Correlation and Source Profiling of Organic Tarry Matter and PAHs in Fine Particulate Matter in Urban Ambient Air

Abstract

In present era, urban air pollution has a serious health concern as the result of rapid urbanization, industrialization, population bloom, increasing automobiles and economic expansion. Air pollution episodes around the world like Meuse valley smog (1930), Donora smog (1948) and London smog (1952 & 1962) caused thousands of deaths due to high air pollution. As per an UNEP and WHO estimate, worldwide more than 500,000 deaths yearly worldwide are caused due to inhalation of particulate matter per annum. Particulate matter plays the significant role on human health in the presence of complex synergistic interrelationships among atmospheric processes such as visibility, precipitation, solar radiation, climate change, cloud formation and acidification. It also affects the features like ecosystems, vegetation and works of art & building materials. The epidemiological studies confirm that the adverse health effects are mainly due to particulate matter, especially smaller particles of PM2.5 (<2.5μm in size) Particulate matter is a complex mixture of organic and inorganic substances suspended in air as solids and liquids. Particulate aerosols are very diverse in size, shape and chemical composition depending on the source, meteorological conditions and geographical localization of the area. It is very essential to elaborate the emission sources of particulate matter in view of the air quality and human health perspectives. The implication of the preventive and control measures to minimize the mass levels of particulate matter is only possible when the emission sources are quantitatively characterized and identified. Source apportionment is based on the fact that the different emission sources of particular location have their characteristic chemical signature or source profile at that site such as potassium has strong association with biomass burning, while aluminum and silicon are strongly associated with crust material. The emissions of various industries are enriched in specific pollutants like iron from steel mills, calcium from cement plants and carbonaceous matter from diesel combustion. An elevation of only 10μg/m3 each in fine particulate matter is associated with approximately 4, 6 and 8% increased risk of cardiopulmonary, lung cancer and mortality respectively. Symptomatic or biological effects are determined by the chemical nature, site of deposition within lungs and physiologic responses of the deposited particulate matter. OC is suspected as carcinogenic and mutagenic, whereas EC causes tissue irritation and interferes in lung clearance mechanism. Polycyclic aromatic hydrocarbons (PAHs) among the organic compounds emitted by various combustion processes are likely to be carcinogenic and interferes the functioning of reproduction, hormone and immune systems. So far much attention has been focused on source apportionment of particulate aerosols in India and abroad, however sources of PM2.5 have not been characterized and identified in metropolitan region of Chandigarh (UT, India). This study presents mass levels, chemical characterization of PAHs and organic tarry matter, seasonal variation and source apportionment of PM2.5 using three years data of summer and winter seasons from the metropolitan region of Chandigarh tri-city. The metropolitan region of Chandigarh Tricity includes Chandigarh-Mohali-Panchkula with over 2 million of population. Chandigarh is a union territory of India and serves as the combined capital of both states of Punjab and Haryana. Whereas Mohali and Panchkula are district head quarters of Punjab and Haryana states respectively. Chandigarh is located in the foothills of Shiwalik range of Himalayas and 162 miles (260 km) north of New Delhi, the national capital of India. The climate of Chandigarh is humid subtropical with varying temperature (−1 to 46 °C) and the annual average rainfall of 1110mm. Ambient air samples for particulate aerosols were collected from four location namely Sector 12 (Chandigarh), Sector 34 (Chandigarh), Sector 74 (Mohali) and Sector 12A (Panchkula). The present study focused on monitoring of fine particulate matter in ambient air of urban area and to source profile the ambient air and correlate with PAHs and organic tarry matter in fine particulate matter. Particulate aerosols (PM10 and PM2.5) were collected from the tricity of Chandigarh, Panchkula and Mohali during summer (April to May) and winter (December to January) seasons of 2013-14, 2014-15 and 2015-16. The mass levels of PM10 and PM2.5 respectively varied from 69.2-187.5 μg/m3 (average 116.4 μg/m3) and 40.5-100.3 μg/m3 (average 61.7 μg/m3) in 2013-14, 79.8-198.0 μg/m3 (average 138.9 μg/m3) and 43.2-105.7 μg/m3 (average 73.1 μg/m3) in 2014-15 and 80.1-194.1 μg/m3 (average 125.6 μg/m3) and 42.4-103.8 μg/m3 (average 66.4 μg/m3) in 2015-16. The values of PM10 and PM2.5 respectively exceeded to 24 hourly NAAQ standards of 100μg/m3 and 60μg/m3 during most of the sampling days which indicate the deteriorating air quality in this tricity. OTM contributes to PM2.5 mass as 36.0% in 2013-14, 40.1% in 2014-15 and 35.7% in 2015-16 whereas OTM/OC ratio ranges from 1.57 to 1.71 indicates carbon as the largest component. The concentration of total PAHs (∑PAHs) varied from 5.16 to 72.59 ng/m3 in 2013-14, 4.95-69.57 ng/m3 in 2014-15 and 5.38-75.62 ng/m3 in 2015-16 at the study area. Presence of these polycyclic hydrocarbons indicates the emissions from combustion processes mainly associated to vehicles and biomass burning. Markers of PAHs and their diagnostic ratio is used to categorize the anthropogenic and biogenic sources of emission. The ratio of IP/(IP+BghiP) as 0.42 under the range 0.37-0.70 and the ratio of BbF/BkF in the range 1.29-1.31 suggests the influence of diesel emissions whereas the ratio of BaA/BaP as 1.21 indicates the biomass burning. The ratio of BaA/(BaA+Chy) as 0.32 (0.20-0.35) indicates coal combustion in the study area. The diagnostic ratio performed in the study highlight the influence of multiple sources as vehicular emissions, coal combustion and Biomass burning as the main emission sources of PAHs in the study area. Pearson correlation shows higher coefficient among Acy, BghiP, BkF, dBahA, Fln, IP, Pery, Pyr, Chry, OC and EC as first group, high loading of Ant, BbF, BaA and NaP in second group and BaP, Flu, Ret and OTM in third group indicating similar and common sources of origin. Principal component analysis shows three contributory sources of particulate aerosols as vehicular emissions (44.03%), coal combustion (18.85%) and wood & biomass burning (15.88%). The study describes existing air quality & source inventory in tricity of Chandigarh based on three years long data and it becomes a base to device an effective management plan for air pollution control and emission reduction strategies. The study recommends a comprehensive and regular monitoring of fine aerosols to understand the nature, strength, trend and potential health impacts of emission sources in the region.