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Measurement programs play a critical role in air pollution and atmospheric chemistry studies. Pressures of costs and changing priorities often make it.

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Presentation on theme: "Measurement programs play a critical role in air pollution and atmospheric chemistry studies. Pressures of costs and changing priorities often make it."— Presentation transcript:

1 Measurement programs play a critical role in air pollution and atmospheric chemistry studies. Pressures of costs and changing priorities often make it difficult to maintain and expand long terms measurement programs. In some cases environmental planning activities are severely hampered by the lack of information on the ambient levels of pollutants. Such issues are presently being faced by the World Meteorological Organization’s Global Atmospheric Watch (GAW) program. GAW is a coordinated network of observing stations and related facilities whose purpose and long term goals are to provide data, scientific assessments, and other information on changes of the chemical composition and related physical characteristics of the background atmosphere from all parts of the world. This information is needed to improve our understanding of the behavior of the atmosphere and its interactions with oceans and the biosphere and to better anticipate the future states of the earth-atmosphere system. One challenge facing the GAW program is the need to expand its activities to include measurements in each principal climatic zone and each biome, and to continue to add important species to the list of observed parameters. Measurement of Air Pollution Concentrations in Asia, Africa, and South America Using Passive Samplers G. R. Carmichael 1, M. Ferm 2, N. Thongboonchoo 1, J.-H. Woo 1, L.Y. Chan 3, K. Murano 4, P. H. Viet 5, C. Mossberg 6, R. Bala 7, J. Boonjawat 8, P. Upatum 9, M.Mohan 10, S.P. Adhikary 11, A. B. Shrestha 12, J.J. Pienaar 13, E.G. Brunke 14, T. Chen 15, T. Jie 16, D. Guoan 17, L. C. Peng 18, S. Dhiharto 19, H. Harjanto 20, A. M. Jose 21, W. Kimani 22, A. Kirouane 23, J.P Lacaux 24, S. Richard 25, O. Barturen 26, J. C. Cerda 27, A. Athayde 28, T. Tavares 29, J. S. Cotrina 30, E. Bilici 31 1 Department of Chemical & Biochemical Engineering, Center for Global & Regional Environmental Research, The University of Iowa, USA 2 IVL Swedish Environment Research Institute, 3 Dept. of Civil & Structural Engineering, Hong Kong Polytechnic University, Kowloon, Hong Kong, 4 National Institute for Environmental Studies,Ibaraki, Japan, 5 Vietnam National University, Environmental Chemistry & Environmental Monitoring, Department of Chemical and Environmental Engineering (CEED),Center of Environmental Chemistry(CECT), Hanoi, Vietnam, 6 C/o ISO/Swedforest,Vientiane, Lao PDR, 7 The National University of Singapore, Dept. of Chemical and Environmental Engineering, Singapore, 8 SEA START RC,Institute of Environmental Research,Chulalongkorn University, Bangkok 10330, Thailand, 9 Chiang Mai, Thailand, 10 Center for Atmospheric Sciences,India Institute of Technology, New Delhi, India, 11 Himalayan Climate Center, Katmandu, Nepal, 12 Department of Hydrology and Meteorology, Kathmandu, Nepal, 13 School of Chemistry & Biochemistry, Potchefstroom University,South Africa, 14 South African Weather Bureau, CSIR,South Africa, 15 Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan, 16 China Meteorological and Administration, Beijing, China, 17 Institute of Atmospheric Chemistry, Chinese Academy of Meteorological Science, Beijing,China, 18 Malaysian Metrological Service, Selangor, Malaysia, 19 BANDAN, Department of Meteorology and Geophysics,Jakarta, Indonesia, 20 Meteorological & Geophysical Agency, Jarkata, Indonesia, 21 PAGADA,Department of Science and Technology, Quezon City, Philippines, 22 Kenya Meteorological Department., Nairobi, Kenya, 23 Office National de la Meteorologie, Deparment de la Recherche, Algiers, Algeria, 24 OMP/ Laboratories de Aerologie, Toulouse, France, 25 HYDRECO,,Laboratoire Environnement de Petit Saut, Kourou Cedex, French Guiana. 26 Ushuaia GAW Station, Ushuaia, Argentina, 27 Department of Climatology, Santiago, Chile, 28 Eixo Monumental, Cruseir, Brasilia, Brazil, 29 Chemistry Istitute Departmento de Quimica Analitica, Universidade Federal da Bahia Salvador, Bahia, Brazil, 30 De Investigacion y Desarrollo, Jr. Cahuida, Jesus Maria-Lima, Peru, 31 Turkish State Meteorological Service, Kalaba-Ankara, Turkey The passive sampler was designed based on molecular diffusion of principles. The gas molecules diffuse into the sampler and are collected on an impregnated filter or an absorbent material specific to each pollutants and was kept sampling rate constant by a diffusion barrier. To ensure that gas is transported to the filter by molecular diffusion, the inlet region of the sampler covering with a fine mesh( stainless steel mesh with a thread diameter of 0.08 mm and mesh aperture of 0.125 mm) that can minimize the convective transport. Therefore, the sampling rate can be calculated using Fick's first law of diffusion across the entrapped air volume from the perpendicular cross section area to transport direction and the distance that the gas has to diffuse. It is crucial to impregnate the collective filter with proper chemical. It must be a solid and stable reagent that selectively and quantively chemisorbed the target species, and transforms it to another stables form in which other pollutants do not interfere is carefully selected. The measurement of SO 2 is done using passive sampler with a sodium hydroxide(NaOH) impregnated cellulose filter.The sulphite is oxidized to sulphate during sampling and the sulphate amount is analyzed using suppressed ion chromatography. For measurement of NO 2, a mixture of iodide,arsenite, and ethylene glycol is recommended as a sorbent. On the filter NO 2 is converted to nitrite and then analyzed using FIA( flow injection analysis) spectrophotometry. The measurement of NH 3 is done using a citric acid as an absorbent. Ammonia is converted to ammonium ion and then analyzed using FIA( flow injection analysis)spectrophotometry. The passive samplers have been developed for monitoring non-methane hydrocarbons(NMHCs). They are being used to measure C 6 to C 9 hydrocarbons in urban air quality monitoring networks in Europe. The sampler consists of swagelock fitting tubes with Tenax TA, a 35-60 mesh, and a porous polymer based on 2,6, diphenyl oxide adsorbent packing that can be directly analyzed by gas chromatograph. Diffusive samplers, or more commonly known as passive samplers, offer new possibilities for measuring the geographical distribution of gaseous pollutants in regional and urban air.The technique is based on molecular diffusion and sorption of the gas on an impregnated filter or a solid sorbent. The sampler is small, lightweight, silent, and does not need electricity or other source of energy. The measurement is made in-situ (no inlet tubing is used). The samplers together with an instruction leaflet on how to expose it can be mailed to remote stations by post. Technical personnel are not needed at the site and the samplers don’t need calibration. The samplers are simple and don’t contain any moving parts. The technique is cost efficient implying that a large number of sites and/or a long time period (for trend analysis) can be used. The pilot network consisted of stations from previous studies in Asia and from existing GAW stations, along with newly established sites; in total, 50 stations in twelve Asian countries (China, India, Indonesia, Japan, Korea, Malaysia, Nepal, Philippines, Singapore, Thailand, Laos and Vietnam), seven African countries (Algeria, Cameroon, Ivory Coast, Niger, Morocco, Kenya and South Africa), five South American countries (Argentina, Brazil, Chile, Peru, and French Guyana) and a minor Asian country(Turkey). At these sites sulfur dioxide (SO 2 ), ammonia (NH 3 ) and ozone (O 3 ) were monitored monthly at the rural sites and with short sampling periods at the urban sites. At the urban sites weekly samples of NO, NO 2, HCOOH, CH 3 COOH, benzene, ethyl benzene, toluene, and xylenes were also obtained. To demonstrate the expanded use of passive samplers in air quality studies a pilot measurement program was initiated as a key component of the newly established WMO/GAW Urban Research Meteorology and Environment (GURME) project. This passive sampler project was done in collaboration and as a component of the IGAC-DEBITS program. This pilot activity combined components of three separate studies: 1) A pilot study funded by NOAA-US Weather Service, to use passive samplers at selected WMO/GAW stations 2) A continuation of the use of passive samplers as part of the RAINS-Asia Phase-II funded by the Japan Trust Fund at The World Bank 3) A pilot study demonstrating the use of passive sampler at both regional and urban scales, funded by The Swedish Consultancy Fund at The World Bank. Figure 1: locations of 50 stations: red square and blue Triangle represent regional and urban site,respectively Regional network Three pollutants, namely sulphur dioxide (SO 2 ), ammonia (NH 3 ) and ozone (O 3 ) were monitored as monthly mean concentrations during 12 months. The samplers are 12 mm long and have a diameter of 25 mm. The samplers are mounted under a rain shield which mounted on a metal strip horizontally out from a wall or on a vertical stick. The samplers should not be situated too close to the ground or a wall. The distance should exceed 1 m to a wall and 3 m above ground. Figure 5: Panoramic picture of regional site in Shui-Li, Taiwan Figure3: Passive samplers mounted under rain shield Figure 4: Picture of regional site in Nakhon Sri Thammarat, Thailand Table 1: Site information of Shui-Li, Taiwan A summary of the observed values is presented in Table 2. The number of samples returned, along with the number of samples within the detection limit, is presented. The observed median concentration of SO 2, NH 3, and O 3 obtained at the regional sites are shown in Figures 6,8 and 9, respectively. The mean, median and maximum and minimum monthly values are shown. The range reflects the strength of the seasonal cycle. The observed SO 2 concentrations (Figure 6) vary from a high of 13 ppb at Linan, China to less than 0.03 ppb at four stations. At 30 of 36 regional stations the observed mean annual concentrations was less than 1.0 ppb. The high concentrations of SO 2 at Linan, China, Elandsfontein, S. Africa, Cochin, India, Shang Dian Zhi China, Marcapomacocha, Peru, and Agra, India reflect major contributions from anthropogenic SO 2 emissions (i.e., power plant, industrial boilers, heating, and cooking). Most stations show a consistency between the median and mean concentration. The largest disagreements occurred at Cape D’ Aequier, Hong Kong, and Mt. Sto. Tomas, Philippines. At the Hong Kong site, this was due to a rusted sampler.Mt. Sto. Tomas levels of SO 2 were impacted by the eruption of the Mayon volcano at the end of February 2000. Figure 2: shows various sized and types of passive samplers The median ozone concentrations (Figure 9) vary from a maximum of 45 ppb at Waliguan Mountain, China to 8 ppb in Petit Saut, French Guiana. The sorted plot of ozone concentration with latitude (Figure 10) shows that the four stations with the highest ozone levels (Oki, Japan; Waliguan Mountain, Shang Dian Zhi, and Linan, China) are in the Northern Hemisphere mid-latitudes. In general the highest values are found in the mid latitudes of the Northern and Southern hemisphere, with the Northern hemisphere mid-latitude values exceeding the Southern hemisphere mid-latitude levels, and with the lowest values typically found in the tropical regions. At a few of the measurement sites in Asia SO 2 was measured in 1994 using the same passive sampler technique.This allows for a comparison of SO 2 levels in 1999/2000 with those in 1994. The results are presented in Figure 7. As illustrated values in Hong Kong and Thailand show a marked decrease, as do the values at Agra. At other India sites the values are either constant or increased (i.e., at Cochin). These differences are consistent with changes in regional SO 2 emissions in Asia. In Hong Kong, China and parts of Thailand, sulfur emissions have been declining due in part to a decrease in the sulfur content of fuels. In Agra local efforts to reduce the impact of pollution on the Taj Mahal have lead to closure of many small industrial sources. Median ammonia concentrations shown in Figure 8 range from 20 ppb at Dhangadi, India to less than 1 ppb at nine stations. At 27 sites, the ambient ammonia levels exceeded 1 ppb. The high median NH 3 concentration in the Indian sub-continent, Southeast and South Asia, and Africa reflect high NH 3 emissions from agricultural activities (including fertilizer use), livestock, and the use of biofuels (such as animal dung) as domestic fuel. Table 2 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Urban Network The following criteria for choosing the urban sites were used. The stations should be situated in the center, not directly exposed to traffic and 4-8 m above street level, but not on a roof. Seven different samplers were used (sulphur dioxide, ammonia, ozone, formaldehyde, nitrogen oxides (nitric oxide and nitrogen dioxide), multi component acids and VOC. Suburban stations, for estimating the ozone production, were established some kilometres outside each city in the urban plume. The samplers should be mounted at least 3m above ground at an open place far from traffic. Figure 11: mounting of passive samplers in a city Figure 12: Panoramic picture of downwind station from city of Taipei, Taiwan Figure 13: Panoramic picture of Taipei’s city station Table 3: Site information of Taipei, Taiwan The result are given in Tables 4. The SO 2 concentrations were not very high at any city. The WHO guideline for annual exposure of 50 µg/m 3 is not exceeded at any occasion. Earlier observations at Fuye Ding in Beijing have given concentrations up to 90 µg m -3. This time Beijing had a concentration of 24 µg m -3 and the regional station Shang Dian Zhi a concentration of 8 µg m -3 (in May). The regional station Lin An had in fact higher SO 2 concentrations than the highest urban station. The background station Mersing showed very low concentrations at both occasions. Ammonia: Several cities show high NH 3 concentrations. Most of the regional stations have concentrations below 5 µg m -3, see Figure 8. There must obviously be strong sources (comparable to the SO 2 sources) in the cities. Formaldehyde: Unfortunately the passive sampler for formaldehyde did not work properly. A new type has, however, been developed. Acids: A multi component diffusive sampler for acids (hydrofluoric acid, hydrochloric acid, formic acid and acetic acid) was tested in the urban cities. All measurements here are below the detection limit (ca 3 µg m -3 ). Ozone: the results of ozone in Table 4 below have been sorted after the calculated (no clouds) average photolysis rate for NO 2 (J NO2 ). The average ozone concentration in the suburb is not very different from the average concentration in the suburb downwind the city. A high NO X concentration together with high VOC concentration (especially unsaturated hydrocarbons or much substituted aromatics) together with a high photolysis rate favours the ozone formation. Vientiane show very high concentrations in March and Petaling Jaya and Mersing in Malaysia very low. WHOs guideline of 120 µg/m 3 for 8 h exposure is not exceeded at any station. Nitrogen oxides : WHOs guideline for annual exposure of 40 µg/m 3 is exceeded for several stations during their one week sampling. There seem to be a relationship between NO 2 and NO for all occasions. Taipei and Bangkok have, however, very high NO 2 /NO X ratios while Mersing has extremely low. VOC (Volatile Organic Compounds, C 6 -C 9 ): Motor vehicle exhaust is usually the main contributor to the atmospheric burden of hydrocarbons in urban areas. Additional sources are domestic heating, chemical industry, fuel distribution, evaporative emissions, petroleum refineries, solvent use and energy production (including the industrial combustion). The concentration and distribution of the different compounds in the atmosphere depend on the relative importance of the various sources and the local dispersion governed by the atmospheric conditions. Each source usually has its own emission signature that can be used to assess the impact on the environment. References: Carmichael, G.R, et.al,2003, Measurements of Sulfur Dioxide, Ozone and Ammonia Concentrations in Asia, Africa, and South America Using Passive Samplers, Atmospheric Environment, 37,1293-1308. Ferm, M., 2001, PASSIVE SAMPLERS PROJECT, An Air Quality Measurement Program in Asia Using a Cost Efficient Measurement Technique, Final Report submitted to World Bank. http://www.cgrer.uiowa.edu/people/nthongbo/Passive/passmain.html Table 4 Figure 7


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