First insight into seasonal variability of urban air quality of northern Pakistan: An emerging issue associated with health risks in Karakoram-Hindukush-Himalaya region

There is a dire need of air quality monitoring in the high-mountain areas of Karakoram-Hindu Kush-Himalaya (HKH) region, particularly related to the recent activities undergoing the China-Pakistan Economic Corridor (CPEC). This study presents the first baseline monitoring and evaluation findings from Gilgit city, Gilgit-Baltistan. Hourly data collection for air quality parameters (PM2.5, NO, NO2, SO2, O3 and CO) were measured using air-pointer (recordum, Austria) from 1 Jan 2018 to 31 Mar 2018 (winter) and 1 Jun 2018 to 31 Aug 2018 (summer). Our findings depict PM2.5 health limits were crossed in the winter season, while NO, NO2 and SO2 remained below their health limits. O3 and CO showed a rising trend in summer months, crossing the 8-h health limits during the season. Seasonal correlation in meteorology found an inverse relationship between most pa-rameters and temperatures; reverse was true for O3 and CO. In parallel, thermal optical carbon analysis filter -based sampling characterized air quality into mass concentrations of PM2.5, organic carbon (OC), elemental carbon (EC) and various heavy metals. Filter-based PM2.5 correlated well with analyzer-based PM2.5 for all months that were studied, except February and March 2018. PM2.5, OC and EC were higher in summer as compared to winter, whereas higher heavy metal contributions were measured predominantly during summer.