Abstract:
Formaldehyde is an intermediate product in the oxidation paths of non-methane hydrocarbons produced through biogenic activities and anthropogenic sources. Formaldehyde is a flammable, colorless, strong-smelling chemical that is used in building materials and to produce numerous domestic products and medical preservatives. Formaldehyde is also present naturally in the environment and produced in lesser amounts by most organisms as part of normal metabolic processes. Pakistan lacks the monitoring facilities on a larger scale to measure the atmospheric gasses on regular basis. The study presents the result of atmospheric Formaldehyde vertical column densities (VCDs) obtained from ground-based and satellite observation over Pakistan during the time period of 2014-2015. In order to explore the spatial distribution of Formaldehyde, various field campaigns were conducted by using Car MAX-DOAS instrument and involved international scientists as well. Level 2 data product of satellite instrument; Ozone Monitoring Instrument (OMI) retrieved by differential optical absorption spectroscopy (DOAS) technique was also compared with ground-based observations. Spatio-temporal distribution of Formaldehyde (HCHO) column densities over main cities and region of Pakistan are discussed. The results show that high Formaldehyde (HCHO) column densities exceeding permissible limit of 83 ppm were found over twin cities Rawalpindi-Islamabad of Pakistan. The highest VCDs were around 1.0×1016 to 8.5 ×1016 molecules/cm2 higher than WHO guide lines, while in Pir Sohawa valley where there is less population and vehicular emission, HCHO VCDs were found within WHO permissible limits. Similarly, areas with major industrial activity and high population densities showed high amount of HCHO concentrations.
Keywords: Air quality, Formaldehyde, MAX-DOAS, Vertical column densities (VCDs)
