Chemical Composition of PM₁₀ and PM_2.5 Collected at Ground Level and 100 Meters during a Strong Winter-Time Pollution Episode in Xi'an, China

Abstract

An intensive sampling of aerosol particles from ground level and 100 m was conducted during a strong pollution episode during the winter in Xi'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: PM10 (PM with aerodynamic diameter < or =10 microm) exceeded the China National Air Quality Standard Class II value on three occasions, and PM2.5 (PM with aerodynamic diameter < or =2.5 microm) exceeded the daily U.S. National Ambient Air Quality Standard more than 10 times. The PM10 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 PM2.5 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.

Characteristics of Organic and Elemental Carbon in PM2.5 and PM0.25 in Indoor and Outdoor Environments of a Middle School: Secondary Formation of Organic Carbon and Sources Identification

“…As also shown in Table 2, for indoors, TC, OC, and EC accounted for on average 21.5%, 15.9%, and 5.6% of PM2.5 mass loading, and 29.4%, 22.6%, and 6.8% of PM0.25 mass loading, respectively; corresponding for outdoors, TC, OC, and EC accounted for on average 20.1%, 14.8%, and 5.3% of PM2.5 mass loading, and 29.6%, 22.5%, and 7.3% of PM0.25 mass loading, respectively. These also showed that TC, OC, and EC tend to concentrate in finer particle fraction (PM0.25), consistent with previous studies [3,13,49]. .…”

“…Total carbon (i.e., the sum of OC and EC or carbonaceous aerosol) contribution to the mean China urban aerosol mass ranges from 20% to 50% in both fine and coarse fractions [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. OC and EC have long been studied to investigate their effects on the regional climate, air quality, and visibility in China [16][17][18].…”

Long-term trends of chemical characteristics and sources of fine particle in Foshan City, Pearl River Delta: 2008–2014

“…where j and k are the two sampling sites, p is the number of investigated components, and x ij and x ik are the average mass concentrations of chemical component i at sites j and k (Shen et al, 2011;Tan et al, 2014b). A value close zero indicates that the two sites have very similar levels of pollutants.…”

A Case Study of Chemical Characteristics of Daytime and Nighttime Ambient Particles in Shanghai, China

“…Total carbon (the sum of OC and EC) contribution to urban aerosol mass ranges from 20% to 50% in both fine and coarse fractions in China [21][22][23][24]. The average concentrations of PM2.5 carbonaceous species were given in for Jinshan nighttime.…”