10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Chemical Characterization and Source Apportionment of PM2.5 Aerosols in the Capital City “New Delhi” of India
S.N. TRIPATHI, Deepika Bhattu, Navaneeth M. Thamban, Vipul Lalchandani, Suneeti Mishra, Purushottam Kumar, Shashi Tiwari, Nidhi Tripathi, L.K. Sahu, S.B. Tiwari, Rangu Venkata Satish, Neeraj Rastogi, Atul K. Srivastava, Deewan S. Bisht, Suresh Tiwari, R. Sutaria, M. Mohan, Dilip Ganguly, Sudipta Ghosh, Pawan Vats, A. Tobler, Varun Kumar, P. Rai, Veronika Pospisilova, Giulia Stefenelli, IIT Kanpur
Abstract Number: 486 Working Group: Aerosol Chemistry
Abstract New Delhi, an Indian megacity suffers from the intense pressure of urbanization, industrialization and densely populated regions. These potential factors have caused sequential degradation of ambient air quality (300% higher PM2.5 than NAAQS) and have been estimated to cause ~12000 premature deaths per year 1. In last five years (2010-2015), a rapid increase (10 ug m-3) in the population-weighted PM2.5 mean concentration over India has been observed and attributed to fifth-ranking mortality risk factor2. Additionally, high pollutants concentrations also lead to urban and regional haze, deleterious impact on the regional ecosystem, crop yield and climate change. Consequently, more ambitious and strict control strategies together with the financial incentive schemes are required to have speedy changes in PM2.5 levels and life expectancy.
Despite of the past efforts (1996-2010)3, such as, cutting down the sulfur content of diesel and petrol and transition (2002) to compressed natural gas (CNG), and shutdown of the “hazardous” industries, the annual average PM2.5 levels persisted at alarming levels (110-120 µg m-3) during 2011-2015. Recent attempt of PM2.5 mitigation as “odd-even traffic intervention, 2016” policy was also proven with no success1. However, to understand the impact of such desperate policy measures and redesign the effective strategies, a more precise long-term characterization and source apportionment of organic/inorganic gaseous and particulate phase species at both local- and regional-scales is required.
Here, we combine a comprehensive set of novel and hybrid approach (offline and online) with statistical techniques to understand the sources and chemical nature of fine particulate matter (PM) in New Delhi. Ambient measurements are performed at 5 sites extending to both upwind (Hisar) and downwind (Kanpur) of New Delhi (IITM, IIT Delhi and MRIU). Sampling sites in New Delhi are partly surrounded by dense vegetation and affected by a mix of local traffic and residential activities. Real-time particle phase organic and inorganic composition at Delhi sites are measured by Aerodyne’s aerosol mass spectrometer (AMS) and time-of-flight aerosol chemical speciation monitor (ToF-ACSM), and extractive electrospray ionization long-time-of-flight mass spectrometer (EESI-LToF-MS), and organic gases using proton transfer reaction time-of-flight mass spectrometer (PTR-ToF-MS). Further, particle number concentration and size distribution (up to 20 µm) are obtained by integrating scanning mobility particle sizer (SMPS, TSI) and optical particle sizer (OPS, TSI) and/or aerodynamic particle sizer (APS, TSI). In addition, real-time BC mass concentration and size distribution, WSOC and BrC, and multi-metal concentrations are measured by 7-wavelength Aethalometer and single particle soot photometer (SP2), particle-into-liquid sampler coupled with a liquid waveguide capillary cell and total organic carbon analyzer (PILS-LWCC-TOC) and XACT®625i, respectively. Supporting meteorological parameters (wind speed, wind direction, RH, Temp. and precipitation) and gas concentrations are provided by automatic weather station (AWS), and O3, SO2, CO and NOx analyzers. Concurrently, day and night time PM2.5 filters collected from all 5 sites are further analyzed for (a) WSOC content by newly developed mass spectrometric techniques, (b) EC-OC content, (c) radiocarbon (14C), (d) ions and (e) trace metals. Further, to understand space-time variability, hot spots and contribution from local vs regional sources and validate satellite observations and chemical transport models, a network of 25 low cost optical aerosol sensors (PM2.5 and PM10) over square grids in National Capital Region of Delhi have also been deployed.
The results of this study will aid in linking the sources and day and night atmospheric processing of the emissions, further elucidating the production pathways of secondary organic aerosol and health relevant oxygenated species. It will provide the relevant information to the regulatory authorities concerning abatement technologies to reduce the environmental, economic and health impacts resulting from particulate pollution.
References: 1. Chowdhury, S.; Dey, S.; Tripathi, S. N.; Beig, G.; Mishra, A. K.; Sharma, S., “Traffic intervention” policy fails to mitigate air pollution in megacity Delhi. Environmental Science & Policy 2017, 74, 8-13. 2. Cohen, A. J.; Brauer, M.; Burnett, R.; Anderson, H. R.; Frostad, J.; Estep, K.; Balakrishnan, K.; Brunekreef, B.; Dandona, L.; Dandona, R.; Feigin, V.; Freedman, G.; Hubbell, B.; Jobling, A.; Kan, H.; Knibbs, L.; Liu, Y.; Martin, R.; Morawska, L.; Pope, C. A., III; Shin, H.; Straif, K.; Shaddick, G.; Thomas, M.; van Dingenen, R.; van Donkelaar, A.; Vos, T.; Murray, C. J. L.; Forouzanfar, M. H., Estimates and 25-year trends of the global burden of disease attributable to ambient air pollution: an analysis of data from the Global Burden of Diseases Study 2015. The Lancet 2017, 389 (10082), 1907-1918. 3. Narain, U.; Krupnick, A., The Impact of Delhi’S CNG Program on Air. 2007.