Document Type : Research Article
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Abstract
Soil contamination by heavy metals and its long-term detrimental effects on environment and human health is a present-day concern of environmental scientists. The aims of this paper is to present the results of spatial distribution mapping of heavy metals in topsoils (0-10 cm) using 315 georeferenced soil samples regularly spaced grid pattern with an interval of 500 meters from Anguran area located in the Zanjan province. Total and available forms of Pb, Zn, and Cd were extracted by HNO3 and DTPA-TEA and measured for the samples. The average for total concentrations of Pb, Zn, and Cd were 109.96, 165.57 and 6.02 mg/kg and for available forms were 46.36, 61.54 and 2.63 mg/kg, respectively. The heavy metal concentration data tended to be positively skewed and outlying values were observed. The Box-Cox transformation technique was applied to normalize the data. Strong positive correlations were observed between the concentrations of heavy metals studied. The results showed that spherical model revealed the best result for describing the spatial variability of Pb, Zn, and Cd. The ranges of influence for variograms of Pb, Zn, and Cd were 4800m, 3987m and 4845m, respectively. The application of the Ordinary Kriging method showed a good performance for estimating heavy metals concentration in the areas not being sampled. The results based on the Kriging Maps showed that the concentration of heavy metals increased around the procreation factories, while decreased in longer distances from the factories. The Kriging Maps of total heavy metals concentration indicate a strong spatial pattern in the Southeast and Center of the study area. These maps can provide valuable information for assessing the pollution hazard.
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