Abstract. Dicarboxylic acids (C 2 -C 10 ), metals, elemental carbon (EC), organic carbon (OC), and stable isotopic compositions of total carbon (TC) and total nitrogen (TN) were determined for PM 10 samples collected at three urban and one suburban sites of Baoji, an inland city of China, during winter and spring 2008. Oxalic acid (C 2 ) was the dominant diacid, followed by succinic (C 4 ) and malonic (C 3 ) acids. Total diacids in the urban and suburban areas were 1546 ± 203 and 1728 ± 495 ng m −3 during winter and 1236 ± 335 and 1028 ± 193 ng m −3 during spring. EC in the urban and the suburban atmospheres were 17±3.8 and 8.0± 2.1 µg m −3 during winter and 20 ± 5.9 and 7.1 ± 2.7 µg m −3 during spring, while OC at the urban and suburban sites were 74 ± 14 and 51 ± 7.9 µg m −3 in winter and 51 ± 20 and 23 ± 6.1 µg m −3 in spring. Secondary organic carbon (SOC) accounted for 38 ± 16% of OC in winter and 28 ± 18% of OC in spring, suggesting an enhanced photochemical production of secondary organic aerosols in winter under an inversion layer development. Total metal elements in winter and spring were 34 ± 10 and 61 ± 27 µg m −3 in the urban air and 18 ± 7 and 32 ± 23 µg m −3 in the suburban air. A linear correlation (r 2 > 0.8 in winter and r 2 > 0.6 in spring) was found between primary organic carbon (POC) and Ca 2+ /Fe, together with a strong dependence of pH value of sample extracts on water-soluble inorganic carbon, suggesting fugitive dust as an important source of the airborne particles. Polycyclic aromatic hydrocarbons (PAHs), sulfate, and Pb in the Correspondence to: G. Wang (wanggh@ieecas.cn) samples well correlated each other (r 2 > 0.6) in winter, indicating an importance of emissions from coal burning for house heating. Stable carbon isotope compositions of TC (δ 13 C) became higher with an increase in the concentration ratios of C 2 /OC due to aerosol aging. In contrast, nitrogen isotope compositions of TN (δ 15 N) became lower with an increases in the mass ratios of NH + 4 /PM 10 and NO − 3 /PM 10 , which is possibly caused by an enhanced adsorption and/or condensation of gaseous NH 3 and HNO 3 onto particles.

Abstract. Size-segregated (9 stages) n-alkanes, polycyclic aromatic hydrocarbons (PAHs) and hopanes in the urban (Baoji city in inland China), mountain (Mt. Tai in east coastal China) and marine (Okinawa Island, Japan) atmospheres over East Asia were studied using a GC/MS technique. Ambient concentrations of n-alkanes (1698±568 ng m −3 in winter and 487±145 ng m −3 in spring), PAHs (536±80 and 161±39 ng m −3 ), and hopanes (65±24 and 20±2.4 ng m −3 ) in the urban air are 1-2 orders of magnitude higher than those in the mountain aerosols and 2-3 orders of magnitude higher than those in the marine samples. Mass ratios of nalkanes, PAHs and hopanes clearly demonstrate coal-burning emissions as their major source. Size distributions of fossil fuel derived n-alkane, PAHs and hopanes were found to be unimodal in most cases, peaking at 0.7-1.1 µm size. In contrast, plant wax derived n-alkanes presented a bimodal distribution with two peaks at the sizes of 0.7-1.1 µm and >4.7 µm in the summer mountain and spring marine samples. Among the three types of samples, geometric mean diameter (GMD) of the organics in fine mode (<2.1 µm) was found to be smallest (av. 0.63 µm in spring) for the urban samples and largest (1.01 µm) for the marine samples, whereas the GMD in coarse mode (≥2.1 µm) was found to be smallest (3.48 µm) for the marine aerosols and largest (4.04 µm) for the urban aerosols. The fine mode GMDs of Correspondence to: G. Wang (wanggh@ieecas.cn) the urban and mountain samples were larger in winter than in spring and summer. Moreover, GMDs of 3-and 4-ring PAHs were larger than those of 5-and 6-ring PAHs in the three types of atmospheres. Such differences in GMDs can be interpreted by the repartitioning of organic compounds and the coagulation and hygroscopic growth of particles during a long-range transport from the inland continent to the marine area, as well as the difference in their sources among the three regions.

4 at Mt. Tai may suggest the changes in chemical composition of the atmosphere over east China due to sharply increasing vehicle emission. pH values of the water-extracts of PM 10 samples indicate that at the two mountain sites aerosols transported from the south regions are more acidic than those from the north and more acidic at Mt. Tai than at Mt. Hua during the non-dust storm period. During the dust storm event particle mass, OC, Na + , K + , Mg 2+ and Ca 2+ at both sites increased by a factor of 1-9, while EC, NO Linear regression for ion equivalents in fine particles indicates that ammonium exists in the forms of NH 4 NO 3 and NH 4 HSO 4 at Mt. Hua and NH 4 NO 3 and (NH 4 ) 2 SO 4 at Mt. Tai during both the nonevent and the event periods. While the regression for coarse mode of Ca 2+ suggests a close coupling of dust with nitrate during the nonevent time and with sulfate during the dust-storm period. pH values of the sizeresolved samples further suggest that during the nonevent period most acidic particles at Mt. Hua are in the range of 0.7-1.1 µm, while those at Mt. Tai are in the range of 1.1-2.1 µm. Aerosols at both sites became alkaline during the event, but the Mt. Tai particles still showed a lower pH value.