DELHI AIR Pollution
Nov 14, 2016
Delhi is among the world’s most polluted cities. In 2014, it was ranked the most polluted globally in terms of PM 2.5, by the World Health Organisation (WHO). This year in 2016, Delhiites has witnessed worst form of pollution at the onset of winters.
Sources of Pollution:
Air pollution in Delhi’s National Capital Region (NCR) is comprised of a complex mix of pollution from human activities (vehicle emissions, industry, construction and residential fuel burning) as well as natural sources like dust and sea salt. The heavy concentration of particulate matter is greatly affected by meteorological conditions –in the winter, cool air causes “inversions” that stagnant the air and trap pollution close to the ground.
- Vehicles: These are the second largest source of particulate matter, particularly PM2.5. According to the report, vehicular pollution grew from 64 per cent to 72 per cent between 1990 and 2000. In winter, on average vehicles can contribute 25 per cent to PM2.5 and at certain locations this could be above 35 per cent. There is a significant contribution of diesel vehicles to PM10 and
- Road dust: The silt load on some of Delhi’s roads is very high and silt can become airborne with the movement of vehicles. The estimated PM10 emission from road dust is over 65 tonnes per day. Soil from open fields too gets airborne in summer. In some parts of the city, roads are broken, poorly maintained and partially paved surfaces and the study found that movement of vehicles may cause non-exhaust road dust emission in significant amounts. PM10 and PM2.5 emission from road dust is 79,626 kg/day and 22,165 kg/day respectively.
- Concrete batching: During the study period massive construction activities were found that required concrete batching, including at 60 DMRC locations where construction was under progress. It was assumed that there will be 40 concrete batching plants of 120 cu.m/hr capacities operating for 16 hours. Several medium and small construction activities were also observed in the city. PM10 and PM2.5 emissions from concrete mix plants is estimated at 14.37 tonnes/day and 3.5 tonnes/day respectively. A few hundred plants in NCR may contribute to this.
- Hotels and Restaurents: The average consumption of coal in tandoors based on the survey was 30 kg/day. The number of hotels and restaurants was 36,099 (Delhi Statistical Handbook, 2014). The study assumes 25% of these enterprises use tandoors for food preparation.
- Municipal solid waste burning: The contribution of burning MSW may surprise many. A study in 2015 in Delhi has estimated 190 to 246 tonnes/day of MSW burning.
- Stubble Burning in neighboring states: NASA image suggests that burning of crop stubble is considerably impacting the pollution levels. Farmers in neighbouring Punjab and Haryana have been setting fire to paddy stubble in their fields after cultivating the crop as part of the slash and burn. As per an NYT report, farmers are burning around 32 million tons of leftover straw.
Meteorological: During the winter months, cool air stagnates over the city, keeping pollution close to the ground where people breathe. Delhi’s persistent winter fog only worsens the problem. Stagnant air explains why pollution levels vary less widely over the day in winter than in spring, as is evident in the chart above. In spring, warm, rising air moves pollution out, so the average pollution at ground level follows more closely the profile of polluting activities throughout the day. During the afternoon when people are at work, it drops, only to rise again with the evening rush hour. It stays relatively high overnight, likely due to the practice of trucking goods, not only in and out but through Delhi.
- every third child in delhihas reduced lung function
- Sputum of Delhi’s children contains four times more iron-laden macrophages than those from cleaner environs, indicating pulmonary hemorrhage.
- Global scientific studies have associated air pollution with a wide range of health effects including respiratory and cardiac problems, stroke, cancer, hyper tension and diabetes, affect on brain and foetus.
Steps that could be taken are
A IIT Kanpur has gave following measures to be adopted
- Mechanical sweeping with water wash: If main roads are swept twice a month, road dust emission will be reduced by 23 per cent; if four times a month, it will be down by 52 per cent Effect: 71 µg/cu.m reduction in PM10 likely.
- Vacuum-assisted sweeping: The report recommends sweeping four times a month. Effect: 93 µg/cu.m reduction likely in PM10 as a result of a 71% reduction in road dust emissionVehicles
Diesel particulate filter: PM emission reduction efficiency of 60-90 per cent.
Effect: 10 µg/cu.m improvement in PM concentration.
Electric/hybrid vehicles: If introduced, then by January 2017, study assumes, 2% two-wheelers, 10% three-wheelers and 2% four-wheelers will be electric/hybrid.
Effect: 4.5% reduction in PM emission, 1-2 µg/cu.m net improvement in air quality.
Sulphur: Bring down sulphur content to 10 parts per million (ppm) by end-2017.
Effect: 6% drop in PM10 and PM2.5 emission from vehicles.51% overall reduction in vehicular emission if all recommendations implemented.
Industries be made to use light diesel oil and high speed diesel with sulphur content 500 ppm or less in boilers or furnaces. Allow no new polluting industry, it adds.
Effect: 15 to 30% control in PM from this source, negligible sulphur-dioxide.
Diesel generators: Recommendation: Reduced sulphur content to 500 ppm.
Effect: 15 to 30% reduction in PM emission from this source from present 1400 kg/d.
Recommendation: Ban coal for cooking, shift to electric or gas-based devices, stop burning municipal solid waste. Every day, these sources contribute an estimated 12.8 tonnes/day of PM 10
Effect: 57% reduction in PM 10 from these sources.
Recommendation: Spray water at construction sites, use wind breakers, bag filters at silos, cover sites.
Effect: 49% reduction in PM10 and PM2.5.
NCR is a contiguous area with similarities in emitting sources, for this it is necessary that the control options are implemented for the entire NCR. With the implementation of control options in Delhi as well as NCR, the overall air quality in Delhi will improve significantly and expected mean PM10 levels will be 120 µg/cu.m and PM2.5 will be 72 µg/cu.m. In addition to the above control options, some local efforts will be required to ensure that city of Delhi and NCR attain the air quality standards all through the year and possibly for many years to come,