Abstract
This paper presents the results of atmospheric Sulfur dioxide (SO_2) column densities obtained from satellite observation over Pakistan during the time period of 2004-2012. The level-2 data product of the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) instrument on-board ENVISAT-l is used. S02 column densities are retrieved by applying differential optical absorption spectroscopy (DOAS) technique. The spatio-temporal distribution of SO_2 column densities along with the seasonal variation over main cities and regions of Pakistan are discussed. The Nabro volcano eruption in the year 2011 caused high SO_2 levels over East Africa, the Middle East and South and Southeast Asia. Satellite images exhibited several episodes of volcanic SO_2 column densities transported to Pakistan. The temporal trend in SO_2 column densities was calculated, and the significance of the data set was tested with statistical analysis. An overall increase of about 70% (8.7% per year) in SO_2 column densitiies over Pakistan during the time period of 2004-2012 has been calculated. This study presents the first spatial and temporal analyses of SO_2 column densities over Pakistan by using satellite observation.
Highlights
Atmospheric Sulfur dioxide (SO2) results from both natural and anthropogenic sources (Krueger et al, 1995; Krotkov et al, 1997; Khokhar et al, 2006; Lee et al, 2008) including the oxidation processes occurring in the soil and over oceans, volcanic eruptions, biomass burning metal smelters and combustion of fossil fuels (Eisinger and Burrows, 1998; Finlayson-Pitts and Pitts, 2000)
This paper presents the results of atmospheric Sulfur dioxide (SO2) column densities obtained from satellite observation over Pakistan during the time period of 2004–2012
SO2 column densities are retrieved by applying differential optical absorption spectroscopy (DOAS) technique
Summary
Atmospheric Sulfur dioxide (SO2) results from both natural and anthropogenic sources (Krueger et al, 1995; Krotkov et al, 1997; Khokhar et al, 2006; Lee et al, 2008) including the oxidation processes occurring in the soil and over oceans, volcanic eruptions, biomass burning metal smelters and combustion of fossil fuels (Eisinger and Burrows, 1998; Finlayson-Pitts and Pitts, 2000). SO2 is very reactive and rapidly converted into other compounds such as sulfuric acid (H2SO4), sulfurous acid (H2SO3) and sulfate particles (SO4–2) These compounds are very harmful to the environment as well as to the human health (Finlayson-Pitts and Pitts, 2000; Ejaz et al, 2009a). SO2 life time varies from few days to several weeks (e.g., Finlayson-Pitts and Pitts, 2000; Platt and Stutz, 2008). Lee et al (2009) calculated the global SO2 life time during different seasons They performed atmospheric chemistry transport model - GEOSChem (Bey et al, 2001) simulations by taking into account gas-phase oxidation, dry deposition, and aqueous-phase oxidation (in clouds) of atmospheric SO2. The longer SO2 lifetime in winter reflects reduced oxidation by both aqueous (i.e., H2O2) and gas-phase (i.e., OH) processes as compare to summer time with relatively larger OH production and monsoon season
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