~~~~~~ Ambient Air Quality in the City of New Delhi, India ~~~~~~

Transcription

1 ~~~~~~ Ambient Air Quality in the City of New Delhi, India ~~~~~~ Prithvi Simha Central European University Department of Environmental Science and Policy Student No

2 1. Introduction The city of New Delhi is located on the banks of River Yamuna between the Aravali and 160 kilometers south of the Himalayan mountain ranges. Lying in the Indo-Gangetic plains there is little difference in elevation in this landlocked city which is spread across an area of 573 square miles. It is the national capital and the seat of the executive, judiciary and legislative branches of the Government of India. The city of New Delhi (the focus of this paper) lies within the Delhi metropolitan area (also called the National Capital Territory). The city has a population of ~11 million while the metropolitan has ~25 million residents as of July 2014, making it the second most populous mega city in the world (UN 2014). Like any other city, the Delhi we see today is a result of various economic, political and environmental pressures over time. Built in the 1930 s, the city was a fully planned venture 1 of the British Indian Empire with numerous arterial roads and broad expanses of green spaces. Following independence from the British Raj, Delhi experienced (and continues to) one of the fastest urbanization trends in world history primarily due to the ability of the capital to provide the conditions to fuel socio-economic growth. Delhi s growing prosperity has resulted into a qualitative change in consumption patterns among the urban rich with less than 8% of the population now living below the poverty line. With population in the capital reaching the levels we see today, the simultaneous increase in environmental externalities and decrease in quality of life should come as no surprise. The rapid economic growth witnessed since the 1990s coupled with large scale in-migration have overburdened the city s infrastructure; more importantly, growing anthropogenic activities have affected the region s environmental capacity to safely incorporate and assimilate externalities. This is exemplified in the case of road transportation in Delhi where the number of registered vehicles as of 2010 stands at 6 million, with an additional 2.2 million contributing to the vehicular population from surrounding areas (DSH 2012). Subsequently, the total air pollution load of the city attributable to vehicles has grown from 23% in 1970 to 72% by 2005 (Goyal et al. 2006). With 1317 vehicles added every single day into the city s traffic, the quality of air when evaluated through traditional indicators have been found to consistently exceed the National Ambient Air Quality Standards (NAAQS) (Hindustan Times 2011). Moreover, among the residents, the use of diesel-based generators is prevalent owing to the perennial power shortage in the city s electricity grid. The use of wood, biomass, refuse and kerosene for cooking is another source of primary pollution. Furthermore, it is a very common sight in the winter months to see wood burnt to make fires for warmth on the streets 1 The city of Delhi was chosen by the British Indian Empire when they decided to move the capital from the port of Calcutta in order to ease administration of the subcontinent.

3 throughout the city. Industries, ranging from small scale enterprises to large industries such as coal-fired power plants have also been significant factors in determining the ambient air quality. Kandlikar and Ramachandran (2000) attribute air pollution in the city to 30% of the population s respiratory disorders. Moreover, epidemiological studies conducted in various countries have established a strong linkage between morbidity and airborne pollutants like Particulate Matter (especially the finer fractions like PM 10 ) (See Bai et al and Dai et al. 2014). In order to analyze the state of air quality in New Delhi this study documents the baseline air pollutant levels in various parts of the city including those in known hotspots at kerbside locations. Aggregation of this data was carried out to analyze citywide monthly pollutant concentrations as well as to discern the effect of climatological factors on pollutant distribution. Additionally, intra-city variation in pollutant distribution has also been provided to identify areas of concern and priority. 2. Methodology Weather in New Delhi is humid bordering on sub-arid (Köppen climate classification Cwa) 2. Characteristics like summer heat storms ( Loo ) and relatively dry winters give the city its arid classification. Summer extends from early April and peaks in May with average temperature of 32 C although blowing heat waves may push this up to 45 C. Monsoon arrives in late June with rainfall (~800 mm) lasting until mid-september. After this, the monsoon recedes and post-monsoon continues till late October between which average temperature falls down from 29 C to 21 C. The city s proximity to the Himalayas makes it susceptible to cold waves in the winter months and low apparent temperatures (average C). Winter is dominated by cold, ground based inversion with low wind velocity (u 1 m.s -1 ) that cause frequent concentration of air pollutants (Anfossi et al., 1990; CPCB, 2000). Usually, NW winds prevail throughout the year except during the months of June and July where SE winds predominate (Sindhwani and Goyal 2014). For the purpose of this study, air pollution data was sourced from the National Air Quality Monitoring Programme of the Central Pollution Control Board, National Environmental Engineering Research Institute, Center of Science and Environment and the Delhi Pollution Control Committee (NEERI 2008; DPCC 2009; CPCB 2010 and CSE 2010). These data sets represent the ambient air quality at 10 different locations across New Delhi (See Fig. 1) to reflect the various land-use patterns and activity profiles (like industrial, residential, commercial and kerbside activities). Prahaladpur was chosen as the reference site on account of low activity in the area relative to others parts of the city. The parameters measured were Sulphur Dioxide (SO 2 ), Nitrogen dioxide (NO 2 ), Suspended Particulate Matter (SPM) and Respirable Suspended 2 Climatological features based primarily on statistics provided by Indian Meteorological Department (2010)

4 Particulate Matter (RSPM/PM 10 ), Ozone and Carbon Monoxide (CO). The monitoring was carried out continuously for 24 hours (4-hourly sampling for gaseous pollutants and 8-hourly sampling for particulate matter), twice a week, to have about 104 observations in a year (NEERI 2008). In the analysis of city-wide pollution levels, firstly, the data from all the 10 sites was averaged for each month to give city-wide monthly values. Secondly, this data was further aggregated into 3 time periods: summer, postmonsoon and winter to depict the variation in pollutant concentration with seasonality. It must be acknowledged that the data collected from all the monitoring sites was coordinated by the CPCB to ensure consistency and uniformity. Fig. 1: Location of ambient air quality monitoring stations for the city of New Delhi; Illustration made by the Author

5 3. Results and Discussions 3.1. The current state of Air Quality in New Delhi The National Ambient Air Quality Standards (NAAQS) for the measured parameters have been summarized below in Table 1. In order to analyze the air quality in New Delhi let us begin by comparing the NAAQS with current trends for each pollutant. As seen in Fig. 2, SO 2 levels in the city are well below those prescribed by NAAQS. The decrease in SO 2 emissions in New Delhi over its past levels can be attributed to mandatory use of CNG in public transportation, implementation of Bharat Stage-III emission norms and offsetting the use of biomass for cooking by cleaner LPG fuel. TABLE 1: NAAQS (in µg.m -3 ) for various pollutants Pollutant Area Type 8 h 24 h Annual SO 2 General NO 2 Residential Industrial Sensitive Areas RSPM/PM 10 Residential 60 Industrial 120 Sensitive Areas 50 TSPM -- NA NA NA Ozone General CO Residential 2000 Industrial 5000 Sensitive Areas 1000 The overall NO x emissions have remained constant over the years as any reduction achieved through the enforcement of policies has been counterbalanced by the rise in vehicular ownership and use. Moreover, incorporating the effect of seasonality it is seen that NO x exhibits clear maxima during the post-monsoon and the winter periods each year (Fig. 3). In terms of particulate matter, New Delhi exceeds the NAAQS by more than twice of the advised figure (Fig. 4). Moreover, the concentration of Respirable Suspended Particulate Matter (RSPM or PM 10 ) is much higher than those in demographically similar cities like Tokyo or Kuala Lumpur (India Today 2011). Though the annual concentrations of many criteria pollutants are within the guidelines of the NAAQS periodic fluctuations occur; this is primarily due to seasonality and establishment of calm weather conditions that encourage their build up and concentration in the atmosphere. Particulate Matter, NO x, SO 2 and CO display distinct peaks in the months of August, November and December. Post-monsoon (August-October) and winter (November-January) are periods of cold temperature (with the low being 1-2 C); this creates surface inversion in the boundary layer that lowers the mixing height and inhibits the vertical dispersion and entrainment of pollutants in the atmosphere. Peak winter with its longer nights also experiences the effect of mid-latitude air circulation and creation of troughs in the westerly winds which provide the ideal platform for creation of radiation fog over the city (IMD 2011). Based on real-time monitoring data for 2010 it can be seen in the figures below that pollutants (PM, SO 2 and NO 2 ) build up

6 rapidly from October onward till end of November as cold weather sets in (Fig. 5). All days in November and December have high concentration with several recorded readings termed critical (CSE 2010). Fig. 5: Rapid build-up in pollutant levels from October to December in Delhi (Adopted from CSE 2010) Contrarily, the months of May and June bring to Delhi, the Loo, a strong, dry, high temperature (45-50 C) afternoon heat wave which originates in the Thar Desert and blows in the NE direction over the Indo-Gangetic Plain. The summer is a period of rising thermals, buoyancy in the boundary layer, vertical dispersion and turbulent mixing which allows better distribution of pollutants in the troposphere despite the level of emissions being the same. The summer concentrations are 50-75% lower than that observed during the other two seasons. To elucidate this difference Guttikunda and Gurjar (2012) use a Lagrangian air transport model to conclude that pollutants are 40-80% higher in winter and 10-60% lower in summer when compared with the annual average. Moreover, the diurnal variation of the mixing height is very pronounced in Delhi. Mixing height decreases substantially during post-monsoon and further more during winter. This effects the night time concentration of pollutants and is significant for a city like New Delhi which allows passage of dieselpowered trucks only at night (after 9 PM). These trucks have an average age of at least 5 years. The night time concentration of PM from such sources is a growing concern as they reach levels nearly twice of that in the day. The pollutants concentrated at night linger during rush after and beyond (~11 AM) increasing the time of exposure and provide the surface for daytime photochemistry (Guttikunda 2009).

7 3.2. Intra-city variation Table 2 summarizes the quality of ambient air in the 10 locations measured at various locations in the city. As mentioned before, Prahaladpur was chosen as the reference site (minimum anthropogenic interference) and concentration of pollutants here were found to be well within the NAAQS requirements for all pollutants except PM. Pitampura with a population of is a predominantly residential area with some commercial activities. This site shows high levels of PM and NO 2 during postmonsoon and winter due to low vertical mixing and recent road construction activities in the area. Ozone and NO 2 follow a diurnal distribution pattern with high levels of ozone coinciding with high levels of NO 2 during these periods. Naraina houses ~1200 small scale industries, people and a railway line passing through it. The volume mixing ratios of pollutants are highest in winter due to adverse meteorology of the area, poor quality of roads, dust re-suspension and heavy industrial activity. SSI-GTK is a located in the Jahangirpuri heavy industry area, and has nearly inhabitants, 60% of which live in slums. There are two national highways present in the area which experience heavy vehicular traffic throughout the day. Also, the period of sampling of this site coincided with the construction activities of the Delhi Metro. Owing to all these factors, the pollutant levels for all components measured exceed the national requirements in all three seasons and most substantially during winter. Moreover, SSI is the only region in the city to surpass its SO 2 concentration. Ashram Chowk is the busiest traffic intersection in Delhi with the road junction connecting two states. During the day there is heavy vehicular traffic and at night heavy duty trucks pass through it; hence, the PM here has high carbonaceous fraction. Moreover, this area is representative of kerbside activity and NO 2 levels are beyond the NAAQS in all seasons. Dhulakaun is a major intersection of five roads including National Highway 8 which connects the city to the airport. It serves as a hub for multimodal travelers as it a primary stop on the Delhi Ring Railway and for the Delhi Metro. Construction of flyovers in the early 2000s has improved the traffic flow here though mixing ratios still do not meet the required standards. Anand Vihar is home to East Delhi s affluent, has only residents and is upcoming commercial center. Construction projects in the area are responsible for the high levels of PM 10 especially in post-monsoon and NO 2 is found to exceed standards only in a few instances. ISBT connects five north Indian states to Delhi, has a metro-rail station, and a bus stand for local transportation. Despite its low inhabitation, the floating population is high and commensurate with commercial activities in the area. Traffic congestion and heavy vehicular movement both during the day and at night make ISBT the most polluted area in New Delhi. This is especially true for RSPM during post-monsoon when the levels surpass the standards by several folds. Loni Road records similar values for PM 10 post rainfall but, the causality here is the poor road conditions and road dust re-suspension throughout the year.

8 4. Conclusion and Recommendations There is a well-established body of literature linking deteriorating air quality with human health (See Samet et al. 2000; Chhabra et al and Pope et al. 2002). However, the effects of adverse environmental conditions (say, air pollution) on human health still remain notoriously difficult to quantify and predict. To estimate the health risk due to air pollution in New Delhi, Gurjar et al. (2011) use a Risk of Mortality/Morbidity due to Air Pollution (Ri-MAP) model and consider three pollutants (PM, SO 2 and NO 2 ). They estimate respiratory mortality as ~1600/yr, cardiovascular mortality at ~3500/yr and hospital admissions due to Chronic Obstructive Pulmonary Disease (COPD) at ~1500/yr. Moreover, due to its high levels of PM especially in the cold winter months, New Delhi ranks 5 th among the mega-cities of the world in terms of air pollution based health effects. In New Delhi, the concentration of air pollutants still remains well above the mandated thresholds despite the implementation of government led initiatives such as the conversion of public road transportation fleet to CNG. As previously mentioned, socio-economic development of the city has increased the number of privately owned diesel-fuel vehicles that have countered such measures. Moreover, as Kumar and Foster (2007) point out, there is substantial intra-regional variation in the effectiveness of such policies in increasing air quality. There have been unintended externalities as a result of regulations outside the region; for instance, the increase in the number of non-cng fuelled vehicles outside the National Capital Territory (Foster and Kumar 2011). Metropolitan Delhi s population is expected to swiftly grow to 36 million people by 2030 (UN 2014). NEERI estimates that based on the past trends, the number of vehicles on the roads of Delhi will continue to grow to keep pace with the population growth. Moreover, NEERI also estimates that the emission loads under BAU scenario indicate that by 2017, an increase of 58%, 54%, 47% and 64% for PM, CO, HC and NOx, respectively will take place compared to the levels of In light of these projections it is imperative to adopt and implement regulatory policies to curb further emissions. To this effect, some implementable measures could be: Effective distribution of population to surrounding areas Implementation of stricter norms (Bharat stage IV) Better construction practices (say, water spraying) Enforcing the ban of open-air biomass burning Shifting small scale industries to Special Economic Zones in the NCT Mandating biofuel blending in vehicles Retro-fitment of Diesel Oxidation Catalyst and Particulate Filters in public transport Banning commercial vehicles older than 10 years and private ones above 15 years Fiscal incentives (parking/congestion fee, fuel price deregulation)

9 TABLE 2: Data Set for Ambient air quality monitoring at 10 different sites across the city of New Delhi (Source: NEERI 2008; DPCC 2009; CPCB 2010; CSE 2010) No. SITE Season Ozone PM 10 SO 2 NO Pralhadpur Reference Low-activity Zone Pitampura Residential Naraina Industrial/Mixed Use SSI-GTK Industrial Ashram Chowk Busiest Traffic Intersection Mayapuri Residential + Industrial Anand Vihar Kerbside Near ISBT Loni Road Residential+Commercial Dhulakaun Kerbside Major Road Intersection ISBT Inter-State Bus Terminal Min Max Avg. Min Max Avg. Min Max Avg. Min Max Avg. Summer Post-Monsoon Winter Summer Post-Monsoon Winter Summer Post-Monsoon Winter Summer Post-Monsoon Winter Summer Post-Monsoon Winter Summer Post-Monsoon Winter NA NA Summer Post-Monsoon Winter NA NA NA Summer Post-Monsoon Winter NA NA NA Summer Post-Monsoon Winter Summer Post-Monsoon Winter

10 FIGURES 2-4: Monthly variation in ambient air pollutants over the city of New Delhi Minimum Maximum 35 Minimum Maximum 800 Average 30 Average SPM Concentration (µg/m3) SO 2 Concentration (µg/m 3 ) Dec. April May June July Aug. Sep. Oct. Nov. Dec. Jan. Feb. Mar. May June (2007) 0 Dec. April May June July Aug. Sep. Oct. Nov. Dec. Jan. Feb. Mar. May June (2007) Minimum Maximum Average Minimum Maximum Average RSPM Concentration (µg/m 3 ) NO 2 Concentration (µg/m 3 ) Dec. April (2007) May June July Aug. Sep. Oct. Nov. Dec. Jan. Feb. Mar. May June 0 May June July Aug. Sep. Oct. Nov. Dec. Jan. Feb. Mar. May June

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