ecological risk assessment and spatial distribution of heavy metals in the alvand mountain ecosystem: a 15-year monitoring study (2008–2022)

Background: soil contamination by heavy metals represents a critical environmental issue that endangers both ecological balance and human well-being. this study investigates the ecological risks of arsenic (as) and cadmium (cd) in the alvand mountain ecosystem over a 15-year monitoring period (2008–2022), emphasizing their sources, spatial distribution, and associated health risks.methods: systematic random sampling was performed across the alvand region. soil samples were analyzed for as and cd using inductively coupled plasma mass spectrometry (icp-ms). contamination and ecological risk levels were quantified using the contamination factor (cf), revised contamination degree index (rcd), and environmental risk potential index (eir). geostatistical interpolation methods (kriging and idw) were applied to generate spatial distribution maps for 2008 and 2022, with model accuracy validated via root mean square error (rmse) and mean absolute error (mae).results: in 2008, as concentrations were highest in the central and northeastern zones, while cd pollution dominated the western and eastern borders. by 2022, as contamination expanded westward, and cd became widespread throughout the region. cd exhibited an eir value exceeding 447, indicating a very high ecological risk according to the hakanson classification.conclusion: as contamination appears to stem from natural geogenic sources, whereas cd accumulation is primarily anthropogenic, driven by agricultural activities. continuous monitoring and stricter fertilizer management are essential to mitigate heavy metal pollution and safeguard the ecological integrity of mountainous ecosystems.