عنوان مقاله [English]
Background and purpose: Due to the importance of soil quality in life and environment, various evaluation methods have been proposed to describe the effect of pollutants such as heavy metals on soil quality. In this study, we evaluated the quality of the soil around Zanjan lead and zinc complex located in Zanjan city by using the mathematical model of the improved weighted index and compared it with the results of Nemerow indices and pollution load index.
Materials and methods: In this study, the results of 71 soil sampling stations around Zanjan lead and zinc complex, located in the northwest of Iran, by inductively coupled plasma emission spectrometry device for reading the concentration of heavy metals Lead, Zinc, Arsenic, Cadmium, Thallium, Barium, Antimony, Vanadium, Cobalt, Molybdenum, Nickel and Copper were used. Soil acidity was also analyzed. In this approach, during the calculation of the improved weighted index, weights were assigned to different heavy metals using statistical tools, including hierarchical cluster analysis and principal component analysis. The result of the index quantitatively determines the amount of pollution.
Results: Based on the improved weight index, 19.9% of the samples were in moderate pollution and 4.2% of the samples were in severe pollution, and the other samples were without pollution or with little pollution. According to the pollution load index, 5.8% of the samples are in moderate pollution and 2.8% are in severe pollution, and according to the pollution index, 19.9% of the samples are in moderate pollution and 42.2% are in severe pollution. Comparing the correlation of the results obtained from the model with the weighted improved index with the pollution load index, the correlation value is 0.907, and with the Nimro index, the correlation value is 0.701, which indicates that it is closer to the pollution load index. The results of the improved weight index showed that the heavy metals Zinc, Lead, Cadmium and Arsenic are of anthropogenic origin and as a result of the industrial activities of Zanjan lead and zinc complex. While heavy metals Barium, Vanadium, Thallium, Molybdenum, Cobalt, Copper, Nickel and Antimony are of earth origin.
Conclusion: The results showed that the improved weighted index has a good match with the previous indices and can be used in wide ranges. It also overcomes the shortcomings of the previous indicators and can be used as a new model to evaluate soil pollution and soil ecological risk. This index can be used to identify and determine possible sources of pollution.