Effect of chemical composition of PM_(2.5) on visibility in Guangzhou,China,2007 spring

The object of this study was to investigate the correlation of visibility with chemical composition of PM2.5 in Guangzhou. In April 2007, 28 PM2.5 samples were collected daily at the monitoring station of the South China Institute of Environmental Sciences (SCIES), in urban Guangzhou. Water-soluble ionic species (Cl-, NO3-, SO42-, NH4+, K+, Na+, Ca2+, and Mg2+) and carbonaceous contents (OC and EC) of the PM2.5 samples were determined to characterize their impact on visibility impairment. The results showed that sulfate was the dominant species that affected both light scattering and visibility. The average percentage contributions of the visibility-degrading species to light scattering coefficient were 40% for sulfate, 16% for nitrate, 22% for organics, and 22% for elemental carbon. Because of its foremost effect on visibility, sulfate reduction in PM2.5 would effectively improve the visibility of Guangzhou.     

Characteristics of organic and elemental carbon in atmospheric fine particles in Tianjin, China

PM2.5 samples were collected at urban, industrial and coastal sites in Tianjin during winter, spring and summer in 2007. Concentrations of elemental carbon （EC） and organic carbon （OC） were analyzed using the IMPROVE thermal-optical reflectance （TOR） method. Both OC and EC exhibited a clear seasonal pattern with higher concentrations observed in the winter than in the spring and summer, due to cooperative effect of changes in emission rates and seasonal meteorology. The concentrations of carbonaceous species were also influenced by the local factors at different sampling sites, ranking in the order of industrial〉 urban 〉 coastal during winter and spring. In the summer, the port emissions, enriched with EC, had a significant impact on carbonaceous aerosols at the coastal site. Total carbonaceous aerosol accounted for 40.0% in winter, 33.8% in spring and 31.4% in summer of PM2.5 mass. Good correlation （R = 0.84-0.93） between OC and EC indicated that they had common dominant sources of combustion such as coal burning and traffic emissions. The daily average OC/EC ratios ranged from 2.1 to 9.1, the elevated OC/EC ratios being found in the winter. The estimated secondary organic carbon （SOC） accounted for 46.9%, 35.3% and 40.2% of the total OC in the winter, spring and summer, respectively, indicating that SOC may be an important contributor to fine organic aerosol in Tianjin.     

Effect of chemical composition of PM2.5 on visibility in Guangzhou,China, 2007 spring

The object of this study was to investigate the correlation of visibility with chemical composition of PM2.5 in Guangzhou. In April 2007, 28 PM2.5 samples were collected daily at the monitoring station of the South China Institute of Environmental Sciences （SCIES）, in urban Guangzhou. Water-soluble ionic species （CI^-, NO3^-, SO4^2-, NH4^＋, K^＋, Na^＋, Ca^2＋, and Mg^2＋） and carbonaceous contents （OC and EC） of the PM2.5 samples were determined to characterize their impact on visibility impairment. The results showed that sulfate was the dominant species that affected both light scattering and visibility. The average percentage contributions of the visibility-degrading species to light scattering coefficient were 40% for sulfate, 16% for nitrate, 22% for organics, and 22% for elemental carbon. Because of its foremost effect on visibility, sulfate reduction in PM2.5 would effectively improve the visibility of Guangzhou.     

SPATIAL AND SEASONAL DISTRIBUTIONS OF ATMOSPHERIC CARBONACEOUS AEROSOLS IN PEARL RIVER DELTA REGION, CHINA

Concentrations and spatial distributions of organic carbon (OC) and elemental carbon (EC) in atmospheric particles were measured at 8 sites in four cities (Hong Kong, Guangzhou, Shenzhen and Zhuhai) of Pearl River Delta Region (PRDR), China during 2001 winter period and 2002 summer period. PM2.5 (particie diameter smaller than 2.5 um) and PM10 (particie diameter smaller than 10 um) samples were collected on pre-fired quartz filters with mini-volume samplers and analyzed using thermal optical reflectance (TOR) method. The average PM2.5and PM10 Ievel were 60.1 and 93.1 μg·m-3, respectively, with PM2.5 constituting 65.3% of the PM10 mass. The average OC and EC concentrations in PM2.5 were 12.0 and 5.1 μg·m-3, respectively, while those in PM10 were 16.0 and 6.5 μg·m-3, respectively. The carbo-naceous aerosol accounted for 37.2% of the PM2.5 and 32.8% of the PM10. The highest concentrations of OC and EC were observed at Guangzhou city in both vvinter and summer seasons. The average OC/EC ratios were 2.     

Characteristics of elemental carbon and organic carbon in PM10 during spring and autumn in Chongqing, China

PM10 （particulate matter with aerodynamic diameter less than 10 μm） samples were collected simultaneously at nine urban sites and one urban background site during two intensive observation campaigns in 2006. Concentrations of elemental carbon （EC） and organic carbon （OC） in PM10 were analyzed using an element analyzer. The characteristics regarding spatial and seasonal distribution patterns of OC and EC concentrations and their contributions to PM10 mass, as well as correlation between OC and EC, were investigated in detail. The average OC and EC concentrations for urban sites were 57.5 ± 20.8 and 8.3 ± 3.9 μg/m^3, respectively, both being around three times higher than those for urban background site. As a whole, EC concentrations did not show distinct seasonal variations, though OC concentrations were generally higher in autumn than in spring. For urban sites, total carbonaceous aerosol （TCA） accounted for 33.2% in spring and 35.0% in autumn of PM10 mass. The OC and EC concentrations were found significantly correlated to each other both in spring and in autumn, implying the existence of similar emission sources such as coal combustion. The OC/EC ratios generally exceeded 2.0, indicating the presence of secondary organic carbon （SOC）, whose estimated concentration for urban Chongqing was 26.7 and 39.4μg/m^3, accounting for 48.9 and 61.9% of the total OC observed in the samples, in spring and in autumn, respectively.     

Chemical composition and source apportionment of the ambient PM_(2.5)in Hangzhou,China

To identify and apportion the sources of the ambient PM_(2.5) in the urban area of Hangzhou,China,PM_(2.5)samples were collected at three sites in the city from April 2004 to March 2005.Water-soluble ions,metal elements,and total carbon(TC) in PM_(2.5) samples were analyzed.The results indicated that the 24-h mean concentrations of PM_(2.5) ranged from 17.1 to 267.0 μg/m~3,with an annual average value of 108.2 μg/m~3.Moreover,the seasonal mean values for PM_(2.5) in spring,summer,autumn,and winter were 116,73.1,114.2,and 136.0 μg/m~3.respectively.According to the Chinese ambient quality standard,at least 70% of the monitoring data exceeded the limit value.The total contribution of water-soluble ions,including F~-,Cl~-,NO_3~-,SO_4~(2-).NH_4~+,K~+,and Na~+.to PM_(2.5) mass varied from 32.3% to 36.7%.SO_4~(2-),NO_3~-,and NH_4~+were the main constituents of the ions,with contributions to PM_(2.5) varying from 14.1% to 14.7%,6.0%to 7.8%,and 6.4% to 7.7%,respectively.In addition,the annual mean mass fraction of TC in PM_(2.5) was27.8%.The annual average total contribution of the group of elements of Zn,Pb,Cu,Mn,Cr,Ni,Se,Mo.Cd,Sb,and Ag to the aerosol was in the range of 1.7-2.0%.Furthermore,positive matrix factorization was applied to analyze the PM_(2.5) data collected from the central area,and five factors were identified.The factor contributions to PM_(2.5) mass were 12.8%,31.9%,10.1%,17.2%,and 27.9%,respectively.Iron/steel manufacturing and secondary aerosol were the main sources for the fine particles.These findings may have significance for controlling the atmospheric contamination in the city.     

Chemical characteristics and Pb isotopic compositions of PM2.5 in Nanchang,China

In mid-September 2013, PM_2.5 samples were collected at six sites in Nanchang, Jiangxi Province, China, to quantify nine water-soluble ions (Ca²⁺, Mg²⁺, K⁺, Na⁺, NH₄⁺, SO₄²⁻, Cl⁻, F⁻, NO₃⁻), 29 trace elements (Ba, Zn, Pb, Ni, Mo, Cr, Cu, Sr, Sb, Rb, Cd, Bi, Zr, V, Ga, Li, Y, Nb, W, Cs, Tl, Sc, Co, U, Hf, In, Re, Be, and Ta), and to characterize Pb isotopic ratios (²⁰⁷Pb/²⁰⁶Pb, ²⁰⁸Pb/²⁰⁶Pb, and ²⁰⁷Pb/²⁰⁴Pb) for identifying the main source(s) of Pb. The results showed that the average daily PM_2.5 concentration (53.16 ± 24.17) μg/m³ was within the secondary level of the Chinese ambient air quality standard. The combined concentrations of SO₄²⁻, NH₄⁺, and NO₃⁻ to total measured water-soluble ion concentrations in PM_2.5 ranged from 79.40% to 95.18%, indicating that anthropogenic sources were significant. Coal combustion and vehicle emissions were both contributors to PM_2.5 based on the NO₃⁻/SO₄²⁻ ratios. Wushu School experienced the lowest concentrations of PM_2.5 and most trace elements among the six sampling sites. Enrichment factor results showed that Tl, Cr, In, Cu, Zn, Pb, Bi, Ni, Sb, and Cd in PM_2.5 were affected by anthropogenic activities. Cluster analysis suggested that Cd, Sb, Pb, Re, Zn, Bi, Cs, Tl, Ga, and In were possibly related to coal combustion and vehicle exhaust, while Ni, Nb, Cr, and Mo may have originated from metal smelting. Pb isotopic tracing showed that coal dust, cement dust, road dust and construction dust were the major Pb sources in PM_2.5 in Nanchang. Combined, these sources contributed an average of 72.51% of the Pb measured, while vehicle exhaust accounted for 27.49% of Pb based on results from a binary Pb isotope mixed model.     

PM2.5 in an industrial district of Zhengzhou,China:Chemical composition and source apportionment

Zhengzhou is a developing city in China,that is heavily polluted by high levels of particulate matter.In this study.fine particulate matter(PM_2.5) was collected and analyzed for their chemical composition（soluble ions,elements,elemental carbon（EC） and organic carbon（OC）） in an industrial district of Zhengzhou in 2010.The average concentrations of PM_2.5 were 181,122,186 and 211μg/m³ for spring,summer, autumn and winter,respectively,with an annual average of 175μg/m³,far exceeding the PM_2.5 regulation of USA National Air Quality Standards（15μg/m³）.The dominant components of PM_2.5 in Zhengzhou were secondary ions（sulphate and nitrate） and carbon fractions.Soluble ions,total carbon and elements contributed 41%,13%and 3%of PM_2.5 mass,respectively.Soil dust,secondary aerosol and coal combustion, each contributing about 26%,24%and 23%of total PM_2.5 mass,were the major sources of PM_2.5,according to the result of positive matrix factorization analysis.A mixed source of biomass burning,oil combustion and incineration contributed 13%of PM_2.5.Fine particulate matter arising from vehicles and industry contributed about 10%and 4%of PM_2.5,respectively.     

Chemical characteristics of PM2.5 during dust storms and air pollution events in Chengdu,China

Daily fine particulate(PM_2.5) 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 PM_2.5 mass concentrations were found during DSs（283.3μg/m³）,followed by FDs（212.7μg/m³）,HDs（187.3μg/m³）,and BBs（130.1μg/m³）.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 PM_2.5 from BBs showed high K⁺ but low SO₄^2-.FDs caused increases in K⁺ and enrichment in SO₄^2-.Ca²⁺ was abundant in DS samples.Ion-balance calculations indicated that PM_2.5 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 26.1μg/m³ during FDs,followed by BBs（23.6μg/m³）,HDs（19.6μg/m³）,and DSs（18.8μg/m³）. In contrast,elemental carbon（EC） concentration was more abundant during HDs（10.6μg/m³） and FDs （9.5μg/m³） than during BBs（6.2μg/m³） and DSs（6.0μg/m³）.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.     

Chemical characteristics and source apportionment of PM_(10) during a brown haze episode in Harbin, China

This study investigates the correlation between PM 10 and meteorological factors such as wind speed, atmospheric visibility, dew point, relative humidity, and ambient temperature during a brown haze episode. In order to identify the potential sources of PM 10 during brown haze episode, respirable particulate matter (PM 10 ) was collected during both non-haze days and haze days and further analyzed for metallic elements, ionic species, and carbonaceous contents. Among them, ionic species contributed 45-64% t...     

Variation of PM2.5 concentration in Hangzhou,China

This observational study investigates the variation of PM_2.5 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 PM_2.5 concentration varied greatly for different weather systems,with the highest PM_2.5 concentration associated with the post-cold-frontal system at 0.091 mg/m³ and the lowest PM_2.5 concentration with the easterlies system at 0.038 mg/m³,although the PM_2.5/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 PM_2.5 concentration of 0.117 mg/m³ 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 PM_2.5/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 PM_2.5 concentration based on weather system and pollution type.     

Assessment of heavy metal pollution characteristics and human health risk of exposure to ambient PM_(2.5) in Tianjin,China

To examine the features of heavy metal pollution of PM_(2.5)(particulate matter less than 2.5 μm) in Tianjin,China,as well as the exposure risk of PM_(2.5) to human health,we analyzed ambient PM_(2.5) samples collected from a campus of Nankai University in June,August,and October 2012.The concentrations of PM_(2.5) and heavy metals(Ni,Cu,Pb,Zn,Cr,Cd,Hg,As and Mn) in PM2.5 were analyzed by gravimetric analysis and inductively coupled plasma-mass spectrometry,respectively.The results show that the heavy metals contained in PM_(2.5) were,in descending order,Cu,Zn,Pb,Mn,Cr,Ni,Cd,As,and Hg.The proportion of Cd exceeded the secondary level of National Ambient Air Quality Standard of China(GB 3095-2012) by 1.3times,while others were within the limit.Enrichment factor analysis indicated that Cu,Zn,Cd,Pb,and Hg are mainly from anthropogenic sources.Principal component analysis indicated that the main sources of the heavy metals are vehicle exhaust,chemical waste,and coal-burning activities.The nine heavy metals which may cause health issues by exposure through the human respiratory system and should be further examined are Cr,Cd,As,Ni,Cu,Pb,Mn,Zn,and Hg,in the order of decreasing risk levels.With reference to the U.S.EPA standard the risk levels of all nine metals were below the acceptable level(10~(-6)/year).     

Molecular distribution and seasonal variation of hydrocarbons in PM2.5 from Beijing during 2006

Normal （n）-alkanes and polycyclic aromatic hydrocarbons （PAHs） in PM_2.5 were collected from Beijing in 2006 and analyzed using a thermal desorption-GC/MS technique. Annual average concentrations of n-alkanes and PAHs were 282±96 and 125± 150ng/m³, respectively: both were highest in winter and lowest in summer. C₁₉-C₂₅ compounds dominated the n-alkanes while benzo[b]fluoranthene, benzo[e]pyrene, and phenanthrene were the most abundant PAHs. The n-alkanes exhibited moderate correlations with organic carbon （OC） and elemental carbon （EC） throughout the year, but the relationships between the PAHs, OC and EC differed between the heating and non-heating seasons. The health risks associated with PAHs in winter were more than 40 times those in spring and summer even though the PM_2.5 loadings were comparable. Carbon preference index values （<1.5） indicated that the n-alkanes were mostly from fossil fuel combustion. The ratios of indeno[123-cd]pyrene to benzo[ghi]pyrelene in summer and spring were 0.58 ± 0.12 and 0.63 ± 0.09, respectively, suggesting that the PAHs mainly originated from motor vehicles, but higher ratios in winter reflected an increased influence from coal, which is extensively burned for domestic heating. A comprehensive comparison showed that PAH pollution in Beijing has decreased in the past 10 years.     

Characterization of summer PM_(2.5) aerosols from four forest areas in Sichuan,SW China

Aerosol samples were collected over 24 and 12 h to represent day/night aerosol characteristics in forest areas at Ya'an Baima Spring Scenic Area(BM),Panzhihua Cycas National Nature Reserve(PZ),Gongga Mountain National Nature Reserve(GG),and Wolong National Nature Reserve(WL),during the summers of 2010-2012.Mass and chemical component concentrations,including organic carbon,elemental carbon,and inorganic ions(F~-,Cl~-,NO_2~-,NO_3~-,SO_4~(2-),C_2O_4~(2-),PO_4~(3-),K~+,Na~+,Ca~(2+),Mg~(2+),and NH_4~+),of PM_(2.5) aerosols were measured.The average PM2.5 concentrations for 24 h were 72.42,104.89,20.55,and29.19 μg/m~3 at BM,PZ,GG,and WL,respectively.Organic matter accounted for 38.0-49.3%,while elemental carbon accounted for 2.0-5.7%of PM2.5 mass.The sum concentrations of SO_4~(2-),NH_4~+,and NO_3~-accounted for 23.0%,17.4%,22.1%,and 30.5%of PM2.5 mass at BM,PZ,GG,and WL,respectively.Soil dust was also an important source of PM2.5,accounting for 6.3%,17.0%,10.4%,and 19.1%of PM2.5 mass at BM,PZ,GG,and WL,respectively.These reconstructed masses accounted for 75.9-102.0%of PM2.5 mass from the four forest areas of SW China.     

Mass and isotopic concentrations of water-insoluble refractory carbon in total suspended particulates at Mt. Waliguan Observatory (China)

Mass concentration and isotopic values δ¹³C and ¹⁴C are presented for the water-insoluble refractory carbon (WIRC) component of total suspended particulates (TSP), collected weekly during 2003, as well as from October 2005 to May 2006 at the WMO-GAW Mt. Waliguan (WLG) site. The overall average WIRC mass concentration was (1183 ± 120) ng/m³ (n = 79), while seasonal averages were 2081 ± 1707 (spring), 454 ± 205 (summer), 650 ± 411 (autumn), and 1019 ± 703 (winter) ng/m³. Seasonal variations in WIRC mass concentrations were consistent with black carbon measurements from an aethalometer, although WIRC concentrations were typically higher, especially in winter and spring. The δ¹³C PDB value (−25.3 ± 0.8)‰ determined for WIRC suggests that its sources are C₃ biomass or fossil fuel combustion. No seasonal change in δ¹³C PDB was evident. The average percent Modern Carbon (pMC) for ¹⁴C in WIRC for winter and spring was (67.2 ± 7.7)% (n = 29). Lower pMC values were associated with air masses transported from the area east of WLG, while higher pMC values were associated with air masses from the Tibetan Plateau, southwest of WLG. Elevated pMC values with abnormally high mass concentrations of TSP and WIRC were measured during a dust storm event.