References

ACP

Atmospheric Chemistry and Physics

ACP

1680-7324

Copernicus GmbH

Göttingen, Germany

10.5194/acp-12-1377-2012

Spatial and seasonal variability of PM2.5 acidity at two Chinese megacities: insights into the formation of secondary inorganic aerosols

¹ Zhao

¹ Ma

¹ Duan

¹ Yang

² Shi

³ Chen

⁴

State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China

Key Laboratory of Computational Geodynamics, College of Earth Science, Graduate University of Chinese Academy of Sciences, Beijing 100049, China

School of Geography, Earth and Environmental Science, University of Birmingham, Edgbaston Birmingham B15 2TT, UK

Chongqing Environmental Protection Bureau, Chongqing 401147, China

06 02 2012

12 3 1377 1395

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Aerosol acidity is one of the most important parameters influencing atmospheric chemistry and physics. Based on continuous field observations from January 2005 to May 2006 and thermodynamic modeling, we investigated the spatial and seasonal variations in PM2.5 acidity in two megacities in China, Beijing and Chongqing. Spatially, PM2.5 was generally more acidic in Chongqing than in Beijing, but a reverse spatial pattern was found within the two cities, with more acidic PM2.5 at the urban site in Beijing whereas the rural site in Chongqing. Ionic compositions of PM2.5 revealed that it was the higher concentrations of NO3− at the urban site in Beijing and the lower concentrations of Ca2+ within the rural site in Chongqing that made their PM2.5 more acidic. Temporally, PM2.5 was more acidic in summer and fall than in winter, while in the spring of 2006, the acidity of PM2.5 was higher in Beijing but lower in Chongqing than that in 2005. These were attributed to the more efficient formation of nitrate relative to sulfate as a result of the influence of Asian desert dust in 2006 in Beijing and the greater wet deposition of ammonium compared to sulfate and nitrate in 2005 in Chongqing. Furthermore, simultaneous increase of PM2.5 acidity was observed from spring to early summer of 2005 in both cities. This synoptic-scale evolution of PM2.5 acidity was accompanied by the changes in air masses origins, which were influenced by the movements of a subtropical high over the northwestern Pacific in early summer. Finally, the correlations between [NO3−]/[SO42−] and [NH4+]/[SO42−] suggests that under conditions of high aerosol acidity, heterogeneous reactions became one of the major pathways for the formation of nitrate at both cities. These findings provided new insights in our understanding of the spatial and temporal variations in aerosol acidity in Beijing and Chongqing, as well as those reported in other cities in China.

References 1

% vor jede Referenz Aas, W., Shao, M., Jin, L., Larssen, T., Zhao, D. W., Xiang, R. J., Zhang, J. H., Xiao, J. S., and Duan, L.: Air concentrations and wet deposition of major inorganic ions at five non-urban sites in China, 2001–2003, Atmos. Environ., 41, 1706–1716, http://dx.doi.org/10.1016/j.atmosenv.2006.10.030doi:10.1016/j.atmosenv.2006.10.030, 2007.

% vor jede Referenz Adams, P. J., Seinfeld, J. H., and Koch, D. M.: Global concentrations of tropospheric sulfate, nitrate, and ammonium aerosol simulated in a general circulation model, J. Geophys. Res.-Atmos., 104, 13791–13823, 1999.

% vor jede Referenz Amdur, M. O. and Chen, L. C.: Furnace-generated acid aerosols – speciation and pulmonary effects, Environ. Health Perspect., 79, 147–150, 1989.

% vor jede Referenz Arimoto, R., Duce, R. A., Savoie, D. L., Prospero, J. M., Talbot, R., Cullen, J. D., Tomza, U., Lewis, N. F., and Jay, B. J.: Relationships among aerosol constituents from Asia and the North Pacific during PEM-West A, J. Geophys. Res.-Atmos., 101, 2011–2023, 1996.

% vor jede Referenz Asman, W. A. H., Sutton, M. A., and Schjorring, J. K.: Ammonia: emission, atmospheric transport and deposition, New Phytol., 139, 27–48, 1998.

% vor jede Referenz Beijing Municipal Bureau of Statistics: Beijing statistical Yearbook, http://www.bjstats.gov.cn/tjnj/2006-tjnj, 2006 (in Chinese).

% vor jede Referenz Bergin, M. H., Cass, G. R., Xu, J., Fang, C., Zeng, L. M., Yu, T., Salmon, L. G., Kiang, C. S., Tang, X. Y., Zhang, Y. H., and Chameides, W. L.: Aerosol radiative, physical, and chemical properties in Beijing during June 1999, J. Geophys. Res.-Atmos., 106, 17969–17980, 2001.

% vor jede Referenz Boucher, O. and Anderson, T. L.: General circulation model assessment of the sensitivity of direct climate forcing by anthropogenic sulfate aerosols to aerosol size and chemistry, J. Geophys. Res.-Atmos., 100, 26117–26134, 1995.

% vor jede Referenz Chan, C. K. and Yao, X.: Air pollution in mega cities in China, Atmos. Environ., 42, 1–42, http://dx.doi.org/10.1016/j.atmosenv.2007.09.003doi:10.1016/j.atmosenv.2007.09.003, 2008.

% vor jede Referenz Cheung, H. C., Wang, T., Baumann, K., and Guo, H.: Influence of regional pollution outflow on the concentrations of fine particulate matter and visibility in the coastal area of southern China, Atmos. Environ., 39, 6463–6474, http://dx.doi.org/10.1016/j.atmosenv.2005.07.033doi:10.1016/j.atmosenv.2005.07.033, 2005.

% vor jede Referenz Chongqing Municipal Bureau of Statistics: Chongqing statistical Yearbook, http://www.cqtj.gov.cn/tjnj/2006/, 2006 (in Chinese).

% vor jede Referenz Chou, C. C. K., Lee, C. T., Yuan, C. S., Hsu, W. C., Lin, C. Y., Hsu, S. C., and Liu, S. C.: Implications of the chemical transformation of Asian outflow aerosols for the long-range transport of inorganic nitrogen species, Atmos. Environ., 42, 7508–7519, http://dx.doi.org/10.1016/j.atmosenv.2008.05.049doi:10.1016/j.atmosenv.2008.05.049, 2008.

% vor jede Referenz Chu, S. H.: PM$_2.5$ episodes as observed in the speciation trends network, Atmos. Environ., 38, 5237–5246, http://dx.doi.org/10.1016/j.atmosenv.2004.01.055doi:10.1016/j.atmosenv.2004.01.055, 2004.

% vor jede Referenz Clegg, S. L., Brimblecombe, P., and Wexler, A. S.: Thermodynamic model of the system H$^+$-NH$_4^+$-SO$_4^2$-NO3-H2O at tropospheric temperatures, J. Phys. Chem. A, 102, 2137–2154, 1998.

% vor jede Referenz Crumeyrolle, S., Gomes, L., Tulet, P., Matsuki, A., Schwarzenboeck, A., and Crahan, K.: Increase of the aerosol hygroscopicity by cloud processing in a mesoscale convective system: a case study from the AMMA campaign, Atmos. Chem. Phys., 8, 6907–6924, http://dx.doi.org/10.5194/acp-8-6907-2008doi:10.5194/acp-8-6907-2008, 2008.

% vor jede Referenz Dillner, A. M., Schauer, J. J., Zhang, Y. H., Zeng, L. M., and Cass, G. R.: Size-resolved particulate matter composition in Beijing during pollution and dust events, J. Geophys. Res.-Atmos., 111, D05203, http://dx.doi.org/10.1029/2005jd006400doi:10.1029/2005jd006400, 2006.

% vor jede Referenz Draxler, R. R., Stunder, B., Rolph, G., and Taylor, A.: HYSPLIT4 user's guide (online version), NOAA Tech. Memo. ERL ARL-230., available at: http://www.arl.noaa.gov/data/web/models/hysplit4/win95/user_guide.pdf, 2006.

% vor jede Referenz Feng, J. L., Guo, Z. G., Chan, C. K., and Fang, M.: Properties of organic matter in PM$_2.5$ at Changdao Island, China – A rural site in the transport path of the Asian continental outflow, Atmos. Environ., 41, 1924–1935, http://dx.doi.org/10.1016/j.atmosenv.2006.10.064doi:10.1016/j.atmosenv.2006.10.064, 2007.

% vor jede Referenz Gong, S. L., Zhang, X. Y., Zhao, T. L., Zhang, X. B., Barrie, L. A., McKendry, I. G., and Zhao, C. S.: A simulated climatology of Asian dust aerosol and its trans-Pacific transport. Part II: Interannual variability and climate connections, J. Climate, 19, 104–122, 2006.

% vor jede Referenz Guo, S., Hu, M., Wang, Z. B., Slanina, J., and Zhao, Y. L.: Size-resolved aerosol water-soluble ionic compositions in the summer of Beijing: implication of regional secondary formation, Atmos. Chem. Phys., 10, 947–959, http://dx.doi.org/10.5194/acp-10-947-2010doi:10.5194/acp-10-947-2010, 2010.

% vor jede Referenz Han, J. S., Moon, K. J., Lee, S. J., Kim, Y. J., Ryu, S. Y., Cliff, S. S., and Yi, S. M.: Size-resolved source apportionment of ambient particles by positive matrix factorization at Gosan background site in East Asia, Atmos. Chem. Phys., 6, 211–223, http://dx.doi.org/10.5194/acp-6-211-2006doi:10.5194/acp-6-211-2006, 2006.

% vor jede Referenz He, K. B., Yang, F. M., Ma, Y. L., Zhang, Q., Yao, X. H., Chan, C. K., Cadle, S., Chan, T., and Mulawa, P.: The characteristics of PM$_2.5$ in Beijing, China, Atmos. Environ., 35, 4959–4970, 2001.

% vor jede Referenz He, K. B., Zhao, Q., Ma, Y. L., Duan, F. K., and Yang, F. M.: Seasonal composition and long-term trend of PM$_2.5$ at Beijing and Chongqing, China, Atmos. Environ., submitted, 2011.

% vor jede Referenz Health Effects Institute: Understanding the health effects of components of the particulate matter mix: progress and next steps, HEI Perspectives, 2002.

% vor jede Referenz Hu, J. H. and Abbatt, J. P. D.: Reaction probabilities for N2O$_5$ hydrolysis on sulfuric acid and ammonium sulfate aerosols at room temperature, J. Phys. Chem. A, 101, 871–878, 1997.

% vor jede Referenz Huang, M. Y., Shen, Z. L., Wu, Y. X., Luo, Q. R., Xu, Y., Zhang, D. B., and Chen, S. L.: Observation on the acidity and chemical compositions of cloudwater and rainwater over Chongqing, Scientia Atmospherica Sinica, 12, 389–395, 1988.

% vor jede Referenz Jang, M. S., Czoschke, N. M., Lee, S., and Kamens, R. M.: Heterogeneous atmospheric aerosol production by acid-catalyzed particle-phase reactions, Science, 298, 814–817, 2002.

% vor jede Referenz Jia, Y. T., Rahn, K. A., He, K. B., Wen, T. X., and Wang, Y. S.: A novel technique for quantifying the regional component of urban aerosol solely from its sawtooth cycles, J. Geophys. Res.-Atmos., 113, D21309, http://dx.doi.org/10.1029/2008jd010389doi:10.1029/2008jd010389, 2008.

% vor jede Referenz Jickells, T. D., An, Z. S., Andersen, K. K., Baker, A. R., Bergametti, G., Brooks, N., Cao, J. J., Boyd, P. W., Duce, R. A., Hunter, K. A., Kawahata, H., Kubilay, N., LaRoche, J., Liss, P. S., Mahowald, N., Prospero, J. M., Ridgwell, A. J., Tegen, I., and Torres, R.: Global iron connections between desert dust, ocean biogeochemistry, and climate, Science, 308, 67–71, 2005.

% vor jede Referenz Johansen, A. M., Siefert, R. L., and Hoffmann, M. R.: Chemical characterization of ambient aerosol collected during the southwest monsoon and intermonsoon seasons over the Arabian Sea: Anions and cations, J. Geophys. Res.-Atmos., 104, 26325–26347, 1999.

% vor jede Referenz John, W., Wall, S. M., Ondo, J. L., and Winklmayr, W.: Modes in the size distributions of atmospheric inorganic aerosol, Atmos. Environ. A-Gen., 24, 2349–2359, 1990.

% vor jede Referenz Larssen, T., Lydersen, E., Tang, D. G., He, Y., Gao, J. X., Liu, H. Y., Duan, L., Seip, H. M., Vogt, R. D., Mulder, J., Shao, M., Wang, Y. H., Shang, H., Zhang, X. S., Solberg, S., Aas, W., Okland, T., Eilertsen, O., Angell, V., Liu, Q. R., Zhao, D. W., Xiang, R. J., Xiao, J. S., and Luo, J. H.: Acid rain in China, Environ. Sci. Technol., 40, 418–425, 2006.

% vor jede Referenz Li, W. J. and Shao, L. Y.: Observation of nitrate coatings on atmospheric mineral dust particles, Atmos. Chem. Phys., 9, 1863–1871, http://dx.doi.org/10.5194/acp-9-1863-2009doi:10.5194/acp-9-1863-2009, 2009.

% vor jede Referenz Li, X. G., Wang, S. X., Duan, L., Hao, J., Li, C., Chen, Y. S., and Yang, L.: Particulate and trace gas emissions from open burning of wheat straw and corn stover in China, Environ. Sci. Technol., 41, 6052–6058, http://dx.doi.org/10.1021/es0705137doi:10.1021/es0705137, 2007.

% vor jede Referenz Li, X. H., Wang, S. X., Duan, L., Hao, J. M., and Nie, Y. F.: Carbonaceous Aerosol Emissions from Household Biofuel Combustion in China, Environ. Sci. Technol., 43, 6076–6081, http://dx.doi.org/10.1021/es803330jdoi:10.1021/es803330j, 2009.

% vor jede Referenz Liu, L. J. S., Burton, R., Wilson, W. E., and Koutrakis, P.: Comparison of aerosol acidity in urban and semirural environments, Atmos. Environ., 30, 1237–1245, 1996.

% vor jede Referenz Liu, S. R. and Huang, M. Y.: Numerical simulation on the acidification of rainwater under cloud and formation of acid rain in Chongqing, Scientia Atmospherica Sinica, 12, 245–257, 1988.

% vor jede Referenz Louie, P. K. K., Chow, J. C., Chen, L. W. A., Watson, J. G., Leung, G., and Sin, D. W. M.: PM$_2.5$ chemical composition in Hong Kong: Urban and regional variations, Sci. Total Environ., 338, 267–281, 2005.

% vor jede Referenz Lu, X. Y., Zhang, X. Z., and Chen, J. N.: Study on the anomaly of the East Asian summer monsoon in June 2005 and the affecting mechanism, J. Trop. Meteorol., 23, 553–562, 2007 (in Chinese with abstract in English).

% vor jede Referenz Luo, C., Zender, C. S., Bian, H. S., and Metzger, S.: Role of ammonia chemistry and coarse mode aerosols in global climatological inorganic aerosol distributions, Atmos. Environ., 41, 2510–2533, http://dx.doi.org/10.1016/j.atmosenv.2006.11.030doi:10.1016/j.atmosenv.2006.11.030, 2007.

% vor jede Referenz Meng, Z. Y., Seinfeld, J. H., Saxena, P., and Kim, Y. P.: Atmospheric gas-aerosol equilibrium .4. thermodynamics of carbonates, Aerosol Sci. Technol., 23, 131–154, 1995.

% vor jede Referenz Meng, Z. Y., Xu, X. B., Wang, T., Zhang, X. Y., Yu, X. L., Wang, S. F., Lin, W. L., Chen, Y. Z., Jiang, Y. A., and An, X. Q.: Ambient sulfur dioxide, nitrogen dioxide, and ammonia at ten background and rural sites in China during 2007–2008, Atmos. Environ., 44, 2625–2631, http://dx.doi.org/10.1016/j.atmosenv.2010.04.008doi:10.1016/j.atmosenv.2010.04.008, 2010.

% vor jede Referenz Meskhidze, N., Chameides, W. L., and Nenes, A.: Dust and pollution: A recipe for enhanced ocean fertilization?, J. Geophys. Res., 110, D03301, http://dx.doi.org/10.1029/2004JD005082doi:10.1029/2004JD005082, 2005.

% vor jede Referenz Mu, J. L., Wang, J. J., and Li, Z. C.: A study of environment and mesoscale convective systems of continuous heavy rainfall in the South of China in June 2005, Acta Meteorol. Sin., 66, 437–451, 2008.

% vor jede Referenz Nenes, A., Pandis, S. N., and Pilinis, C.: ISORROPIA: A new thermodynamic equilibrium model for multiphase multicomponent inorganic aerosols, Aquat. Geochem., 4, 123–152, 1998.

% vor jede Referenz Nenes, A., Krom, M. D., Mihalopoulos, N., Van Cappellen, P., Shi, Z., Bougiatioti, A., Zarmpas, P., and Herut, B.: Atmospheric acidification of mineral aerosols: a source of bioavailable phosphorus for the oceans, Atmos. Chem. Phys., 11, 6265–6272, http://dx.doi.org/10.5194/acp-11-6265-2011doi:10.5194/acp-11-6265-2011, 2011.

% vor jede Referenz Ooki, A. and Uematsu, M.: Chemical interactions between mineral dust particles and acid gases during Asian dust events, J. Geophys. Res.-Atmos., 110, D03201, http://dx.doi.org/10.1029/2004jd004737doi:10.1029/2004jd004737, 2005.

% vor jede Referenz Pakkanen, T. A., Kerminen, V. M., Hillamo, R. E., Makinen, M., Makela, T., and Virkkula, A.: Distribution of nitrate over sea-salt and soil derived particles – Implications from a field study, J. Atmos. Chem., 24, 189–205, 1996.

% vor jede Referenz Pathak, R. K., Yao, X. H., Lau, A. K. H., and Chan, C. K.: Acidity and concentrations of ionic species of PM$_2.5$ in Hong Kong, Atmos. Environ., 37, 1113–1124, http://dx.doi.org/10.1016/s1352-2310(02)00958-5doi:10.1016/s1352-2310(02)00958-5, 2003.

% vor jede Referenz Pathak, R. K., Louie, P. K. K., and Chan, C. K.: Characteristics of aerosol acidity in Hong Kong, Atmos. Environ., 38, 2965–2974, http://dx.doi.org/10.1016/j.atmosenv.2004.02.044doi:10.1016/j.atmosenv.2004.02.044, 2004a.

% vor jede Referenz Pathak, R. K., Yao, X. H., and Chan, C. K.: Sampling artifacts of acidity and ionic species in PM$_2.5$, Environ. Sci. Technol., 38, 254–259, http://dx.doi.org/10.1021/es0342244doi:10.1021/es0342244, 2004b.

% vor jede Referenz Pathak, R. K., Wu, W. S., and Wang, T.: Summertime PM$_2.5$ ionic species in four major cities of China: nitrate formation in an ammonia-deficient atmosphere, Atmos. Chem. Phys., 9, 1711–1722, http://dx.doi.org/10.5194/acp-9-1711-2009doi:10.5194/acp-9-1711-2009, 2009.

% vor jede Referenz Quan, H. N. and Zhang, X. S.: Assessing the role of ammonia in sulfur transformation and deposition in China, Atmos. Res., 88, 78–88, http://dx.doi.org/10.1016/j.atmosres.2007.10.006doi:10.1016/j.atmosres.2007.10.006, 2008.

% vor jede Referenz Richter, A., Burrows, J. P., Nuss, H., Granier, C., and Niemeier, U.: Increase in tropospheric nitrogen dioxide over China observed from space, Nature, 437, 129–132, http://dx.doi.org/10.1038/nature04092doi:10.1038/nature04092, 2005.

% vor jede Referenz Roger, G. B. and Andrew, M. C.: Synoptic and dynamic climatology, New York, Routledge, 735–876, 2002.

% vor jede Referenz Seinfeld, J. H. and Pandis, S. N.: Atmos. Chem. Phys.: From Air Pollution to Climate Change, New York, Wiley, 1998.

% vor jede Referenz Shen, Z. L., Wu, Y. X., Xiao, H., and Huang, M. Y.: Annual variation of chemical characteristics of cloudwater in Chongqing area, Acta Scientiae Circumstantiae, 12, 193–199, 1992.

% vor jede Referenz Shen, Z. X., Arimoto, R., Cao, J. J., Zhang, R. J., Li, X. X., Du, N., Okuda, T., Nakao, S., and Tanaka, S.: Seasonal Variations and Evidence for the Effectiveness of Pollution Controls on Water-Soluble Inorganic Species in Total Suspended Particulates and Fine Particulate Matter from Xi'an, China, J. Air Waste Manage., 58, 1560–1570, http://dx.doi.org/10.3155/1047-3289.58.12.1560doi:10.3155/1047-3289.58.12.1560, 2008.

% vor jede Referenz Shi, Z., Bonneville, S., Krom, M. D., Carslaw, K. S., Jickells, T. D., Baker, A. R., and Benning, L. G.: Iron dissolution kinetics of mineral dust at low pH during simulated atmospheric processing, Atmos. Chem. Phys., 11, 995–1007, http://dx.doi.org/10.5194/acp-11-995-2011doi:10.5194/acp-11-995-2011, 2011.

% vor jede Referenz Song, C. H., Park, M. E., Lee, K. H., Ahn, H. J., Lee, Y., Kim, J. Y., Han, K. M., Kim, J., Ghim, Y. S., and Kim, Y. J.: An investigation into seasonal and regional aerosol characteristics in East Asia using model-predicted and remotely-sensed aerosol properties, Atmos. Chem. Phys., 8, 6627–6654, http://dx.doi.org/10.5194/acp-8-6627-2008doi:10.5194/acp-8-6627-2008, 2008.

% vor jede Referenz Stohl, A.: Computation, accuracy and applications of trajectories – A review and bibliography, Atmos. Environ., 32, 947–966, 1998.

% vor jede Referenz Sun, J. Y., Zhang, Q., Canagaratna, M. R., Zhang, Y. M., Ng, N. L., Sun, Y. L., Jayne, J. T., Zhang, X. C., Zhang, X. Y., and Worsnop, D. R.: Highly time- and size-resolved characterization of submicron aerosol particles in Beijing using an Aerodyne Aerosol Mass Spectrometer, Atmos. Environ., 44, 131–140, http://dx.doi.org/10.1016/j.atmosenv.2009.03.020doi:10.1016/j.atmosenv.2009.03.020, 2010.

% vor jede Referenz Sun, Y. L., Zhuang, G. S., Wang, Z. F., Wang, Y., Zhang, W. J., Tang, A. H., Zhao, X. J., and Jia, L.: Regional characteristics of spring Asian dust and its impact on aerosol chemistry over northern China, Atmos. Chem. Phys. Discuss., 6, 12825–12864, http://dx.doi.org/10.5194/acpd-6-12825-2006doi:10.5194/acpd-6-12825-2006, 2006.

% vor jede Referenz Takahama, S., Davidson, C. I., and Pandis, S. N.: Semicontinuous measurements of organic carbon and acidity during the Pittsburgh air quality study: Implications for acid-catalyzed organic aerosol formation, Environ. Sci. Technol., 40, 2191–2199, http://dx.doi.org/10.1021/es050856+doi:10.1021/es050856+, 2006.

% vor jede Referenz Takami, A., Miyoshi, T., Shimono, A., Kaneyasu, N., Kato, S., Kajii, Y., and Hatakeyama, S.: Transport of anthropogenic aerosols from Asia and subsequent chemical transformation, J. Geophys. Res.-Atmos., 112, D22S31, http://dx.doi.org/10.1029/2006jd008120doi:10.1029/2006jd008120, 2007.

% vor jede Referenz Vlasenko, A., Sjogren, S., Weingartner, E., Stemmler, K., Gäggeler, H. W., and Ammann, M.: Effect of humidity on nitric acid uptake to mineral dust aerosol particles, Atmos. Chem. Phys., 6, 2147–2160, http://dx.doi.org/10.5194/acp-6-2147-2006doi:10.5194/acp-6-2147-2006, 2006.

% vor jede Referenz Wai, K. M. and Tanner, P. A.: Relationship between ionic composition in PM$_10$ and the synoptic-scale and mesoscale weather conditions in a south China coastal city: A 4-year study, J. Geophys. Res.-Atmos., 110, D18210, http://dx.doi.org/10.1029/2004jd005385doi:10.1029/2004jd005385, 2005.

% vor jede Referenz Wang, W., Jiang, Z. Y., Zhang, M. H., and Wang, W. X.: Pollution characteristic of atmospheric aerosol and relationship between aerosol and acid precipitation in south China, J. Environ. Sci., 12, 7–15, 1992 (in Chinese with abstract in English).

% vor jede Referenz Wang, W., Tang, D. G., Liu, H. J., Yue, X., Pan, Z., and Ding, Y.: Research on Corrent Pollution Sataus and Pollution, Characteristic s of PM$_2.5$ in China, Res. Environ. Sci., 13, 1–5, 2000 (in Chinese with abstract in English).

% vor jede Referenz Wang, Y., Zhuang, G. S., Tang, A. H., Yuan, H., Sun, Y. L., Chen, S. A., and Zheng, A. H.: The ion chemistry and the source of PM$_2.5$ aerosol in Beijing, Atmos. Environ., 39, 3771–3784, http://dx.doi.org/10.1016/j.atmosenv.2005.03.013doi:10.1016/j.atmosenv.2005.03.013, 2005.

% vor jede Referenz Wang, Y., Zhuang, G. S., Zhang, X. Y., Huang, K., Xu, C., Tang, A. H., Chen, J. M., and An, Z. S.: The ion chemistry, seasonal cycle, and sources of PM$_2.5$ and TSP aerosol in Shanghai, Atmos. Environ., 40, 2935–2952, http://dx.doi.org/10.1016/j.atmosenv.2005.12.051doi:10.1016/j.atmosenv.2005.12.051, 2006.

% vor jede Referenz Watson, J. G.: Visibility: Science and Regulation, J. Air Waste Manage., 52, 628–713, 2002.

% vor jede Referenz Wu, D., Tie, X. X., and Deng, X. J.: Chemical characterizations of soluble aerosols in southern China, Chemosphere, 64, 749–757, http://dx.doi.org/10.1016/j.chemosphere.2005.11.066doi:10.1016/j.chemosphere.2005.11.066, 2006.

% vor jede Referenz Wu, Z. J., Cheng, Y. F., Hu, M., Wehner, B., Sugimoto, N., and Wiedensohler, A.: Dust events in Beijing, China (2004–2006): comparison of ground-based measurements with columnar integrated observations, Atmos. Chem. Phys., 9, 6915–6932, http://dx.doi.org/10.5194/acp-9-6915-2009doi:10.5194/acp-9-6915-2009, 2009.

% vor jede Referenz Xin, J. Y., Wang, Y. S., Li, Z. Q., Wang, P. C., Hao, W. M., Nordgren, B. L., Wang, S. G., Liu, G. R., Wang, L. L., Wen, T. X., Sun, Y., and Hu, B.: Aerosol optical depth (AOD) and Angstrom exponent of aerosols observed by the Chinese Sun Hazemeter Network from August 2004 to September 2005, J. Geophys. Res.-Atmos., 112, D05203, http://dx.doi.org/10.1029/2006jd007075doi:10.1029/2006jd007075, 2007.

% vor jede Referenz Xiu, G. L., Zhang, D. N., Chen, J. Z., Huang, X. J., Chen, Z. X., Guo, H. L., and Pan, J. F.: Characterization of major water-soluble inorganic ions in size-fractionated particulate matters in Shanghai campus ambient air, Atmos. Environ., 38, 227–236, http://dx.doi.org/10.1016/j.atmosenv.2003.09.053doi:10.1016/j.atmosenv.2003.09.053, 2004.

% vor jede Referenz Yang, H., Yu, J. Z., Ho, S. S. H., Xu, J. H., Wu, W. S., Wan, C. H., Wang, X. D., Wang, X. R., and Wang, L. S.: The chemical composition of inorganic and carbonaceous materials in PM$_2.5$ in Nanjing, China, Atmos. Environ., 39, 3735–3749, http://dx.doi.org/10.1016/j.atmosenv.2005.03.010doi:10.1016/j.atmosenv.2005.03.010, 2005.

% vor jede Referenz Yang, L. X., Wang, D. C., Cheng, S. H., Wang, Z., Zhou, Y., Zhou, X. H., and Wang, W. X.: Influence of meteorological conditions and particulate matter on visual range impairment in Jinan, China, Sci. Total Environ., 383, 164–173, http://dx.doi.org/10.1016/j.scitotenv.2007.04.042doi:10.1016/j.scitotenv.2007.04.042, 2007.

% vor jede Referenz Yao, X. H., Chan, C. K., Fang, M., Cadle, S., Chan, T., Mulawa, P., He, K. B., and Ye, B. M.: The water-soluble ionic composition of PM$_2.5$ in Shanghai and Beijing, China, Atmos. Environ., 36, 4223–4234, 2002.

% vor jede Referenz Yao, X. H., Lau, A. P. S., Fang, M., Chan, C. K., and Hu, M.: Size distributions and formation of ionic species in atmospheric particulate pollutants in Beijing, China: 1 – inorganic ions, Atmos. Environ., 37, 2991–3000, http://dx.doi.org/10.1016/s1352-2310(03)00255-3doi:10.1016/s1352-2310(03)00255-3, 2003.

% vor jede Referenz Yao, X. H., Ling, T. Y., Fang, M., and Chan, C. K.: Comparison of thermodynamic predictions for in situ pH in PM$_2.5$, Atmos. Environ., 40, 2835–2844, http://dx.doi.org/10.1016/j.atmosenv.2006.01.006doi:10.1016/j.atmosenv.2006.01.006, 2006.

% vor jede Referenz Ye, B. M., Ji, X. L., Yang, H. Z., Yao, X. H., Chan, C. K., Cadle, S. H., Chan, T., and Mulawa, P. A.: Concentration and chemical composition of PM$_2.5$ in Shanghai for a 1-year period, Atmos. Environ., 37, 499–510, 2003.

% vor jede Referenz Zhang, L., Liao, H., and Li, J. P.: Impacts of Asian summer monsoon on seasonal and interannual variations of aerosols over eastern China, J. Geophys. Res.-Atmos., 115, D00K05, http://dx.doi.org/10.1029/2009jd012299doi:10.1029/2009jd012299, 2010.

% vor jede Referenz Zhang, Q., Jimenez, J. L., Worsnop, D. R., and Canagaratna, M.: A case study of urban particle acidity and its influence on secondary organic aerosol, Environ. Sci. Technol., 41, 3213–3219, http://dx.doi.org/10.1021/es061812jdoi:10.1021/es061812j, 2007a.

% vor jede Referenz Zhang, Q., Streets, D. G., He, K., Wang, Y., Richter, A., Burrows, J. P., Uno, I., Jang, C. J., Chen, D., Yao, Z., and Lei, Y.: NOx emission trends for China, 1995–2004: The view from the ground and the view from space, J. Geophys. Res.-Atmos., 112, D22306, http://dx.doi.org/10.1029/2007jd008684doi:10.1029/2007jd008684, 2007b.

% vor jede Referenz Zhang, X. Y., Cao, J. J., Li, L. M., Arimoto, R., Cheng, Y., Huebert, B., and Wang, D.: Characterization of Atmospheric Aerosol over XiAn in the South Margin of the Loess Plateau, China, Atmos. Environ., 36, 4189–4199, 2002.

% vor jede Referenz Zhao, D. W., Seip, H. M., and Zhang, D. B.: Pattern and cause of acidic deposition in the chongqing region, sichuan-province, china, Water Air Soil Poll., 77, 27–48, 1994.

% vor jede Referenz Zhao, Q., He, K. B., Ma, Y. L., Jia, Y. T., Cheng, Y., Liu, H., and Wang, S. W.: Regional PM Pollution in Beijing and Surrounding Area During Summertime, Environ. Sci., 30, 1873–1880, 2009.

% vor jede Referenz Zhao, Q., He, K., Rahn, K. A., Ma, Y., Jia, Y., Yang, F., Duan, F., Lei, Y., Chen, G., Cheng, Y., Liu, H., and Wang, S.: Dust storms come to Central and Southwestern China, too: implications from a major dust event in Chongqing, Atmos. Chem. Phys., 10, 2615–2630, http://dx.doi.org/10.5194/acp-10-2615-2010doi:10.5194/acp-10-2615-2010, 2010.

% vor jede Referenz Zhuang, H., Chan, C. K., Fang, M., and Wexler, A. S.: Formation of nitrate and non-sea-salt sulfate on coarse particles, Atmos. Environ., 33, 4223–4233, 1999.

% vor jede Referenz Ziemba, L. D., Fischer, E., Griffin, R. J., and Talbot, R. W.: Aerosol acidity in rural New England: Temporal trends and source region analysis, J. Geophys. Res.-Atmos., 112, D10S22, http://dx.doi.org/10.1029/2006jd007605doi:10.1029/2006jd007605, 2007.