Sources Apportionment of Fine and Coarse Aerosol in Bangi, Selangor Using Positive Matrix Factorization
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Jurnal Sains Nuklear Malaysia, 2018, 30(1): 19 – 29 ISSN: 2232-0946 SOURCES APPORTIONMENT OF FINE AND COARSE AEROSOL IN BANGI, SELANGOR USING POSITIVE MATRIX FACTORIZATION Shamsiah Abdul Rahman, Md Suhaimi Elias, Nazaratul Ashifa Abdullah Salim, Zalina Laili, Azian Hashim, Shakirah Abd Shukor, Siti Aminah Omar and Muhammad Azfar Azman Waste and Environmental Technology Division Malaysian Nuclear Agency, Bangi 43000 Kajang, Selangor, Malaysia Correspondence email: [email protected] ABSTRACT Samples of fine (PM2.5) and coarse (PM10-2.5) fraction of airborne particulate were collected on weekly basis during the period from May 2012 to July 2014 at Bangi, Selangor. The samples were collected using a Gent Stacked Filter Sampler in two fractions of < 2.5 µm and 2.5 - 10 µm sizes. This research paper aims at establishing the concentration level of PM2.5, PM10-2.5 and PM10 at Bangi area and investigates their possible sources and contribution to the ambient aerosol of the area. The samples were analyzed for their elemental composition and black carbon content by Particle Induced X-ray Emission (PIXE) and Smoke Stain Reflectometer, respectively. The average 3 3 3 3 for PM2.5, PM10-2.5 and PM10 ranged from1.8 µg/m to 78.0 µg/m , 9.6 µg/m to 76.8 µg/m and 12 µg/m3 to 134 µg/m3, respectively. Positive Matrix Factorization (PMF) technique was also applied to fine and coarse data set in order to identify the possible sources of particulate matter (PM) and their contribution to the ambient particulate matter concentrations in the area. The best solution was found to be five factors for both elemental compositions of fine and coarse PM, respectively. The PMF results show that motor vehicles and secondary sulphate contribute about 40.3% and 33.0% of the fine mass respectively followed by soil, sea salt and smoke/biomass burning with the average contribution of 10.5%, 10.3% and 6.4%, respectively. In case of coarse particles the PMF results show that a large fraction of about more than 50% of the coarse mass comes from motor vehicle. Soil dust including road dust and soil construction contribute about 32.5% of the coarse mass whilst the smoke/biomass burning factor contributes about 6.7% of the coarse mass Keywords: Airborne particulate, Bangi, elemental composition, Positive Matrix Factorization INTRODUCTION Bangi is a small town situated on the south of the district of Hulu Langat in Selangor, Malaysia. It is a suburban area located in Klang Valley (southeastern), about 10 kms from the city of Kajang and 10 kms from Putrajaya, the Malaysia’s federal administrative capital. There is a main road with shops houses on both side of the road. The town is linked to KTM commuter train services via the Bangi Komuter station and is surrounded by small Malays villages, within 3 kilometers distance, namely, Kampung Bangi, Kampung Bahagia, Kampung Batu Lima and Kampung Rinching. Twenty years ago the town was also surrounded by many palm oil estates and rubber estates but it is now suffered with the development threatened to turn it all to concrete. Many palm oil estates had been converted into townships, learning institution, research centre and residential area. Within a 3 kilometers distance, there are residential areas namely Seri Putra Bangi, Bukit Mahkota Bangi, Bangi Avenue, Taman Impian and many more. About 7 kms north there is a larger township namely Bandar Baru Bangi, named after the town (Bangi). It has a population about 1,500,000 and Jurnal Sains Nuklear Malaysia, 2018, 30(1): 19 – 29 ISSN: 2232-0946 located between Kajang and Putrajaya about 25 kms away from the capital city, Kuala Lumpur. The town was developed in stages beginning in 1974 and provides commercial, industrial, business, training, recreation and higher learning institutions (Najihah and Rozilah, 2012). Basically, development of the area around Bangi (especially 10 to 20 kms radius) such as road upgrading, construction of buildings, opening of new residential area and shopping centre take place continuously since 20 years ago. In 2011 for example the Mass Rapid Transit (MRT) project with a span of 51 km from Sungai Buloh to Kajang city centre was launched and was formally opened on 17 July 2017 (http://www.mymrt.com.my/en/sbk/the-mrt-sungai-buloh-kajang-line). In 2012 new residential area namely Southville City located only few km from the town has been developed (https://www.propwall.my/insight/3269/southville_city) and still under construction. Dust and particulate matter (PM) emissions can come from a number of sources during construction activities, as well as from off-site vehicles associated with the construction works and on-site machinery (off-road emissions), including both static and non-road mobile machinery. Fine particles (particulate matter smaller than 2.5 µm in diameter) can travel further than coarser dust (particulate matter between 2.5 µm and 10 µm in diameter) and can therefore affect the health of people living and working in the surrounding area of the site. The measurements of chemical composition have been reported for different city of Malaysia (Azman et al., 2015; Norhayati et al., 2008; Rahman et al., 2011). However, most of the studies were focused on PM10 - particles up to ten micrometres in size. Fewer studies of this kind have considered fine particles of less than 2.5 µm (PM2.5) or particles between 2.5 µm and 10 µm (PM10-2.5). This paper reports about monitoring activities conducted in the year 2012 to 2014 of the continuous study on air paticulate pollution in Bangi area. The main objective of the study is to presents the first comprehensive investigation of particulate matter with an aerodynamic diameter less than 2.5 µm (PM2.5) and between 2.5-10 µm (PM10-2.5) compositions and sources in the area. With the growth of the area over the last twenty years, the study enhances an understanding of chemical properties of atmospheric pollution in the area and apportions the chemical constituents of particulate matter (PM) to their emitting sources. This work is an ongoing project undertaken by the Malaysian Nuclear Agency on air particulate pollution in collaboration with International Atomic Energy Agency (IAEA) through Regional Cooperative Agreement (RCA) program. The project involves sampling of air dust, measurement of mass, black carbon (BC) and elemental concentrations. The concept of receptor model was used in this study whereby the concentrations of elements at the sampling site were used to identify the fingerprints of major pollution sources and to estimate the contribution of major pollution sources to the area. MATERIALS AND METHODS Sampling The Bangi monitoring site (Figure 1) is located at Malaysian Nuclear Agency Complex, Bangi (2°54'24.56"N, 101°46'1.34"E) which is 35 kms south of Kuala Lumpur. The complex is just a few hundred meters to the road side and the north - south highway. Air particulate samples were collected from May 2012 to July 2014 using Gent Stack sampler (Hopke, 1997) provided by IAEA. The sampler was placed on a rooftop of a two storey building at approximately 10 meters height. The sampler was programmed to run automatically to collect two 24 hours duration sample (< 2.5 µm and 2.5 -10 µm aerodynamic diameter particles) twice a week from 12 noon to 12 noon. A total of 217 pair of samples were collected and analyzed covering the period of May 2012 to July 2014. Statistics of samples collected yearly starting from 2012 to 2014 were 61, 118 and 38 pairs. 20 Jurnal Sains Nuklear Malaysia, 2018, 30(1): 19 – 29 ISSN: 2232-0946 Sampling station at Malaysian Nuclear Agency, Bangi Figure 1: Location of sampling station at Malaysian Nuclear Agency, Bangi Mass and Black Carbon Measurement The total mass of each sample was determined by weighing the filter using a microbalance (METTLER Model MT5) equipped with a Po-212 (alpha emitter) electrostatic charge eliminator (STATICMASTER) to eliminate the static charge accumulated on the filters before each weighing. Black carbon (BC) measurements for both fine and coarse fraction were performed using an EEL Smoke Stain Reflectometer and the black carbon concentration was determined according to the method for 47 mm polycarbonate filter (Cohen et al., 2000). Elemental Analysis Concentration of the elements for each sample was analyzed by Particle Induced X-ray Emission (PIXE) (Cohen, 1998; Koltay, 1994) at Geological and Nuclear Science Limited, GNS Science, New Zealand under RRU services. Elemental analysis of samples was also performed by Neutron Activation Analysis (NAA) (EPA, 1999) at the Analytical Chemistry Laboratory of Malaysian Nuclear Agency. The concentration of the following twenty elements were measured and analyzed for each sample i.e Al, As, Br, Ca, Cl, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, Pb, S, Si, Ti, V and Zn. 21 Jurnal Sains Nuklear Malaysia, 2018, 30(1): 19 – 29 ISSN: 2232-0946 Data Analysis by Positive Matrix Factorization (PMF) A factor analysis method, Positive Matrix Factorization (PMF), utilizes error estimates of the data to provide optimum data scaling (Paatero and Tapper, 1993). The method is based on solving the factor analysis problem by least squares approach using a data point weighting method which decomposes a matrix of data of dimension n rows and m columns into two matrix, G(nxp) and F(pxm), where n is the number of samples while m is the number of species. The model can be written as: (1) Briefly, a data matrix X of i by j dimensions, in which i is the number of samples and j is the chemical species, which can be written as: (2) Where p is the number of factor, f is species profile, g is amount of mass and is the residual for each sample.