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18 pages, 5092 KiB

Open AccessArticle

Impact of Meteorological Conditions on PM_2.5 Pollution in China during Winter

by Yanling Xu, Wenbo Xue, Yu Lei, Yang Zhao, Shuiyuan Cheng, Zhenhai Ren and Qing Huang

Atmosphere 2018, 9(11), 429; https://doi.org/10.3390/atmos9110429 - 6 Nov 2018

Cited by 69 | Viewed by 6682

Abstract

Fine particulate matter (PM_2.5) poses a risk to human health. In January 2017, the PM_2.5 pollution in China was severe, and the average PM_2.5 concentration had increased by 14.7% compared to that in January 2016. Meteorological conditions greatly influence [...] Read more.

Fine particulate matter (PM_2.5) poses a risk to human health. In January 2017, the PM_2.5 pollution in China was severe, and the average PM_2.5 concentration had increased by 14.7% compared to that in January 2016. Meteorological conditions greatly influence PM_2.5 pollution. The relationship between PM_2.5 and meteorological factors was assessed using monitoring data and the Community Multiscale Air Quality modeling system (CMAQ) was used to quantitatively evaluate the impacts of variations of meteorological conditions on PM_2.5 pollution. The results indicate that variations of meteorological conditions between January 2017 and January 2016 caused an increase of 13.6% in the national mean concentration of PM_2.5. Unlike the Yangtze River Delta (YRD), where meteorological conditions were favorable, unfavorable meteorological conditions (such as low wind speed, high humidity, low boundary layer height and low rainfall) contributed to PM_2.5 concentration worsening by 29.7%, 42.6% and 7.9% in the Beijing-Tianjin-Hebei (JJJ) region, the Pearl River Delta (PRD) region and the Chengdu-Chongqing (CYB) region, respectively. Given the significant influence of local meteorology on PM_2.5 concentration, more emphasis should be placed on employing meteorological means to improve local air quality. Full article

(This article belongs to the Special Issue Air Quality in China: Past, Present and Future)

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14 pages, 2049 KiB

Open AccessEditor’s ChoiceArticle

Atmospheric Chemistry of 2-Methoxypropene and 2-Ethoxypropene: Kinetics and Mechanism Study of Reactions with Ozone

by Chen Lv, Lin Du, Narcisse T. Tsona, Xiaotong Jiang and Wenxing Wang

Atmosphere 2018, 9(10), 401; https://doi.org/10.3390/atmos9100401 - 14 Oct 2018

Cited by 2 | Viewed by 4707

Abstract

Rate coefficients at ambient temperature and atmospheric pressure for the reaction of ozone with 2-methoxypropene (2-MPE) and 2-ethoxypropene (2-EPE) were determined in an evacuable 100 L Teflon reaction chamber using absolute and relative rate methods. The product experiments were carried out using a [...] Read more.

Rate coefficients at ambient temperature and atmospheric pressure for the reaction of ozone with 2-methoxypropene (2-MPE) and 2-ethoxypropene (2-EPE) were determined in an evacuable 100 L Teflon reaction chamber using absolute and relative rate methods. The product experiments were carried out using a 50 L Teflon reaction chamber in conjunction with FTIR as the detection technique. The rate coefficients (k in units of cm³ molecule⁻¹ s⁻¹) obtained are 1.18 ± 0.13 × 10⁻¹⁷ and 1.89 ± 0.23 × 10⁻¹⁷ for reactions with 2-MPE and 2-EPE, respectively. The effects of the alkoxy group on the gas-phase reactivity of alkyl vinyl ethers toward ozone are compared and discussed. The major ozonolysis products are methyl acetate, formaldehyde and CO₂ for 2-MPE, and ethyl acetate, formaldehyde and CO₂ for 2-EPE. Possible mechanisms for the two vinyl ethers are proposed based on the observed reaction products. Additionally, atmospheric lifetimes of 32 h and 21 h for 2-MPE and 2-EPE were estimated based on the measured rate constants and the ambient tropospheric concentration of ozone, respectively. The obtained values of the lifetimes indicate that the reaction with ozone is an important loss process for these vinyl ethers in the atmosphere, especially in polluted areas. Full article

(This article belongs to the Special Issue Air Quality in China: Past, Present and Future)

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16 pages, 4364 KiB

Open AccessArticle

Characteristics of Atmospheric Boundary Layer Structure during PM_2.5 and Ozone Pollution Events in Wuhan, China

by Yassin Mbululo, Jun Qin, Jun Hong and Zhengxuan Yuan

Atmosphere 2018, 9(9), 359; https://doi.org/10.3390/atmos9090359 - 18 Sep 2018

Cited by 10 | Viewed by 4454

Abstract

In this study, we investigated six air pollutants from 21 monitoring stations scattered throughout Wuhan city by analyzing meteorological variables in the atmospheric boundary layer (ABL) and air mass backward trajectories from HYSPLIT during the pollution events. Together with this, ground meteorological variables [...] Read more.

In this study, we investigated six air pollutants from 21 monitoring stations scattered throughout Wuhan city by analyzing meteorological variables in the atmospheric boundary layer (ABL) and air mass backward trajectories from HYSPLIT during the pollution events. Together with this, ground meteorological variables were also used throughout the investigation period: 1 December 2015 to 30 November 2016. Analysis results during this period show that the city was polluted in winter by PM_2.5 (particulate matter with aerodynamics of less than 2.5 microns) and in summer by ozone (O₃). The most polluted day during the investigation period was 25 December 2015 with an air quality index (AQI) of 330 which indicates ‘severe pollution’, while the cleanest day was 26 August 2016 with an AQI of 27 indicating ‘excellent’ air quality. The average concentration of PM_2.5 (O₃) on the most polluted day was 265.04 (135.82) µg/m³ and 9.10 (86.40) µg/m³ on the cleanest day. Moreover, the percentage of days which exceeded the daily average limit of NO₂, PM₁₀, PM_2.5, and O₃ for the whole year was 2.46%, 14.48%, 23.50%, and 39.07%, respectively, while SO₂ and CO were found to be below the set daily limit. The analysis of ABL during PM_2.5 pollution events showed the existence of a strong inversion layer, low relative humidity, and calm wind. These observed conditions are not favorable for horizontal and vertical dispersion of air pollutants and therefore result in pollutant accumulation. Likewise, ozone pollution events were accompanied by extended sunshine hours, high temperature, a calm wind, a strongly suspended inversion layer, and zero recorded rainfall. These general characteristics are favorable for photochemical production of ozone and accumulation of pollutants. Apart from the conditions of ABL, the results from backward trajectories suggest trans-boundary movement of air masses to be one of the important factors which determines the air quality of Wuhan. Full article

(This article belongs to the Special Issue Air Quality in China: Past, Present and Future)

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19 pages, 3625 KiB

Open AccessEditor’s ChoiceArticle

Spatio-Temporal Characteristics of Tropospheric Ozone and Its Precursors in Guangxi, South China

by Yapeng Wang, Chao Yu, Jinhua Tao, Zifeng Wang, Yidan Si, Liangxiao Cheng, Hongmei Wang, Songyan Zhu and Liangfu Chen

Atmosphere 2018, 9(9), 355; https://doi.org/10.3390/atmos9090355 - 14 Sep 2018

Cited by 10 | Viewed by 5166

Abstract

The temporal and spatial distributions of tropospheric ozone and its precursors (NO₂, CO, HCHO) are analyzed over Guangxi (GX) in South China. We used tropospheric column ozone (TCO) from the Ozone Monitoring Instrument (OMI) and Microwave Limb Sounder (MLS) onboard the [...] Read more.

The temporal and spatial distributions of tropospheric ozone and its precursors (NO₂, CO, HCHO) are analyzed over Guangxi (GX) in South China. We used tropospheric column ozone (TCO) from the Ozone Monitoring Instrument (OMI) and Microwave Limb Sounder (MLS) onboard the Aura satellite (OMI/MLS), NO₂ and HCHO from OMI and CO from the Measurements of Pollution in the Troposphere (MOPITT) instrument in the period 2005–2016. The TCO shows strong seasonality, with the highest value in spring and the lowest value observed in the monsoon season. The seasonal variation of HCHO is similar to that of TCO, while NO₂ and CO show slightly different patterns with higher values in spring and winter compared to lower values in autumn and summer. The surface ozone, NO₂ and CO observed by national air quality monitoring network sites are also compared with satellite-observed TCO, NO₂ and CO, showing good agreement for NO₂ and CO but a different seasonal pattern for ozone. Unlike TCO, surface ozone has the highest value in autumn and the lowest value in winter. To reveal the difference, the vertical profiles of ozone and CO from the measurement of ozone and water vapor by airbus in-service aircraft (MOZAIC) observations over South China are also examined. The seasonal averaged vertical profiles of ozone and CO show obvious enhancements at 2–6 km altitudes in spring. Furthermore, we investigate the dependence of TCO and surface ozone on meteorology and transport in detail along with the ECMWF reanalysis data, Tropical Rainfall Measuring Mission (TRMM) 3BV42 dataset, OMI ultraviolet index (UV index) dataset, MODIS Fire Radiative Power (FRP) and back trajectory. Our results show that the wind pattern at 800 hPa plays a significant role in determining the seasonality of TCO over GX, especially for the highest value in spring. Trajectory analysis, combined with MODIS FRP suggests that the air masses that passed through the biomass burning (BB) region of Southeast Asia (SEA) induced the enhancement of TCO and CO in the upper-middle troposphere in spring. However, the seasonal cycle of surface ozone is associated with wind patterns at 950 hPa, and the contribution of the photochemical effect is offset by the strong summer monsoon, which results in the maximum surface ozone concentration in post-monsoon September. The variations in the meteorological conditions at different levels and the influence of transport from SEA can account for the vertical distribution of ozone and CO. We conclude that the seasonal distribution of TCO results from the combined impact of meteorology and long-term transport. Full article

(This article belongs to the Special Issue Air Quality in China: Past, Present and Future)

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15 pages, 3655 KiB

Open AccessArticle

The Reducing Effect of Green Spaces with Different Vegetation Structure on Atmospheric Particulate Matter Concentration in BaoJi City, China

by Ling Qiu, Fang Liu, Xiang Zhang and Tian Gao

Atmosphere 2018, 9(9), 332; https://doi.org/10.3390/atmos9090332 - 22 Aug 2018

Cited by 34 | Viewed by 6023

Abstract

With the acceleration of urbanisation and industrialisation, atmospheric particulate pollution has become one of the most serious environmental problems in China. In this study, green spaces in Baoji city were classified into different patterns on the basis of vegetation structural parameters, i.e., horizontal [...] Read more.

With the acceleration of urbanisation and industrialisation, atmospheric particulate pollution has become one of the most serious environmental problems in China. In this study, green spaces in Baoji city were classified into different patterns on the basis of vegetation structural parameters, i.e., horizontal structure, vertical structure and vegetation type. Eleven types of green space with different structures were selected for investigating the relationships between atmospheric particulate matter (PM) concentration and green spaces with different vegetation structure, based on the “matrix effect” of environmental factors, i.e., location, time, wind velocity, temperature, humidity and area to the concentration of PM2.5 and PM10 in the green spaces. The results showed that: (1) Location, time, wind velocity, temperature and humidity had highly significant effects on the concentration of PM2.5 and PM10. In sunny and breeze weather conditions, PM2.5 and PM10 concentration increased with the wind velocity and humidity, and decreased with the temperature. The range of PM10 concentration was greater than the range of PM2.5 concentration. (2) Less than 2 hectares of the green space had no significant influence on the concentration of PM2.5 and PM10. (3) The concentration of PM2.5 and PM10 showed no significant difference between all the green spaces and the control group. There was no significant difference in the reduction of PM2.5 concentration between different structural green spaces, but there was a significant difference in the reduction of PM10 concentration. The above results will provide a theoretical basis and practical methods for the optimisation of urban green space structures for improving urban air quality effectively in the future. Full article

(This article belongs to the Special Issue Air Quality in China: Past, Present and Future)

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17 pages, 4360 KiB

Open AccessArticle

Long-Term Atmospheric Visibility Trends and Characteristics of 31 Provincial Capital Cities in China during 1957–2016

by Weicong Fu, Ziru Chen, Zhipeng Zhu, Qunyue Liu, Jinda Qi, Emily Dang, Minhua Wang and Jianwen Dong

Atmosphere 2018, 9(8), 318; https://doi.org/10.3390/atmos9080318 - 17 Aug 2018

Cited by 12 | Viewed by 4107 | Correction

Abstract

Millions of pulmonary diseases, respiratory diseases, and premature deaths are caused by poor ambient air quality in developing countries, especially in China. A proven indicator of ambient air quality, atmospheric visibility (AV), has displayed continuous decline in China’s urban areas. A better understanding [...] Read more.

Millions of pulmonary diseases, respiratory diseases, and premature deaths are caused by poor ambient air quality in developing countries, especially in China. A proven indicator of ambient air quality, atmospheric visibility (AV), has displayed continuous decline in China’s urban areas. A better understanding of the characteristics and the factors affecting AV can help the public and policy makers manage their life and work. In this study, long-term AV trends (from 1957–2016, excluding 1965–1972) and spatial characteristics of 31 provincial capital cities (PCCs) of China (excluding Taipei, Hong Kong, and Macau) were investigated. Seasonal and annual mean values of AV, percentage of ‘good’ (≥20 km) and ‘bad’ AV (<10 km), cumulative percentiles and the correlation between AV, socioeconomic factors, air pollutants and meteorological factors were analyzed in this study. Results showed that annual mean AV of the 31 PCCs in China were 14.30 km, with a declining rate of −1.07 km/decade. The AV of the 31 PCCs declined dramatically between 1973–1986, then plateaued between 1987–2006, and rebounded slightly after 2007. Correlation analysis showed that impact factors (e.g., urban size, industrial activities, residents’ activities, urban greening, air quality, and meteorological factors) contributed to the variation of AV. We also reveal that residents’ activities are the primary direct socioeconomic factors on AV. This study hopes to help the public fully understand the characteristics of AV and make recommendations about improving the air environment in China’s urban areas. Full article

(This article belongs to the Special Issue Air Quality in China: Past, Present and Future)

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11 pages, 5351 KiB

Open AccessArticle

Variations of Haze Pollution in China Modulated by Thermal Forcing of the Western Pacific Warm Pool

by Yingchang You, Xugeng Cheng, Tianliang Zhao, Xiangde Xu, Sunling Gong, Xiaoye Zhang, Yu Zheng, Huizheng Che, Chao Yu, Jiacheng Chang, Guoxu Ma and Ming Wu

Atmosphere 2018, 9(8), 314; https://doi.org/10.3390/atmos9080314 - 11 Aug 2018

Cited by 10 | Viewed by 4457

Abstract

In addition to the impact of pollutant emissions, haze pollution is connected with meteorology and climate change. Based on the interannual change analyses of meteorological and environmental observation data from 1981 to 2010, we studied the relationship between the winter haze frequency in [...] Read more.

In addition to the impact of pollutant emissions, haze pollution is connected with meteorology and climate change. Based on the interannual change analyses of meteorological and environmental observation data from 1981 to 2010, we studied the relationship between the winter haze frequency in central-eastern China (CEC) and the interannual variations of sea surface temperature (SST) over Western Pacific Warm Pool (WPWP) and its underlying mechanism to explore the thermal effect of WPWP on haze pollution variation in China. The results show a significant positive correlation coefficient reaching up to 0.61 between the interannual variations of SST in WPWP and haze pollution frequency in the CEC region over 1981–2010, reflecting the WPWP’s thermal forcing exerting an important impact on haze variation in China. The anomalies of thermal forcing of WPWP could induce to the changes of East Asian winter monsoonal winds and the vertical thermal structures in the troposphere over the CEC region. In the winter with anomalously warm SST over the WPWP, the near-surface winds were declined, and vertical thermal structure in the lower troposphere tended to be stable over the CEC-region, which could be conducive to air pollutant accumulation leading to the more frequent haze occurrences especially the heavy haze regions of Yangtze River Delta (YRD) and Pearl River Delta (PRD); In the winter with the anomalously cold WPWP, it is only the reverse of warm WPWP with the stronger East Asian winter monsoonal winds and the unstable thermal structure in the lower troposphere, which could attribute to the less frequent haze pollution over the CEC region. Our study revealed that the thermal forcing of the WPWP could have a modulation on air environment change in China. Full article

(This article belongs to the Special Issue Air Quality in China: Past, Present and Future)

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10 pages, 2794 KiB

Open AccessEditor’s ChoiceArticle

Difference in PM_2.5 Variations between Urban and Rural Areas over Eastern China from 2001 to 2015

by Changqing Lin, Alexis K. H. Lau, Ying Li, Jimmy C. H. Fung, Chengcai Li, Xingcheng Lu and Zhiyuan Li

Atmosphere 2018, 9(8), 312; https://doi.org/10.3390/atmos9080312 - 10 Aug 2018

Cited by 26 | Viewed by 6096

Abstract

To more effectively reduce population exposure to PM_2.5, control efforts should target densely populated urban areas. In this study, we took advantage of satellite-derived PM_2.5 data to assess the difference in PM_2.5 variations between urban and rural areas over [...] Read more.

To more effectively reduce population exposure to PM_2.5, control efforts should target densely populated urban areas. In this study, we took advantage of satellite-derived PM_2.5 data to assess the difference in PM_2.5 variations between urban and rural areas over eastern China during the past three Five-Year Plan (FYP) periods (2001–2015). The results show that urban areas experienced less of a decline in PM_2.5 concentration than rural areas did in more than half of the provinces during the 11th FYP period (2006–2010). In contrast, most provinces experienced a greater reduction of PM_2.5 concentration in urban areas than in rural areas during the 10th and 12th FYP periods (2001–2005 and 2011–2015, respectively). During the recent 12th FYP period, the rates of decline in PM_2.5 concentration in urban areas were more substantial than in rural areas by as much as 1.5 μg·m⁻³·year⁻¹ in Beijing and 2.0 μg·m⁻³·year⁻¹ in Tianjin. These results suggest that the spatial difference in PM_2.5 change was conducive to a reduction in the population exposure to PM_2.5 in most provinces during recent years. Full article

(This article belongs to the Special Issue Air Quality in China: Past, Present and Future)

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13 pages, 2032 KiB

Open AccessArticle

The Effect of Nonlocal Vehicle Restriction Policy on Air Quality in Shanghai

by Junjie Li, Xiao-Bing Li, Bai Li and Zhong-Ren Peng

Atmosphere 2018, 9(8), 299; https://doi.org/10.3390/atmos9080299 - 30 Jul 2018

Cited by 18 | Viewed by 8069

Abstract

In recent years, road space rationing policies have been increasingly applied as a traffic management solution to tackle congestion and traffic emission problems in big cities. Existing studies on the effect of traffic policy on air quality have mainly focused on the odd–even [...] Read more.

In recent years, road space rationing policies have been increasingly applied as a traffic management solution to tackle congestion and traffic emission problems in big cities. Existing studies on the effect of traffic policy on air quality have mainly focused on the odd–even day traffic restriction policy or one-day-per-week restriction policy. There are few studies paying attention to the effect of nonlocal license plate restrictions on air quality in Shanghai. Restrictions toward nonlocal vehicles usually prohibit vehicles with nonlocal license plates from entering certain urban areas or using certain subsets of the road network (e.g., the elevated expressway) during specific time periods on workdays. To investigate the impact of such a policy on the residents’ exposure to pollutants, CO concentration and Air Quality Index (AQI) were compared during January and February in 2015, 2016 and 2017. Regression discontinuity (RD) was used to test the validity of nonlocal vehicle restriction on mitigating environmental pollution. Several conclusions can be made: (1) CO concentration was higher on ground-level roads on the restriction days than those in the nonrestriction days; (2) the extension of the restriction period exposed the commuters to high pollution for a longer time on the ground, which will do harm to them; and (3) the nonlocal vehicle restriction policy did play a role in improving the air quality in Shanghai when extending the evening rush period. Additionally, some suggestions are mentioned in order to improve air quality and passenger health and safety. Full article

(This article belongs to the Special Issue Air Quality in China: Past, Present and Future)

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18 pages, 5833 KiB

Open AccessArticle

Sources Profiles of Volatile Organic Compounds (VOCs) Measured in a Typical Industrial Process in Wuhan, Central China

by Longjiao Shen, Ping Xiang, Shengwen Liang, Wentai Chen, Ming Wang, Sihua Lu and Zuwu Wang

Atmosphere 2018, 9(8), 297; https://doi.org/10.3390/atmos9080297 - 30 Jul 2018

Cited by 88 | Viewed by 8813

Abstract

Industrial emission is an important source of ambient volatile organic compounds (VOCs) in Wuhan City, Hubei Province, China. We collected 53 VOC samples from petrochemical, surface coating, electronic manufacturing, and gasoline evaporation using stainless canisters to develop localized source profiles. Concentrations of 86 [...] Read more.

Industrial emission is an important source of ambient volatile organic compounds (VOCs) in Wuhan City, Hubei Province, China. We collected 53 VOC samples from petrochemical, surface coating, electronic manufacturing, and gasoline evaporation using stainless canisters to develop localized source profiles. Concentrations of 86 VOC species, including hydrocarbons, halocarbons, and oxygenated VOCs, were quantified by a gas chromatography–flame ionization detection/mass spectrometry system. Alkanes were the major constituents observed in the source profile from the petrochemical industry. Aromatics (79.5~81.4%) were the largest group in auto-painting factories, while oxygenated VOCs (82.0%) and heavy alkanes (68.7%) were dominant in gravure printing and offset printing factories, respectively. Acetone was the largest contributor and the most frequently monitored species in printed circuit board (PCB) manufacturing, while VOC species emitted from integrated chip (IC) were characterized by high contents of isopropanol (56.4–98.3%) and acetone (30.8%). Chemical compositions from vapor of gasoline 92#, 93#, and 98# were almost identical. Alkanes were the dominant VOC group, with i-pentane being the most abundant species (31.4–37.7%), followed by n-butane and n-pentane. However, high loadings of heavier alkanes were observed in the profile of diesel evaporation. Full article

(This article belongs to the Special Issue Air Quality in China: Past, Present and Future)

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18 pages, 2808 KiB

Open AccessArticle

The Impacts of Taklimakan Dust Events on Chinese Urban Air Quality in 2015

by Xiaoyu Li, Xiaodong Liu and Zhi-Yong Yin

Atmosphere 2018, 9(7), 281; https://doi.org/10.3390/atmos9070281 - 19 Jul 2018

Cited by 16 | Viewed by 4939

Abstract

Aerosols are an important factor affecting air quality. As the largest source of dust aerosol of East Asia, the Taklimakan Desert in Northwest China witnesses frequent dust storm events, which bring about significant impacts on the downstream air quality. However, the scope and [...] Read more.

Aerosols are an important factor affecting air quality. As the largest source of dust aerosol of East Asia, the Taklimakan Desert in Northwest China witnesses frequent dust storm events, which bring about significant impacts on the downstream air quality. However, the scope and timing of the impacts of Taklimakan dust events on Chinese urban air quality have not yet been fully investigated. In this paper, based on multi-source dust data including ground observations, satellite monitoring, and reanalysis products, as well as air quality index (AQI) and the mass concentrations of PM₁₀ and PM_2.5 at 367 urban stations in China for 2015, we examined the temporal and spatial characteristics of the impacts of the Taklimakan dust events on downstream urban air quality in China. The results show that the Taklimakan dust events severely affected the air quality of most cities in Northwest China including eastern Xinjiang, Hexi Corridor and Guanzhong Basin, and even northern Southwest China, leading to significant increases in mass concentrations of PM₁₀ and PM_2.5 in these cities correlating with the occurrence of dust events. The mass concentrations of PM₁₀ on dust days increased by 11–173% compared with the non-dust days, while the mass concentration of PM_2.5 increased by 21–172%. The increments of the mass concentrations of PM₁₀ and PM_2.5 on dust days decreased as the distances increased between the cities and the Taklimakan Desert. The influence of the Taklimakan dust events on the air quality in the downstream cities usually persisted for up to four days. The mass concentrations of PM₁₀ and PM_2.5 increased successively and the impact duration shortened gradually with increasing distances to the source area as a strong dust storm progressed toward the southeast from the Taklimakan Desert. The peaks of the PM₁₀ concentrations in the downstream cities of eastern Xinjiang, the Hexi Corridor and the Guanzhong Basin occurred on the second, third and fourth days, respectively, after the initiation of the Taklimakan dust storm. Full article

(This article belongs to the Special Issue Air Quality in China: Past, Present and Future)

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17 pages, 5363 KiB

Open AccessArticle

Changes in Haze Trends in the Sichuan-Chongqing Region, China, 1980 to 2016

by Hongke Cai, Ke Gui and Quanliang Chen

Atmosphere 2018, 9(7), 277; https://doi.org/10.3390/atmos9070277 - 19 Jul 2018

Cited by 14 | Viewed by 4554

Abstract

This study analyzed the long-term variations and trends of haze pollution and its relationships with emission and meteorological factors using the haze days (HDs) data derived from surface observation stations in Sichuan-Chongqing (SCC) region during 1980–2016. The results showed that the multi-year mean [...] Read more.

This study analyzed the long-term variations and trends of haze pollution and its relationships with emission and meteorological factors using the haze days (HDs) data derived from surface observation stations in Sichuan-Chongqing (SCC) region during 1980–2016. The results showed that the multi-year mean number of HDs were 68.7 and 4.9 days for the Sichuan-Basin (SCB) and the rest of SCC region, respectively. The seasonally averaged HDs over SCB reached its maximum in winter (34.7 days), followed by autumn (17.0 days) and spring (11.6 days), and with the minimum observed in summer (5.5 days). The inter-annual variations of HDs in 18 main cities revealed that Zigong, Neijiang, and Yibin, which are located in the southern of SCB, have been the most polluted areas over the SCC region in the past decades. A notable increasing trend in annual HDs over the majority of SCC region was found during 1980–1995, then the trend sharply reversed during 1996–2005, while it increased, fluctuating at some cities after 2006. Seasonally, the increased trend in spring and autumn seems to be the strongest during 1980–1995, whereas the decreased trend in spring and winter was stronger than other seasons during 1996–2005. In addition, a remarkable increasing trend was found in winter since 2006. Using correlation analysis between HDs and emission and meteorological factors during different periods, we found that the variability of local precipitation days (PDs), planetary boundary layer height (PBLH), near-surface wind speed (WS), and relatively humidity (RH) play different roles in influencing the haze pollution change during different historical periods. The joint effect of sharp increase of anthropogenic emissions, reduced PDs and WS intensified the haze pollution in SCB during 1980–1995. In contrast, decreased HDs during 1996–2005 are mainly attributable to the reduction of PM_2.5 emission and the increase of PDs (especially in winter). In addition, the decrease of PDs is likely to be responsible for the unexpected increase in winter HDs over SCB in the last decade. Full article

(This article belongs to the Special Issue Air Quality in China: Past, Present and Future)

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15 pages, 2731 KiB

Open AccessArticle

Effects of Urban Greenspace Patterns on Particulate Matter Pollution in Metropolitan Zhengzhou in Henan, China

by Yakai Lei, Yanbo Duan, Dan He, Xiwen Zhang, Lanqi Chen, Yonghua Li, Yu Gary Gao, Guohang Tian and Jingbiao Zheng

Atmosphere 2018, 9(5), 199; https://doi.org/10.3390/atmos9050199 - 21 May 2018

Cited by 37 | Viewed by 5275

Abstract

This case study was conducted to quantify the effects of urban greenspace patterns on particle matter (PM) concentration in Zhengzhou, China by using redundancy and variation partitioning analysis. Nine air-quality monitoring stations (AQMS) were selected as the central points. Six distances of 1 [...] Read more.

This case study was conducted to quantify the effects of urban greenspace patterns on particle matter (PM) concentration in Zhengzhou, China by using redundancy and variation partitioning analysis. Nine air-quality monitoring stations (AQMS) were selected as the central points. Six distances of 1 km, 2 km, 3 km, 4 km, 5 km, and 6 km were selected as the side lengths of the squares with each AQMS serving as the central point, respectively. We found: (1) the fine size of PM (PM_2.5) and coarse size of PM (PM₁₀) among four seasons showed significant differences; during winter, the concentration of PM_2.5 and PM₁₀ were both highest, and PM_2.5 and PM₁₀ concentration in summer were lowest. (2) To effectively reduce the PM_2.5 pollution, the percentage of greenspace, the differences in areas among greenspace patches, and the edge complexity of greenspace patches should be increased at distances of 2 km and 3 km. To effectively reduce PM₁₀, the percentage of greenspace at a distance of 4 km, the edge density at distances of 2 km and 4 km, and the average area of greenspace patches at a distance of 1 km should be increased. (3) Greenspace pattern significantly affected PM_2.5 at a distance of 3 km, and PM₁₀ at a distance of 4 km. From shorter distance to longer distance, the proportion of variance explained by greenspace showed a decline–increase–decline–increase trend for PM_2.5, and a decline–increase–decline trend for PM₁₀. At shorter distances, the composition of greenspace was more effective in reducing the PM pollution, and the configuration of greenspace played a more important role at longer distances. The results should lead to specific guidelines for more cost-effective and environmentally sound greenspace planning. Full article

(This article belongs to the Special Issue Air Quality in China: Past, Present and Future)

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21 pages, 8034 KiB

Open AccessArticle

PM_2.5 Characteristics and Regional Transport Contribution in Five Cities in Southern North China Plain, During 2013–2015

by Lili Wang, Wenjie Li, Yang Sun, Minghui Tao, Jinyuan Xin, Tao Song, Xingru Li, Nan Zhang, Kang Ying and Yuesi Wang

Atmosphere 2018, 9(4), 157; https://doi.org/10.3390/atmos9040157 - 21 Apr 2018

Cited by 31 | Viewed by 5236

Abstract

PM_2.5 data from major cities in the southern North China Plain during 2013–2015 were comprehensively analyzed relative to variation features, meteorology effects, and regional transport contributions. The annual average ranged from 87 to 123 μg m⁻³, with the highest in [...] Read more.

PM_2.5 data from major cities in the southern North China Plain during 2013–2015 were comprehensively analyzed relative to variation features, meteorology effects, and regional transport contributions. The annual average ranged from 87 to 123 μg m⁻³, with the highest in Baoding and Shijiazhuang, the moderate in Handan and Hengshui, and the lowest in Cangzhou, which revealed an evident concentration gradient with distance from the mountains. PM_2.5 pollution indicated significantly regional characteristics and high correlations in daily PM_2.5 changes and similar seasonal and diurnal variations in five cities. The highest concentrations mainly occurred in the winter, then autumn, spring, and summer, and the diurnal variations were bimodal with peaks during the morning rush hours and at night, which were mostly dominated by the differences in source emissions and the boundary layer. The PM_2.5 concentrations were significantly positively correlated with relative humidity, especially during winter. The highest PM_2.5 concentrations in all cities were associated with the south, southeast, and southwest pathways, while the short northwest pathway in the winter for Baoding and Shijiazhuang experienced the highest concentration. Regional contributions ranged from 19.6 to 33.7% annually, with the largest in Baoding and Shijiazhuang. These results provide a scientific basis for pollution forecasting and control in these heavily polluted cities. Full article

(This article belongs to the Special Issue Air Quality in China: Past, Present and Future)

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18 pages, 4401 KiB

Open AccessArticle

Influential Factors and Dry Deposition of Polychlorinated Biphenyls (PCBs) in Atmospheric Particles at an Isolated Island (Pingtan Island) in Fujian Province, China

by Qibin Lao, Liping Jiao, Fajin Chen, Liqi Chen and Xia Sun

Atmosphere 2018, 9(2), 59; https://doi.org/10.3390/atmos9020059 - 9 Feb 2018

Cited by 13 | Viewed by 4609

Abstract

To explore the polychlorinated biphenyl (PCB) pollution characteristics of atmospheric particles, influential factors, and dry deposition fluxes, 28 PCB congeners were examined over a 2-year period in the environment of an isolated island in Fujian Province. In 2006 and 2007, PCB concentrations ranged [...] Read more.

To explore the polychlorinated biphenyl (PCB) pollution characteristics of atmospheric particles, influential factors, and dry deposition fluxes, 28 PCB congeners were examined over a 2-year period in the environment of an isolated island in Fujian Province. In 2006 and 2007, PCB concentrations ranged from 1.12 to 87.32 pg m⁻³ and ND (not detected) to 44.93 pg m⁻³, respectively, and were predominantly highly-chlorinated PCBs. The levels were much lower than those from industrial, urban, and rural areas, but slightly higher than those found in coastal areas of Europe and in the ocean. Obvious seasonal variations were found in the PCB levels, with high levels appearing in the winter, whereas low levels appeared in the summer, which indicated a significant positive correlation with the atmospheric particle mass level. The distribution pattern of the PCB concentration was largely affected by the meteorological conditions and total organic carbon (TOC) levels. Moreover, air mass originating from Northern China may be responsible for the higher PCB levels over Pingtan Island during the winter, and tracing the source of atmospheric particles by the stable carbon isotope suggested that the PBC levels may be influenced by coal combustion during the “heating season” of Northern China. The total dry deposition flux of the 28 PCBs on Pingtan Island was 3.94 ng m⁻² d⁻¹ and 2.94 ng m⁻² d⁻¹ in 2006 and 2007, respectively, and the average yearly input to the adjacent waters was 7531.2 g y⁻¹. Full article

(This article belongs to the Special Issue Air Quality in China: Past, Present and Future)

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10 pages, 2556 KiB

Open AccessArticle

Sources and Health Risks of Heavy Metals in PM_2.5 in a Campus in a Typical Suburb Area of Taiyuan, North China

by Kankan Liu, Qingmin Shang and Changyuan Wan

Atmosphere 2018, 9(2), 46; https://doi.org/10.3390/atmos9020046 - 2 Feb 2018

Cited by 38 | Viewed by 4910

Abstract

To evaluate air pollution and the public health burden of heavy metals in PM_2.5 in a campus with a population of approximately 40,000 in a typical suburb area of Taiyuan, North China, PM_2.5 measurements were conducted during the spring and winter [...] Read more.

To evaluate air pollution and the public health burden of heavy metals in PM_2.5 in a campus with a population of approximately 40,000 in a typical suburb area of Taiyuan, North China, PM_2.5 measurements were conducted during the spring and winter of 2016. The average concentrations of PM_2.5 in spring and winter were 97.3 ± 35.2 µg m⁻³ and 205.9 ± 91.3 µg m⁻³, respectively. The order of concentration of heavy metals in PM_2.5 was as follows: Zn > Pb > Mn > Cu > Cr > Ni > Cd > As, in both spring and winter. The concentrations of Cd and Pb in winter and the concentrations of Cr in both spring and winter in this study were significantly higher than the corresponding air quality standard values. Road/soil dust, industrial emissions/coal combustion, and vehicle emissions/oil combustion and coal combustion/industrial emissions, road/soil dust, and vehicle emissions/oil combustion were identified by principal component analysis to be the major sources of heavy metals for spring and winter, respectively. The carcinogenic risks posed by Cr via the three exposure pathways (except for inhalation exposure to children) and by Pb via ingestion exposure exceeded the acceptable level for both children and adults. The non-carcinogenic risks posed by Mn via inhalation for both children and adults, and by Cr and Pb for children via ingestion exceeded the acceptable level. Full article

(This article belongs to the Special Issue Air Quality in China: Past, Present and Future)

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