Investigating the temporal variation of formaldehyde using MAX-DOAS and satellite observations over Islamabad, Pakistan

Özet

Formaldehyde (HCHO) being an oxygenated Volatile Organic Compound (VOC), essentially contributes to thehazardous tropospheric ozone pollution in urban areas. Emissions from automobiles are the major contributorstowards elevated formaldehyde concentrations in major urban cities of Pakistan. The current study is designed toexplore the formaldehyde columns at a stationary site, Institute of Environmental Science and Engineering(IESE), National University of Science and Technology (NUST) Islamabad from September 2015 to August 2017using Multi-Axis – Differential Optical Absorption Spectroscopy (MAX-DOAS). Observations from MAX-DOASinstrument were used to measure the diurnal, weekly and annual cycle of formaldehyde (HCHO). The diurnalconcentrations of HCHO were found to be at its maximum during early morning and evening hours. Relativelyinsignificant weekly cycle with higher concentrations on working days and lesser during the weekend was observedat IESE-NUST monitoring site. While annual cycle showed the highest columns in summer followed byspring, autumn and winter. The suspected sources of HCHO at a fixed station were identified as natural gasconsumption, biogenic emissions from vegetation, emissions from industries and vehicular emissions.Furthermore, ground-based measurements were compared with monthly Ozone Monitoring Instrument (OMI)satellite observations. A good correlation with Pearson value of 0.68 is noticed during the whole study period.