Measurement of Ambient Concentration of NO2 In Obafemi Awolowo University Campus Using Passive Samplers
Keywords:
NO2, Passive Sampler, Diffusion, Absorption, SpectrophotometryAbstract
This study measured ambient concentration of NO2 in Obafemi Awolowo University (OAU) campus using locally fabricated passive samplers designed based on the principles of mass transfer and diffusion. Two types of samplers studied were tubes of varying lengths (2cm and 7cm) at three locations for different sampling durations. A mixture of sodium hydroxide (NaOH) and sodium iodide (NaI) in Methanol was used as absorbent for NO2. Samplers loaded with absorbents were exposed for durations of 1, 2, 3 and 4 weeks. Withdrawn samplers from sampling sites at the end of respective sampling periods were analysed in the laboratory using modified Griess-Saltzman method. Optical absorbance values of coloured solutions formed were measured with UV/VIS Spectrophotometer at 540nm. Results showed that the two sampler types were effective for sampling and both gave acceptable estimates in the 1 week sampling duration. The ambient air concentration of NO2 in Site 1 (7.0ppb-12.4ppb) is highest followed by Site 2 (4.2ppb-10.6ppb) and then Site 3 (0.2ppb-4.1ppb). All these values are below the limits set by the Federal Ministry of Environment which is 40ppb-60ppb.
References
Atkins, D. H. F. and Lee, D. S., “Spatial and temporal variation of rural nitrogen dioxide concentrations across the United Kingdom”. Atmospheric Environment 29:223–239, 1995.
Atkins, D.H.F., Sandalls, J., Law, D.V., Hough, A.M. and Stevenson, K., “The measurement of nitrogen dioxide in the outdoor environment using passive diffusion tube samplers”. AERE-R12133, United Kingdom Atomic Energy Authority, Harwell, 1986.
Campbell, G. W., Stedman, J. R. and Stevenson, K., “A survey of nitrogen dioxide concentrations in the United Kingdom using diffusion tubes, July–December 1991”. Atmospheric Environment 28:477–486, 1994.
Coulson, J. M., Richardson, J. F., Backhurst, J. R., and Harker, J. H., “Chemical Engineering, Volume 1”, Sixth Edition, Butterworth-Heineman, Elsevier, Oxford, 2004.
Dimari, G.A., Abdulrahman, F.I., Akan, J.C. and Ogugbuaja, V.O., “Levels of Nitrogen Dioxide of Atmospheric Air, in Maiduguri, Borno State, Nigeria”. Research Journal of Applied Sciences 2(7): 846-849, 2007.
EPA, Environmental Protection Agency/Air Trends/Nitrogen Dioxide, September 21, 2004, http://www.epa.gov/airtrends/nitrogen.html, accessed on November 2, 2009.
EPA, Environmental Protection Agency/Office of mobile sources, January 17, 1997, http://www.epa.gov/otaq/consumer/05-autos.pdf, accessed on November 2, 2009.
Hangartner, M. and Burri, P., “Passive sampling of nitrogen dioxide and sulphur dioxide in ambient air”. Communique of European Communities, [Rep.], (EUR 10555, Diffusive Sampling), 387-391, 1987.
Hewitt, C. N., “Spatial variations in nitrogen dioxide concentrations in an urban area”. Atmospheric Environment 25:429–434, 1991.
Hino, M, “Maximum ground-level concentration and sampling time”. Atmos. Environ. 2:149-165, 1968.
Hopke, P. and Markowitz, D., “A survey of monitoring instruments for measurement of airborne pollutants”. CEC Consultant report no. 500-03-053F, New York State Energy Research and Development Authority (NY SERDA) Potsdam, New York, 2002.
IDAF, Measurements/Gas, March 3, 2004, http://idaf.mediasfrance.org/measurement/gas/index, accessed on January 27, 2009.
Kirby, C., Fox, M. and Waterhouse, J., “Reliability of nitrogen dioxide passive diffusion tubes for ambient measurement: in situ properties of the triethanolamine absorbent”. Journal of Environmental Monitoring 2:307- 312, 2000.
Kirby, C., Greig, A. and Drye, T., “Temporal and spatial variations in nitrogen dioxide concentrations across an urban landscape: Cambridge, U.K”. Environmental Monitoring and Assessment 52:65–82, 1998.
Lodge J.P. (ed.), “Method 406: Determination of the Nitrogen Dioxide Content of the Atmosphere (Griess-Saltzman Reaction)”. In Methods of Air Sampling and Analysis, 3rd ed. Intersociety Committee (APCA, ACS, AIChE, APWA, ASME, AOAC, HPS, ISA). Michigan, USA, Lewis Publishers Inc., 389-393, 1989.
Massman, W. J., “A review of the molecular diffusivities of H2O, CO2, CH4, CO, O3, SO2, NH3, N2O, NO, and NO2 in air, O2 and N2 near STP”. Atmospheric Environment, 32(6):1111-1127, 1998.
Microsoft® Encarta® 2009 [DVD], “Air Quality”. Redmond, WA: Microsoft Corporation, 2008.
Nonhebel, G., “Recommendations on heights for new industrial chimneys”. J. Inst. Fuel 33:479-511, 1960.
Palmes, E.D., Gunnison, A.F., DiMattio, J. and Tomczyk, C., “Personal sampler for nitrogen dioxide”. American Industrial Hygiene Association 37: 570-577, 1976.
Parra, J. and George, L., “Performance and Application of an Inexpensive method for Measurement of Nitrogen Dioxide”, Portland State University, 2004. (Unpublished).
Plaisance, H., Piechocki-Minguy, A., Garcia-Fouque, S. and Galloo, J. C., “Influence of Meteorological factors on the NO2 measurements by passive diffusion tube”. Atmospheric Environment 38:573-580, 2002.
Shooter, D., Brimblecombe, P., Shooter, J., Lowe, D., Day, P. J. and Du, S., “Some characteristics of nitrogen dioxide passive samplers”. Environmental Technology 18:243-254, 1997.
Sonibare, J. A. and Jimoda, L. A., “Criteria air pollutants from some anthropogenic combustion processes in Lagos, Nigeria”. Energy Sources, Part A: Recovery, Utilization and Environmental Effects 31(11):923-935, 2009.
Targa, J. and Loader, A. Diffusion tubes for ambient NO2 monitoring: Practical guidance. Report to Defra and the Devolved Administrations, ED48673043, AEA/ENV/R/2504-Issue 1a, February 2008.
Targa, J., Rendell, A. and Truesdale, V., “Investigation on pH, TEA and colour reagent dependency during nitrite analysis”. Report in preparation to Defra & the Devolved Administrations by AEA Energy & Environment, 2007.
Van Reeuwijk, H., Fischer, P. H., Harssema, H., Briggs, D. J., Smallbone, K. and Lebret, E., “Field comparison of two NO2 passive samplers to assess spatial variation”. Environmental Monitoring and Assessment 50:37–51, 1998.
Vrana, B., Mills, G., Allan, I., Dominiak, E., Svensson, K., Knutsson, J., Morrison, G. and Greenwood, R., “Passive sampling techniques for monitoring pollutants in water”. Trends in Analytical Chemistry 24:845-868, 2005