Quantitative Source Apportionment of Potentially Toxic Elements Input Into The Urban Soils of Hamedan

Introduction: The urban soil contamination with potentially toxic elements (PTEs) has elicited great public attention worldwide due to its potential threats to urban dwellers health and environmental sustainability. In this regard, identifying and quantifying the PTE pollution sources are of particular importance in urban soil pollution control as well as management and reduce potential environmental and health risk. Therefore, this research was conducted to identify and quantify of potentially toxic element sources (As, Pb, Cu, Mn, and Ni) in surface soil of Hamedan city in 2023.

Materials and methods: In this study, a total of 162 urban surface soil samples were collected from 18 sampling sites from three different functional regions (i.e. residential, commercial, and industrial). Following sample preparation and acid digestion, the concentrations of the analyzed elements were determined using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Additionally, the enrichment factor (EF) was calculated to assess the level of contamination and enrichment associated with these elements. Also, The Pearson’s correlation coefficient (PCC), Principal Component Analyses (PCA), Hierarchical Cluster Analysis (HCA), and Absolute principal component score followed by multiple linear regression (APCS/MLR) model were utilized to identify and quantify the sources of soil PTEs pollution. Statistical analyses of data were done using SPSS software.

Results and discussion: The results from determining the content of the elements showed that the highest average content of As, Cu, and Ni (mg/kg) with 6.88, 30.9, and 24.3, respectively, were belonged to the industrial areas and for Pb and Mn with 31.2 and 293, respectively, were belonged to the commercial areas, revealing the effect of various urban activities and land uses on the spatial variations of the PTE contents. The average EF value reflected "moderate" to "very severe" enrichment conditions in the study area. The results of source identifying based on the PCC, PCA, and HCA showed that the traffic emissions, industrial-geological emissions, and fossil fuel combustion have been three main sources of soil PTEs contamination in Hamedan city. The results obtained of the APCS/MLR model showed that the traffic emissions, industrial-geological emissions, and fossil fuel combustion accounted 56.0%, 30.0% and 14.0%, of contribution the PTE pollution in study area, respectively. Additionally, the results of determining the quantitative contribution of pollution sources for each PTEs represented that Pb and Mn mainly originated from traffic emissions; whereas, Cu and Ni emitted from industrial-geological emissions; meanwhile, As mainly derived from fossil fuel combustion emissions. Notably, the PTEs contamination in soil of city of Hamedan were mainly released from the anthropogenic origin (70.0%) and the traffic emissions as the primary pollution source (56.0%) had the highest contribution to the PTE pollution in study area.

Conclusion: Based on the results obtained, traffic was the major contribution sources of As, Pb, Cu, Mn, and Ni pollution in the soil of city of Hamedan; therefore, reducing the emission of elements from traffic sources is the most effective and necessary strategy of pollution control for maintaining the health of both the urban ecosystem and citizens. In this regard, optimize and improve of urban transportation is recommended for management and control policies and strategies, plan to create and develop special ways for public transportation, modernize the public transportation fleet using electric vehicles, and encourage citizens to use public transportation. In general, the results of this research emphasized the need to determine the quantitative contribution of pollution sources to facilitate the management and effective reduction of environmental pollutants.