Variations of Particle Size Distribution, Black Carbon, and Brown Carbon during a Severe Winter Pollution Event over Xi'an, China

Real-time particulate matter (PM) size distributions, 4-hour time resolution, PM2.5, carbonaceous materials, and their optical properties were measured during a severe pollution event in Xi'an, China High PM2.5 /PM10 ratios were observed on both pollution (0.83) and non-pollution (0.73) days, emphasizing the abundance of fine particles during sampling days. The particle number (PN) first peaked with a wide size range (30-100 nm) before morning rush hours (approximately 01:00-05:00) on pollution and non-pollution days, demonstrating that PN was governed by the accumulation of freshly emitted diesel particles and characterized by distinct aerosol condensation growth. By contrast, the second peak time and size range differed between pollution and non-pollution days because of different formation mechanisms The light-absorbing coefficients of both black carbon (BC, b(abs-880nm,BC)) and brown carbon (BrC, b(abs-370nm, BrC)) were high on pollution days and decreased to approximately half of those values on non-pollution days, indicating that the degree of light absorption is reduced by rain. The diurnal variation in b(abs-880nm, BC) pollution peaked with traffic on January 1 and 2. By contrast, it remained in relatively stable and high ranges (120-160 Mm(-1)) in the second period (January 3-5) without traffic peaks, illustrating that the dominant sources changed even during the same pollution period. High values of both b(abs-370nm, BrC) and b(abs-880nm,) (BC )coincided in the afternoon and evening due to emissions from primary sources, and abundant aqueous secondary organic carbon, respectively. A highly variable mass absorption coefficient of BrC also indicated the variety of fuel combustion sources of primary BrC in Xi'an

Fine Particulate Matter Constituents and Cardiopulmonary Mortality in a Heavily Polluted Chinese City

BACKGROUND: Although ambient fine particulate matter (PM(2.5); particulate matter &lt;= 2.5 mu m in aerodynamic diameter) has been linked to adverse human health effects, the chemical constituents that cause harm are unknown. To our knowledge, the health effects of PM(2.5) constituents have not been reported for a developing country. OBJECTIVES: We examined the short-term association between PM(2.5) constituents and daily mortality in Xi&#39;an, a heavily polluted Chinese city. METHODS: We obtained daily mortality data and daily concentrations of PM(2.5), organic carbon (OC), elemental carbon (EC), and 10 water-soluble ions for 1 January 2004 through 31 December 2008. We also measured concentrations of fifteen elements 1 January 2006 through 31 December 2008. We analyzed the data using overdispersed generalized linear Poisson models. RESULTS: During the study period, the mean daily average concentration of PM(2.5) in Xi&#39;an was 182.2 mu g/m(3). Major contributors to PM(2.5) mass included OC, EC, sulfate, nitrate, and ammonium. After adjustment for PM(2.5) mass, we found significant positive associations of total, cardiovascular, or respiratory mortality with OC, EC, ammonium, nitrate, chlorine ion, chlorine, and nickel for at least one lag period. Nitrate demonstrated stronger associations with total and cardiovascular mortality than PM(2.5) mass. For a 1-day lag, interquartile range increases in PM(2.5) mass and nitrate (114.9 and 15.4 mu g/m(3), respectively) were associated with 1.8% [95% confidence interval (CI): 0.8%, 2.8%] and 3.8% (95% CI: 1.7%, 5.9%) increases in total mortality, CONCLUSIONS: Our findings suggest that PM(2.5) constituents from the combustion of fossil fuel may have an appreciable influence on the health effects attributable to PM(2.5) in Xi&#39;an.</p

Elemental compositions of PM2.5 and TSP in Lijiang, southeastern edge of Tibetan Plateau during pre-monsoon period

PM2.5 and total suspended particulate (TSP) samples were collected at Lijiang, southeastern Tibetan Plateau, China. Sixteen elements (Al, Si, S, K, Ca, Cr, Mn, Ti, Fe, Ni, Zn, As, Br, Sb, Pb and Cu) were analyzed to investigate their elemental compositions during the pre-monsoon period. The results showed that Ca was the most abundant element in both PM2.5 and TSP samples. The enrichment factors (EFs) of Si, Ti, Ca, Fe, K and Mn were all below 10 for both PM2.5 and TSP, and these elements also had lower PM2.5/TSP ratios (0.32-0.34), suggesting that they were mainly derived from crustal sources. Elements Cu, Zn, S, Br and Sb showed strong enrichment in PM2.5 and TSP samples, with their PM2.5/TSP ratios ranging from 0.66 to 0.97, indicating that they were enriched in the fine fractions and influenced by anthropogenic sources. Analysis of the wind field at 500 hPa and calculations of back trajectories indicated that Al, Si, Ca, Ti, Cr, Mn and Fe can be influenced by transport from northwestern China during the dust-storm season, and that S, K, Ni, Br and Pb reached high concentrations during westerly transport from south Asia. Combined with the principle component analysis and correlation analysis, elements of PM2.5 samples were mainly from crustal sources, biomass burning emissions and regional traffic-related sources.</p

Soil-derived sulfate in atmospheric dust particles at Taklimakan desert

Dust-associated sulfate is believed to be a key species which can alter the physical and chemical properties of dust particles in the atmosphere. Its occurrence in the particles has usually been considered to be the consequence of particles&#39; aging in the air although it is present in some crustal minerals. Our observation at the north and south edge of Taklimakan desert, one of the largest dust sources in the Northern Hemisphere, during a dust episode in April 2008 revealed that sulfate in atmospheric dust samples most likely originated directly from surface soil. Its TSP, PM10 and PM2.5 content was proportional to samples&#39; mass and comprised steadily about 4% in the differently sized samples, the ratio of elemental sulfur to iron was approximately constant 0.3, and no demonstrable influence of pollutants from fossil fuel combustion and biomass burning was detected. These results suggest that sulfate could be substantially derived from surface soil at the desert area and the lack of awareness of this origin may impede accurate results in any investigation of atmospheric sulfur chemistry associated with Taklimakan dust and its subsequent local, regional and global effects on the atmosphere.</p

Particle size distribution and air pollution patterns in threeurban environments in Xi’an, China

Three urban environments, office, apartment and restaurant, were selected to investigate the indoor and outdoor air quality as an inter-comparison in which CO2, particulate matter (PM) concentration and particle size ranging were concerned. In this investigation, CO2 level in the apartment (623 ppm) was the highest among the indoor environments and indoor levels were always higher than outdoor levels. The PM10 (333 lg/m3), PM2.5 (213 lg/m3), PM1 (148 lg/m3) concentrations in the office were 10&ndash;50 % higher than in the restaurant and apartment, and the three indoor PM10 levels all exceeded the China standard of 150 lg/m3. Particles ranging from 0.3 to 0.4 lm, 0.4 to 0.5 lm and 0.5 to 0.65 lm make largest contribution to particle mass in indoor air, and fine particles number concentrations were much higher than outdoor levels. Outdoor air pollution is mainly affected by heavy traffic, while indoor air pollution has various sources. Particularly, office environment was mainly affected by outdoor sources like soil dust and traffic emission; apartment particles were mainly caused by human activities; restaurant indoor air quality was affected by multiple sources among which cooking-generated fine particles and the human steam are main factors.</p

Chemical composition and sources of PM2.5 and TSP collected at Qinghai Lake during summertime

PM2.5 and total suspended particulate (TSP) samples were collected from June to September 2010 at Qinghai Lake, northeastern Tibetan Plateau. The concentrations of major water-soluble ions, 10 elements, elemental carbons (ECs) and organic carbons (OCs) were quantified. Mass concentrations of PM2.5 and TSP were 21.27&plusmn;10.70&mu;gm-3 and 41.47&plusmn;20.25&mu;gm-3, respectively, and the mean ratio of PM2.5/TSP was 0.51. The greatest anion and cation in both PM2.5 and TSP samples were SO42- and Ca2+, respectively. Crustal elements, such as Ca, Fe and K, were the main elements in our aerosol samples, and their enrichment factors (EFs) were lower than 10. EFs for Pb, As, and Zn were greater than 10, indicating that they were influenced by anthropogenic sources. EC concentrations were 0.33&plusmn;0.17&mu;gm-3 and 0.47&plusmn;0.28&mu;gm-3, whereas OC concentrations were 1.49&plusmn;0.63&mu;gm-3 and 2.30&plusmn;0.95&mu;gm-3 in PM2.5 and TSP, respectively. Based on the calculated ratios of EC/TC and K+/EC, most of the ECs were found to be related to biomass burning emissions. Because of the pollution from local sources, the ratios of OC/EC were 4.77&plusmn;1.32 and 5.23&plusmn;1.39 in PM2.5 and TSP, respectively, which were lower than those of other remote sites. Salt particles produced by the salty lake reacted with acid gases and caused most of the nitrates and a small fraction of sulfate to be distributed in coarse mode; Cl deficit was also observed in our aerosol samples. Results of backward trajectories and correlation analysis show that the concentrations of SO42-, OCs, As, Pb, and Zn, were influenced by the long-distance transport from eastern China.</p

Personal exposure of PM2.5 emitted from solid fuels combustion forhousehold heating and cooking in rural Guanzhong Plain, northwesternChina

Household solid fuel combustion for heating and cooking in rural areas is an important source of fine particulate matter (PM2.5) in northwestern China, which largely contributes to PM2.5 personal exposure concentrations during the cold winter. There is a general lack of understanding about the personal exposure to PM2.5 and to its chemical components emitted from domestic solid fuel combustion in northwestern Chinese rural populations. In this work, personal exposure to PM2.5 was sampled using a portative device together with fixed indoor and outdoor fixed samplings in Guanzhong Plain in December 2016 for the purpose of characterizing personal exposure to PM2.5 as a function of different solid fuels used in rural households. The average housewife&#39;s personal exposure to PM2.5 concentration was 263.4 &plusmn; 105.8 &mu;g m&minus;3 (1&sigma;, n = 30), which was about 40% higher than the values found indoors (186.5 &plusmn; 79.5 &mu;g m&minus;3, 1&sigma;, n = 30) and outdoors (191.0 &plusmn; 85.3 &mu;g m&minus;3, 1&sigma;, n = 30). High personal exposure PM2.5 levels were mainly related to the ignition of solid fuels for heating and cooking. Correlations among personal exposure, indoor and outdoor PM2.5 levels and their mutual ratios were computed to investigate how personal exposure to fine aerosols can be related to microenvironmental PM2.5 levels and to individual activities. The results showed that households using electric power for heating and cooking were characterized by an average personal exposure PM2.5 value of 156.8 &plusmn; 36.6 &mu;g m&minus;3 (1&sigma;, n = 6) while personal exposure to PM2.5 in households using solid fuels was twice higher (310.8 &plusmn; 90.4 &mu;g m&minus;3, 1&sigma;, n = 24). Solid fuel combustion products and related secondary formed species dominated PM2.5 mass in personal exposure, indoor and outdoor samples. Motor vehicle emission and various dust sources were two other main contributors identified. Our results demonstrated that the use of clean energy could be an effective measure to reduce personal exposure levels of PM2.5 emitted from domestic solid fuels combustion in winter in rural areas, which implied that the government should speed up the upgrade of the heating and cooking equipment fleet to protect the health of rural residents in northwestern China

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

Normal (n)-alkanes and polycyclic aromatic hydrocarbons (PAHs) in PM2.5 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 +/- 150 ng/m(3), respectively: both were highest in winter and lowest in summer. C-19-C-25 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 PM2.5 loadings were comparable. Carbon preference index values (&lt;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.</p

Chemical Composition of PM(10) and PM(2.5) Collected at Ground Level and 100 Meters during a Strong Winter-Time Pollution Episode in Xi'an, China

An intensive sampling of aerosol particles from ground level and 100 m was conducted during a strong pollution episode during the winter in Xi&#39;an, China. Concentrations of water-soluble inorganic ions, carbonaceous compounds, and trace elements were determined to compare the composition of particulate matter (PM) at the two heights. PM mass concentrations were high at both stations: PM(10) (PM with aerodynamic diameter &lt;= 10 mu m) exceeded the China National Air Quality Standard Class II value on three occasions, and PM(2.5) (PM with aerodynamic diameter &lt;= 2.5 mu m) exceeded the daily U.S. National Ambient Air Quality Standard more than 10 times. The PM(10) organic carbon (OC) and elemental carbon (EC) were slightly lower at the ground than at 100 m, both in terms of concentration and percentage of total mass, but OC and EC in PM(2.5) exhibited the opposite pattern. Major ionic species, such as sulfate and nitrate, showed vertical variations similar to the carbonaceous aerosols. High sulfate concentrations indicated that coal combustion dominated the PM mass both at the ground and 100 m. Correlations between K(+) and OC and EC at 100 m imply a strong influence from suburban biomass burning, whereas coal combustion and motor vehicle exhaust had a greater influence on the ground PM. Stable atmospheric conditions apparently led to the accumulation of PM, especially at 100 m, and these conditions contributed to the similarities in PM at the two elevations. Low coefficient of divergence (CD) values reflect the similarities in the composition of the aerosol between sites, but higher CDs for fine particles compared with coarse ones were consistent with the differences in emission sources between the ground and 100 m.</p