Detection of Trends and Seasonal Variation in Tropospheric Nitrogen Dioxide over Pakistan

Abstract

In this study, spatial and temporal distributions of tropospheric NO 2 vertical column densities over Pakistan during the time period of 2002-2012 are discussed. Data products from the satellite instrument SCIAMACHY are used. The results show a large NO 2 growth over major cities of Pakistan, particularly the areas with rapid urbanization. Different seasonal cycles were observed in different regions of Pakistan. In the provinces of Punjab (north east), Khyber Paktunkhwa (north west) and Sindh (south east), NO 2 columns are maximum in winter and minimum in summer months while a reversed seasonality was observed in the province of Baluchistan (south west). We compared the observed spatio-temporal patterns to existing emission inventories and found that for the most populated provinces the NO x emissions are clearly dominated by anthropogenic sources. In these areas also the strongest positive trends were observed. NO x released from soils and produced by lightning both together contribute about 20% for the provinces of Punjab, Sindh, and Khyber Paktunkhwa, while its contribution in Baluchistan is much stronger (~50%). NO x emissions from biomass burning are negligible. This finding can also explain the observed summer maximum in Baluchistan, since the highet lightning activity occurs during the Monsoon season. Our comparison also indicates that the inventories of anthropogenic NO x emissions over Pakistan seem to underestimate the true emissions by about a factor of two.

Traffic ‐and Industry‐Related Air Pollution Exposure Assessment in an Asian Megacity

“…In addition to ground based measurements, some satellitebased studies have also been carried out about the tropospheric levels of the gaseous pollutants from 2002 to 2014. Khokhar et al [68] analyzed the tropospheric NO 2 column densities over Pakistan with the help of satellite observations from the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography/Chemistry (SCIAMACHY) from 2002 to 2012. This study has a caveat that a major extent of the data were not validated from ground instruments across the spatio-temporal extent analyzed.…”

“…Therefore, in Baluchistan, NO 2 columns are higher during summer contrary to the other provinces. [68] SO 2 is mainly emitted from burning of fossil fuels for power generation, whereas on a smaller scale it is emitted from extraction processes of metals and from smoke of locomotives. [69] Similarly, CO is massively produced from vehicular exhaust systems due to inefficient burning of fossil fuel.…”

“…Total ozone column [66] From road sites and small scale industrial estate having brick kilns CO, NO 2 , SO 2 , and PM10 [13] From Pakistan including Punjab (Faisalabad, Lahore, Islamabad, Multan), Khyber Paktunkhwa (Peshawar), Sindh (Karachi), and Baluchistan (Quetta) from 2002 to 2012 NO 2 column [68] In total, 24 samples were collected from 24 randomly selected sites (having backgrounds of all types) with duration of 24 h per sample (thrice a week) from June to August 2010 NO x , SO x , and CO [69] From industries located on link roads to other neighboring cities of Faisalabad during pre-monsoon months June and July…”

Temporal Assessment of NO2 Pollution Levels in Urban Centers of Pakistan by Employing Ground-Based and Satellite Observations

“…Motor vehicle numbers are growing at a rate of 11% per annum in Pakistan (ESoP, 2013;Khokhar et al, 2015a). Over the last two decades, the number of motor vehicles has risen from 2.71 million to nearly 9.08 million.…”

“…The combustion processes in vehicles and industry are the major source of air pollutants such as sulfur dioxide (SO 2 -WHO, 2005;Johansson et al, 2008;Kalabokas et al, 2012;Khattak et al, 2014), carbon monoxide (CO -WHO, 2005;Seinfeld and Pandis, 2012), nitrogen oxides (NO x -WHO, 2005;Frins et al, 2012;Shabbir et al, 2015;Khokhar et al, 2015a) and particulate matter (PM - Khokhar et al, 2016a and references therein) in the air. Globally, nitrogen oxides (NO x = NO + NO 2 ) are released through combustion of fossil fuel, biomass burning, lightning and microbiological processes in soil (Lee et al, 1997;Boersma et al, 2005;HSDB, 2007).…”