Publications by authors named "Shengrong Lou"

Nitrous acid (HONO) is crucial in atmospheric chemistry as it is a major precursor for hydroxyl radicals (OH), the dominant atmospheric oxidant. Hydroxyl radicals are essential in the formation of secondary air pollutants like ozone and particulate matter. This study presents a newly developed Incoherent Broadband Cavity Enhanced Absorption Spectroscopy (IBBCEAS) system for precise and rapid measurements of HONO and nitrogen dioxide (NO) emissions.

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Reactive nitrogen (Nr) emissions significantly affect air quality and the nitrogen cycle in ecosystems. Heavy-duty diesel vehicles (HDDVs), as major sources of these emissions, exhibit complex emission characteristics because of the combined effects of different driving conditions and aftertreatment technologies. This study first investigated the emission factors (EFs) of Nr species, including NO, NO, HONO, NO, and NH, from HDDVs under different emission standards (China IV/V/VI) and cheating strategies, with a particular focus on the impact of selective catalytic reduction (SCR) systems.

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Article Synopsis
  • Accurate identification and quantification of nitro-containing species are crucial for understanding their chemical behavior in the atmosphere, which this study investigates through different mass spectrometry techniques.
  • The research compared the performance of two ionization modes—HO (hydroxyl) and NO (nitric oxide)—in detecting various nitroaromatics and organonitrates, finding that each had unique strengths in sensitivity and fragmentation.
  • A calibration-based framework was developed to improve sensitivity estimation, revealing significant discrepancies in measurements and leading to enhanced accuracy in quantifying nitro compounds using I CIMS (iodide chemical ionization mass spectrometer).
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  • Submicron particles caused poor visibility during pollution, but we don't know why their effects change by season.
  • A study in Shanghai checked how these particles scatter light and found that different chemicals were more common in different seasons.
  • For example, in winter, ammonium nitrate was the main cause of reduced visibility, while organics were more common in spring, summer, and autumn.
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Secondary organic aerosol (SOA) formation from gasoline vehicles spanning a wide range of emission types was investigated using an oxidation flow reactor (OFR) by conducting chassis dynamometer tests. Aided by advanced mass spectrometric techniques, SOA precursors, including volatile organic compounds (VOCs) and intermediate/semivolatile organic compounds (I/SVOCs), were comprehensively characterized. The reconstructed SOA produced from the speciated VOCs and I/SVOCs can explain 69% of the SOA measured downstream of an OFR upon 0.

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Submicron particulate matter (PM) poses significant risks to health risks and global climate. In this study, secondary organic aerosols (SOA) and inorganic compositions were examined for their physicochemical characteristics and evolution using high-resolution aerosol instruments in Changzhou over one-month period. The results showed that transport accompanied by regional static conditions leaded to the occurrence of heavy pollution.

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Article Synopsis
  • * This study found that the peroxide-bicyclic intermediate pathway is the dominant process in the oxidation of alkylbenzenes, significantly affecting the yields of various products generated during reactions with hydroxyl radicals (OH) and nitrogen oxides (NO).
  • * The research revealed that yields of bicyclic nitrates were lower than expected, and introduced new findings on carbonyl olefinic acids, highlighting complex interactions between different chemical reactions and shedding light on why there are differences between experimental and model predictions.
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The characteristics and main factors of causes of haze in Zhoukou in January 2022 were analyzed. Six air pollutants, water-soluble ions, elements, OC, EC, and other parameters in fine particulate matter were monitored and analyzed using a set of online high-time-resolution instruments in an urban area. The results showed that the secondary inorganic aerosols(SNA), carbonaceous aerosols(CA, including organic carbon OC and inorganic carbon EC), and reconstructed crustal materials(CM, such as AlO, SiO, CaO, and FeO, etc.

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Considerable efforts have been devoted to characterising the chemical components of vehicle exhaust. However, these components may not accurately reflect the contribution of vehicle exhaust to atmospheric reactivity because of the presence of species not accounted for ("missing species") given the limitations of analytical instruments. In this study, we improved the laser photolysis-laser-induced fluorescence (LP-LIF) technique and applied it to directly measure the total OH reactivity (TOR) in exhaust gas from light-duty gasoline vehicles in China.

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Atmospheric nitrous acid (HONO) is an important precursor of atmospheric hydroxyl radicals. Vehicle emissions and heterogeneous reactions have been identified as major sources of urban HONO. Here, we report on HONO emissions from residential natural gas (RNG) for water and space heating in urban areas based on in situ measurements.

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Oxidation of volatile organic compounds (VOCs) forms oxygenated organic molecules (OOMs), which contribute to secondary pollution. Herein, we present measurement results of OOMs using chemical ionization mass spectrometry with nitrate as the reagent ion in Shanghai. Compared to those in forests and laboratory studies, OOMs detected at this urban site were of relatively lower degree of oxygenation.

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Both concentrations and emissions of many air pollutants have been decreasing due to implement of control measures in China, in contrast to the fact that an increase in emissions of non-methane hydrocarbons (NMHCs) has been reported. This study employed seven years continuous NMHCs measurements and the related activities data of Shanghai, a megacity in China, to explore evolution of emissions and effectiveness of air pollution control measures. The mixing ratio of NMHCs showed no statistical interannual changes, of which their compositions exhibited marked changes.

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High particulate matter (PM) pollution episodes still occur occasionally in urban China, despite of improvements in recent years. Investigating the influencing factors of high-PM episodes is beneficial in the formulation of effective control measures. We herein present the effects of weather condition, emission source, and chemical conversion on the occurrence of high-PM episodes in urban Shanghai using multiple online measurements.

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Particulate nitrate (pNO) is now becoming the principal component of PM during severe winter haze episodes in many cities of China. To gain a comprehensive understanding of the key factors controlling pNO formation and driving its trends, we reviewed the recent pNO modeling studies which mainly focused on the formation mechanism and recent trends of pNO as well as its responses to emission controls in China. The results indicate that although recent chemical transport models (CTMs) can reasonably capture the spatial-temporal variations of pNO, model-observation biases still exist due to large uncertainties in the parameterization of dinitrogen pentoxide (NO) uptake and ammonia (NH) emissions, insufficient heterogeneous reaction mechanism, and the predicted low sulfate concentrations in current CTMs.

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Vehicular exhaust is an important source of reactive gases responsible for the formation of ozone and secondary organic aerosols (SOAs) in the atmosphere. Although significant efforts have been made to characterize the chemical compounds associated with vehicular exhaust, there is still a wealth of compounds that are unable to be detected, posing uncertainties in estimating their contribution to atmospheric reactivity. In this study, by improving laser-induced fluorescence techniques, we achieved the first-ever direct measurement of the total OH reactivity (TOR) from light-duty diesel truck (LDDT) exhaust with different emission standards.

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Secondary organic aerosol, formed through atmospheric oxidation processes, plays an important role in affecting climate and human health. In this study, we conducted a comprehensive campaign in the megacity of Shanghai during the 2019 International Import Expo (EXPO), with the first deployment of a chemical ionization─Orbitrap mass spectrometer for ambient measurements. With the ultrahigh mass resolving power of the Orbitrap mass analyzer (up to 140,000 Th/Th) and capability in dealing with massive spectral data sets by positive matrix factorization, we were able to identify the major gas-phase oxidation processes leading to the formation of oxygenated organic molecules (OOM) in Shanghai.

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Atmospheric oxidation is a driving force of complex air pollution, and accurate hydroxyl radical (OH) measurement is helpful in investigating the radical-cored photooxidation mechanism in the troposphere. A self-developed laser-induced fluorescence instrument by the Anhui Institute of Optics Fine Mechanics, Chinese Academy of Sciences (AIOFM-LIF), was able to measure OH concentration with high sensitivity and good time resolution, and a detection limit of 1.7 × 10 cm (1σ, 30 s).

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Comprehensive observations of the nocturnal atmospheric oxidation of NO and NO were conducted at a suburban site in Changzhou in the YRD using cavity ring-down spectroscopy (CRDS) from 27 May to 24 June, 2019. High concentrations of NO precursors were observed, and the nocturnal production rate of NO was determined to be 1.7 ± 1.

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A continuous wintertime observation of ambient OH and HO radicals was first carried out in Shanghai, in 2019. This effort coincided with the second China International Import Expo (CIIE), during which strict emission controls were implemented in Shanghai, resulting in an average PM concentration of less than 35 μg/m. The self-developed instrument based on the laser-induced fluorescence (LIF) technique reported that the average OH radical concentration at noontime (11:00-13:00) was 2.

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Real-world vehicle emission factors (EFs) for the total intermediate volatile organic compounds (total-IVOCs) and volatile organic compounds (VOCs) from mixed fleets of vehicles were quantified in the Yangtze tunnel in Shanghai. Relationships of EFs of IVOCs with fleet compositions and vehicle speed as well as secondary organic formation potentials (SOAFPs) from IVOCs and VOCs were studied. Multiple linear regression (MLR) was used to estimate EFs of total-IVOCs for gasoline and diesel vehicles.

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Intermediate-volatility organic compounds (IVOCs) emitted from vehicles are generally in the gas phase but may partly partition into particle phase when measured under ambient temperature. To have a complete and accurate picture of IVOC emissions from vehicles, gas- and particle-phase IVOCs from a fleet of gasoline and diesel vehicles were simultaneously characterized by dynamometer testing in Guangzhou, China. The total IVOC emission factors of the diesel vehicles were approximately 16 times those of the gasoline vehicles, and IVOCs were mainly concentrated in the particle phase in the form of the unresolved complex mixture (UCM).

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Article Synopsis
  • - Volatile organic compounds (VOCs) are significant contributors to ozone and particulate matter pollution, particularly from industrial parks in China, which have not been extensively studied.
  • - A study measuring VOC levels around industrial parks in the Yangtze River Delta found average concentrations of 183 μg·m, with peaks reaching up to 12,006 μg·m, and highlighted that toluene, xylene, and benzene were the most prevalent compounds.
  • - Results indicated that VOC levels were highest in textile industrial parks, while electronics parks had the lowest, and the measured species accounted for only about 50% of the total VOCs, suggesting underestimation of pollution in these areas.
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The variations of non-refractory submicron aerosol (NR-PM) were characterized using an high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and other online instruments measurements sampled at an urban site in Shanghai from 2016 to 2017. Spring (from 18 May to 4 June 2017), summer (from 23 August to 10 September 2017) and winter (from 28 November 2016 to 23 January 2017) seasons were chosen for detail investigating the seasonal variations in the aerosol chemical characteristics. The average PM (NR-PM + BC) mass concentration showed little difference in the three seasons in Shanghai.

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This study reports on the first continuous measurements of ambient OH and HO radicals at a suburban site in Chengdu, Southwest China, which were collected during 2019 as part of a comprehensive field campaign 'CompreHensive field experiment to explOre the photochemical Ozone formation mechaniSm in summEr - 2019 (CHOOSE-2019)'. The mean concentrations (11:00-15:00) of the observed OH and HO radicals were 9.5 × 10 and 9.

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In the present work, we propose a novel algorithm to determine the scattering coefficient of OA by evaluating the relationships of the MSEs for primary organic aerosol (POA) and secondary organic aerosol (SOA) with their mass concentrations at three distinct sites, i.e. an urban site, a rural site, and a background site in China.

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