Comparison between idling and cruising gasoline vehicles in primary emissions and secondary organic aerosol formation during photochemical ageing.

Driving conditions are among the important factors determining gasoline vehicle emissions, yet their relation with exhaust-derived secondary pollutants is poorly understood. Here, we introduced exhaust from a gasoline vehicle under hot idling and cruising conditions into an indoor smog chamber by using a chassis dynamometer and investigated the formation of secondary organic aerosols (SOA) during photochemical ageing under light after characterizing the primary emission of non-methane hydrocarbons (NMHCs), nitrogen oxide (NO) and primary organic aerosol (POA) in the dark. When compared to emission factors (EFs) at idling, during cruising at 20 km h or 40 km h, the EFs of NMHCs decreased by more than an order of magnitude, while the EFs of NO were more than doubled, resulting in a large drop in the NMHC-to-NO ratios.

Comprehensive study of regional haze in the North China Plain with synergistic measurement from multiple mobile vehicle-based lidars and a lidar network.

Recently, haze pollution has emerged as a regional characteristic that needs to be monitored and mitigated sensibly in China, particularly in the North China Plain (NCP). Clarifying the distribution and source characteristics of haze is necessary to better understand its formation mechanism on a regional scale. In this study, a comprehensive study of regional haze using synergistic measurement from multiple mobile vehicle-based lidars, a ground-based lidar network, and in suit instruments is presented.

Vacuum ultraviolet photodynamics of the methyl peroxy radical studied by double imaging photoelectron photoion coincidences.

The vacuum ultraviolet photoionization of the methyl peroxy radical, CHO, and unimolecular dissociation of internal energy selected CHO cations were investigated in the 9.7-12.0 eV energy range by synchrotron-based double imaging photoelectron photoion coincidence.

Fully Integrated Photoacoustic NO Sensor for Sub-ppb Level Measurement.

A fully integrated photoacoustic nitrogen dioxide (NO) sensor is developed and demonstrated. In this sensor, an embedded photoacoustic cell was manufactured by using an up-to-date 3D printing technique. A blue laser diode was used as a light source for excitation of photoacoustic wave in the photoacoustic cell.

BaGeO: A Mid-IR Transparent Crystal with Superstrong Raman Response.

Stimulated Raman scattering processes based on Raman crystals offer a simple and effective method to generate mid-IR lasers. However, currently available mid-IR Raman crystals are extremely scarce. Herein, a new type of mid-IR Raman crystal, BaGeO, is reported.

Analysis of the Stable Isotope Ratios (O/O, O/O, and D/H) in Glacier Water by Laser Spectrometry.

A compact isotope ratio sensor based on laser absorption spectroscopy at 2.7 μm was developed for high precision and simultaneous measurements of the D/H, O/O and O/O isotope ratios in glacier water. Measurements of the oxygen and hydrogen isotope ratios in glacier water demonstrate a 1σ precision of 0.

Simulation of three-stage operating temperature for supersaturation water-based condensational growth tube.

In order to realize accurate dynamic control of supersaturation and to study condensation growth characteristics of nanoparticles through different levels of supersaturation, a series of parametric analyses and systematic comparisons between two-stage and three-stage operating temperature designs were simulated with COMSOL Multiphysics. The simulation results showed that the three-stage operating temperature did not change peak supersaturation compared with two operating temperatures, and the three-stage operating temperature was superior in decreasing the amount of water vapor and the temperature, thus lowering particle loss and variation in detection and collection. The peak supersaturation level increased by 0.

Identifying the wintertime sources of volatile organic compounds (VOCs) from MAX-DOAS measured formaldehyde and glyoxal in Chongqing, southwest China.

Ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) observations were performed from 27 December 2018 to 16 January 2019 in Changshou, one of subdistricts of Chongqing, China. Primary atmospheric pollutant in Changshou during wintertime was PM, whose contribution averaged about 70.15% ± 9.

Comparison of four different types of planetary boundary layer heights during a haze episode in Beijing.

The planetary boundary layer (PBL) height mainly determines the environmental capacity for the diffusion of atmospheric pollutants, and has always been a hot issue in the study of air pollution. However, there still remains great uncertainty, partly because different PBL heights definitions and the PBL heights are obtained by various measurement instruments. Pollutants are the substances emitted, different from the atmospheric background physical properties such as wind, temperature and turbulence flux that always exist even without pollution.

Time-Resolved Laser-Flash Photolysis Faraday Rotation Spectrometer: A New Tool for Total OH Reactivity Measurement and Free Radical Kinetics Research.

The total OH reactivity (') is an important parameter for quantitative assessment of the atmospheric oxidation capacity. Although laboratory measurement of ' has been achieved 20 years ago, the instruments required are often costly and complex. Long-term atmospheric observations remain challenging and elusive.

The observation of isotopic compositions of atmospheric nitrate in Shanghai China and its implication for reactive nitrogen chemistry.

The occurrence of PM pollution in China is usually associated with the formation of atmospheric nitrate, the oxidation product of nitrogen oxides (NO = NO + NO). The oxygen-17 excess of nitrate (ΔO(NO)) can be used to reveal the relative importance of nitrate formation pathways and get more insight into reactive nitrogen chemistry. Here we present the observation of isotopic composition of atmospheric nitrate (ΔO and δN) collected from January to June 2016 in Shanghai China.

Identifying Phase-Dependent Electrochemical Stripping Performance of FeOOH Nanorod: Evidence from Kinetic Simulation and Analyte-Material Interactions.

Metal hydroxide nanomaterials are widely applied in the energy and environment fields. The electrochemical performance of such materials is strongly dependent on their crystal phases. However, as there are always multiple factors relating to the phase-dependent electrochemistry, it is still difficult to identify the determining one.

Laser heterodyne spectroradiometer assisted by self-calibrated wavelength modulation spectroscopy for atmospheric CO column absorption measurements.

We have developed a laser heterodyne spectroradiometer in combination with self-calibrated wavelength modulation spectroscopy based on a software-based lock-in amplifier to observe the atmospheric carbon dioxide (CO) column absorption near wavelength 1.57 μm in solar occultation mode. This combination facilitates miniaturization of laser heterodyne radiometer.

High resolution vibronic state-specific dissociation of NO in the 10.0-15.5 eV energy range by synchrotron double imaging photoelectron photoion coincidence.

Vacuum ultraviolet (VUV) photoionization and dissociative photoionization of NO in the 10.0-15.5 eV energy range have been investigated in detail by using high-resolution double imaging photoelectron photoion coincidence (iPEPICO) at synchrotron SOLEIL.

Synthesis of Monodispersedly Sized ZnO Nanowires from Randomly Sized Seeds.

We demonstrate the facile, rational synthesis of monodispersedly sized zinc oxide (ZnO) nanowires from randomly sized seeds by hydrothermal growth. Uniformly shaped nanowire tips constructed in ammonia-dominated alkaline conditions serve as a foundation for the subsequent formation of the monodisperse nanowires. By precisely controlling the sharp tip formation and the nucleation, our method substantially narrows the distribution of ZnO nanowire diameters from σ = 13.

Computational study on the mechanism and kinetics for the reaction between HO and -propyl peroxy radical.

The -propyl peroxy radical (-CHO) is the key intermediate during atmospheric oxidation of propane (CH) which plays an important role in the carbon and nitrogen cycles in the troposphere. In this paper, a comprehensive theoretical study on the reaction mechanism and kinetics of the reaction between HO and -CHO was performed at the CCSD(T)/aug-cc-pVDZ//B3LYP/6-311G(d,p) level of theory. Computational results show that the HO + -CHO reaction proceeds on both singlet and triplet potential energy surfaces (PESs).

Influence of Spatial Inhomogeneity of Detector Temporal Responses on the Spectral Fidelity in Continuous Wave Cavity Ringdown Spectroscopy.

Due to their advantages of having a wide bandwidth, low cost, and being easy to obtain, traditional photodetectors (PDs) are being widely applied in measurements of transient signals. The spatial inhomogeneity of such PD temporal responses was measured directly to account for the PD spatial effect of decay rate due to poor alignment in continuous wave cavity ringdown spectroscopy (CW-CRDS) experiments. Based on the measurements of three PDs (i.

Analysis and Adjustment of Positioning Error of PSD System for Mobile SOF-FTIR.

A PSD-based solar spot position detection system is developed for solar tracking closed-loop control of mobile SOF-FTIR (Solar Occultation Flux method based on Fourier Transform Infrared spectrometer). The positioning error factors of PSD (position sensitive detector) are analyzed in detail. A voltage model for PSD signal conditioning circuit has been established to investigate the noise factors.

Pinpointing nitrogen oxide emissions from space.

Satellite observations of nitrogen dioxide (NO) provide valuable information on the location and strength of NO emissions, but spatial resolution is limited by horizontal transport and smearing of temporal averages due to changing wind fields. In this study, we map NO emissions on high spatial resolution from TROPOMI observations of NO combined with wind fields based on the continuity equation. The divergence of horizontal fluxes proves to be highly sensitive for point sources like exhaust stacks.

Satellite UV-Vis spectroscopy: implications for air quality trends and their driving forces in China during 2005-2017.

Abundances of a range of air pollutants can be inferred from satellite UV-Vis spectroscopy measurements by using the unique absorption signatures of gas species. Here, we implemented several spectral fitting methods to retrieve tropospheric NO, SO, and HCHO from the ozone monitoring instrument (OMI), with radiative simulations providing necessary information on the interactions of scattered solar light within the atmosphere. We analyzed the spatial distribution and temporal trends of satellite-observed air pollutants over eastern China during 2005-2017, especially in heavily polluted regions.

Drivers of improved PM air quality in China from 2013 to 2017.

From 2013 to 2017, with the implementation of the toughest-ever clean air policy in China, significant declines in fine particle (PM) concentrations occurred nationwide. Here we estimate the drivers of the improved PM air quality and the associated health benefits in China from 2013 to 2017 based on a measure-specific integrated evaluation approach, which combines a bottom-up emission inventory, a chemical transport model, and epidemiological exposure-response functions. The estimated national population-weighted annual mean PM concentrations decreased from 61.

High temporal resolution measurements of ammonia emissions following different nitrogen application rates from a rice field in the Taihu Lake Region of China.

Ammonia emission is one of the dominant pathways of nitrogen fertilizer loss from rice fields in China. It is difficult to measure ammonia emissions by high-frequency sampling with the chamber methods widely used in China, which is of great significance for investigating the environmental effects on the ammonia emissions. The chamber methods also can not accurately determine the ammonia emissions.

Mechanism and kinetics of the atmospheric reaction of 1,3,5-trimethylbenzene bicyclic peroxy radical with OH.

The bicyclic peroxy radical (BPR) is the key intermediate during atmospheric oxidation of aromatics. In this paper, the reaction mechanisms and kinetics of the atmospheric reaction of the 1,3,5-trimethylbenzene (1,3,5-TMB) BPR with the OH radical were studied by density functional theory (DFT) and conventional transition-state theory (CTST) calculations. The product channels of formation of the 1,3,5-TMB trioxide (ROOOH), OH-adducts and Criegee intermediate (CI) have been identified, and the geometries and energies of all the stationary points were calculated at the M08-HX/6-311 + g(2df,2p) level of theory.

Surface oxygen vacancy defect engineering of p-CuAlOvia Ar&H plasma treatment for enhancing VOCs sensing performances.

Ar&H2 plasma treatment was proposed to enhance the response of a p-CuAlO2 sensor toward volatile organic compounds. Comprehensive defect characterization studies indicate a substantial increase of surface unsaturated oxygen vacancy (VO) defects via plasma treatment, which could provide active sites for molecule adsorption and the subsequent interfacial redox reaction.

Absorption lines measurements of carbon disulfide at 4.6 μm with quantum cascade laser absorption spectroscopy.

We report measured line intensities and air- and self-broadening coefficients for fifty-one carbon disulfide transitions in the ν1 + ν3 band near 4.6 μm. This spectral region was chosen due to the strong carbon disulfide absorption strength and in the range of the mid-infrared atmospheric window for laser-based sensing applications.