What causes SPM contamination in cities?
A few years back I could clearly see the blue outline of the Nandi Hills (55 kms away) when I just looked to my left through the 11th floor window of my office in Brigade Road, Bangalore. Nowadays this is almost never. Rarely ( about once a month) I see a hazy grey out line if I look hard. Two days of rain followed by sun allows the sight of the hills for a few hours till the dust again draws a veil.
The blame is always laid on the nearly 75 lakhs motor vehicles emitting pollutants in Bangalore.
We are all engineers. Most of us are aware of particles settling in air. Assuming that the dust is mostly silica with a density of 2.65 gms/cc and a particle size of 2.5 micrometers why not we attempt to see if there could be an alternative explanation for the high SPM levels in cities other than the fall guy of motor vehicle emissions?