Spatial distribution of heavy metals in soils and plants in Zinc Town, northwest Iran

Abstract

Identification of heavy metals spatial variability in soil and plants may provide useful information on how to manage the polluted sites. The main objective of this study was to determine the spatial distribution of selected heavy metals in soils and natural plants of Zanjan city, northwest Iran. A total of 184 composite topsoil samples (0–10 cm) and 98 natural plant samples were systematically taken from an area of about 4000 ha located around an industrial complex, covering rangeland and agricultural and industrial land uses. All samples were analyzed for their total concentration of Zn, Pb and Cd. The results showed that the average concentrations of Zn, Pb and Cd in the soil samples were up to 294.2, 152.8 and 5.6 mg kg−1, respectively, whereas in the plant samples, these values decreased to 131.4, 113.2 and 2.5 mg kg−1, respectively. These contents are much higher than the normal range in soil and plant communities, leading to classify the studied area as a polluted site. Variography analyses revealed a similar spatial structure for the studied heavy metals in the soil and plant samples. Based on interpolated maps, the highest concentrations of the selected heavy metals in the soil and plant samples were found in the vicinity of industrial complex. These findings clearly highlight the role of industrial activities in simplifying the entrance of dangerous trace elements to the human food chain. Application of ordinary kriging technique to predict the heavy metals spatial variability in the plant community resulted in logical estimations with acceptable error values.