SO₂ and HCHO over the major cities of Kazakhstan from 2005 to 2016: influence of political, economic and industrial changes

Abstract

Satellite observations from the Ozone Monitoring Instrument (OMI) were used to analyze tropospheric column mass densities (CMD) of sulfur dioxide (SO₂) and formaldehyde (HCHO) over major Kazakh cities between 2005 and 2016. Ekibastuz—home to large thermal power plants—emerged as the main SO₂ hotspot, with elevated CMD linked to industrial activity, the 2008 financial crisis (leading to use of low-quality coal), wildfires, and capital relocation to Nur‑Sultan. HCHO concentrations peaked in summer in cities like Atyrau and Nur‑Sultan due to photooxidation of VOCs; reductions between 2012–2015 were attributed to policy interventions such as implementation of an emission trading system and Euro‑4 vehicle standards in 2013.,