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More diesel vehicles hit efforts to combat pollution in Delhi

Experts claimed that while the reduction of SO2 has been possible because of a gradual shift to cleaner fuels and shutting down of thermal power plants, the NO2 level is constantly on the rise because of the increase in number of vehicles using diesel.

delhi Updated: Jul 19, 2017 10:53 IST
Joydeep Thakur
Joydeep Thakur
Hindustan Times, New Delhi
Delhi pollution,Delhi air pollution,Delhi AQI
SO2 level in Delhi has dropped from 15 micrograms per metre cube in 2000 to 7 micrograms per metre cube in 2016. During the same period, the NO2 level has shot up by 1.8 times, shows CPCB data.(Sonu Mehta/HT Photo)

Delhi’s pollution scenario has undergone a sea change in the last 16 years. While the good news is that the level of Sulphur Dioxide (SO2) has dropped, Nitrogen Dioxide (NO2) emission has nearly doubled.

Experts claimed that while the reduction of SO2 has been possible because of a gradual shift to cleaner fuels and shutting down of thermal power plants, the NO2 level is constantly on the rise because of the increase in number of vehicles using diesel.

Data available with the Central Pollution Control Board (CPCB) reveals that the SO2 level in Delhi has dropped from 15 micrograms per metre cube in 2000 to 7 micrograms per metre cube in 2016. During the same period, the NO2 level has shot up by 1.8 times from 36 micrograms per metre cube to 65 micrograms per metre cube.

“One of the main reasons behind the plummeting SO2 level is the use of cleaner and better fuel with low sulphur content in vehicles,” said D Saha head of the air laboratory in CPCB.

While in BS-II the sulphur content in diesel was 500 ppm, in BS-III and BS-IV it is just 100 ppm and 50 ppm respectively.

“The shutting down of coal-based power plants in Delhi and cutting down on the use of coal for domestic purposes have also helped bring down the level of SO2,” said Anumita Roychowdhury, executive director (research and advocacy) at the Centre for Science and Environment.

Experts, however, pointed out multiple reasons which could have led to the rise in NO2 levels in Delhi.

“One of the possible reasons could be the vehicle engine technology. In a bid to bring down the particulate matter in tail pipe emissions, the engines burn less fuel at very high temperature. This in turn gives rise to NO2,” said professor SN Tripathi, coordinator of Centre for Environmental Science and Engineering at IIT Kanpur.

The rising number of diesel-driven vehicles in the Capital has been attributed as one of the primary reasons behind the increasing NO2 levels.

“Back in 2000 less than 10% of the cars sold in Delhi used to be diesel engines. But now more than 50% of the vehicles sold are diesel engines,” said Roychowdhury.

The government in January 2016 announced that India will be skipping BS V norms and enforcing BS VI norms starting 2020. This would further help bring down SO2 and particulate matter. To reduce NO2, waste burning and biomass burning have to be cut down, experts have suggested.

First Published: Jul 19, 2017 07:32 IST