Measurements of PM<sub>2.5</sub> with PurpleAir under atmospheric conditions

Atmospheric measurement techniques, Год журнала: 2020, Номер 13(10), С. 5441 - 5458

Опубликована: Окт. 13, 2020

Abstract. The PurpleAir PA-II unit is a low-cost sensor for monitoring changes in the concentrations of particulate matter (PM) various sizes. There are currently more than 10 000 units use worldwide; some located areas where no other reference air system present. Previous studies have examined performance these (or sensors within them) comparison to co-located system. However, because installed by customers, most not with and, many cases, near one. This study aims examine how each performs under atmospheric conditions when exposed variety pollutants and PM2.5 (PM an aerodynamic diameter smaller 2.5 µm), at distance from sensor. We perform Environmental Protection Agency (EPA) Air Quality Monitoring Stations (AQMSs) that them. For this study, we selected four different regions, containing multiple (minimum seven per region). In addition, region needed least one AQMS was unit, all be up 5 km between other. Correction values implemented multivariate linear regression (MLR), taking into account temperature relative humidity. fit coefficients, received MLR, were then used correct remaining region. Hourly measurements compared those AQMSs its correction improved R-squared value (R2), root-mean-square error (RMSE), mean absolute (MAE) slope units. found good agreement (75 % comparisons had R2>0.8); they measured similar followed trends; is, increased or decreased, so did high-pollution events, corrected slightly higher AQMS. Distance impact Overall, after corrections values, seems promising tool identifying concentration potential complement sparsely distributed stations aid assessing minimizing public exposure PM.

Язык: Английский

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Deep Learning for Prediction of the Air Quality Response to Emission Changes

Environmental Science & Technology, Год журнала: 2020, Номер 54(14), С. 8589 - 8600

Опубликована: Июнь 17, 2020

Efficient prediction of the air quality response to emission changes is a prerequisite for an integrated assessment system in developing effective control policies. Yet, representing nonlinear controls with accuracy remains major barrier quality-related decision making. Here, we demonstrate novel method that combines deep learning approaches chemical indicators pollutant formation quickly estimate coefficients functions using ambient concentrations 18 simulated comprehensive atmospheric transport model (CTM). By requiring only two CTM simulations application, new significantly enhances computational efficiency compared existing methods achieve lower despite 20+ (the benchmark statistical model). Our results utility capturing nonlinearity chemistry and physics prospects support policymaking other environment systems.

Язык: Английский

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Heterogeneous Nitrate Production Mechanisms in Intense Haze Events in the North China Plain

Journal of Geophysical Research Atmospheres, Год журнала: 2021, Номер 126(9)

Опубликована: Апрель 24, 2021

Abstract Studies of wintertime air quality in the North China Plain (NCP) show that particulate‐nitrate pollution persists despite rapid reduction NO x emissions. This intriguing ‐nitrate relationship may originate from non‐linear nitrate‐formation chemistry, but it is unclear which feedback mechanisms dominate NCP. In this study, we re‐interpret observations 17 O excess nitrate (∆ O(NO 3 − )) Beijing using GEOS‐Chem (GC) chemical transport model to estimate importance various nitrate‐production pathways and how their contributions change with intensity haze events. We also analyze relationships between other metrics y chemistry [PM 2.5 ] simulations. find on average has a negative bias −0.9‰ −36% for ∆ ) [O x,major (≡ + [NO 2 [p‐NO ]), respectively, while overestimating nitrogen oxidation ratio ([NO ]/([NO ])) by +0.12 intense haze. The discrepancies become larger more attribute biases an overestimate ‐uptake aerosols underestimate concentrations. Our findings highlight need address uncertainties related heterogeneous air‐quality models. combined assessment results suggest N 5 uptake clouds dominant pathway Beijing, its rate limited ozone under high‐NO ‐high‐PM conditions. Nitrate production rates continue increase as long increases ], creating reduces effectiveness mitigation.

Язык: Английский

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Variability and Time of Day Dependence of Ozone Photochemistry in Western Wildfire Plumes

Environmental Science & Technology, Год журнала: 2021, Номер 55(15), С. 10280 - 10290

Опубликована: Июль 13, 2021

Understanding the efficiency and variability of photochemical ozone (O3) production from western wildfire plumes is important to accurately estimate their influence on North American air quality. A set measurements were made NOAA Twin Otter research aircraft as a part Fire Influence Regional Global Environments Air Quality (FIREX-AQ) experiment. We use zero-dimensional (0-D) box model investigate chemistry driving O3 in modeled plumes. Modeled afternoon reached maximum mixing ratio 140 ± 50 ppbv (average standard deviation) within 20 10 min emission compared 76 12 60 30 evening Afternoon isopleths indicate that near peak NOx efficiency. radical budget describes volatile - organic compound (VOC) sensitivities these displayed rapid transition VOC-sensitive NOx-sensitive chemistry, driven by HOx (=OH + HO2) photolysis nitrous acid (HONO) (48 20% primary HOx) formaldehyde (HCHO) (26 9%) emitted directly fire. Evening exhibit slower caused reduction rates fire emissions. controlled HONO (53 7%), HCHO (18 9%), alkene ozonolysis (17 9%).

Язык: Английский

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Direct observations indicate photodegradable oxygenated volatile organic compounds (OVOCs) as larger contributors to radicals and ozone production in the atmosphere

Atmospheric chemistry and physics, Год журнала: 2022, Номер 22(6), С. 4117 - 4128

Опубликована: Март 30, 2022

Abstract. Volatile organic compounds (VOCs) regulate atmospheric oxidation capacity, and the reactions of VOCs are key in understanding ozone formation its mitigation strategies. When evaluating their impact, most previous studies did not fully consider role oxygenated due to limitations measurement technology. By using a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS) combined with gas chromatograph–mass (GC–MS), large number (OVOCs) have been quantified Guangzhou city, China. Based on new dataset, we demonstrate that constraints OVOC observations essential modeling radical production, as modeled OVOCs can be substantially lower than measurements, potentially primary emissions and/or missing secondary sources. Non-formaldehyde (HCHO) contribute fractions (22 %–44 %) total ROx which comparable or larger contributions from nitrous acid formaldehyde. Our results show models without ambient measurements will underestimate production rates ozone, they may also affect determination sensitivity regime formation. Therefore, thorough quantification photodegradable species is urgent need understand accurately chemistry develop effective control

Язык: Английский

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Non-linear response of PM<sub>2.5</sub> to changes in NO<sub><i>x</i></sub> and NH<sub>3</sub> emissions in the Po basin (Italy): consequences for air quality plans

Atmospheric chemistry and physics, Год журнала: 2021, Номер 21(12), С. 9309 - 9327

Опубликована: Июнь 17, 2021

Abstract. Air pollution is one of the main causes damages to human health in Europe, with an estimate about 380 000 premature deaths per year EU28, as result exposure fine particulate matter (PM2.5) only. In this work, we focus on specific region Po basin, a where chemical regimes are most complex, showing important non-linear processes, especially those related interactions between NOx and NH3. We analyse sensitivity PM2.5 concentration NH3 emissions by means set EMEP model simulations performed different levels emission reductions, from 25 % up total switch-off emissions. Both single combined precursor reduction scenarios applied determine efficient strategies quantify reductions. The results confirmed peculiarity secondary formation characterised contrasting within distances few (hundred) kilometres, well responses reductions during wintertime. One striking slight increase when NOx-rich areas, such surroundings Bergamo. increased oxidative capacity atmosphere cause induced emission. This process could have contributed absence significant decrease COVID-19 lockdowns many European cities. It account for designing air quality plans, since it lead transitionary increases at some locations winter measures gradually implemented. While regimes, determined relative importance vs. show large variations seasonally spatially, they not very sensitive moderate (up 50 %–60 %) Beyond strength, concentrations become certain areas basin mainly

Язык: Английский

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Synergetic PM2.5 and O3 control strategy for the Yangtze River Delta, China

Journal of Environmental Sciences, Год журнала: 2022, Номер 123, С. 281 - 291

Опубликована: Апрель 14, 2022

Язык: Английский

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Linking gas, particulate, and toxic endpoints to air emissions in the Community Regional Atmospheric Chemistry Multiphase Mechanism (CRACMM)

Atmospheric chemistry and physics, Год журнала: 2023, Номер 23(9), С. 5043 - 5099

Опубликована: Май 4, 2023

Abstract. Chemical mechanisms describe the atmospheric transformations of organic and inorganic species connect air emissions to secondary such as ozone, fine particles, hazardous pollutants (HAPs) like formaldehyde. Recent advances in our understanding several chemical systems shifts drivers chemistry warrant updates used transport models Community Multiscale Air Quality (CMAQ) modeling system. This work builds on Regional Atmospheric Chemistry Mechanism version 2 (RACM2) develops Multiphase (CRACMM) 1.0, which demonstrates a fully coupled representation leading ozone aerosol (SOA) with consideration HAPs. CRACMMv1.0 includes 178 gas-phase species, 51 particulate 508 reactions spanning heterogeneous pathways. To support estimation health risks associated HAPs, nine CRACMM cover 50 % total cancer 60 non-cancer emission-weighted toxicity estimated for primary HAPs from anthropogenic biomass burning sources US, coverage higher (> 80 %) when formaldehyde acrolein are considered. In addition, new mechanism were added based importance their aerosol, or burden reactive carbon (ROC): sesquiterpenes, furans, propylene glycol, alkane-like low- intermediate-volatility compounds (9 species), oxygenated (16 aromatic hydrocarbons (2 slowly reacting carbon. Intermediate- lower-volatility increase ROC by 40 compared current operational mechanisms. Autoxidation, reaction particularly effective producing SOA, was C10 larger alkanes, hydrocarbons, monoterpene including second-generation aldehydes. Integrating radical SOA put additional constraints both enabled implementation previously unconsidered pathways phenolic furanone compounds, predicted account ∼ 30 hydrocarbon under typical conditions. found span atmospherically relevant range number, number oxygens per carbon, oxidation state slight high bias hydrogens total, 11 emitted implemented precursors CMAQv5.3.3 representations, resulting bottom-up prediction is required accurate source attribution design control strategies. available CMAQv5.4.

Язык: Английский

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Ozone pollution mitigation strategy informed by long-term trends of atmospheric oxidation capacity

Nature Geoscience, Год журнала: 2023, Номер 17(1), С. 20 - 25

Опубликована: Ноя. 27, 2023

Язык: Английский

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Elucidating HONO formation mechanism and its essential contribution to OH during haze events

npj Climate and Atmospheric Science, Год журнала: 2023, Номер 6(1)

Опубликована: Май 30, 2023

Abstract Atmospheric nitrous acid (HONO) chemistry is of critical importance to air quality during polluted haze events, especially in China. However, current models (such as WRF-CHEM, WRF-CMAQ, Box-MCM) generally underestimate the concentration HONO, leading a lack fundamental understanding pollution. Here, by combining field observations events Beijing and modeling results, we developed new parameterization scheme for heterogeneous nitrogen dioxide (NO 2 ) reaction on aerosol surfaces with synergistic effects relative humidity ammonia, which has not been considered existing models. Including NO reactions into significantly improves estimation accuracy HONO OH levels, contribution reaching up 91% 78% pollution episodes. The derived can partly explain high concentrations particulate matter. Together, our work provides approach illustrate formation OH, consideration → chemistry.

Язык: Английский

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