Assessing the impact of clean air action on air quality trends in Beijing using a machine learning technique

Atmospheric chemistry and physics, Journal Year: 2019, Volume and Issue: 19(17), P. 11303 - 11314

Published: Sept. 6, 2019

Abstract. A 5-year Clean Air Action Plan was implemented in 2013 to reduce air pollutant emissions and improve ambient quality Beijing. Assessment of this action plan is an essential part the decision-making process review its efficacy develop new policies. Both statistical chemical transport modelling have been previously applied assess plan. However, inherent uncertainties these methods mean that independent are required support assessment process. Here, we a machine-learning-based random forest technique quantify effectiveness Beijing's by decoupling impact meteorology on quality. Our results demonstrate meteorological conditions important year-to-year variations Further analyses show PM2.5 mass concentration would broken target (2017 annual PM2.5<60 µg m−3) were it not for winter 2017 favouring dispersion pollutants. over whole period (2013–2017), primary emission controls led significant reductions PM2.5, PM10, NO2, SO2, CO from approximately 34 %, 24 17 68 33 respectively, after correction. The marked decrease SO2 largely attributable reduction coal combustion. indicate has highly effective reducing pollution improving offers successful example developing policies other regions China countries.

Language: Английский

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Significant Changes in Chemistry of Fine Particles in Wintertime Beijing from 2007 to 2017: Impact of Clean Air Actions

Environmental Science & Technology, Journal Year: 2019, Volume and Issue: 54(3), P. 1344 - 1352

Published: Nov. 26, 2019

The Beijing government implemented a number of clean air action plans to improve quality in the last 10 years, which contributed changes concentration fine particles and their compositions. However, quantifying impacts these interventions is challenging as meteorology masks real observed concentrations. Here, we applied machine learning technique decouple effect evaluate chemistry nonrefractory PM1 (particulate matter less than 1 μm) winter 2007, 2016, 2017 result actions. mass concentrations were 74.6, 90.2, 36.1 μg m–3 three winters, while deweathered 74.2, 78.7, 46.3 m–3, respectively. PM1, organics, sulfate, ammonium, chloride, SO2, NO2, CO decreased by −38, −46, −59, −24, −51, −89, −16, −52% comparison 2007. On contrary, nitrates increased 4%. Our results indicate that actions highly effective reducing ambient CO, but control nitrate organics remains major challenge.

Language: Английский

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Evaluating the sensitivity of radical chemistry and ozone formation to ambient VOCs and NO&lt;sub&gt;&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt; in Beijing

Atmospheric chemistry and physics, Journal Year: 2021, Volume and Issue: 21(3), P. 2125 - 2147

Published: Feb. 12, 2021

Abstract. Measurements of OH, HO2, complex RO2 (alkene- and aromatic-related RO2) total radicals taken during the integrated Study AIR Pollution PROcesses in Beijing (AIRPRO) campaign central summer 2017, alongside observations OH reactivity, are presented. The concentrations were elevated, with reaching up to 2.8×107moleculecm-3, HO2 peaking at 1×109moleculecm-3 concentration 5.5×109moleculecm-3. reactivity (k(OH)) peaked 89 s−1 night, a minimum afternoon ≈22s-1 on average. An experimental budget analysis, which rates production destruction compared, highlighted that although sources sinks balanced under high NO concentrations, exceeded known (by 15 ppbv h−1) very low conditions (<0.5 ppbv) experienced afternoons, demonstrating missing source consistent previous studies volatile organic compound (VOC) emissions loadings. Under highest mixing ratios (104 ppbv), rate by ≈50ppbvh-1, whilst same rate, indicating net propagation may be substantially slower than assumed. If just 10 % propagate upon reaction NO, budgets could closed but this lower revealed sink was similar magnitude source. A detailed box model incorporated latest Master Chemical Mechanism (MCM3.3.1) reproduced observed well over-predicted (<1 under-predicted (both fraction other types we classify as simple most significantly concentrations. also k(OH) consistently ≈10s-1 across all NOx levels, highlighting good agreement for fortuitous due cancellation terms its budget. Including heterogeneous loss aerosol surfaces did reduce modelled line only <0.3 ppbv. inclusion Cl atoms, formed from photolysis nitryl chloride, enhanced several mornings when atom calculated exceed 1×104atomscm-3 reconcile measured these times. However, mornings, lower, large under-predictions remained. Furthermore, chemistry not enhance beyond first few hours after sunrise so unable resolve under-prediction times day. Model scenarios, VOC included an additional converted RO2, sensitive choice product. level simple) improved if larger species able undergo followed isomerisation reactions reforming species, before eventually generating HO2. In work α-pinene-derived used example. simulation, underestimated uncertainty, regards present they form (HO2 directly or another species), leads over order less O3 predicted peroxy This demonstrates indeed needs understood accurately simulate ozone environments such Beijing, where multifunctional VOCs likely present.

Language: Английский

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Atmospheric boundary layer height from ground-based remote sensing: a review of capabilities and limitations

Atmospheric measurement techniques, Journal Year: 2023, Volume and Issue: 16(2), P. 433 - 479

Published: Jan. 26, 2023

Abstract. The atmospheric boundary layer (ABL) defines the volume of air adjacent to Earth's surface for dilution heat, moisture, and trace substances. Quantitative knowledge on temporal spatial variations in heights ABL its sub-layers is still scarce, despite their importance a series applications (including, example, quality, numerical weather prediction, greenhouse gas assessment, renewable energy production). Thanks recent advances ground-based remote-sensing measurement technology algorithm development, continuous profiling entire vertical extent at high resolution increasingly possible. Dense networks autonomous instruments, such as microwave radiometers, radar wind profilers, Doppler lidars or automatic ceilometers are hence emerging across Europe other parts world. This review summarises capabilities limitations various instrument types monitoring provides an overview vast number retrieval methods developed detection sub-layer from different quantities (temperature, humidity, wind, turbulence, aerosol). It outlined how diurnal evolution can be monitored effectively with combination methods, pointing out where instrumental methodological synergy considered particularly promising. highlights fact that harmonised data acquisition carefully designed sensor well tailored processing key obtaining high-quality products again essential capture complexity lowest part atmosphere which we live breathe.

Language: Английский

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Recent developments and applications of selected ion flow tube mass spectrometry (SIFT‐MS)

Mass Spectrometry Reviews, Journal Year: 2023, Volume and Issue: unknown

Published: Feb. 12, 2023

Abstract Selected ion flow tube mass spectrometry (SIFT‐MS) is now recognized as the most versatile analytical technique for identification and quantification of trace gases down to parts‐per‐trillion by volume, pptv, range. This statement supported wide reach its applications, from real‐time analysis, obviating sample collection very humid exhaled breath, adoption in industrial scenarios air quality monitoring. review touches on recent extensions underpinning chemistry kinetics library alternative challenge using nitrogen carrier gas instead helium. The addition reagent anions Voice200 series SIFT‐MS instruments has enhanced capability, thus allowing analyses volatile compounds that cannot be analyzed cations alone, clarified outlining anion involved. Case studies are reviewed breath analysis bacterial culture organic compound (VOC), emissions, environmental applications such air, water, soil workplace safety transport container fumigants, airborne contamination semiconductor fabrication, food flavor spoilage, drugs VOC emissions packaging demonstrate stated qualities uniqueness new generation instrumentation. Finally, some advancements can made improve capability mentioned.

Language: Английский

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Elevated levels of OH observed in haze events during wintertime in central Beijing

Atmospheric chemistry and physics, Journal Year: 2020, Volume and Issue: 20(23), P. 14847 - 14871

Published: Dec. 2, 2020

Abstract. Wintertime in situ measurements of OH, HO2 and RO2 radicals OH reactivity were made central Beijing during November December 2016. Exceptionally elevated NO was observed on occasions, up to ∼250 ppbv. The daily maximum mixing ratios for radical species varied significantly day-to-day over the ranges 1–8×106 cm−3 (OH), 0.2–1.5×108 (HO2) 0.3–2.5×108 (RO2). Averaged full observation period, mean daytime peak 2.7×106, 0.39×108 0.88×108 total RO2, respectively. main source new via initiation processes (primary production) photolysis HONO (∼83 %), dominant termination pathways reactions with NO2, particularly under polluted haze conditions. Master Chemical Mechanism (MCM) v3.3.1 operating within a box model used simulate concentrations RO2. underpredicted especially when high (above 6 ppbv). observation-to-model ratio increased from ∼1 (for all radicals) at 3 ppbv factor ∼3, ∼20 ∼91 respectively, ∼200 NO. significant underprediction by MCM suggests deficiency representation gas-phase chemistry NOx. surprisingly similar (within 20 % day) outside events, despite j(O1D) decreasing 50 periods. These observations provide strong evidence that oxidation can continue generate secondary pollutants even high-pollution episodes, reduction rates haze.

Language: Английский

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Effects of China’s current Air Pollution Prevention and Control Action Plan on air pollution patterns, health risks and mortalities in Beijing 2014–2018

Chemosphere, Journal Year: 2020, Volume and Issue: 260, P. 127572 - 127572

Published: July 11, 2020

Language: Английский

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Characterization of black carbon-containing fine particles in Beijing during wintertime

Atmospheric chemistry and physics, Journal Year: 2019, Volume and Issue: 19(1), P. 447 - 458

Published: Jan. 11, 2019

Abstract. Refractory black carbon (BC) is a product of incomplete combustion fossil fuel, biomass and biofuel, etc. By mixing with other species, BC can play significant roles in climate change, visibility impairment human health. Such BC-containing particles densely populated megacities like Beijing may have specific sources properties that are important to haze formation air quality. In this work, we exclusively characterized the urban by using laser-only Aerodyne soot particle aerosol mass spectrometer (SP-AMS), as part Atmospheric Pollution &amp; Human Health (APHH) 2016 winter campaign. The average ratio coating core (RBC) was found be ∼5.0. Positive matrix factorization shows presence primary fuel biomass-burning organics (64 % total organics). Yet secondary including sulfate, nitrate oxygenated organic (OA) could impacts on particles, especially for ones larger sizes thicker coatings. Analyses diurnal cycles reveal afternoon photochemical production OA (SOA), well nighttime aqueous portion highly OA. Besides SOA, nitrate, not appeared important. Further investigations during different periods show that, average, more polluted would contributions from species thickly coated tended associate indicating role chemical aging pollution wintertime. However, individual events, (fossil coal emissions) also dominant role, revealed compositions two episodes sampling period.

Language: Английский

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Effect of aerosol composition on the performance of low-cost optical particle counter correction factors

Atmospheric measurement techniques, Journal Year: 2020, Volume and Issue: 13(3), P. 1181 - 1193

Published: March 10, 2020

Abstract. There is considerable interest in using low-cost optical particle counters (OPCs) to supplement existing routine air quality networks that monitor mass concentrations. In order do this, OPC data need be comparable with reference instrumentation; however, there currently no widely agreed upon methodology accomplish this. Aerosol hygroscopicity known a key parameter consider when correcting concentrations derived from OPCs, particularly at high ambient relative humidity (RH). Correction factors have been developed apply κ-Köhler theory correct for the influence of water uptake by hygroscopic aerosols. We used datasets co-located measurements and (OPC-N2, Alphasense) measurements, collected four cities on three continents, explore performance this correction factor. provide evidence elevated concentrations, reported instrumentation, are due bulk aerosol under different RH conditions, which determined composition and, particular, levels aerosols (sulfate nitrate). exploit made volcanic plumes Nicaragua, predominantly composed sulfate aerosol, as natural experiment demonstrate behaviour atmosphere; observed humidogram these closely resembles calculated pure sulfuric acid humidogram. The results indicate OPCs during periods (>60 %) corrected growth. employed factor based OPC-N2 PM2.5 were within 33 % all sites. indicated κ value situ (using suitable instrumentation) would lead most accurate instruments. Applying values literature also resulted improved performance, being 50 values. Therefore, areas where instrumentation developing local lacking, can result reasonable correction. For locations low values, simple calibration against gravimetric likely sufficient. Whilst study generated specific Alphasense sensor, amenable other PM sensors.

Language: Английский

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Intercomparison of nitrous acid (HONO) measurement techniques in a megacity (Beijing)

Atmospheric measurement techniques, Journal Year: 2019, Volume and Issue: 12(12), P. 6449 - 6463

Published: Dec. 9, 2019

Abstract. Nitrous acid (HONO) is a key determinant of the daytime radical budget in boundary layer, with quantitative measurement required to understand OH abundance. Accurate and precise measurements HONO are therefore needed; however challenging compound measure field, particular chemically complex highly polluted environment. Here we report an intercomparison exercise between performed by two wet chemical techniques (the commercially available long-path absorption photometer (LOPAP) custom-built instrument) broadband cavity-enhanced spectrophotometer (BBCEAS) instruments at urban location Beijing. In addition, comparison time-of-flight ionization mass spectrometer (ToF-CIMS) selected ion flow tube (SIFT-MS) more established (wet BBCEAS). The finding from current work was that all agree on temporal trends variability (r2 > 0.97), yet they displayed some divergence absolute concentrations, methods consistently higher overall than BBCEAS systems 12 % 39 %. We found no evidence for any systematic bias instruments, exception near instrument detection limits. causes concentrations were unclear, may part have been due spatial variability, i.e. differences and/or inlet position, but this observation associative casual.

Language: Английский

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