OICC Press Anthropogenic Pollution 2588-4646 10 1 2026 06 30 Chemical Speciation and Mobility of Potentially Toxic Elements (PTEs) in Urban Park Soils: Insights from Sequential Extraction and Visual MINTEQ Modeling 10.57647/AP.2026.1001.08 EN Ali Farbodnia Department of Environment, Dam.C., Islamic Azad university, Damavand, Iran Shahrzad Khoramnejadian Department of Civil & Environmental Engineering, CT.C., Islamic Azad University, Tehran, Iran Hooman Bahmanpour Department of HSE, Sha.C., Islamic Azad University, Shahrood, Iran Behnaz Moradi Ghias Abadi Department of Environment, Dam.C., Islamic Azad university, Damavand, Iran Mina Torabifard Department of Environment, Dam.C., Islamic Azad university, Damavand, Iran Journal Article 2026 06 30 Potentially toxic element (PTE) contamination in urban soils, particularly in public green spaces, can pose environmental and human health risks. This study evaluated the geochemical behavior, mobility, and potential bioavailability of Pb, Cd, Ni, and as in surface soils collected from two urban parks (Chitgar and Lavizan) in Tehran, Iran. Total concentrations were measured, and metal partitioning among operationally defined geochemical fractions was determined using a sequential extraction procedure. In addition, metal speciation under site-specific soil geochemical conditions was simulated using Visual MINTEQ. Potential ecological risk was evaluated using the Risk Assessment Code (RAC), based on the proportion of metals in the exchangeable fraction. Mean total concentrations of Pb, Cd, Ni, and as were 68.4, 1.92, 34.7, and 8.6 mg kg−1−1, respectively, in Chitgar Park soils, compared with 52.1, 1.35, 29.4, and 7.2 mg kg−1−1 in Lavizan Park soils. The exchangeable fractions of Pb and Cd accounted for ~24% and ~31% in Chitgar and ~18% and ~22% in Lavizan, indicating higher mobility and potential bioavailability than Ni and As, which were predominantly associated with more stable soil fractions. RAC results indicated moderate-to-high ecological risk for Cd and moderate risk for Pb across the studied soils. The novelty of this work lies in integrating sequential extraction results with geochemical speciation modeling (Visual MINTEQ) to better interpret PTE mobility and environmental risk in urban park soils. Overall, the findings suggest that assessments based solely on total concentrations may underestimate risk, whereas combining chemical fractionation/speciation information with RAC provides a more realistic evaluation of PTE behavior in urban soils.