IOSR Journal of Applied Chemistry (IOSR-JAC) e-ISSN: 2278-5736.Volume 11, Issue 1 Ver. I (January. 2018), PP 90-99 www.iosrjournals.org DOI: 10.9790/5736-1101019099 www.iosrjournals.org 90 |Page Spatial distribution and contamination assessment of heavy metalsin urban road dusts from Dhaka city, Bangladesh M.D.H. Khan 1,* , A. Talukder 2 , M. Safiur. Rahman 3 1 Department of Microbiology, Stamford University Bangladesh, Dhaka, Bangladesh 22 Department of Chemistry, University of Dhaka, Bangladesh 3 Atmospheric and Environmental Chemistry Laboratory, Chemistry Division, Atomic Energy Centre,P.O. Box 164, Dhaka 1000, Bangladesh*Corresponding author: dulal.hossain@stamforduniversity.edu.bd Abstract : Street dusts were collected from twenty two road side locations in Dhaka City, Bangladesh. Dusts samples were sieved below 90 μm and analyzed by Energy Dispersive X-ray Fluorescence (EDXRF) for eight toxic heavy metals (Pb, Cr, Cu, Cd, Ni, As, Zn and Mn). This study revealed that the concentrations of these metals were higher than that of the background value of the respective metals in soil. For the assessment of pollution level in the street dusts in Dhaka City, several important indices: enrichment factor (EF), pollution index (PI), pollution load index (PLI), and geo-accumulation index (I geo ) were followed in this study. ArcGIS software is used to generate the spatial distribution map for the heavy metals, which specifies high and low concentrated zone of toxic heavy metals in the study area. Enrichment factors analysis indicated the anthropogenic and natural sources of metal contamination. Pearson’s correlation coefficients analysis show that Cu, Pb, Cd, Ni, Zn, As and Mn which are significantly positively correlated, likely originate from common anthropogenic sources. Chromium was found at high concentrations in all the samples that seems also to have anthropogenic sources, but not the same ones as for the other contaminants. All the models agreed that contamination levels is in increasing order of Mn>Zn >Cr>Cu>Ni>Pb>Cd>As. Keywords -Street dusts; Enrichment factor; Heavy metals; Chromium, Contamination factor; Dhaka city. I. Introduction Air pollution today is a major problem for modern societies. It has long been recognized as a potentially lethal form of pollution. In recent times, studies of air pollution especially in the urban environment have focused largely on road deposited dust [1], [2], [3], [4], [5], [6], [7], [8], [9]. The particles of dust that deposit from the atmosphere and accumulate along roadside are called road dust or road deposit dust[10]. Road dust represents complex chemical composition and originates from the interaction of solid, liquid and gaseous materials produced from different sources and activities [11], [12]. However, heavy metals of the different sources accumulate in top soils from atmospheric deposition by sedimentation, impaction, and interception [13],[14]. Accumulations of heavy metals on urban surfaces arise from vehicle exhausts, industrial discharges, oil lubricants, automobile parts, corrosion of building materials, and atmospheric deposition [13], [15]. Thus, the heavy metals are good indicators of contamination in surface environments, especially in the urban areas. Street dust acts as recipient of pollutants from different sources and makes a significant contribution to the pollution in the urban environment [15]. With the increase of population, the tightly packed buildings limit air circulation, leading to increase of heavy metal accumulations in the street dust [16]. Many studies of concentrations of heavy metals in street dusts in large cities have been conducted in developed countries ([17], [18], [19], [13], [20]) but little has been done in less developed countries. At present, air pollution has become a main environmental issue in many nations, including Bangladesh [15]. Subsequently, heavy metal pollution in urban road dusts in Bangladesh becomes serious with the rapidly urbanization and industrialization during the last two decades. Ahmed et al. [20] reported that total numbers of vehicles and auto-rickshaws (two-stroke engine vehicles) in Dhaka City of Bangladesh have been increased several folds in the last decade. According to Bangladesh Road Transport Authority (BRTA, 2016), the number of registered motor vehicles in 2011 was 72,377, which has been increased to 93,934 in 2015 (BRTA, 2016).Numerous studies have tried to ascertain various aspects of this problem: especially potential health effects of exposure to this materials through inhalation, ingestion and dermal contact ( [19], [20], [21]). But unfortunately quite a few studies associated with the health risk assessment for the toxic metals in urban road dust samples in the capital city of Bangladesh (Dhaka), especially in the smelting district have not been carried out during the past decade/s. In the present study, an attempt has been made to generate and evaluate levels of trace heavy metals, As, Cu, Cr, Pb, Mn, Cd, Ni and Zn in road deposited dust in the Dhaka city. The study would form the basis of establishing baseline data regarding heavy metals in road dust of the city and identifying the patterns spatial distribution of Pb, Cr, Mn, Ni, Cu, Zn, As, Zn using geographical information system method. The study is also important in that it can be used as basis for planning management strategy to achieve better environmental quality and substantial development of the district. II. Materials and methods 2.1 The study site: Dhaka City, Bangladesh: Bangladesh is located in the eastern part of south Asia. It is surrounded by India to the west, north, and northeast, by Myanmar to the southeast, and by the Bay of Bengal to the south. Dhaka City, the capital city, is almost in the middle of Bangladesh (Fig. 1). Total area of the city is about 150 km 2 . In 1950, the population of Dhaka City was only 0.43 million ([20], [22])and now the present population in Dhaka is above 158million [23] with a rate of increment of about 7% per year [24]. Numbers of vehicles and industries are also multiplying rapidly, and recent observation of smog in the Dhaka City indicates the onset of air pollution [25]. On the other hand, there are many different types of industries (i.e., textile, glass, ceramic, pharmaceutical) have been established in Dhaka City.