Mobile Real-time Air Monitoring Platform (MAP)

MAP VIDEO

Sponsor - HK Jockey Club Charities Trust
PM: Dr. Ming Fang, IESD; PI: Dr. Chak Chan
Status: On-going project

MAP stands for Mobile real-time Air monitoring Platform, a new project funded by the Hong Kong Jockey Club and it is a new concept to obtain high intensity and continuous air quality data from a moving platform. MAP is a vehicle equipped with state-of-the-art equipment and instruments to monitor air pollution on the road in a real-time, in situ mode, in contrast to the conventional stationary techniques. Real-time mapping is more cost effective than the stationary because of the high quality and intensity of the data and its ability to cover a much larger territory in a short time.

The first phase of MAP is to build the platform and it is scheduled for completion in June 2002. Once completed and thoroughly tested, MAP will embark on the second phase of the project by taking regularly scheduled on-the-road measurements across the entire territory. Also included in the project is an educational aspect: monthly visits to secondary schools will be conducted to give
lectures and demonstration to the school children to instigate their scientific interest and environmental awareness, and to show them how the platform works. Researchers from the other institutions will be invited to participate in the building and operation of the platform.

MAP contains the following instruments:
(1)       Real-time particle size counter, 1 scan per second.
(2)       Real-time VOC analyzer (FTIR), 5-30 seconds per scan, 5 to 30 ppb.
(3)       Real-time gas analyzers, 5 seconds.
(4)       Pseudo real-time elemental carbon analyzer.
(5)       Global positioning system.
(6)       Automatic weather stations.

Sponsor: Hong Kong Research Grants Council Earmarked Grant (HKUST6071/99P)
PM & PI:  Dr. Chak K. Chan
Status: Completed

The strong acidity and the concentrations of ammonium, sodium, sulfate, nitrate and chloride in PM_2.5 in Hong Kong, using a Harvard honeycomb denuder/filter-pack system were measured at the different sites  (HKUST, TST and Ho Man Tin) in Hong Kong during March 2000 - May 2001. We investigated the role of atmospheric mixing height in the variation in concentrations of the species in PM_2.5 and quantitatively determined the contribution of the long-range transport to the ambient aerosols in Hong Kong. In total, about 40% of the measured sulfate and ammonium of PM_2.5 in Hong Kong was from the non-local sources in this study. The effects of aerosol composition on the extents of sampling artifacts in PM_2.5 and the contributions of individual reactions to particle evaporation were investigated. The [NH₄⁺]/[SO₄^2-] ratio of 1.5 is a critical ratio in the sampling artifacts of nitrate and chloride in PM_2.5. Furthermore, over 250 datasets of 24-hr Respirable Suspended Particles (RSP) samples collected in 2001 from seven air-quality-monitoring sites run by the Hong Kong Environmental Protection Department were analyzed. Overall, the fine mode fraction of RSP is acidic with an average estimated molar [NH₄⁺]/[SO₄^2-] ratio of 1.24. The particles are highly acidic in nature with an average in-situ pH of –0.05 (–0.65 to 2.5).

Publications:
Pathak R.K. and Chan C.K.(2005) “Inter-Particle and Gas-Particle Interactions in Sampling Artifacts of PM_2.5 in Filter-Based Samplers”, Atmospheric Environment, 39, 1597-1607.
Pathak R.K., Louie P. and Chan C.K. (2004) “Characteristics of Aerosol Acidity in Hong Kong”, Atmospheric Environment, 38, 2965-2974.
Pathak R.K., Yao X.H., and Chan C.K. (2004) “Sampling Artifacts of Acidity and Ionic Species in PM_2.5”, Environmental Science and Technology, 38, 254-259.
Pathak, R.K., Yao, X.H., Alexsis, K.H.L. and Chan, C.K. (2003) “Acidity and concentration of ionic species of PM2.5 in Hong Kong”, Atmospheric Environment, 37,  1113-1124.
Yao, X., Chan C. K., and Fang M. (2001) “Experimental study of the artifact of chloride depletion from collected sea-salt aerosols in sampling”, Environ. Sci. Tech., 35(3), 600-605.
Yao X., Fang M., and Chan C. K. (2000) “Comparison of chloride depletion of sea-salt aerosols in MOUDI and PMDS measurements”, J. Aerosol Sci., 31 (S1), S540-541.

Conference Presentation
Pathak R. K., Yao X., Chan C. K. (2003) “Sampling artifacts of acidity and ionic species of PM_2.5”, to be presented at the 22^nd Annual Conference of the American Association for Aerosol Research, October 20-24, Anaheim, California, USA.
Pathak R. K., Yao X., Chan C. K. (2003) “Sampling artifacts of acidity and ionic species of PM_2.5”, presented at the European Aerosol Conference, September 1-5, Madrid, Spain.
Pathak R. K., Yao X., Chan C. K. (2002) “Sampling artifacts of acidity and ionic species of PM_2.5”, presented at 6^th International Aerosol Conference, September 8-13, Paper ThPao04, Taipei, Taiwan.
Pathak R. K., Yao X., Lau K.H., Chan C. K. (2002) “Acidity and concentrations of ionic species of PM_2.5 in Hong Kong”, presented at 6^th International Aerosol Conference, September 8-13, Paper TuPK28, Taipei, Taiwan.
Pathak R. K., Yao X., Chan C. K. (2001) “Acidity measurements and sampling artifacts of PM_2.5”, presented at the 2^nd Asian Aerosol Conference, July 2-4, Paper II-B2, Pusan, Korea.

Student Trained:
Pathak R. K., PhD in Chemical Engineering, graduated in Jan 04.

The Characteristics of water soluble species of PM2.5 in Beijing and Shanghai, China
Sponsor: GM Research & Development
PM & PI: Dr. Chak K. Chan, CI: Dr. Xiao H. Yao (HKUST), Dr. Steven Cadle and Dr. Tai Chan (GM); Dr. Kebin He (Tsinghua University, China); Bo Ming. Ye (Tongji University, China)
Status: Completed

The two sampling sites in Beijing are located in Tsinghua University (residential site) and Chegongzhuang avenue (downtown site). At Tsinghua sampling site, the sampler was placed on the roof of university building inside the campus of Tsinghua University, which is the northwest suburb of Beijing. The CGZ sampling site is located in the center of urban area, where the highest air pollution index was often registered in Beijing. The two sampling sites in Shanghai are both downtown sites and are 5 km apart. One is inside the Tongji University campus and the other is on Hainan Road. At the sampling site of Tongji University campus, the sampler was placed on the roof of three-story building (16 m above ground level). At 150 m northwest from this sampling site is a heavily trafficked road. At the sampling site of Hainan Road, the sampler is 18 m above the ground level. A heavy traffic road is about 150 m far away from this sampling site in southeast.

The sampler is a special low flow rate sampler equipped with three cassettes for collecting PM2.5 at a flow rate of 0.4 L min-1 (Aerosol Dynamics, USA).  It has three parallel trains of sampling cassettes for sampling aerosols for mass and metal analysis, EC/OC analysis and ionic analysis. In the cassette for ionic analysis, a denuder coated with Na2CO3 and back nylon filter (Gelman Sciences, TeflonTM #R2PJ047) were used to remove acidic gases and to absorb the HNO3 and HCl evaporated from the Teflon filter (Gelman Sciences, #66509), respectively. Sampling artifacts of NH4+ may be present because neither denuder nor back filter coated with citric acid was used. Concurrent weekly (7days) samples were collected at the two sites in each city.

Publications
Ye B., Ji X., Yang H., Yao X.2, Chan C.K., Cadle S., Chan T., and Mulawa P. (2003) “Concentration and Composition of PM2.5 in Shanghai for a One Year Period”, Atmospheric Environment 37, 499-510.
Yao X.H., Chan C.K.*, Fang M., Cadle S., Chan T., Mulawa P., He K. and Ye B. (2002) “The Water-Soluble Ionic Composition of PM2.5 in Shanghai and Beijing, China”, Atmospheric Environment, 36, 4223-4234.
He K., Yang F., Ma Y., Zhang Q., Yao X.H.2, Chan C.K., Cadle S., Chan T. and Mulawa P. (2001) “The Characteristics of PM2.5 in Beijing, China”, Atmospheric Environment, 35, 4959-4970.

Source Apportionment by Chemical Analysis of Size Segregated Aerosols in Hong Kong
Sponsor: Hong Kong Research Grants Council Earmarked Grant (HKUST585/95P)
PM and PI: Dr. Chak K. Chan; CI: Prof. Chi Ming Chan(HKUST) and Dr. John Porter (HKUST)
Status: Completed

In this project, we have employed an advanced receptor modeling tool called the Positive Matrix Factorization (PMF), developed by Professor Pentti Paatero at the Physics Department of the University of Helsinki, Finland. Through the experimentation of PMF in this project, we have devised a methodology in aiding the development of the final results from PMF (Lee et al., 1999), which has been incorporated in the latest User’s manual of PMF.

Size distributions (0.054 - 10 micron) of particulate SO42-, NO3-, NH4+, Cl-, Na+, K+, Mg2+ and Ca2+ were measured using a MOUDI cascade impactor for 33 days in 1996 and 1997 at HKUST. Sulfate and ammonium were the dominant species in fine particles (Dp < 1.8 micron), co-existing in the condensation (0.20 micron) mode and droplet (0.57 micron) modes. The droplet mode dominated the distributions of these two ions. Higher concentrations of droplet mode sulfate were associated with high relative humidity and low clouds. Molar ratio of ammonium to sulfate was found to be about 1.5. Transport of aerosols from southern China by strong northerly wind also increased the sulfate concentration in Hong Kong. Mode diameters of coarse sulfate and ammonium were about  4 to 6 micron. Nitrate was mainly distributed in the coarse particles with mode diameter of 3.95 ± 0.69 micron. Coarse mode nitrate was formed by the reaction of gas phase nitric acid with  sea salt or soil particles. Little fine mode nitrate was found (Zhuang et al., 1999a, 1997). We further studied the formation of nitrate and sulfate on coarse particles and its relationships with meteorological conditions and relative abundance of sea-salt and soil particles.  Competition of nitrate formation between sea-salt and soil compounds was found in this study.  Significant ((74% to 88%) chloride depletion of coarse mode sea-salt aerosols was found.  It was mainly due to nitrate formation although sulfate accounted for 11% to 29% of the chloride depletion during an episode, registering 18 ug m-3 and 3 ug m-3 of fine and coarse mode sulfates (Zhuang et al., 1997, 1999b).

Analysis of the 1992-1994 HKEPD data revealed that secondary species of NH4+, SO42-, and NO3- are spatial uniformly distributed while those of Cu and crustal species are not. Significantly high concentrations of Cu were found at industrial sites (Kwai Chung, Tsuen Wan, and Hong Kong South)  (Qin et al., 1997).  Seasonal profiles can be primarily explained by rainfall. Based on PMF, 9 factors were identified to contribute to RSP in HK.  We also reported the first published profiles of RSP in HK. (Lee et al., 1997, 1998, 1999).

Publications

Zhuang, H., Chan, C. K., Fang, M., and Wexler, A. S. (1999a) “Formation of nitrate and non-seasalt sulfate on coarse particles”, Atmospheric Environment, 33(26), 4223-4233.
Lee, E., Chan, C. K., and Paatero, P. (1999) “Application of Positive Matrix Factorization in source apportionment of particulate pollutants in Hong Kong”, Atmospheric Environment, 33(19), 3201-3212.
Zhuang, H., Chan, C. K., Fang, M., and Wexler, A. S. (1999b) “Size distributions of particulate sulfate, nitrate and ammonium at a coastal site in Hong Kong”, Atmospheric Environment, 33(6), 843-853.
Qin, Y., Chan, C. K., Chan, L. Y., and Chan, C. Y. (1997) “Characteristics of chemical compositions of atmospheric aerosols in Hong Kong: spatial and seasonal distributions”, Science Total Environment, 206, 25-37.

Conference Papers
Zhuang, H. and Chan C. K. (1998) “ An investigation on sulfate, nitrate size distributions and chloride depletion of coastal aerosols”, 5th International Aerosols Conference, Sept 12-18, Edinburgh, UK , J. Aerosol Science. Supplement, 29(S1), S27-S28.
Lee, E., Chan, C. K., and Paatero, P. (1998) “Source apportionment of particulate pollutants in Hong Kong by Receptor Modeling”, presented at the 17th Annual Conference of the American Association for Aerosol Research, June 22-26 Cincinnati, Ohio, USA.
Zhuang H. and Chan C. K. (1997) “Size distribution of inorganic aerosols at a coastal site”, European Aerosol Conference, 15th-19th Sept., Hamburg, Germany, J. Aerosol Science, 28, Suppl. 1, S213-S214.
Lee, E., Chan, C. K., and Paatero, P. (1997) “Receptor Modeling of Atmospheric Aerosols in Hong Kong by Positive Matrix Factorization”, presented at the International Conference on Aerosol Technology / Environmental Measurement and Control, 1-3 October, Tainan, Taiwan.