Characterization of PM2.5 in Delhi: Role and Impact of Secondary Aerosol, Burning of Biomass, and Municipal Solid Waste and Crustal Matter
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Environ Sci Pollut Res (2017) 24:25179–25189 DOI 10.1007/s11356-017-0171-3 RESEARCH ARTICLE Characterization of PM2.5 in Delhi: role and impact of secondary aerosol, burning of biomass, and municipal solid waste and crustal matter Pavan K. Nagar1 & Dhirendra Singh1 & Mukesh Sharma1 & Anil Kumar2 & Viney P. Aneja 3 & Mohan P. George4 & Nigam Agarwal2 & Sheo P. Shukla5 Received: 15 June 2017 /Accepted: 7 September 2017 /Published online: 18 September 2017 # Springer-Verlag GmbH Germany 2017 Abstract Delhi is one among the highly air polluted cities in were the important sources. It was observed that secondary the world. Absence of causal relationship between emitting aerosol and crustal matter accounted for over 50% of mass. sources of PM2.5 and their impact has resulted in inadequate The PM2.5 levels were not solely result of emissions from actions. This research combines a set of innovative and state- Delhi; it is a larger regional problem caused by contiguous of-the-art analytical techniques to establish relative predomi- urban agglomerations. It was argued that emission reduction nance of PM2.5 sources. Air quality sampling at six sites in of precursors of secondary aerosol, SO2,NOx, and volatile summer and winter for 40 days (at each site) showed alarm- organic compounds, which are unabated, is essential. A sub- 3 ingly high PM2.5 concentrations (340 ± 135 μg/m ). The col- stantial reduction in BMB and suspension of crustal dust is lected PM2.5 was subjected to chemical speciation including equally important to ensure compliance with air quality ions, metals, organic and elemental carbons which followed standards. application of chemical mass balance technique for source apportionment. The source apportionment results showed that Keywords PM2.5 .Sourceapportionment .Biomassburning . secondary aerosols, biomass burning (BMB), vehicles, fugi- MSW burning . Secondary aerosols tive dust, coal and fly ash, and municipal solid waste burning Introduction Responsible editor: Gerhard Lammel The first 2 weeks of November 2016 witnessed a high air Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11356-017-0171-3) contains supplementary pollution episode in the city of Delhi and surrounding areas material, which is available to authorized users. causing widespread panic among general population, forcing closure of schools and limiting outdoor activities. The air * Mukesh Sharma quality index at five sites in Delhi was in worst pollution [email protected] category (severe) for all these days (Fig. S1). The episodic conditions led to interventions from the courts and regulatory 1 Department of Civil Engineering, Center for Environmental Science agencies. The important issue that came to the fore was to and Engineering, Indian Institute of Technology Kanpur, identify the sources and establish causal source-impact Kanpur, Uttar Pradesh 208016, India linkage and work out short and long-term action plans to 2 Department of Environment, Government of National Capital prevent such episodes. Territory of Delhi, New Delhi 110002, India It is important not to see Delhi in isolation but as a large 3 Department of Marine, Earth and Atmospheric Sciences, North area of the Indo-Gangetic Plain (IGP; extending from Carolina State University, Raleigh, NC 27695-8208, USA 21°45′N, 74°15′E to 31°00′N, 91°30′E) (Nair et al. 4 Delhi Pollution Control Committee, Government of National Capital 2007). The IGP supports 40% of India’s population (Nair Territory of Delhi, New Delhi 110002, India et al. 2007) that includes the national capital region (NCR: 5 Department of Civil Engineering, Institute of Engineering & 27°03′N, 76°07′E to 29°29′N, 78°29′E), of which, Delhi is Technology, Lucknow, Uttar Pradesh 226021, India a subset. About 46 million people (equivalent to about six 25180 Environ Sci Pollut Res (2017) 24:25179–25189 contiguous New York cities) reside in the NCR (population Fig. 1 Chemical composition and source apportionment of PM2.5 in a density of 11,297 persons per square kilometer). The NCR Delhi during winter and summer (November 2013–June 2014) at the six is the center of the nation having important commercial, sites and b National Capital Region at three sites during winter (January 2015) economical, defense, industrial, and political establish- ments (Census-India 2012; NCRPB 2015). Unfortunately, the NCR which includes Delhi is one of the world’smost air polluted regions (WHO 2014). meteorology, over Indian sub-continent, mostly favors the The large scale urbanization, industrialization, land-use transport of emissions eastward along the Himalayas changes, biomass, and fossil fuel burning, along with the (Kaskaoutis et al. 2014). The increased PM concentration in unique topography of the basin (constrained dispersion due October–November is possibly due to the effect of post- to the Himalayas in the north and north east) are responsible monsoon BMB which takes place in the states of Punjab and for the alarming levels of particulate pollution in the region Haryana in North-West of Delhi. About 70–80 million tons of (Nair et al. 2007; Prasad and Singh 2007; Ram et al. 2010; rice crop residue is disposed of through open field burning Pant et al. 2015). In addition, lack of year-round precipita- (Badarinath et al. 2006; Gadde et al. 2009). As soon as the tion further leads to high aerosol loading over the entire BMB is reduced after the second week of November, the air IGP. Measurements of aerosol optical depth (AOD) have quality begins to improve (Fig. S1). characterized IGP as a hotspot for anthropogenic aerosols Behera and Sharma (Behera and Sharma 2010)have in South-Asia (Ramanathan et al. 2007; Ram et al. 2012a). reported that secondary aerosols contribute about 50% In IGP, the monthly mean of AOD levels suggest (Fig. S2) mass in PM 2.5; 34% of secondary inorganic aerosol that the particulate levels are much higher in winter than in (SIA) and 17% of secondary organic aerosol (SOA) in an any other season. The region witnesses extreme variability urban area of IGP. Various studies have suggested that a in the climate throughout the year, which causes significant significant mass of atmospheric PM in the IGP comprised shifts in air quality from summer to winter (Mohan and carbonaceous aerosol (~ 30–35% of the PM) and water- Kandya 2007; Ram et al. 2010). soluble inorganic aerosol (~ 10–20% of the PM) (Tare et al. The IGP is characterized by severe haze during winter 2006; Rengarajan et al. 2007; Ram et al. 2010, 2012a; (November–January), which disrupts normal life and affects Deshmukh et al. 2011;Kothaietal.2011). the public health. During 2001–2010, the annual mean In India, the causal relationship between emitting source concentration of PM10 (particulate matter of size 10 μm and its impact in terms of PM2.5 concentrations is not under- or less) in major cities in IGP (Delhi, Kanpur, Lucknow, stood. This has resulted in inadequate actions and insignificant Agra,Faridabad,Amritsar,Meerut,andAllahabad) improvements in air quality. This research combines innova- exceeded the annual Indian National Ambient Air Quality tive and state-of-the-art analytical techniques to explain the Standard (NAAQS) of 60 μg/m3 (three times of the WHO chemical characteristics and relative predominance of the guideline of 20 μg/m3) by a factor of 1.6–4.3 (CPCB 2012) sources of particulate pollution during two seasons (winter: and the mean concentrations in winter (October–March) November 2013–February 2014 and summer: April– 3 3 were 338–548 μg/m for PM10 and 236–389 μg/m for June 2014) in Delhi and in NCR (outside Delhi; winter: PM2.5 (Tiwari et al. 2012). The pollution levels are higher January 2015). Our analyses of results have set in a process in winter than in other seasons due to increased emissions of practical measures for PM2.5 emission reductions and assist from biomass burning (BMB; which includes crop residue in preparation of action plan. burning), heating, and unfavorable meteorological conditions In summary, this research presents a comprehensive study for dispersion (Guttikunda and Gurjar 2012; Ram et al. 2012b). that provides a framework for conducting a systematic and Delhi being the capital city, its high pollution receives organized study for addressing most issues of air quality in much attention from media, politicians, and even foreign em- urban areas which are relevant to developing countries. bassies and High Commissions. The annual mean PM10 con- Specifically, the framework includes air quality monitoring, centration is 261 μg/m3 with a maximum daily mean of detailed particulate characterization, identification of sources, 748 μg/m3 in 2010 (CPCB 2012), and the annual mean and their contributions to ambient air pollution. 3 PM2.5 concentration was153 μg/m (WHO 2014;Myllyvirta and Dahiya 2015). The acute winter particulate pollution 3 (PM2.5 ∼ 200 μg/m ) was accompanied by extremely poor Materials and methods visibility and sharp increase in respiratory diseases (Liu et al. 2013; Huang et al. 2014; Saraswat et al. 2016). Six air quality monitoring sites in the city of Delhi, which October–November months see a dramatic increase in the represented typical land-use patterns, were selected for air fine mode particulate levels (Badarinath et al. 2009; Awasthi quality sampling (Fig. 1). The overall sampling plan, descrip- et al. 2011; Ram et al. 2012b;Kaskaoutisetal.2014). The tion of sites, and data capturedarepresentedinTable1. Environ Sci Pollut Res (2017) 24:25179–25189 25181 (a) Delhi 1. RHN (380 µg/m³) 2. OKH (422 µg/m³) 3. DWK (297 µg/m³) 20.1 17.4 17.7 28.9 31.1 28.3 6.3 5.7 6.7 0.2 0.2 0.2 4.5 5.7 7.7 5.9 14.3 17.6 10.2 7.0 23.9 6.9 5.2 6.6 3.8 7.5 10.4 13.7 16.4 18.6 17.2 18.7 4.5 29.0 0.0 4.6 11.7 0.0 11.8 15.8 0.0 2.9 12.0 27.6 21.2 1.0 16.0 20.9 1.8 11.0 0.8 1.8 19.7 1.1 4.