An intercomparison of ozone taken from the Copernicus atmosphere monitoring service and the second Modern-Era retrospective analysis for research and applications over China during 2018 and 2019.

Spatiotemporal variations of ozone (O) taken from the Copernicus Atmosphere Monitoring Service (CAMS) and the second Modern-Era Retrospective Analysis for Research and Applications (MERRA-2) were intercompared and evaluated with ground and ozone-sonde observations over China in 2018 and 2019. Intercomparison of the surface ozone from CAMS and MERRA-2 reanalysis showed significant negative bias (CAMS minus MERRA-2, same below) at Tibetan Plateau of up to 80 µg/m, and the average R was about 0.6 across China.

Transport Patterns and Potential Sources of Atmospheric Pollution during the XXIV Olympic Winter Games Period.

The attainment of suitable ambient air quality standards is a matter of great concern for successfully hosting the XXIV Olympic Winter Games (OWG). Transport patterns and potential sources of pollutants in Zhangjiakou (ZJK) were investigated using pollutant monitoring datasets and a dispersion model. The PM concentration during February in ZJK has increased slightly (28%) from 2018 to 2021, mostly owing to the shift of main potential source regions of west-central Inner Mongolia and Mongolian areas (2015-18) to the North China Plain and northern Shanxi Province (NCPS) after 2018.

Increasing impacts of the relative contributions of regional transport on air pollution in Beijing: Observational evidence.

Benefiting from the pollution controls implemented by the Chinese government, the concentrations of PM, SO, NO and CO showed a significant decrease in Beijing during 2013-2017. In this study, an observation-based method was employed to estimate the relative contributions of regional transport (MaxRTC) and local emissions (MinLEC) to air pollutant levels during 2013-2017 in Beijing. The results showed that the MaxRTC to SO and PM increased significantly over the five years, while those to CO and NO changed little.

Reductions in crop yields across China from elevated ozone.

Exposure of crops to high concentrations of ozone can cause substantial reductions in yield that pose a serious threat to global food security. Here we provide comprehensive estimates of yield losses for key crops across China between 2014 and 2017 attributed to ozone using a number of new approaches. We use an air quality model at 5 km resolution and crop-specific dose-response functions developed for both concentration- and flux-based metrics.

Effects of different corticosteroid therapy on severe COVID-19 patients: a meta-analysis of randomized controlled trials.

Background: To assess the efficacy and safety of corticosteroids in COVID-19 patients compared with standard care or placebo.

Methods: Electronic databases were searched to identify relevant studies. The mortality, adverse events, and other data from studies were pooled for statistical analysis.

Sources of PM and its responses to emission reduction strategies in the Central Plains Economic Region in China: Implications for the impacts of COVID-19.

The Central Plains Economic Region (CPER) located along the transport path to the Beijing-Tianjin-Hebei area has experienced severe PM pollution in recent years. However, few modeling studies have been performed on the sources of PM, especially the impacts of emission reduction strategies. In this study, the Nested Air Quality Prediction Model System (NAQPMS) with an online tracer-tagging module was adopted to investigate source sectors of PM and a series of sensitivity tests were conducted to investigate the impacts of different sector-based mitigation strategies on PM pollution.

Nonlinear response of SIA to emission changes and chemical processes over eastern and central China during a heavy haze month.

This study used a chemical transport model to investigate the response of secondary inorganic aerosols (SIA) to chemical processes and its precursor emissions over northern and southern city-clusters of China in January 2014. Unexpectedly, SIA concentrations with low levels of precursor emissions were much higher over the southern regions than those over the northern region with high levels of precursor emissions, based on ground observations and high-precision simulations. The sensitivity analysis of chemical processes suggests that the gas-phase chemistry was a critical factor determining the SIA pattern, especially the higher efficiency of nitrogen conversion to nitrate in southern cities controlled by favorable meteorological elements than that in northern city.

Impacts of COVID-19 lockdown, Spring Festival and meteorology on the NO variations in early 2020 over China based on in-situ observations, satellite retrievals and model simulations.

The lockdown measures due to COVID-19 affected the industry, transportation and other human activities within China in early 2020, and subsequently the emissions of air pollutants. The decrease of atmospheric NO due to the COVID-19 lockdown and other factors were quantitively analyzed based on the surface concentrations by in-situ observations, the tropospheric vertical column densities (VCDs) by different satellite retrievals including OMI and TROPOMI, and the model simulations by GEOS-Chem. The results indicated that due to the COVID-19 lockdown, the surface NO concentrations decreased by 42% ± 8% and 26% ± 9% over China in February and March 2020, respectively.

Size-resolved mixing state and optical properties of black carbon at an urban site in Beijing.

The size-resolved (200-700 nm) mixing state and optical properties of black carbon (BC) in Beijing in the spring of 2019 were investigated using a tandem system consisting of an aerodynamic aerosol classifier, a nephelometer, and a single particle soot photometer. The results showed that the coating thickness distribution exhibited a clear bimodal pattern for BC-containing particles with a fixed aerodynamic diameter (D). Based on the coating thickness, BC-containing particles can be classified as having external and internal mixing states.

Health impacts of long-term ozone exposure in China over 2013-2017.

Increasing ozone concentrations are becoming a severe problem for air pollution in China and have an adverse impact on human health. Here we evaluate premature deaths attributable to long-term exposure to ambient ozone in China between 2013 and 2017 with an air quality model at 5 km resolution and the latest estimates of the relative risk to health. We use a modified inverse distance weighting method to bias-correct the key model-simulated ozone metrics.

Improving PM Forecasts in China Using an Initial Error Transport Model.

Efforts of using data assimilation to improve PM forecasts have been hindered by the limited number of species and incomplete vertical coverage in the observations. The common practice of initializing a chemical transport model (CTM) with assimilated initial conditions (ICs) may lead to model imbalances, which could confine the impacts of assimilated ICs within a day. To address this challenge, we introduce an initial error transport model (IETM) approach to improving PM forecasts.

Simulation on different response characteristics of aerosol particle number concentration and mass concentration to emission changes over mainland China.

Unlabelled: In this study, Nested Air Quality Prediction Modeling System with Advance Particle Microphysics module (NAQPMS+APM) is applied to simulate the response characteristics of aerosol particle number concentration and mass concentration to emission changes over mainland China. It is the first attempt to investigate the response of both aerosol mass concentration and number concentration to emission changes using a chemical transport model with detailed aerosol microphysics over mainland China. Results indicate that the response characteristics are obviously different between aerosol particle number concentration and mass concentration.

Radiative and heterogeneous chemical effects of aerosols on ozone and inorganic aerosols over East Asia.

Currently, many challenges are faced in simulating ozone(O), sulfate(SO), and nitrate(NO) concentrations over East Asia, particularly the overestimation of surface O and NO concentrations and underestimation of the SO concentration during haze episodes. In this study, we examined the radiative and heterogeneous chemical effects of aerosols by incorporating recently reported mechanisms, including self-amplifying SO formation, dinitrogen pentoxide (NO) hydrolysis, and a heterogeneous reaction converting gaseous nitric acid (HNO) to nitric oxide (NO), into a Nested Air Quality Prediction Modeling System. Uptakes by aerosols can be computed through a simple parameterization that is dependent on the aerosol core and shell species, shell thickness, and amount of aerosol liquid water.

Importance of mineral dust and anthropogenic pollutants mixing during a long-lasting high PM event over East Asia.

A long-lasting high particulate matter (PM) concentration episode persisted over East Asia from May 24 to June 3, 2014. The Nested Air Quality Prediction Model System (NAQPMS) was used to investigate the mixing of dust and anthropogenic pollutants during this episode. Comparison of observations revealed that the NAQPMS successfully reproduced the time series PM and PM concentrations, as well as the nitrate and sulfate concentrations in fine (aerodynamic diameter ≤ 2.

Explaining the spatiotemporal variation of fine particle number concentrations over Beijing and surrounding areas in an air quality model with aerosol microphysics.

In this study, a three-dimensional air quality model with detailed aerosol microphysics (NAQPMS + APM) was applied to simulate the fine particle number size distribution and to explain the spatiotemporal variation of fine particle number concentrations in different size ranges over Beijing and surrounding areas in the haze season (Jan 15 to Feb 13 in 2006). Comparison between observations and the simulation indicates that the model is able to reproduce the main features of the particle number size distribution. The high number concentration of total particles, up to 26600 cm in observations and 39800 cm in the simulation, indicates the severity of pollution in Beijing.