| Abstrakt: |
Introduction Dusts are suspended particles in air, originating from natural and/or anthropogenic origins. There are two main sources for dust streets. They consist of (1) precipitating from suspended particles (with natural and/or anthropogenic origins) and (2) movement of urban soils (natural). Potentially, dust streets could be considered as a distributing agent for metals. However, the concentration of metal in dust street is the function of speed and direction of wind, composition of dust, and environmental acidity (Al-Khashman and Shawabkeh, 2006; Yang et al., 2011). Previous studies have indicated that presence of heavy metals (e.g., Cu, Ni, Cd, Cr, and Zn) in the dust streets is due to the anthropogenic activities. Examples of such include agricultural activates, energy producing, industrial plants, outwearing of vehicles, and fossil fuel combustion (Moller et al., 2005; Al-Khashman, 2013). On the other hand, the combustion of coal, crude oil and natural gas for industrial and domestic uses can produce polycyclic aromatic hydrocarbons (PAHs). The PAHs can also be produced and subsequently being absorbed in dust streets by other activities such as incomplete combustion of fuels, and friction of automobile wheels with asphalt rods (Takada et al., 1991). Because of mutagenesis and carcinogenic properties, the investigation of PAHs is very interesting in the environmental assessments (i.e., Al-Khashman, 2013; Zarasvandi et al., 2014). For example, the presences of 16 PAHs in the dust streets of China have been detected in Long et al. (2013), who revealed that the sources of PAHs are mostly from coal combustion, oil and plants burning, with coke, and car's exhaust. One of the first studies on the dust streets of Khuzestan Province have been carried out by Zarasvandi et al. (2014). They indicate that PAHs in the dust streets of Ahvaz generally have a pyrogenic origin and PAHs with high molecular weight (HMW) are dominated in Ahvaz dust streets. The Mahshahr is an industrial town in south western of Iran. This is exposed to a wide variety of pollutants due to the presence of various environmental polluter sources. The present work is an attempt in order to evaluate the pollutant effects and the source of heavy metal, and PAHs in the dust streets of Mahshahr city. Materials and methods In the study area, sampling sites were selected from areas with different utility (e.g., industrial, commercial, educational, high traffic, hospitals, residential, and park). For avoiding the rain effects, all samples were collected during the dry season (July), using polyethylene brush and tray. Subsequently, collected samples were assembled in polyethylene bags. After each sampling, brush and tray were cleaned using distilled water and acetone. In order to removing the waste materials, all collected samples sieved through 2mm stainless-steel sieve. The samples were subsequently pulverized and homogenized using porcelain mortar. Finally, samples sieved through a stainless-steel mesh, 75 mm sieve. Consequently, heavy metals wer e determined using Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) at the Zarazma Company. In order to correctly measuring the PAHs, the collected dust street samples were stored in sealed amber glass vials. Then, the amber glass vials were sealed by aluminum foils. In the laboratory, all selected samples were completely dried at room temperature and then sieved through 200 mesh stainless-steel sieve. Dust samples (10 g dry weight) were weighed into a Soxhelt extractor. All the steps of sample preparation (descript in Long et al., 2013) were carried out in the organic chemistry lab of the Shahid Chamran University of Ahvaz. Finally the PAHs were analyzed by gas chromatography (GC Agilent 7890)-mass spectrometry (MS Agilent 5975) in the comprehensive research laboratory of Jundishapour University of Medical Sciences. Results and discussion 3-1-Heavy metals The results indicate that the concentration of heavy metals (e.g., Cu, Pb, Zn, Co, Sb, and Mo) in the dust street samples of Mahshahr is higher than average crustal composition. Also, the measured values of Cu, Cr, Pb, Zn, Mn, Ni, V and Fe are much higher than control sample. The calculating of enrichment factor (EF) using formula (eq. 1) with considering the alumina as reference metal, indicates that EF values have a decreasing trend from Pb to Cu, Zn, Fe, Mo, Cr, V, Mn, Ni, Sb and Co. Moreover, the results of the calculating geo-accumulation index (Igeo; eq. 2) revealed the Fe, Cu, Zn and Pb in the dust samples belong to contaminated to medium contaminated categories, whereas Co, Sb Cr, Mn, Ni, Mo, and V belong to uncontaminated class of geoaccumulation index (Muller, 1979).... Conclusions The main conclusions of this study could be summarized as follows: 1) The dust street sample of special economic zone is characterized by highest values of Cu, Mn, Mo, V, Sb and Fe which is due to the presence of oil and petrochemical industries, as well as steel equipments in this area. 2) The results of calculating the geoaccumulation index revealed that Fe, Cu, Zn and Pb belong to contaminated to medium contaminated categories of Igeo, while other heavy metals belong to uncontaminated category. 3) The results of principal component analysis (PCA) indicate that all studied heavy metals could be arranged in three main orders. However, heavy metals in all orders mostly sourced from traffic, industrial activates and burning of gasoline in the car engine (especially, Pb and Ni). 4) There are 13 PAHs components in the dust streets of Mahshahr. They are mostly sourced from combustion of oil and coal, as well as biomass. Thus, a pyrogenic source could be specified for all PAHs. 5) The sum of carcinogenic PAHs in all sampling sites is higher than sum of non-carcinogenic PAHs. This feature highlights the danger of PAHs and should be considered in urban planning. [ABSTRACT FROM AUTHOR] |
