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Tan J.,University of Chinese Academy of Sciences | Tan J.,Tsinghua University | Tan J.,CAS Research Center for Eco Environmental Sciences | Duan J.,Chinese Research Academy of Environmental Sciences | And 7 more authors.
Science of the Total Environment

Foshan is a major international ceramic center and the most polluted city in the Pearl River Delta (PRD). Here we present the results of the first long-term PM2.5 (particles <2.5 μm) sampling and chemical characterization study of the city. A total of 2774 samples were collected at six sites from 2008 to 2014, and analyzed for water soluble species, elements and carbonaceous species. The major constituents of PM2.5 were sulfate, OC (Organic Carbon), nitrate, ammonium and EC (Elemental Carbon), which accounted for 50%-88% of PM2.5. PM2.5 and the most abundant chemical species decreased from 2008 to 2011, but rebounded in 2012-2013. After 2008, the chemical composition of PM2.5 changed dramatically due to the implementation of pollution control measures. From 2008 to 2011, SO4 2- and NO3 - were the two largest components; subsequently, however, OC was the largest component. The respective contributions of SO4 2-, NO3 - and OC to the sum of water soluble species and carbonaceous species were 30.5%, 22.9% and 19.9% in 2008; and 20.2%, 16.5% and 30.2% in 2014. Distinct differences in nitrate and sulfate, and in mass ratio [NO3 -]/[SO4 2-] imply that mobile sources tended to more important in Foshan during 2012-2014. The results indicate that pollution control measures implemented during 2008-2014 had a large effect on anthropogenic elements (Pb, As, Cd, Zn and Cu) and water soluble species, but little influence on crustal elements (V, Mn, Ti, Ba and Fe) and carbonaceous species. The PMF method was used for source apportionment of PM2.5. Industry (including the ceramic industry and coal combustion), vehicles and dust were the three most important sources and comprised 39.2%, 20.0% and 18.4% of PM2.5 in 2008, respectively. However, secondary aerosols, vehicles and industry were the three most important sources and comprised 29.5%, 22.4% and 20.4% of PM2.5 in 2014, respectively. During the seven year study interval, the contributions of primary sources (industry and dust) decreased significantly, but secondary sources increased dramatically. Industry, dust and vehicles contributed 36.6 μg m-3, 13.9 μg m-3, and 9.2 μg m-3 to the reduction of PM2.5, respectively. © 2016 Elsevier B.V. Source

Tan J.,University of Chinese Academy of Sciences | Guo S.,Guangxi University | Ma Y.,Tsinghua University | He K.,Tsinghua University | And 3 more authors.
Environmental Monitoring and Assessment

Foshan is the most air-polluted city in Pearl River Delta. Non-methane hydrocarbons (NMHCs) were investigated for the first time in Foshan in winter 2008. Ethene, ethane, ethyne, propane, i-pentane, and toluene were the most abundant hydrocarbons and observed to be higher in Foshan than those in many other cities in China. Different from other cities, ethene and ethane were observed to be the two highest compounds in Foshan. Generally, the most abundant hydrocarbons showed high mixing ratios in the morning (0930-1030 hours), decreased to the lowest level in the afternoon (1430-1530 hours), and increased to higher value in the evening (1930-2030 hours). But i-pentane exhibited a different diurnal pattern with the highest level (13.4 ± 5.8 ppbv) in the afternoon, implying the acceleration of solvent evaporation resulting from higher temperature. Correlation coefficients (R 2= 66% for n= 6 at 95% confidence level) of the individual hydrocarbons with ethyne and i-pentane indicated vehicular emissions were the main sources of ethene, propene, i-butene, isoprene, benzene and toluene, while gasoline evaporation was responsible for n-pentane, n-hexane, and n-heptane. The good correlation of most of the hydrocarbons with ethyne, indicating vehicular emissions, were the main sources of NMHCs. B/T ratio was 0.36 ± 0.06, implying vehicular emissions acted as the major contributors as well as additional emissions of toluene emitted from solvent usage. According to investigation, it also suggested that LPG leakage was the main source of propane, while NG leakage was responsible for ethane in Foshan City. © 2011 Springer Science+Business Media B.V. Source

Wang Q.-Q.,University of Chinese Academy of Sciences | Tan J.-H.,University of Chinese Academy of Sciences | Ma Y.-L.,Tsinghua University | He K.-B.,Tsinghua University | And 4 more authors.
Zhongguo Huanjing Kexue/China Environmental Science

To investigate the characteristics of heavy metals in fine particles (PM 2.5) during winter in Foshan, a typical industrial city in Pearl River Delta, 24h integrated PM 2.5 samples were simultaneously collected at a pair of sites, one urban site and one background site, and 16 elements (Fe, Ti, Zn, V, Mn, Cu, As, Rb, Sr, Cd, Cs, Ba, Hg, Tl, Pb and Bi) of the samples were analyzed. Heavy metals at the urban site were at a high level of pollution, and generally higher than those at the background site, except Fe, Ti, Sr, and Cd. Compared with the national standard of heavy metals, the concentrations of As, and Cd were much higher and Pb exceeded slightly at the urban site, while those of As and Cd at the background site were much higher. The enrichment factors of Zn, Cu, As, and Pb were greater than 10, indicating that they were mainly from anthropogenic activities. There were clear increases in the concentrations of heavy metals during the haze period, while their daily variations at the urban site were more consistent than those in the background site. Air mass back trajectory analysis showed that the concentration distribution of heavy metals was affected by four kinds of air masses: the ones close to or starting from the northeast of Guangdong or Fujian, the ones along the coast of Guangdong and Fujian, the ones from marine and the ones from Jiangxi. The first kind of air masses increased the heavy metals concentrations, while the others decreased the levels. Source

Guo S.,Guangxi University | Guo S.,University of Chinese Academy of Sciences | Tan J.,Guangxi University | Tan J.,Tsinghua University | And 4 more authors.
Atmospheric Research

Atmospheric non-methane hydrocarbons (NMHCs) were firstly studied during high PM10 episodes and normal days in December 2008 in Foshan, China. Ethyne, ethene, i-pentane, toluene, ethane and propane are six abundant hydrocarbons, accounting for round 80% of total NMHCs. Both diurnal variations and concentration ratios of morning (evening)/afternoon implied vehicular emission for most hydrocarbons. Correlation coefficients (R2) of ethene, propene, i-butene, benzene, toluene and i-/n-butanes with ethyne were 0.60-0.88 (they were 0.64-0.88 during high PM10 episode and 0.60-0.85 in normal days) except for ethene and i-butene in normal days, indicating these hydrocarbons are mainly related to vehicular emission. It suggests liquefied petroleum gas (LPG) and natural gas (NG) leakages are responsible for propane and ethane, respectively. The measured mean benzene/toluene (B/T) ratio (wt/wt) was 0.45±0.29 during total sampling periods together with R2 analysis, again indicating vehicular emission is main contributor to ambient hydrocarbons. And the lower B/T ratio (0.29±0.11) during high PM10 episodes than that (0.75±0.29) in normal days is likely caused by air transport containing low B/T value (0.23) from Guangzhou as well as solvent application containing toluene in Foshan. © 2011 Elsevier B.V. Source

Tan J.-H.,University of Chinese Academy of Sciences | Tan J.-H.,Tsinghua University | Duan J.-C.,Chinese Research Academy of Environmental Sciences | Ma Y.-L.,Tsinghua University | And 5 more authors.
Science of the Total Environment

Foshan is a ceramics manufacturing center in the world and the most polluted city in the Pearl River Delta (PRD) in southern China measured by the levels of atmospheric heavy metals. PM2.5 samples were collected in Foshan in winter 2008. Among the 22 elements and ions analyzed, 7 heavy metals (Zn, V, Mn, Cu, As, Cd and Pb) were studied in depth for their levels, spatiotemporal variations and sources. The ambient concentrations of the heavy metals were much higher than the reported average concentrations in China. The levels of Pb (675.7±378.5ng/m3), As (76.6±49.1ng/m3) and Cd (42.6±45.2ng/m3) exceeded the reference values of NAAQS (GB3095-2012) and the health guidelines of the World Health Organization. Generally, the levels of atmospheric heavy metals showed spatial distribution as: downtown site (CC, Chancheng District)>urban sites (NH and SD, Nanhai and Shunde Districts)>rural site (SS, Shanshui District). Two sources of heavy metals, the ceramic and aluminum industries, were identified during the sampling period. The large number of ceramic manufactures was responsible for the high levels of atmospheric Zn, Pb and As in Chancheng District. Transport from an aluminum industry park under light north-west winds contributed high levels of Cd to the SS site (Shanshui District). The average concentration of Cd under north-west wind was 220ng/m3, 20.5times higher than those under other wind directions. The high daily maximum enrichment factors (EFs) of Cd, Pb, Zn, As and Cu at all four sites indicated extremely high contamination by local emissions. Back trajectory analysis showed that the heavy metals were also closely associated with the pathway of air mass. A positive matrix factorization (PMF) method was applied to determine the source apportionment of these heavy metals. Five factors (industry including the ceramic industry and coal combustion, vehicle emissions, dust, transportation and sea salt) were identified and industry was the most important source of atmospheric heavy metals. The present paper suggests a control policy on the four heavy metals Cd, Pb, Zn, and Cu, and suggests the inclusion of As in the ceramic industry emission standard in the future. © 2014 Elsevier B.V. Source

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