Including Cng-run vehicles will help cut NOX levels: Study

NEW DELHI : The Delhi government’s decision to include private CNG vehicles in the oddeven rule will help bring down nitrogen oxide (NOX) levels in the city’s air, scientists at the Delhi Technological University (DTU) said on Tuesday.

Rajeev Kumar Mishra, assistant professor at the department of environment engineering at DTU, said even though CNG is a cleaner fuel compared to petrol and diesel, the emission of NOX in vehicles run by CNG is higher.

“The temperature required to burn the fuel in CNG vehicles is higher, which emits NOX. This is a dicey situation because it is this high temperature that reduces the emission of PM 2.5 (fine particulate matter with diameter less than 2.5 micrometres) in such vehicles,” said Mishra.

NOX is a family of poisonous gases that include nitric oxide and nitrogen dioxide. Often appearing as a brownish gas, NOX also gives rise to other secondary pollutants. For example, it can react with gases in the atmosphere to turn into nitric acid, which is a particulate pollutant. NOX can also react with volatile organic compounds in the atmosphere to produce ozone (O3) and smog.

This is Mishra’s second study on the odd-even road rationing scheme. His team had studied the effect of the drive on PM 2.5 and PM 1 levels in the ambient air in three traffic heavy corridors in the city.

PM1 is among the finest particles that can reach the blood stream and percolate the organs. These fine particles are nearly 50 to 70 times finer than human hair.

Based on their initial findings on the first two days of the scheme, Mishra said that the dip in the pollution levels in Pitampura (Madhuban Chowk), Panchkuian Road, Western Yamuna Canal Link Road and Najafgarh Road, was not much on Monday morning because of high humidity and low wind speed. However, since Monday afternoon the pollution levels have seen a dip.

“These are just the initial findings, but the weather conditions have been favourable and we are seeing a reduction in the pollution levels now. Apart from just recording the PM levels, this time we are doing something different and analysing the toxicity of the particulate matter,” he added.

The first peer reviewed study by DTU had found that in the 15 days, between January 1 and January 15, when the vehicle rationing plan was in place in Delhi, PM 2.5 levels reduced by 5.73%, while the PM1 levels in the ambient air around these corridors came down by 4.70%.