STUDY OF TRACE GASES AND AEROSOLS IN MIXED USE AREA OF DELHI

Abstract

The study of trace gases and aerosol concentrations were carried out in urban area (Naraina Industrial Area) of Delhi, India. This location represents the mixed use area (combination of residential, commercial, institutional and industrial uses) of Delhi India. The samples were collected from January to December, 2011. The study revealed the poor ambient air quality in the selected hotspot location was mostly anthropogenic. The particulate matter (PM10 and PM2.5) both were beyond the permissible limit of National Ambient Air Quality Standards (NAAQS) notification published by Central Pollution Control Board (CPCB), Government of India, New Delhi on 18th November, 2009. The average contribution of total carbonaceous aerosol in PM10 and PM2.5 were 62% and 50% respectively and contribution of secondary organic aerosol in PM2.5 was 27% of PM2.5 mass. The concentrations of PM10 and the concentrations of trace gases like SO2 NO2 and NH3 are interlinked to a large extent due to atmospheric reactions. The contribution of atmospheric inorganic secondary particles (sulfates, nitrates and ammonium) in PM10 during the study period was 20%. Heavy metal and particulate polycyclic aromatic hydrocarbon contributions in PM10 were 3%, and 1%, respectively. 14% of total aerosol mass of PM10 was not identified in this study. The unknown mass may be contributed by bioaerosols, heavy metals, inorganic salts and PAHs which are not included in the proposed study objectives. PCA-MLR explained the eight major sources which had contribution to increase the concentrations of particulate matter at Naraina mixed use area of Delhi. The contribution of sources are like Industrial emission was (30%), vehicular emission (25%), road dust (16%), iron and steel foundries (14%), pigment industry (6%), biomass burning (5%), smoke (4%) and miscellaneous sources (2%). The mass concentrations of particulate matter (PM10 and PM2.5) were followed the order of postmonsoon> winter> pre-monsoon > monsoon. Mass closure analysis (MCA) was also carried out for both PM10 and PM2.5.The chemicals compositions of PM10 were grouped into nine classes. The annual distributions of chemical compositions in percentage are of: organic matter (41%), elemental carbon (8%), non-sea salt sulphate (6%), nitrate (5%), ammonium (3%), sea-salt (0%), mineral dust (19%), non-dust elements (1%) and unaccounted mass (17%). The chemical components of PM2.5 were grouped into two classes. Only organic matter and elemental carbon were measured for PM2.5. The other chemical components like non-sea salt sulphate, nitrate, ammonium, sea-salt, mineral dust are considered in unaccounted mass of PM2.5. The annual distributions of chemical compositions in percentage are of: organic matter (39%), elemental carbon (9%) and unaccounted mass (52%). Biomass

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combustion is also a significant source of fine particle emissions and their characterization and reduction is an important issue. The emission control of effluent gases, proper maintenance of roads and plantation of dust capturing plants may reduce the emission at urbanized industrial area. More attention is required to control emission of air pollutants at source itself.