Delhi pollution: As farm fire impact declines, experts suggest long-term plan and monitoring of vehicular emissions

Stubble burning contributes about 35 to 40 per cent of the total pollution load in Delhi-NCR

Delhi has been engulfed in a cloud of dense smog yet again this year and the debate on how far are the neighboring states responsible for creating this toxic air still persists. The System of Air Quality and Weather Forecasting And Research (SAFAR), meanwhile, using satellite information has come out with an approximate share of farm fires on PM 2.5 concentration in Delhi air.

According to SAFAR, stubble burning caused 48 per cent of PM 2.5 concentration in Delhi air resulting in severe 428 AQI  on November 7. The satellite information about total number of farm fires is fed into Chemistry Transport Forecast Model that then adds this data to existing conditions like speed, wind direction, temperature, precipitation, cloud cover, etc to come out with its share of PM 2.5.

PM 2.5 reached its peak at 48 per cent and has been dipping since. It was 10 per cent on Monday. Moreover, the contribution has varied distinctively in two weeks from 2 per cent on October 24 to 48 per cent on November 7. Moreover, the Delhi air quality has been consistently in the ‘very poor’ to ‘severe’ category since Diwali and is expected to be in the ‘very poor range’ in the next three days.

According to Commission for Air Quality Management paddy stubble burning contributes about 35 to 40 per cent of the total pollution load in Delhi-NCR. Another 2015 space-apportionment study by IIT-Kanpur on Delhi air pollution suggests that between 17 to 26 per cent of all particulate matter in Delhi is because of the burning of the biomass.

Experts also suggested that stubble burning cannot be the only factor for Delhi’s poor air as this farm activity lasts for 45 days but Delhi air stays polluted till February. The air quality, hence, is affected by several other factors like vehicles and industries.

A Delhi government official said Delhi needs a long-term plan to tackle pollution from its own sources as well. According to Professor S N Tripathi from IIT-Kanpur, industries and vehicular emissions contribute to pollution all through the year. Stubble burning will contribute 25 to 35 percent at its peak and has already started decreasing, he noted. Vehicular emissions can turn PM over time as secondary particles can contribute up to 25 percent to the pollution, he further suggested.

Moreover, traditional sources of pollution remain at their own level and if the contribution from industries is accounted for, it is also responsible for primary and secondary particles., Prof Tripathi informed. Urgent action is needed to address pollution from BSS IV compliant vehicles and retrofitting needs to be done to address this, he added.