Overview of ecological risk assessment of heavy metals with the approach of land uses affecting soil pollution.

Soil contamination with toxic elements is a major environmental concern. This study has attempted to provide an overall assessment of heavy metal (HM) pollution status in Iran's soil, particularly due to a lack of information on determining contamination levels across different land uses (LUs). A systematic review was utilized to extract manuscripts in which anthropogenic activities affect the HM level in soil. 195 papers were selected by March 2025. 10 HMs (As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, and Zn) within 9 LUs (industrial areas, mining areas, landfill areas, river sediments, roadside, agricultural areas, urban areas, coastal sediments, and wetland sediments) were analyzed for 7 soil pollution indices (CF (contamination factor), EF (enrichment factor), PLI (pollution load index), Eri (ecological risk), PERI (potential ecological risk index, RAC (risk assessment code), and Igeo (geoaccumulation index)). The impact of human activities was traced in all LUs, with smoother conditions for Mn and V in the CF mean calculation, Co, Ni, Mn, and V in the EF mean calculation, and Co, Cr, Mn, and V in the Igeo calculation. Low ecological risk was only recorded in wetland sediments (136.89), and PLI values fell within low pollution (PLI < 1) in wetland and river sediments with 0.837 and 0.856, respectively. RAC mean values for Cd (46%), Hg (46%), Mn (37%), Pb (34%), As (32%), and V (32%) were estimated to pose a high risk to the environment due to high potential for mobility. Eri mean value was only estimated with high ecological risk potential for Hg (in agricultural, roadside, coastal, and river sediments) and Cd (in roadside and industrial areas). By comparing the HM average concentration in all LUs, the industrial area was found to have the worst status. Some reported concentrations were up to around two orders of magnitude higher than corresponding ranges on a global scale. The output of this paper can help environmental planners establish strategies for optimal management of HM pollution in different LUs and pave the way for future research to have a more precise understanding of HM pollution levels in developing countries, specifically in the Middle East.