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3.
J Environ Sci (China) ; 87: 49-59, 2020 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-31791517

RESUMEN

To clarify the aerosol hygroscopic growth and optical properties of the Pearl River Delta (PRD) region, integrated observations were conducted in Heshan City of Guangdong Province from October 19 to November 17, 2014. The concentrations and chemical compositions of PM2.5, aerosol optical properties and meteorological parameters were measured. The mean value of PM2.5 increased from less than 35 (excellent) to 35-75 µg/m3 (good) and then to greater than 75 µg/m3 (pollution), corresponding to mean PM2.5 values of 24.9, 51.2, and 93.3 µg/m3, respectively. The aerosol scattering hygroscopic growth factor (f(RH = 80%)) values were 2.0, 2.12, and 2.18 for the excellent, good, and pollution levels, respectively. The atmospheric extinction coefficient (σext) and the absorption coefficient of aerosols (σap) increased, and the single scattering albedo (SSA) decreased from the excellent to the pollution levels. For different air mass sources, under excellent and good levels, the land air mass from northern Heshan had lower f(RH) and σsp values. In addition, the mixed aerosol from the sea and coastal cities had lower f(RH) and showed that the local sources of coastal cities have higher scattering characteristics in pollution periods.


Asunto(s)
Aerosoles/análisis , Contaminantes Atmosféricos/análisis , Contaminación del Aire/estadística & datos numéricos , Monitoreo del Ambiente , China , Material Particulado/análisis , Humectabilidad
4.
Chemosphere ; 243: 125267, 2020 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-31734594

RESUMEN

In 2015, comprehensive observations were carried out in Chengdu, Sichuan Province, China, to elucidate the seasonal variation characteristics of the concentrations, chemical compositions, and the sources of PM2.5 pollution. The meteorological parameters, gaseous pollutants and chemical compositions of PM2.5 were measured. The annual average concentration of PM2.5 in Chengdu was 67.44 ±â€¯48.78 µg/m3. The highest seasonal PM2.5 mass concentration occurred in winter with an average of 103.04 ±â€¯66.76 µg/m3, followed by spring, autumn, and summer, and the wind speed had an important impact on the diffusion of PM2.5. The seasonal variation characteristics of chemical components in PM2.5 were analysed. The contribution and chemical conversion ability of secondary aerosols increased with increasing of PM2.5 concentration. Source appointment of positive matrix factorization (PMF) shows that the main sources of PM2.5 were secondary aerosols, coal combustion, biomass burning, vehicle emissions, dust and industrial sources, which have more obvious seasonal differences than other sources, and secondary aerosols and coal combustion were the major sources. Conditional probability function (CPF) analysis showed that the local sources of high PM2.5 concentrations were mainly from the eastern and southeastern areas of Chengdu. Potential source contribution function (PSCF), concentration weighted trajectory (CWT) and backward trajectory cluster analyses indicated that the southern, southeast and eastern parts of the Sichuan Basin were the most likely potential sources of PM2.5, and the unique geographical and topographical factors in Chengdu play important roles in the transport and diffusion of pollutants in this region.


Asunto(s)
Contaminantes Atmosféricos/análisis , Monitoreo del Ambiente , Material Particulado/análisis , Aerosoles/análisis , Biomasa , China , Clima , Carbón Mineral/análisis , Polvo/análisis , Contaminación Ambiental/análisis , Gases/análisis , Estaciones del Año , Emisiones de Vehículos/análisis
5.
J Environ Sci (China) ; 81: 225-237, 2019 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-30975325

RESUMEN

In this study, an analysis framework based on the regular monitoring data was proposed for investigating the annual/inter-annual air quality variation and the contributions from different factors (i.e., seasons, pollution periods and airflow directions), through a case study in Beijing from 2013 to 2016. The results showed that the annual mean concentrations (MC) of PM2.5, SO2, NO2 and CO had decreased with annual mean ratios of 7.5%, 28.6%, 4.6% and 15.5% from 2013 to 2016, respectively. Among seasons, the MC in winter contributed the largest fractions (25.8%~46.4%) to the annual MC, and the change of MC in summer contributed most to the inter-annual MC variation (IMCV) of PM2.5 and NO2. For different pollution periods, gradually increase of frequency of S-1 (PM2.5, 0~75 µg/m3) made S-1 become the largest contributor (28.8%) to the MC of PM2.5 in 2016, it had a negative contribution (-13.1%) to the IMCV of PM2.5; obvious decreases of frequencies of heavily polluted and severely polluted dominated (44.7% and 39.5%) the IMCV of PM2.5. For different airflow directions, the MC of pollutants under the south airflow had the most significant decrease (22.5%~62.5%), and those decrease contributed most to the IMCV of PM2.5 (143.3%), SO2 (72.0%), NO2 (55.5%) and CO (190.3%); the west airflow had negative influences to the IMCV of PM2.5, NO2 and CO. The framework is helpful for further analysis and utilization of the large amounts of monitoring data; and the analysis results can provide scientific supports for the formulation or adjustment of further air pollution mitigation policy.


Asunto(s)
Contaminantes Atmosféricos/análisis , Contaminación del Aire/estadística & datos numéricos , Monitoreo del Ambiente , Contaminación del Aire/prevención & control , Beijing , Estaciones del Año
6.
J Environ Sci (China) ; 79: 297-310, 2019 May.
Artículo en Inglés | MEDLINE | ID: mdl-30784453

RESUMEN

A continuous online observation of ozone and its precursors (NOx, VOCs) was carried out in central urban Wuhan from September 2016 to August 2017. The concentration levels of ozone, NOx, VOCs and their variations in urban Wuhan were analyzed, as well as effects of VOCs on ozone photochemical generation and the main controlling factors for ozone production. During the observation period, the average concentrations of ozone and NOx in Wuhan was 22.63 and 30.14 ppbv, respectively, and the average concentration of VOCs was 32.61 ppbv (42.3% alkanes, 13.0% alkenes, 10.0% aromatics, 7.3% acetylene, 9.9% OVOCs, and 10.5% halohydrocarbons). Ozone concentration was higher in spring and summer as compared with autumn and winter, wheras VOCs and NOx concentratios were lower in spring and summer but higher in autumn and winter. Aromatics and alkenes, two of VOCs species, showed the highest contributions to ozone formation potential in Wuhan (35.7% alkenes, 35.4 aromatics, 17.5% alkanes, 8.6% OVOCs, 1.6% halogenated hydrocarbons, and 1.4% acetylene). Among all VOCs species, those with the highest contribution were ethylene, m-xylene, toluene, propylene and o-xylene. The contribution of these five compounds to the total ozone formation potential concentration was 43.90%. Ozone-controlling factors in Wuhan changed within one day; during the early morning hours (6:00-9:00), VOCs/NOx was low, and ozone generation followed a VOCs-limited regime. However, during the peak time of ozone concentration (12:00-16:00), the ratio of VOCs/NOx was relatively high, suggesting that ozone generation followed a NOx-limited regime.


Asunto(s)
Contaminantes Atmosféricos/análisis , Hidrocarburos/análisis , Óxidos de Nitrógeno/análisis , Ozono/análisis , Compuestos Orgánicos Volátiles/análisis , China , Ciudades , Monitoreo del Ambiente , Ozono/química , Estaciones del Año
7.
Environ Pollut ; 245: 29-37, 2019 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-30408762

RESUMEN

Recently, ground ozone has become one major airborne pollutant and the frequency of ozone-induced pollution episodes has increased rapidly across China. However, due to the lack of long-term observation data, relevant research on the characteristics and influencing factors of urban ozone concentrations remains limited. Based on ground ozone observation data during 2006-2016, we quantified the causality influence of individual meteorological factors on ozone concentrations in Beijing using a convergent cross mapping (CCM) method. The result indicated that the influence of each meteorological factor on ozone concentrations varied significantly across seasons and years. At the inter-annual scale, all-year meteorological influences on ozone concentrations were much more stable than seasonal meteorological influences. At the seasonal scale, meteorological influences on ozone concentrations were stronger in spring and autumn. Amongst multiple individual factors, temperature was the key meteorological influencing factor for ozone concentrations in all seasons except winter, when wind, humidity and SSD exerted major influences on ozone concentrations. In addition to temperature, air pressure was another meteorological factor that exerted strong influences on ozone concentrations. At both the inter-annual and seasonal scale, the influence of temperature and humidity on ozone concentrations was generally stable whilst that of other factors experienced large variations. Different from PM2.5, meteorological influences on ozone concentrations were relatively weak in summer, when ozone concentrations were the highest in Beijing. Given the generally stable meteorological influences on ozone concentrations and human-induced emissions of VOCs and NOx across seasons, warming induced notable increase in summertime biogenic emissions of VOCs and NOx can be a major driver for the increasing ozone pollution episodes. This research provides useful references for understanding long-term meteorological influences on ozone concentrations in mega cities in China.


Asunto(s)
Contaminantes Atmosféricos/análisis , Monitoreo del Ambiente , Ozono/análisis , Suelo/química , Tiempo (Meteorología) , Beijing , China , Ciudades , Cambio Climático , Humedad , Estaciones del Año , Temperatura , Viento
8.
Sci Total Environ ; 650(Pt 2): 2624-2639, 2019 Feb 10.
Artículo en Inglés | MEDLINE | ID: mdl-30373049

RESUMEN

Based on detailed data on 102 volatile organic compounds (VOCs) measured continuously from 2016.10.9 to 2016.11.17 in Wuhan, the VOC characteristics, secondary organic aerosol (SOA) characteristics, SOA formation potential (SOAP), potential source regions, sources and contributions during different haze episodes were analyzed. The total VOC (TVOC) concentrations on clear days (visibility >10 km), slight haze days (visibility of 5-10 km), and severe haze days (visibility <5 km) were 34.87 ±â€¯14.89 ppbv, 45.06 ±â€¯26.69 ppbv, and 49.55 ±â€¯24.82 ppbv, respectively. The SOAP on haze days (447.04 ±â€¯253.85 ppbv) was significantly higher than that on clear days (300.62 ±â€¯138.48 ppbv), and aromatics were the dominant contributors to SOA formation under different visibility conditions, accounting for approximately 97% of the total SOAP. The ratio of ethylbenzene to m/p-xylene (E/X) indicated that atmospheric photochemical reactions were slightly stronger on haze days. The ratio of toluene to benzene (T/B) indicated that vehicle exhaust had significant effects on VOCs, but no significant changes occurred during different haze episodes. The ratio of benzene, toluene, ethylbenzene and xylenes (BTEX) to CO indicated that VOCs from solvent usage in painting/coating and industrial emissions increased with increasing haze pollution. Based on backward trajectories and the potential source contribution function (PSCF), short-distance transport was the main source influencing VOC pollution, especially transport from the southwest. Seven sources were identified by positive matrix factorization (PMF): industrial sources, vehicular exhaust, solvent usage in painting/coating, fuel evaporation, liquefied petroleum gas (LPG) usage, biogenic sources and biomass burning. Moreover, solvent usage in painting/coating, vehicle exhaust and LPG usage were the most important sources that significantly aggravated VOC pollution during haze events. The results can provide references for local governments developing control strategies of VOCs during haze pollution events.

9.
Artículo en Inglés | MEDLINE | ID: mdl-30018203

RESUMEN

In recent years, particulate matter (PM) pollution has increasingly affected public life and health. Therefore, crop residue burning, as a significant source of PM pollution in China, should be effectively controlled. This study attempts to understand variations and characteristics of PM10 and PM2.5 concentrations and discuss correlations between the variation of PM concentrations and crop residue burning using ground observation and Moderate Resolution Imaging Spectroradiometer (MODIS) data. The results revealed that the overall PM concentration in China from 2013 to 2017 was in a downward tendency with regional variations. Correlation analysis demonstrated that the PM10 concentration was more closely related to crop residue burning than the PM2.5 concentration. From a spatial perspective, the strongest correlation between PM concentration and crop residue burning existed in Northeast China (NEC). From a temporal perspective, the strongest correlation usually appeared in autumn for most regions. The total amount of crop residue burning spots in autumn was relatively large, and NEC was the region with the most intense crop residue burning in China. We compared the correlation between PM concentrations and crop residue burning at inter-annual and seasonal scales, and during burning-concentrated periods. We found that correlations between PM concentrations and crop residue burning increased significantly with the narrowing temporal scales and was the strongest during burning-concentrated periods, indicating that intense crop residue burning leads to instant deterioration of PM concentrations. The methodology and findings from this study provide meaningful reference for better understanding the influence of crop residue burning on PM pollution across China.


Asunto(s)
Agricultura/métodos , Contaminantes Atmosféricos/análisis , Productos Agrícolas , Material Particulado/análisis , Contaminación del Aire/análisis , China , Monitoreo del Ambiente/métodos , Imágenes Satelitales , Estaciones del Año
10.
J Environ Sci (China) ; 69: 141-154, 2018 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-29941250

RESUMEN

Characteristics of two serious air pollution episodes (9-15 January, as the winter case; and 30 June to 1 July, as the summer case), which occurred in Beijing in 2013 were investigated and compared using multi-method observations and numerical simulations. During these two air pollution episodes, PM2.5 concentrations varied significantly within Beijing, with PM2.5 concentrations in southern parts of Beijing being significantly higher than in northern areas. Typically, heavy air pollution episodes begin in the southern parts and disperse towards the northern parts of Beijing. Clearly, synoptic patterns and the stability of atmospheric circulation patterns were the main factors controlling air pollution in Beijing. During the winter case, a warm center above 900hPa occurred over Beijing. Meanwhile, in the summer case, although there was only a weak inversion, the convective inhibition energy was strong (over 200J/kG). This clearly influenced the duration of the air pollution event. Except for the local accumulation and secondary atmospheric reactions in both cases, regional straw burnings contributed a lot to the PM2.5 concentrations in summer case. Using the CAMx model, we established that regional transport contributed almost 59% to the PM2.5 averaged concentration in Beijing in the winter case, but only 31% in the summer case. Thus, the winter case was a typical regional air pollution episode, while the summer case resulted from local accumulation straw burnings transportation and strong secondary atmospheric reactions. Given that air pollution is a regional problem in China, consistent and simultaneous implementation of regional prevention and control strategies is necessary to improve regional air quality.


Asunto(s)
Contaminantes Atmosféricos/análisis , Contaminación del Aire/estadística & datos numéricos , Monitoreo del Ambiente , Material Particulado/análisis , Beijing , Estaciones del Año
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