidity improved the <em>R</em><small><sup>2</sup></small> values with the Boosted Decision Tree demonstrating the best predictive capability. Seasonal variability was found to have a strong influence on model performances with the dry season model performing significantly better than the wet season model. Consistent with other studies, AOD explained only a small proportion of ground-level PM<small><sub>2.5</sub></small> variations. Evidence from this sensor network in Accra suggests that AOD predicts ground-level PM<small><sub>2.5</sub></small> measured with low-cost sensors in a manner similar to conventional air monitoring instrumentation. However, for low-cost sensors to be deemed a good substitute for satellite AOD, data correction with complex algorithms developed in the same research location will be required.</p>","PeriodicalId":72942,"journal":{"name":"Environmental science: atmospheres","volume":" 4","pages":" 517-529"},"PeriodicalIF":2.8,"publicationDate":"2025-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.rsc.org/en/content/articlepdf/2025/ea/d4ea00140k?page=search","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143809085","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Anwar H. Khan, Rayne Holland, Asan Bacak, Thomas J. Bannan, Hugh Coe, Richard G. Derwent, Carl J. Percival and Dudley E. Shallcross
{"title":"Investigation of organic hydrotrioxide (ROOOH) formation from RO2 + OH reactions and their atmospheric impact using a chemical transport model, STOCHEM-CRI†","authors":"M. Anwar H. Khan, Rayne Holland, Asan Bacak, Thomas J. Bannan, Hugh Coe, Richard G. Derwent, Carl J. Percival and Dudley E. Shallcross","doi":"10.1039/D5EA00009B","DOIUrl":"https://doi.org/10.1039/D5EA00009B","url":null,"abstract":"<p >Incorporating the reactions of fifty peroxy radicals (RO<small><sub>2</sub></small>) with the hydroxyl radical (OH) into the global chemistry transport model, STOCHEM-CRI, affected the composition of the troposphere by changing the global burdens of NO<small><sub><em>x</em></sub></small> (−2.7 Gg, −0.5%), O<small><sub>3</sub></small> (−2.3 Tg, −0.7%), CO (−3.2 Tg, −0.8%), HO<small><sub><em>x</em></sub></small> (+2.1 Gg, +7.7%), H<small><sub>2</sub></small>O<small><sub>2</sub></small> (+0.5 Tg, +18.3%), RO<small><sub>2</sub></small> (−8.0 Gg, −18.2%), RONO<small><sub>2</sub></small> (−19.4 Gg, −4.7%), PAN (−0.1 Tg, −3.4%) HNO<small><sub>3</sub></small> (−7.4 Gg, −1.3%) and ROOH (−96.9 Gg, −3.8%). The RO<small><sub>2</sub></small> + OH addition reactions have a significant impact on HO<small><sub>2</sub></small> mixing ratios in tropical regions with up to a 25% increase, resulting in increasing H<small><sub>2</sub></small>O<small><sub>2</sub></small> mixing ratios by up to 50% over oceans. Globally, a significant amount of organic hydrotrioxides (ROOOH) (86.1 Tg per year) are produced from these reactions with CH<small><sub>3</sub></small>OOOH (67.5 Tg per year, 78%), isoprene-derived ROOOH (5.5 Tg per year, 6%) and monoterpene-derived ROOOH (4.2 Tg per year, 5%) being the most significant contributors. The tropospheric global burden of CH<small><sub>3</sub></small>OOOH is found to be 0.48 Gg. The highest mixing ratios of ROOOH, of up to 0.35 ppt, are found primarily in the oceans near the tropical land areas. The RO<small><sub>2</sub></small> + OH reactions have a small, but noticeable, contribution to OH reactivity (∼5%) over tropical oceans. Additionally, these reactions have a significant impact on RO<small><sub>2</sub></small> reactivity over tropical oceans where losses of the CH<small><sub>3</sub></small>O<small><sub>2</sub></small> radical, isoprene derived peroxy radical (ISOPO<small><sub>2</sub></small>) and monoterpene derived peroxy radical (MONOTERPO<small><sub>2</sub></small>) by OH can contribute up to 25%, 15% and 50% to the total RO<small><sub>2</sub></small> loss, respectively. The changes in RO<small><sub>2</sub></small> reactivity influence the global abundances of organic alcohols (ROH) which are important species due to their crucial impact on air quality. The ROOOH generate secondary organic aerosol (SOA) of up to 0.05 μg m<small><sup>−3</sup></small> which affects the Earth's radiation budget because of enhancing modelled organic aerosol by up to 5% and 2000% on land surfaces and the remote tropical oceans, respectively.</p>","PeriodicalId":72942,"journal":{"name":"Environmental science: atmospheres","volume":" 4","pages":" 442-454"},"PeriodicalIF":2.8,"publicationDate":"2025-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.rsc.org/en/content/articlepdf/2025/ea/d5ea00009b?page=search","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143809081","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}