Studies on Particulate Matter in Ambient Air of Urban Mangalore

Abstract

A city’s ambient air quality could determine the life standard of the residing population. In a developing nation like India, the industrial sector growth is on an ever-increasing trend in order to cater the demands of the burgeoning population. With the addition of industries and automobiles which could potentially process and deliver non- environmental friendly substances result in air pollution. In the realm of air pollutants, Particulate Matter (PM) and its chemical constituents like elements, ions and organic compounds (Polycyclic Aromatic Hydrocarbons (PAHs)) are carcinogenic and mutagenic and thus requires attention to reduce the health impacts in any urban environment. Among the fast-growing cities in India, the coastal city of Mangalore accommodates various industries and educational institutes and there is a large population of natives and non-natives dwelling in the city. The given research thesis aims to identify the types of particulate matter (PM 10 & PM 2.5 ) prevailing in the ambient air of Mangalore and to estimate their source contributions by using a receptor modeling technique Chemical Mass Balance (CMBv8.2). A dispersion modeling study is also carried out using AERMOD v 9.1 to estimate the dispersion of particles in the urban city of Mangalore. Source apportionment studies on Particulate matter (PM 10 and PM 2.5 ) have been carried out by identifying six sampling sites to be hotspots of urban Mangalore. The sampling sites across the city were selected with emphasis to industries, traffic junction, places of public gathering and regions near to schools. The particulate samples have been collected according to the guidelines proposed by Central Pollution Control Board (CPCB), India. The mass concentrations of PM 10 and PM 2.5 have been measured by gravimetric technique and found to be exceeding the NAAQS limits, with the highest concentration of 231.5 μg/m 3 of PM 10 particles and 120.3 μg/m 3 of PM 2.5 particles were found at Town Hall and KMC Attavar sites respectively. The elemental analysis using Inductively Coupled Plasma Optical Emission Spectrophotometer (ICPOES) revealed twelve different elements (As, Ba, Cd, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Sr and Zn) for PM 10 particles and nine different elements (Ba, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Sr and Zn) for PM 2.5 particles. Similarly ionic composition of these samples measured by Ion Chromatography (IC) divulged nine different ions (F - , Cl - , NO 3- , PO 4- , SO 42- , Na + , K + , Mg 2+ and Ca 2+ ) for PM 10 particles and ten different ions (F - , Cl - , NO 3-, PO 4- , SO 4- , Na +, NH 3- , K + , Mg 2+ and Ca 2+ )for PM 2.5 particles. Estimation of PAHs for the collected samples revealed the presence of Fluorene (Flu), Acenaphthene (Ace), Chrysene (Chr), Benz(a)anthracene (B(a)A), Benzo(a)pyrene (B(a)P), Benzo(b)fluoranthene (B(b)F), Indeno (1,2,3-c,d) pyrene at significant concentrations. The Total Polycyclic Aromatic Hydrocarbons (TPAHs) concentration was observed to be higher at Town Hall sampling site with a concentration of 112.89 ng/m 3 . Likewise, the chemical compositions of PM 2.5 samples collected in the school premises were analysed using ICP OES (Ba, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Sr, Ti, V and Zn) and Ion Chromatography (F - , Cl - , NO 3- , PO 43- , SO 42- , K + , Ca 2+ , Mg 2+ , NH 4+ , Na + ). A simulation study on the dispersion of particulate matter have been carried out to assess and predict the urban air quality using AERMOD, and validated with the experimental data. The performance of AERMOD is evaluated for prediction of PM 2.5 concentrations at various hotspots in the city. Future control scenarios have also been proposed VR: Vehicles older than 10 years are phased out; CF1: Diesel car to petrol car; CF2: Diesel and petrol car to CNG car; CF3: Diesel bus to CNG bus to predict the reduction in particulate concentration. The source apportionment study for PM for urban Mangalore region in accordance with these six sample sites using USEPA CMBv8.2 revealed nine and twelve predominant contributors for PM 10 and PM 2.5 particles respectively. The highest contributor of PM 10 particles was found to be paved road dust followed by diesel and gasoline vehicle emissions. Correspondingly, PM 2.5 particles were found to be contributed mainly from two-wheeler vehicle emissions followed by four-wheeler and heavy vehicle emissions (Diesel vehicles). The PAHs have been contributed majorly from eight different sources with its highest contribution from diesel powered passenger cars and heavy vehicles combustion. Similarly, the predominant sources contributing to school premises was found to be Paved Road Dust, Soil Dust, Gasoline Vehicle Emissions, Diesel Vehicle Emissions and Marine Source Emissions. However, vehicular emissions contribution was found to be higher in the schools located near to any roadway than the school located away from the major roadways. The difference in location and dissimilarity in activities going on has been found to be the sole cause for variation in sources among the schools. Hence, the source apportionment study carried out for particulate matter and PAHs in urban Mangalore and for particulate matter in the school premises clearly depicts that these pollutants prevailing in the ambient atmosphere of urban Mangalore has around70% of their contribution from vehicular emissions (both exhaust and non-exhaust). The dispersion study results show that the predicted pollutant concentrations are in satisfactory limits at all the sampling sites. The statistical descriptors such as correlation coefficient (R 2 ), index of agreement (d), Normalized mean square error (NMSE) and Fractional Bias (FB) have been found to be satisfactory. The proposed future control scenarios were found to reveal significant results. Among the proposed scenarios CF3 shows a higher reduction of PM concentration up to 23%. Thus, the source apportionment and dispersion modeling studies on urban Mangalore clearly portrays that the emissions from vehicular exhaust, resuspension of road dust and vehicular traffic at hotspots plays a major role in deteriorating the air quality of urban Mangalore by releasing the harmful pollutant particulate matter into the ambient atmosphere of the city