M.A. Delavar; Y. Safari
Abstract
Introduction: The accumulation of heavy metals (HMs) in the soil is of increasing concern due to food safety issues, potential health risks, and the detrimental effects on soil ecosystems. HMs may be considered as the most important soil pollutants, because they are not biodegradable and their physical ...
Read More
Introduction: The accumulation of heavy metals (HMs) in the soil is of increasing concern due to food safety issues, potential health risks, and the detrimental effects on soil ecosystems. HMs may be considered as the most important soil pollutants, because they are not biodegradable and their physical movement through the soil profile is relatively limited. Therefore, root uptake process may provide a big chance for these pollutants to transfer from the surface soil to natural and cultivated plants, which may eventually steer them to human bodies. The general behavior of HMs in the environment, especially their bioavailability in the soil, is influenced by their origin. Hence, source apportionment of HMs may provide some essential information for better management of polluted soils to restrict the HMs entrance to the human food chain. This paper explores the applicability of multivariate statistical techniques in the identification of probable sources that can control the concentration and distribution of selected HMs in the soils surrounding the Zanjan Zinc Specialized Industrial Town (briefly Zinc Town).
Materials and Methods: The area under investigation has a size of approximately 4000 ha.It is located around the Zinc Town, Zanjan province. A regular grid sampling pattern with an interval of 500 meters was applied to identify the sample location, and 184 topsoil samples (0-10 cm) were collected. The soil samples were air-dried and sieved through a 2 mm polyethylene sieve and then, were digested using HNO3. The total concentrations of zinc (Zn), lead (Pb), cadmium (Cd), Nickel (Ni) and copper (Cu) in the soil solutions were determined via Atomic Absorption Spectroscopy (AAS). Data were statistically analyzed using the SPSS software version 17.0 for Windows. Correlation Matrix (CM), Principal Component Analyses (PCA) and Factor Analyses (FA) techniques were performed in order to identify the probable sources of HMs in the studied soils.
Results and Discussion: Comparing the measured HMs contents with their normal range in uncontaminated soils demonstrated the contamination of soils by Pb, Zn and Cd, with average concentrations of 152.8, 294.2 and 5.6 mg kg-1, respectively,whereas Ni and Cu did not show any pollution risk. The total concentration of Zn, Pb and Cd in the soil showed a great degree of variability, indicated by large coefficients of variation (CV) from 228.5 % of Cd to 354.8 % ofPb. These elevated CVs may indicate that these elements’ distribution in the studied area is influenced by an anthropogenic source. In contrast, the relatively low calculated CVs for Ni and Cu may imply that natural sources are responsible for these elements’ distribution in the studied soils. Correlation matrix (CM) analysis revealed high correlation coefficients between Zn-Cd and Ni-Cu, indicating the influence of the same factors in controlling their distribution. On the other hand, Pb contents showed low correlation with Ni and Cu values, whereas its correlation with Zn and Cd was relatively high. Therefore, it seems that Pb distribution in the studied soils is more influenced by the factor which controls the Zn and Cd distribution, rather than another factor that is responsible for accumulation of Ni and Cu in the studied soils. According to the PCA analysis, two significant components were extracted explaining about 84% of total variance. FA analysis showed that studied variables have a relatively high communality with two extracted principal components, indicating that almost all of the measured total variation can be efficiently explained by the extracted principals. Industrial activities in the Zinc Town seem to be the main factor which caused the high concentrations of Pb, Zn and Cd in the soil environment in this area; whereas Ni and Cu were associated with the natural sources including geology of the studied area (parental material’s factor). The obtained results from this study coincide with the prior studies indicating that multivariate statistics is a powerful technique for identification of probable sources of HMs in the soil.
Conclusions: The studied soils are classified as polluted soils with Zn, Pb and Cd,whereas Ni and Cu did not show any pollution risk. PCA and correlation analyses between HMs indicated that HM pollution in the studied area may originate from natural and anthropogenic factors. It can be concluded that Zinc Town controls the distribution of Zn, Pb and Cd in the surrounding soils, but Ni and Cu distribution in the studied area is mainly influenced by natural factors.Totally, industrial activities related to Zn production caused simultaneous entrance of several HMs to the adjacent soils and led to degradation of the lands in the studied area.
