Temp dip causes AQI spike at three out of seven stations in Kol
Times of India | 4 January 2025
123 Kolkata: With the dip in temperature, the air quality at three — Ballygunge, Salt Lake, Fort William — out of seven automatic air quality monitoring stations in Kolkata plunged to ‘poor' (AQI: 201-300). The thermal inversion (cooler air closer to the ground, with a layer of warmer air above) lowers the vertical wind flow, reducing the dispersal ability of wind.
At these three stations, the graded response action plan (GRAP), an area-specific, multi-stakeholder pollution containment measure, was initiated as the air turned ‘poor'.
Earlier this week, with the rise in ambient temperature, the cleansing of air quality happened quite dramatically, leaving the overall air quality during the year-end and new year ‘moderate'.
Thermal inversion, also known as a temperature inversion, is a natural phenomenon that traps air pollution near the ground. This can be a serious public health issue when the AQI keeps spiking beyond ‘poor'. The particulate matter, particularly the tiniest PM2.5, can evade the body's natural defences and penetrate deep into the lungs and bloodstream, said a WBPCB scientist.
The AQI on Wednesday reflected worsening air quality as the day progressed. Ballygunge AQI monitoring stations showed ‘poor' levels that escalated from 227 at 6 am to 256 by 6 pm. Salt Lake followed a similar trend, with ‘poor' levels rising from 199 in the morning to 231 in the evening. Fort William shifted from ‘moderate' to ‘poor', starting at 184 at 6 am and reaching 219 by 6 pm.
Jadavpur, though better, remained in the ‘moderate' range with a slight rise from 146 to 158. RBU (B T Road) and Sarobar stayed ‘moderate' throughout, with AQI rising from 122 to 138 and 117 to 139, respectively. Victoria Memorial saw ‘moderate' levels rise steadily from 152 in the morning to 167 in the evening.
WBPCB officials said besides its own emission, Kolkata bears the brunt of being at the tail end of \Indo-Gangetic Plain and thus at the receiving end of trans-boundary pollution of IGP that flows from north to south during winter.