AS THE debate over stubble burning in Punjab and Haryana, and Delhi’s toxic air rages on, scientist Sachchida Nand Tripathi said while the region’s own pollution sources are a problem, stubble burning was an important factor in deterioration of air quality in October-end and November.
Tripathi, a professor at IIT Kanpur who has worked extensively on air pollution, especially in the Indo-Gangetic Plains, said, “We have come to the conclusion that concerted straw burning happens in a period of 10-15 days in 7-10 districts. The wind direction is also north-westerly and brings the plume of smoke from Punjab, through Haryana, to Delhi and then onwards to Kanpur and beyond… Even 8,000 (farm) fires during this period can make a major impact on air quality in this short period,” he said.
Giving an example, Tripathi, who was speaking at The Indian Express Idea Exchange, said that as paddy straw burning starts, the concentration of PM 2.5 rises from around 100 micrograms per cubic metre to around 200 micrograms per cubic metre.
“When it reaches 200, for example, 40 per cent is from biomass. So we can see that a lot is still from other local sources. The weather conditions also play a role, because the pollutants are not dispersed due to unfavourable weather conditions,” he said.
Delhi has seen three consecutive severe air quality days, with Friday’s AQI settling at 447. The contribution of stubble burning in the concentration of PM 2.5 stood at 30 per cent, down from 34 per cent on Thursday.
According to IARI’s paddy straw burning monitoring portal, over 26,000 fire incidents have been observed in Punjab since September 15. In Haryana, 2,440 incidents have been observed.
To deal with the issue of stubble burning, Tripathi said that states, especially Punjab, should look at crop diversification.
Rice is a water-intensive crop and to deal with the issue of dipping water tables across the state, the sowing of paddy was shifted from June to July, when the monsoon reaches Punjab. This also meant that the harvest was shifted to the latter part of October. This shift, in turn, coincides with weather conditions turning unfavourable for the dispersion of pollutants. The season when farmers are left to deal with the stubble left behind after the paddy harvest is also the season that temperatures drop, wind brings smoke towards Delhi and dispersion is low leading to high concentrations of pollutants in air.
Experts over the years have suggested that farmers should move away from growing paddy in the quantities that they do, and shift to other crops such as maize, cotton, pulses and oil seeds.
“Mainly we have to shift to other crops and diversify. This has to happen in four-five years. The prerequisite is convincing farmers. It is possible. In places where people agree, it should be implemented,” Tripathi said.
To tackle pollution, primary schools in Delhi and Noida have been ordered shut; trucks, except those carrying essentials, have been banned from entering Delhi and diesel cars that are not BS VI compliant have been banned from running on Delhi roads.
Tripathi said that Delhi’s geographical location also makes it more susceptible to pollution.
“With the Deccan Plateau 500 km to its south and the Himalayas to its north, the region that stretches from Haryana to Bihar is a valley between two large structures. Delhi, moreover, sits on the Aravallis, which has an elevation of a few hundred metres. This makes Delhi a table-top city of sorts. It has a peculiar geography within the Indo-Gangetic Plains. This makes it more susceptible to these critical episodes. This doesn’t mean we don’t do anything about it. Our effort should be to factor in these peculiar conditions and work around this,” he said.