Air quality deteriorates over past week, affects visibility slightly

PUNE: The air quality in the city, which was “satisfactory” just a few days ago, has deteriorated to “moderate” over the past week. To be blamed are rising vehicular emissions and a drop in night temperatures.



Though the visibility too has deteriorated at some places, experts clarified that the city is not experiencing smog conditions yet. They labelled the current drop in visibility as haze.

Meanwhile, the average levels of two common pollutants — PM10 and PM2.5 — have been increasing over the past one week, data from SAFAR (System of Air Quality and Weather Forecasting and Research) revealed. Three out of the 10 locations in Pune seemed the most affected — Shivajinagar, Katraj and Manjri Katraj.

“The air quality seems to have worsened now in comparison to the same period last year. Last year, the PM2.5 levels were between 25µg/m3 and 40µg/m3 during this time. This year, the range is between 50µg/m3 and 56µg/m3,” a SAFAR source said.

Experts said the dip in air quality could also be causing some haze in the city during the morning hours. They, however, did not consider it to be smog.

Haze is traditionally an atmospheric phenomenon where dust, smoke and other dry particles obscure the clarity of the sky. It slightly limits visibility. Smog, however, is what happens when smoke — most commonly in the form of vehicular emission and industrial fumes — gets mixed with fog. Visibility, in this case, is reduced to 1 km or less.

“If it were smog, the pollution levels would have been higher,” the source said.

A dip the temperatures and vehicular emissions have been responsible for the sudden rise in pollution.

“The areas where pollution is highest also have significant traffic and vehicular movement. As per the available data, the pollution level is higher during the night, especially after midnight. This only means that a dip in the temperature at night worsens the pollution,” the source said.

On why the pollution level gets worse when the mercury drops, the source said when the temperature is cooler near the Earth’s surface, the cool air gets trapped near the surface by a layer of warm air. This causes pollutants to hang near the surface and not escape, hindering their dispersal or upward movement.