Chemical characterization of aerosols at the summit of Mountain Tai in the middle of central east China
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Abstract. PM2.5 and TSP samples were collected at the summit of Mountain Tai (MT) (1534 m a.s.l.) in spring 2006/2007 and summer 2006 to investigate the characteristics of aerosols over central eastern China. For comparison, aerosol samples were also collected at Tazhong, Urumqi, Tianchi in Xinjiang in northwestern China, Duolun and Yulin in northern China, and two urban sites in the megacities, Beijing and Shanghai, in spring 2007. Daily mass concentrations of TSP and PM2.5 ranged from 39.6276.9 g/m3 and 17.2235.7 g/m3 respectively at the summit of MT. Averaged concentrations of PM2.5 showed a pronounced seasonal variation with higher concentration in summer than spring. 17 water-soluble ions (SO42, NO3, Cl, F, PO43, NO2, CH3COO, CH2C2O42, C2H4C2O42, HCOO, MSA, C2O42, NH4+, Ca2+, K+, Mg2+, Na+), and 19 elements of 176 samples from MT were measured. SO42, NO3, and NH4+ were the major water-soluble species in PM2.5, accounting for 61.5% and 73.8% of the total measured ions in spring and summer, respectively. The average ratio of PM2.5/TSP was 0.37(2006) and 0.49(2007) in spring, while up to 0.91 in summer, suggesting that aerosol particles were primarily comprised of fine particles in summer and of considerable coarse particles in spring. Crustal elements (e.g., Ca, Mg, Al, Fe, etc.) showed higher concentration in spring than summer, while most pollution species (SO42, NO3, K+, NO2, NH4+, Cl, organic acids, Pb, Zn, Cd, and Cr) from local/regional anthropogenic emissions and secondary formation presented higher concentration in summer. The ratio of Ca/Al and back trajectories of air mass suggested the impact of Asian dust from Gobi and deserts on the air quality in this region. The high concentration of K+ in aerosols (4.56 g/m3) and its good correlation with black carbon (r = 0.90), oxalic acid (r = 0.87), and Cl (r = 0.71) were due to the severe pollution from biomass burning, which was proved to be a main source of fine particles over central eastern China in summer. Biomass burning contributed 36.71% of PM2.5 in mass in summer. As and Pb were two of the most enriched elements, especially in spring both for TSP and PM2.5, which revealed that the long-range transport of aerosols spread the heavy pollution from coal burning everywhere over China. Anthropogenic aerosols at MT were evidently rather severe at MT, though it has been declared by UNESCO to be a World Heritage site.
