Chemical characteristics of PM_(2.5) during dust storms and air pollution events in Chengdu,China

Daily fine particulate （PM2.5） samples were collected in Chengdu from April 2009 to February 2010 to investigate their chemical profiles during dust storms （DSs） and several types of pollution events, including haze （HDs）, biomass burning （BBs）, and fireworks displays （FDs）. The highest PM2.5 mass concentrations were found during DSs （283.3 μg/m^3）, followed by FDs （212.7 μg/m^3）, HDs （187.3 μg/m^3 ）, and BBs （130.1 μ g/m^3）. The concentrations of most elements were elevated during DSs and pollution events, except for BBs. Secondary inorganic ions （NO3^- , SO4^2-, and NH4^＋） were enriched during HDs, while PM2.5 from BBs showed high K^＋ but low SO4^2- , FDs caused increases in K^＋ and enrichment in SO4^2-. Ca^2＋. was abundant in DS samples, Ion-balance calculations indicated that PM2.5 from HDs and FDs was more acidic than on normal days, but DS and BB particles were alkaline. The highest organic carbon （OC） concentration was 26.1 μg/m^3 during FDs, followed by BBs （23.6 μg/m^3 ）, HDs （19.6 μg/m^3 ）, and DSs （18.8 μg/m^3 ）. In contrast, elemental carbon （EC） concentration was more abundant during HDs （10.6μg/m^3） and FDs （9.5 μg/m^3） than during BBs （6.2μg/m^3） and DSs （6.0 μg/m^3）. The highest OC/EC ratios were obtained during BBs, with the lowest during HDs. SO4^2＋ /K^＋ and TCA/SO4^2- ratios proved to be effective indicators for differentiating pollution events. Mass balance showed that organic matter, SO4^2-, and NO3^- were the dominant chemical components during pollution events, while soil dust was dominant during DSs.

Temporal Trend in Lung Cancer Burden Attributed to Ambient Fine Particulate Matter in Guangzhou, China

Objective To estimate the lung cancer burden that may be attributable to ambient fine particulate matter （PM2.5） pollution in Guangzhou city in China from 2005 to 2013. Methods The data regarding PM2.5 exposure were obtained from the ＆#39;Ambient air pollution exposure estimation for the Global Burden of Disease 2013＇ dataset at 0.1° ×0.1° spatial resolution. Disability-adjusted life years （DALYs） were estimated based on the information of mortality and incidence of lung cancer. Comparative risk analysis and integrated exposure-response function were used to estimate attributed disease burden. Results The population-weighted average concentration of PM2.5 was increased by 34.6% between 1990 and 2013, from 38.37 μg/m3 to 51.31 μg/m^3. The lung cancer DALYs in both men and women were increased by 36.2% from 2005 to 2013. The PM2.5 attributed lung cancer DALYs increased from 12105.0 （8181.0 for males and 3924.0 for females） in 2005 to 16489.3 （11291.7 for males and 5197.6 for females） in 2013. An average of 23.1% lung cancer burden was attributable to PM2.5 pollution in 2013. Conclusion PM2.5 has caused serious but under-appreciated public health burden in Guangzhou and the trend deteriorates. Effective strategies are needed to tackle this major public health problem.

Study on the Effect of Reducing Haze by Urban Greening Trees

Although small in size, PM25 can do great harm to the environment, and city greening trees can reduce PM2.5 pollution to a certain extent. This paper reviewed the mechanism of city greening trees to reduce PM2.5 pollution, screening and classification of green land allocation model of PM2.5 reducing greening trees, and made prospect on how to construct the evaluation index system of PM2.5 re- ducing greening trees and urban green land allocation.

Spatial and Temporal Variability of PM_(2.5) Concentration in China

PM_（2.5） has become an increasing public concern recently because of its visibility reduction and severe health risks. For the whole year of 2013, hourly PM_（2.5） data of 496 monitoring sites scattered in 74 cities of China are collected to analyze temporal and spatial variability of PM_（2.5） concentration. Different temporal scales（seasonal variation, monthly variation and daily variation） and spatial scales（urban versus rural, typical areas and national scale） are discussed. Results show that PM_（2.5） concentration changes significantly in both long-term and short-term scales. An apparent bimodal pattern exists in daily variation of PM_（2.5） concentration and the daytime peak appears around 10：00 am while the lowest concentration appears around 16：00 pm. Spatial autocorrelation analysis and Ordinary Kriging are used to characterize spatial variability. Moran＇s I of PM_（2.5） concentration in three typical regions, the Beijing-Tianjin-Hebei region, the Yangtze River Delta region and the Pearl River Delta region, is 0.906, 0.693, 0.746, respectively, which indicates that PM_（2.5） is strong spatial correlated. Spatial distribution of annual PM_（2.5） concentration simulated by Ordinary Kriging shows that 7.94 million km2（83%） areas fail in meeting the requirement of China＇s National Ambient Air Quality Standards Level-2（35 mg/m3） and there are at least three concentrated highly polluted areas across the country.

Variation of PM_(2.5) concentration in Hangzhou,China

This observational study investigates the variation of PM2.5 concentration and its ratio against PM10 concentration under different weather systems and pollution types. The study was conducted in Hangzhou on east China＇s Yangtze River Delta using data collected at seven ambient air quality monitoring stations around the metropolitan area between 2006 and 2008 and using weather information in the same period. Nine predominant weather systems affecting the city were classified through careful analysis of the 11- year surface and upper air weather charts from 1996 to 2006. Each observational day was then assigned to one of the nine weather systems. It was found that the PM2.5 concentration varied greatly for different weather systems, with the highest PM2.5 concentration associated with the post-cold-frontal system at 0.091 mg/m^3 and the lowest PM2.5 concentration with the easterlies system at 0.038 mg/m^3, although the PM2.5/PM10 ratio remained consistently above 0.5 for all systems. The post-cold-frontal system typically occurs in autumn and winter while the easterlies system is more a summer phenomenon. Among all types of pollution, the highest PM2.5 concentration of 0.117 mg/m^3 coincided with the large-scale continuous pollution events, suggesting that this type of pollution was more conducive to the formation of secondary particulate matters. The ratio of PM2.5/PM10 was above 0.5 in non-pollution days and all pollution types but one under the influence of dust storms when the ratio decreased to 0.3 or less. The outcomes of this study could be used to develop a rudimental predictive model of PM2.5 concentration based on weather system and pollution type.

Variation of airborne quartz in air of Beijing during the Asia-Pacific Economic Cooperation Economic Leaders' Meeting

Quartz particles are a toxic component of airborne paniculate matter（PM）.Quartz concentrations were analyzed by X-ray diffraction in eighty-seven airborne PM samples collected from three locations in Beijing before,during,and after the Asia-Pacific Economic Cooperation（APEC） Leaders＇ Meeting in 2014.The results showed that the mean concentrations of quartz in PM samples from the two urban sites were considerably higher than those from the rural site.The quartz concentrations in samples collected after the APEC meeting,when the pollution restriction lever was lifted,were higher than those in the samples collected before or during the APEC meeting.The quartz concentrations ranged from 0.97 to 13.2 μg/m^3,which were among the highest values amid those reported from other countries.The highest quartz concentration exceeded the Californian Office of Environmental Health Hazard Assessment reference exposure level and was close to the occupational threshold limit values for occupational settings.Moreover,a correlation analysis showed that quartz concentrations were positively correlated with concentrations of pollution parameters PM10,PM2.5,SO2 and NOx,but were negatively correlated with O3 concentration.The results suggest that the airborne quartz particles may potentially pose health risks to the general population of Beijing.