كليدواژه :
سيستم اطلاعات جغرافيايي , غبار خياباني , شاخص جامع آلودگي نمرو , شاخص آلودگي , فلزات سنگين
چكيده فارسي :
گرد و غبار خياباني يكي از شاخص‌هاي مهم، از وضعيت آلودگي محيط زيست شهري است. جهت شناسايي غلظت، منبع، و ارزيابي سطح آلودگي فلزات سنگين در گرد و غبار خياباني شهر اهواز، تعداد 115 نمونه از پياده‌رو خيابان‌هاي اصلي جمع آوري شد. غلظت فلزات سنگين به روش جذب اتمي (AAS) اندازه گيري شدند. ميانگين غلظت فلزات سنگين Cu، Pb، Zn، Cr، As و Cd به ترتيب: 179/7،179/6، 150/1، 101، 14/2 و 5/6 mg/kg بدست آمد. ضرايب همبستگي بدست آمده بين فلزات نشان داد كه عناصر سرب، روي، مس و كرم داراي همبستگي معني داري بوده كه ناشي از منشاء يكسان از جمله انسان زاد مي‌باشد. از طرفي فلزاتي مانند كادميم و آرسنيك داراي همبستگي پاييني با ديگر فلزات بوده كه نشان از زمين‌زاد بودن اين فلزات به ويژه آرسنيك و منابع آلودگي ديگر براي كادميم مي‌باشد. نتايج شاخص آلودگي(PI) ، شاخص جامع فاكتور آلودگي اصلاح شده نمرو (NIPI) و نقشه توزيع فضايي هر كدام از عناصر نشان داد كه آلودگي فلزات سنگين در گرد و غبار خياباني شهر اهواز در سطح بسيار بالايي بوده و در مناطق با تراكم جمعيت بالا، ترافيك سنگين و فعاليت‌هاي صنعتي داراي آلودگي شديدي از فلزات سنگين هستند.
چكيده لاتين :
Environmental investigation of heavy metals concentration in Ahvaz city street dust, by using Geographical Information Systems (GIS) Introduction Rapid urbanization and continuous demand for land for infrastructural development in urban areas have placed great stress on the local environment. Consequently, varieties of environmental problems have emerged, which among them toxic metal pollution is a major issue, especially in urban soil and street's dust. Street's dust receives varying inputs of heavy metals, mineral constituents, organic matter (humus), living organism, air, and water; the anthropogenic materials are vehicle exhaust particles, lubricating oil residues, tire wear particles etc…; and the natural biogenic materials are tree leaves and other plant matters. To certain degree, street's dust is a more pertinent indicator to urban environ-mental quality than single compartmental monitoring of air, water and soil, because it reflects pollutants from the different sources. Heavy metals may come from many different sources in urbanized areas, including vehicle emissions, industrial discharges and other activities. It is important to identify the origin and distribution of heavy metals in street dust, and estimate population from heavy metal exposure via street's dust in smelting district. There were many recent investigations on Heavy metals from many different sources in urbanized areas, including vehicle emissions, industrial discharges and other activities. Ahvaz, a metropolis city located in Southwest Iran, with a population of over 1.2 million, has experienced a rapid urbanization and industrialization in the last few decades. Industrial growth along with expansion of population and increase in number of vehicles in Ahvaz caused increase of heavy metals accumulation in airborne particles and urban soils. Ahvaz city is considered as one of the heavily polluted cities in the world. However, the spatial distribution patterns and contamination levels of heavy metals in road dust in the area is still not clear. The aim of this paper is to: 1) identifying the patterns of spatial distribution of Cd, Cr, Cu, Pb, As and Zn; 2) assess contamination levels of these metals by integrated pollution index (IPI) and Nemerow integrated pollution index (NIPI). Multivariate statistical methods and spatial analyses were used to achieve these goals. Geographic Information System (GIS) mapping was applied to evaluate the results by visualizing the spatial patterns. Material and Methods Soil sampling and analytical methods A total of 115 street's dust samples were collected form urban area in July 2014 when it was dry season. The sampling compagain was chosen in driest month of the year to avoid rain-washing out the heavy metals. The weather condition was stable during the sampling period and no rain had occurred during one month prior to sample collection. The street dust samples were mainly collected by sweeping an area of about 1×1 m2 from road pavement using a clean plastic dustpan and brushes for each sampling site. The sampling points and background of samples locations are marked in Fig. 1. Geographical coordinates of samples collection locations were recorded at each sampling point with a GPS device. The streets' dust samples were analyzed for toxic metals by Atomic Absorption Spectrophotometer (AAS). Fig.1. location of samples sites in Ahvaz city Metal pollution index PI was calculated for all the six elements under study and the minimum, maximum, and mean values of PI are given in Table 4. The pollution index IPI is defined as the mean value of the pollution index PI of an element. It is classified as. Non-pollution (PI≤1), low level pollution (1]>
