Kolkata: Air quality falls further, inches closer to 'severe' category

KOLKATA: The city’s ambient air quality on Thursday worsened, with air quality index spiking further, putting it closer to the worst possible category of air quality — ‘severe’ (401-500). In fact, the air quality of good zones in the city, including Rabindra Sarobar (lung of south Kolkata) and Maidan (lung of the entire city) also swung to ‘very poor’ category.
The wind velocity on Thursday also remained very poor — 2 meter/second.In this calm wind condition, city’s ambient air has had a pile-up effect, with the day’s pollutants adding up to the previous day’s pollution level. The thermal inversion (soil is cooler than the air) has lowered the vertical wind movement causing very low dispersion of pollutants — particulate matters.
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In winter — November to January — the calm condition was reported to be as high as 42%. February being a transition month, condition improves to a moderate 32% calm. The condition further improves and remains between 7-18% calm due to shifting southerly wind. The meteorological factors now govern movement of air and its pollutants in a big way, said a senior WBPCB scientist.

“When the air quality at Rabindra Sarobar deteriorates to such a degree, then be sure that air quality in the rest of the city is really bad,” said Sudipta Bhattacharya of Saviour and Friends of Environment.
Under this current situation, the government must immediately look to compressed natural gas (CNG). “CNG can be used as a cleaner alternative of diesel and reduce the burden of pollutants in the air,” said environment crusader Subhas Datta.