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Measurement of NO 2 Concentration in Ambient Air in Karachi using Diffusion Sampling

Learn about the critical role NO2 plays in atmospheric chemistry and its effects on air quality and crop yield. Discover the method and results of monitoring NO2 levels in Karachi through diffusion sampling.

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Measurement of NO 2 Concentration in Ambient Air in Karachi using Diffusion Sampling

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  1. Measurement of NO2 Concentration in Ambient Air in Karachi using Diffusion Sampling By Zia-ul-Islam Director, Pak-EPA

  2. Why NO2? • Important Air Pollutant and very Critical Role in the Atmospheric Chemistry • In Atmosphere, NO2 Converted to Nitric Acid and Nitrate. • NO2 is Phytotoxic in nature and adverse effects on crop yield. • NO2 is an important precursor of Ozone formation.

  3. Measurement Methods ► Passive Sampling (Diffusion Sampling) ► Active Sampling (Semi-Automatic) ► Automatic Sampling ► Remote Sensors Diffusion (Passive) sampling was used to monitor the NO2 Concentration in Karachi and other major cities of Pakistan.

  4. Why Diffusion Sampling? Pollutants in the atmosphere are influenced by the weather and chemistry, thus making it difficult to know, where they will concentrate and cause poor air quality. The only way to be certain of this is to monitor the air pollution at as many sites as possible in one time. This can only be done by Diffusion (Passive) sampling.

  5. Structure of Diffusion Sampler

  6. Diffusion Method Used in the Present Study • The method used in this study has been developed by Japanese Scientist Kazuyuki Aoki in 1978. • This method has application for outdoor measurements due to improvement of diffusion path. • This method can be used for measuring a wide range of gas species like NO2, NO, NH3 and SO2.

  7. Procedure for Using Diffusion Sampler for NO2 Monitoring • Preparation of Diffusion Sampler -Chemicals • Triethanolamine • Dimethyl Sulfoxide • Phosphoric Acid • Sulphanilamide • NEDA.2HCl • Sodium Nitrite

  8. Sampler Preparation

  9. Exposure of Diffusion Samplers

  10. Meteorological Monitoring • Meteorological Equipment used during this study • Thermo-hygrometer (for ambient temperature & Relative Humidity) • Anemometer (Wind Speed Meter and Direction Detector)

  11. Maximum and Minimum temperature varied between 30.9oC and 23.2oC Maximum and Minimum Relative Humidity varied between 30.3% and 20.8% Relative Humidity & Average Ambient Temperature in Karachi During Study Period

  12. Wind Direction and Wind Speed During Monitoring in Karachi • Easterly wind was blowing throughout the monitoring period • Maximum and Minimum wind speed were 2.54 m/s and 1.2 m/s respectively

  13. Sampling Locations in Karachi • 35 sampling sites were selected in Karachi • These sites were categorized as: • Industrial • Residential • Commercial • Kerbsides

  14. Sampling Locations in Karachi

  15. NO2 Concentration in Ambient Air at Various Locations in Karachi

  16. Distribution Pattern of NO2 in Karachi

  17. Highlights of the Results • The Highest Concentration was found at Karimabad Junction (399.65 µg/m3) • The second highest concentration was found at Aaladin Park on Shahrah-e-Rashid Minhas (137.13 µg/m3) • The Third most polluted site was Civic Center near Hasan Square (104.09 µg/m3) • NO2 Concentration at Korangi Industrial Area was 110.84 µg/m3.

  18. Comparison with International Standards • If compared with Japanese standard (80 µg/m3 for 24 hours average), NO2 concentration at 8 locations are higher in Karachi. • WHO Guidelines (150 µg/m3), Only one location Karimabad showed two fold higher conc.

  19. Conclusion • Emission of NO2 is used as an indicator to evaluate the environmental performance of national policies. • In the recent years, the ambient NO2 concentration has exhibited an increase. Even though by the introduction of cleaner fuel (CNG). • Due to Non-existence of fixed ambient air monitoring stations, the increasing or otherwise trend could not be established. Presently Pak-EPA with the grant aid of Japan is establishing two fixed and one mobile monitoring stations in Karachi. After establishment of these stations, Pak-EPA will be in a position to formulate the policies of air emission abatement.

  20. Conclusion • With respect to traffic density viz e viz Kerbside installed samplers, the present study revealed: • NO2 concentration decreases according to distance from road • The samplers, which are installed more than 30 meters from road, their NO2 concentration are more or less similar (Stable) • It means background concentration in Karachi is ≈ 30 ppb ( which is still in the safe limits).

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