Monitoring and analysis of formaldehyde columns over Rawalpindi-Islamabad, Pakistan using MAX-DOAS and satellite observation

摘要

The oxidation pathway of non-methane hydrocarbons, originated from biogenic emissions and anthropogenic sources, culminates in the production of formaldehyde (HCHO) as an intermediate product. HCHO is used to manufacture domestic products and medical preservatives. It is found naturally, and in trace amounts is also produced during metabolic process of many organism. Pakistan is lacking of regular monitoring system on a larger scale to monitor the trace gases present in the atmosphere. For this study, the ground-based data and satellite-based observations of HCHO were gathered during the time period of years 2014–2015. By using car MAX-DOAS instrument several field campaigns were carried out to explore the spatial distribution of HCHO within twin cities of Pakistan. The DOAS technique was used to retrieve level-2 satellite data product from Ozone Monitoring Instrument (OMI) which was then compared with ground-based observations. HCHO column densities distributed spatio-temporally are described in this study. Within twin cities of Islamabad-Rawalpindi, the highest HCHO concentrations of 108?ppbv was found which exceeded the permissible limit of 83?ppbv from World Health Organization (WHO). Furthermore, the maximum VCDs were around 1.0?×?1?016 to 8.5?×?1?016 molecules/cm2, higher than those in Pir-Sohawa valley, which were within the WHO limit, due to less population and vehicular emissions. Similarly, higher amounts of HCHO concentrations were found in areas with higher population densities, increased industrial activity, and along the major highways.