ُSaeid Hojati
Abstract
Introduction Khuzestan province in southwestern Iran is one of the most critical areas affected by dust storms due to the arid climate and the abundance of desert areas in its western and southern parts. Dust storms in these areas are among the most critical environmental issues. Air pollution, the development ...
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Introduction Khuzestan province in southwestern Iran is one of the most critical areas affected by dust storms due to the arid climate and the abundance of desert areas in its western and southern parts. Dust storms in these areas are among the most critical environmental issues. Air pollution, the development or increase of respiratory diseases, reduced soil fertility, damage to crops, and reduced solar radiation are among the most critical consequences of dust storms. Dust particles can absorb significant amounts of heavy metals, which facilitate their transport on a large scale due to their fine particle size distribution. Street dust is considered the major source of pollutants from a wide range of traffic, industrial emissions, pesticides, and mining activities. Although many studies have been conducted to identify the origin and pollution status of dust particles in the country, the assessment of pollution and source of street dust particles during dust storms, especially in Ahvaz city, has received less attention. .Thus, this study was conducted to: (1) identify the source of street dust in Ahvaz city, and (2): determine the level of contamination to Pb, Zn, and Cu.Materials and Methods Dust and soil samples were collected respectively at 69 and 23 points from streets and the surface soil (0-5 cm) in Ahvaz city in February 2015. To determine the particle size distribution pattern in the dust samples, they were first dispersed in 1 M sodium hydroxide and 10% sodium hexaphosphate solutions for 2 hours. Then, they were analyzed using A Malvern Hydro 2000g laser diffraction device. The ionic compositions of the dust and soil samples were also determined after extraction from 1 (dust/soil): 5 (water) suspension with an advanced Meterohm 861 model ion chromatography apparatus. The heavy metal contents of soil and dust particles were determined using inductively coupled plasma (ICP) spectroscopy. To determine the Pb, Fe, Cu, and Zn contents, 0.5 g of the dust or soil samples were digested with 60% nitric acid, and after 24 hours, the samples were heated for 0.5 hours at a temperature of 80 ° C. Then, they were filtered with Whatman 42 paper and finally were examined using an Agilent 7000 inductively coupled plasma (ICP) spectrometer. To assess the degree of street dust pollution in Ahvaz city, various indicators, including the single element pollution index and Nemerow integrated pollution index, were calculated. A pollution index is expressed as the ratio of the concentration of an element in soil or dust samples to the same component's baseline value in soil or dust sample. If this index is greater than 1, it indicates different levels of pollution.Results and Discussion The particle size distribution in the studied samples showed a bimodal pattern with more abundance of particles in the size of silt and fine sand. Accordingly, 57 to 89% of the particles were in the silt size, and 5 to 16% were in the size of fine sand. The results also indicated that the abundance of sodium, calcium, chloride, and sulfate ions was comparably higher than the local soils. Similarly, the average concentration of each heavy metal was higher than those of the local soils and the upper earth crust, which followed the order Zn> Cu> Pb. Accordingly, The average Pb, Cu, and Zn concentrations were 5.23, 6.37, and 6.89 times more than their corresponding values in the earth's upper crust. Accordingly, and based on the values obtained from the pollution index (PI), all the studied elements in the street dust of Ahvaz city could be categorized as highly polluted. The average of Nemrow integrated pollution index was found 7.26, which shows a high pollution level for street dust in Ahvaz cityConclusion It seems that dust particles collected from streets and sidewalks of the Ahvaz city are mainly originated from regional focal points in eastern and southeastern parts of the city. When Pb, Cu, and Zn concentrations in the street dust of Ahvaz city and those reported from different cities in Iran and other countries are compared, it is concluded that dust particles deposited over the streets and sidewalks in Ahvaz county have a higher degree of pollution. Therefore, Prompt actions are needed to lower the risk of these elements for the environment.
Saeid Hojati; Ahmad Landi; Heyam Alekasiri
Volume 36, Issue 1 , September 2013, , Pages 13-22
Abstract
Wastewaters from different industries contain great amounts of heavy metals which can contaminate the ground water after entering the soil. Few studies have been conducted on the application of clay minerals such as sepiolite in preventing the leaching of these elements. This study was conducted to evaluate ...
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Wastewaters from different industries contain great amounts of heavy metals which can contaminate the ground water after entering the soil. Few studies have been conducted on the application of clay minerals such as sepiolite in preventing the leaching of these elements. This study was conducted to evaluate sepiolite as a strong and inexpensive adsorbent in preventing the leaching of lead and zinc from sandy soil columns under laboratory conditions. Therefore, 400 ml of solutions containing lead and zinc with a concentration of 75 mg/l, were passed through pre-saturated soil columns with different amounts of sepiolite (2, 4, 6 and 8 weight percent) in two sizes, < 2 and 20- 50 microns, under a flow rate of 1.2 liter h-1. The concentration of lead and zinc in the successive 20 ml leachate was then measured using atomic absorption spectrophotometer. Results showed that application of sepiolite in soil columns decreased leached amount of Pb and Zn as compared to control treatments. Also, with increasing sepiolite application rate, and decreasing its particle size, leaching of zinc and lead from the soils was reduced. However, the amount of lead leached was less than that of zinc. It seems that sepiolite mineral could be utilized as suitable materials to reduce the leaching of lead and zinc from soil to ground waters.
