Risk Assessment and Spatial Distribution of Heavy Metals with an Emphasis on Antimony (Sb) in Urban Soil in Bojnourd, Iran

Abstract

Recently, one of the major environmental issues is the pollution of soil with Antimony (Sb), which is ecologically detrimental and potentially carcinogenic to humans. In developing countries such as Iran, Sb concentrations in soils have not yet been accurately determined. Therefore, the purpose of this study was to examine the levels of Sb and the other HMs (Pb, Cd, As, Ni, Hg and Cr) in the surface soils of Bojnourd, Iran, as well as their distribution and potential risks to the environment and human health. A total of 37 soil samples (0–20 cm) were taken from different sampling stations: 900 × 900 m regular grid for traffic areas (TA), residential areas (RA) and suburb areas (SA). The contamination factor (CF) and geo-accumulation index (Igeo) are two indices that were used to reflect the potential ecological risk from HMs. Geographic information system (GIS), Spearman correlation matrix and health risk indexes were utilized to investigate the source and potential hazard of HMs. The results showed that the average concentration of HMs in TA was highly enriched compared to other areas. Most soil samples were identified to have low levels of Sb and Ni pollution, while having moderate to high levels of Pb, Cr, As, Hg and Cd pollution, as determined by the pollution indices (Igeo and CF). Geostatistical analysis and GIS mapping of the spatial distribution of HM concentrations showed that there have been similar patterns of spatial distribution for Cd, Cr, Ni and Sb and their hot spots were in the southeast, west and center of the city. Neither the hazard quotient (HQ) nor the hazard index (HI) of the examined HMs indicated any non-carcinogenic risk to adults or children. However, carcinogenic risk assessment revealed that cancer risk was raised from Cr and Cd contents for children, while these elements showed an acceptable risk for adults. Furthermore, children’s carcinogenic and non-carcinogenic values were greater than adults’, indicating more potential health hazards associated with these HMs. Therefore, assessing the risk posed by HM pollution in urban surface soil is vital and urgent for children. A more detailed investigation is also required to identify the spatial distribution of soil pollution in areas recognized as enriched in Sb. A proper assessment of the environmental risk and the corresponding risk to humans from HM in a study area can be critical to developing an appropriate remediation method.

Potentially Toxic Elements in Urban and Peri-Urban Soils – A Critical Meta-Analysis of their Sources, Availability, Interactions, and Spatial Distribution

“…Over the last decades the necessity to monitor and evaluate HM, both in rural and urban soils has emerged. Scientists have developed various methods and indices to quantify HM ecological risk assessment (Rouhani et al, 2023). Frequently used indices include Geo-Accumulation Index (Igeo), Comprehensive Ecological Risk Index (RI), Single Pollution Index (Pi), and Ecological Risks Index for Individual HMs (Ei).…”

“…According to the literature review many authors support that high HM and PTEs pollution load in urban soils is mainly due to human activity (Kannan et al, 2023;Qiao et al, 2023). Furthermore, traffic and industrial emissions are the primary sources of Cd, Cu, Pb, Zn, Cr, and Ni in urban soils (Li et al, 2023;Rouhani et al, 2023). Soleymani et al (2022), reported that in urban areas with heavy traffic, HM levels are higher than those with lower traffic.…”

Application of Selected Methods to Modify Pyrolyzed Biochar for the Immobilization of Metals in Soil: A Review

“…The rapid expansion of cities, industries, and agriculture over the past few decades has led to a significant increase in soil contamination caused by heavy metals (HMs) [1,2]. Important concerns have been raised about the long-term effects, toxicity, and persistence of HMs in the soil [3], and these contaminants could potentially be the form of pollution that constitutes the largest risk to human health [4].…”