[Spatial Distribution Characteristics of PM and O in Beijing-Tianjin-Hebei Region Based on Time Series Decomposition].

Notably, clear spatial differences occur in the distribution of air pollution among cities in the Beijing-Tianjin-Hebei (BTH) Region. Clarifying the concentration distribution of PM and O at different time scales is helpful to formulate scientific and effective pollution prevention and control measures. Here, the concentrations of PM and O were decomposed using a seasonal-trend decomposition procedure based on the loess (STL) method; their long-term, seasonal, and short-term components were obtained; and their temporal and spatial distribution characteristics were studied.

[Characteristics and Driving Factors of O Pollution During 13 Five-Year Period in Tianjin].

The spatial distribution, accumulation features, and driving factors of O pollution were analyzed using spatial autocorrelation and hotspot analysis and the STIRPAT model based on the high spatiotemporal resolution online monitoring data from 2016 to 2020 in Tianjin. The results showed that the variation characteristics of O concentration in Tianjin from 2016 to 2020 had the trend of pollution occurring in advance and the scope of the pollution expanding. The distribution of O pollution showed significant aggregation from June to October.

[Analysis of Change Trend and Influencing Factors of PM-O Pollution in Tianjin from 2013 to 2020].

The change trend, relationship, and influencing factors of PM and O concentrations were analyzed by using a Kolmogorov-Zurbenko (KZ) filter coupled with stepwise multiple linear regression analysis and the spatiotemporal resolution monitoring data of PM and O and meteorological data observed in Tianjin from 2013 to 2020. The results showed that a significant decreasing trend of PM concentrations by 50.0% was observed from 2013 to 2020, whereas an increasing trend for O concentrations by 25.

[Assessment of Emission Reduction Effect of Major Air Pollution Control Measures on PM Concentrations During 13th Five-Year Period in Tianjin].

The emission reduction effect of major air pollution control measures on PM concentrations was assessed using air quality simulations based on the calculation data of emission reductions from different air pollution control measures and the high spatiotemporal resolution online monitoring data of PM during the 13th Five-Year Period in Tianjin. The results showed that the total emission reductions of SO, NO, VOCs, and PM from 2015 to 2020 were 4.77×10, 6.

[Spatio-temporal Distribution Characteristics of Secondary Aerosol in Beijing-Tianjin-Hebei Urban Agglomeration in Winter].

The secondary component is an important factor causing PM pollution in the Beijing-Tianjin-Hebei urban agglomeration in winter. In this study, the CO tracer method was used to estimate the secondary PM concentration of the Beijing-Tianjin-Hebei urban agglomeration in the winter of 2017-2021. The temporal and spatial distribution characteristics were analyzed, and the influencing factors of regional secondary PM were discussed.

[Observation Analyses of Aerosol Size Distribution Properties from February to March, 2019 in Tianjin Urban Area].

The aerosol size distribution is an important physical parameter reflecting the source, formation process, and pollution characteristics of aerosol particles. In order to study the properties of aerosol number concentration and size distributions in the Tianjin urban area,the aerosol number concentration and size distributions ranging from 10-600 nm were detected using a scanning mobility particle sizer (SMPS) during February and March, 2019. The results showed that in the Tianjin urban area, the aerosol number concentration,surface area concentration.

[Characteristics and Meteorological Factors of PM-O Compound Pollution in Tianjin].

The characteristics, pollutant concentration distribution, and key meteorological factors of PM-O compound pollution in Tianjin were analyzed based on the high-resolution online monitoring data of PM, Oand meteorological data observed in Tianjin from 2013 to 2019. Total PM-O compound pollution was 94 days and showed a decreasing trend by year; a significant decreasing trend of PM-O compound pollution days were observed in the early stage, with a decline rate of 52.2% from 2013 to 2015.

[Exploring Formation of Ozone in Typical Cities in Beijing-Tianjin-Hebei Region Using Process Analysis].

As the problem of O pollution in the Beijing-Tianjin-Hebei region becomes increasingly prominent, it is of great significance to explore and analyze the ozone variation characteristics and causes of the pollution process in the Beijing-Tianjin-Hebei region for regional air pollution prevention and control. The observations in this study showed that high O concentration in spring and summer of the Beijing-Tianjin-Hebei region was higher in the south and lower in the north. The high O concentration in Beijing, Tianjin, and Shijiazhuang was often accompanied by the influence of southern wind.

[Characteristics and Sources of PM-O Compound Pollution in Tianjin].

The characteristics and sources of PM-O compound pollution were analyzed based on the high-resolution online monitoring data of PM, O and volatile organic compounds(VOCs) observed in Tianjin from 2017 to 2019. The results showed that total PM-O compound pollution was 34 days, which only appeared between March and September and slightly increased by year. The peak value of (O)(301-326 μg·m) appeared when (PM) ranged from 75 μg·m to 85 μg·m.

[Analysis of Change and Driving Factors of PM Mass Concentration in Tianjin from 2000 to 2020].

Based on real-time tracking data, PM mass concentration, and meteorological observations of the Tianjin Meteorological Bureau and the Ecological Environment Bureau, combined with the fine particle meteorological condition diffusion index constructed using the environmental model, the change and driving factors of the PM mass concentration in Tianjin from 2000 to 2020 were studied to analyze the impact of meteorology on the atmospheric environment. The study showed that change in PM mass concentration in Tianjin took place in three stages from 2000 to 2020; the first stage showed a continuous increase from 2000 to 2007. The rapid increase in emissions in this stage was the dominant factor, and its effect was four times that of the annual fluctuation in meteorological conditions.

[Impact of Air Humidity on PM Mass Concentration and Visibility During Winter in Tianjin].

Air humidity is a key meteorological factor in regulating visibility changes and haze episodes. Based on multi-year historical data of PM mass concentration, visibility, relative humidity(RH), and specific humidity() during winter in Tianjin, the impact of air humidity on PM mass concentration and visibility was investigated. Between 2015 and 2020, the PM mass concentration showed an overall decline of 28.

[Extinction Characteristics of Aerosols and the Contribution of Pollution Sources to Light Extinction During Three Heavy Pollution Episodes in the Winter of 2020 in Tianjin].

This study examined high-resolution online monitoring data from January to February 2020 to study the extinction characteristics and sources of heavy pollution episodes during winter in Tianjin. Heavy pollution episodes occurred during this period from January 16 to 18 (episode Ⅰ), from January 24 to 26 (episode Ⅱ), and from February 9 to 10 (episode Ⅲ). The results showed that the concentrations of PM during the three heavy pollution episodes were (229±52), (219±48), and (161±25) μg·m, respectively, with NO, SO, NH, OC, EC, Cl, and K comprising the main species.

[Heavy Pollution Episode in Tianjin Based on UAV Meteorological Sounding and Numerical Model].

Pollution occurs in the boundary layer, and the thermal and dynamic vertical structure of the boundary layer has a significant influence on the formation of heavy pollution episodes. Based on unmanned aerial vehicle (UAV) sounding, ground-based remote sensing and numerical modeling, this paper analyzes the vertical structure of the boundary layer and the causes of pollution during the heavy pollution episode in Tianjin from January 10 to 15, 2019, with a view to strengthening the understanding of the influence law of boundary layer processes on heavy pollution in northern coastal cities and improving the accuracy of weather forecasts and heavy pollution warnings. The results show that atmospheric temperature stratification had a significant influence on the formation, persistence, and dissipation of heavy pollution episodes.

[Characterization of Two Heavy Pollution Episodes in Tianjin in 2020].

High-resolution online monitoring data from January to February in 2020 was used to study the characterization of two heavy pollution episodes in Tianjin in 2020; the heavy pollution episode that lasted from January 16 to 18, 2020 (referred to as episode Ⅰ) and that from February 9 to 10, 2020 (referred to as episode Ⅱ) were analyzed. The results showed that two heavy pollution episodes were influenced by regional transportation in the early stage and local adverse meteorological conditions in the later stage. During these episodes, the average wind speed was low, the average relative humidity was close to 70%, and relative humidity approached the saturated, the boundary layer heights were below 300 m, and the horizontal and vertical diffusion conditions were poor.

[Transport Characteristics of Air Pollution in Tianjin Based on Weather Background].

Regional transport is an important factor when considering the prevention and control of air pollution. The aim of this study was to provide support for the joint prevention and control of air pollution in the Beijing-Tianjin-Hebei region. With a focus on an analysis of the relationship between regional transport and meteorological conditions based on the weather background, an atmospheric chemical model was developed to quantitatively estimate the impact of regional transport on Tianjin from October 2016 to September 2017.

[Effects of VOCs on Ozone Formation in the Tianjin Suburbs in Summer].

Volatile organic compounds (VOCs) play an important role in the formation of ozone. The concentrations of VOCs in the Jinnan District of Tianjin were monitored by the Syntech Spectras GC955 online monitoring system, and the ozone generation potential of VOCs was calculated by the maximum incremental activity factor. The results showed that the total concentration of VOCs in the Jinnan District was (32.

[Transport Characteristics of PAN and O in the Lower Atmosphere of the Boundary Layer in Tianjin in Summer].

The volume concentration of peroxyacetyl nitrate (PAN) and O in the atmosphere were measured at the Tianjin Meteorological Tower in summer 2017 by using the online instrument with meteorological parameters and back trajectory analysis to analyze the delivery characteristics of PAN and O. The average volume concentrations of PAN and O during the observational period are (0.73±0.

[Construction and Application of Vertical Diffusion Index for Analyzing Weather During Pollution Events in Tianjin].

Based on temperature and wind speed data from the 255 meter tall meteorological tower, the characteristics of atmospheric stability were analyzed in Tianjin, with the vertical diffusion index and constructed by atmospheric chemical models. This provided information to use the vertical dispersion analysis method to forecast pollution from weather data. The results show that the comprehensive use of atmospheric stability and the vertical diffusion index can provide a better pollution forecast.

[Characteristics of the Size Distribution of Water-soluble Ions During a Heavy Pollution Episode in the Winter in Tianjin].

To characterize the size distribution of water-soluble inorganic ions (WSⅡ) during a heavy pollution episode, particle samples were collected by an Andersen cascade sampler in Tianjin in January 2014, and the concentrations of eight WSⅡ (Na, NH, K, Mg, Ca, Cl, NO, and SO) during a typical haze episode were analyzed by ion chromatography. The sources and formation mechanisms of WSⅡ were analyzed based on their size distributions. The results showed that the daily average concentrations of PM and PM were (138±100) μg·m and (227±142) μg·m, respectively, and the average concentration of total WSⅡ concentrations (TWSⅡ) in the coarse and fine particles were (34.

Vertical observation and analysis on rapid formation and evolutionary mechanisms of a prolonged haze episode over central-eastern China.

To clarify the rapid formation and evolutionary mechanisms of an extremely severe and persistent haze and fog (HF) episode that occurred in central-eastern China from Dec 20 to 25, 2015, a novel campaign was conducted and vertical profiles of wind, temperature, light extinction coefficient (LEC) and PM concentration were used to analyze the rapid formation and evolutionary mechanisms of this HF episode. The substantial downward transportation of regional pollution from high layers and stagnant weather conditions favorable for the local pollution accumulation were the two main causes of the rapid increase in pollutant concentration. Southwest wind speeds of 4m/s between 300 and 600m and obvious downward flows were observed, whereas the southwest wind speeds were low below 300m, and strong temperature inversion with intensity of 4.

Vertical characteristics of PM2.5 during the heating season in Tianjin, China.

In this study, PM2.5 samples were collected at four heights (10m, 40m, 120m and 220m) at a meteorological tower in the daytime and nighttime during the heating season in Tianjin, China. The vertical variation and diurnal variability of the concentrations of PM2.