Dam Operation Alters Nutrient Dynamics and Intensifies Heavy Metal Pollution in Riparian Soils: A 15‐Year Study of the Three Gorges Reservoir Area, China

ABSTRACT The operation of the Three Gorges Dam (TGD) has profoundly altered riparian ecosystems, which serve as critical transitional zones for maintaining riverine water quality. Although numerous studies have examined soil nutrients and heavy metals dynamics in riparian zones, their long‐term trajectories remain poorly understood. In this study, we established a long‐term monitoring site and compiled data from literature covering riparian soils in 15 districts over 15 years of dam operation (2007–2021). Generalized Linear Mixed Models (GLMMs) were employed to assess the contributions of key factors influencing soil properties in the riparian reservoir zone (RRZ). RRZ soils showed higher soil organic carbon (SOC) and heavy metal concentrations (Cd, Cr, Cu, Zn) compared to adjacent Upland soils. Interannual flooding frequency emerged as the dominant factor, explaining over 50% of the variability in most soil properties. Specifically, pH, total nutrients (SOC, TP TK) and heavy metal concentrations (Cd, Cr, Cu, Pb, Zn) all significantly increased with interannual flooding frequency, while soil available nutrients (AN, AP, AK) significantly declined. Elevation also played a critical role, with soils at 145–155 m showing higher SOC and heavy metal concentrations, while those at 165–175 m had higher TN, TK, AN, and AK levels. To mitigate these impacts, ecological management strategies, including vegetation restoration, are urgently needed. This study offers critical insights for the protection and restoration of riparian zones in the Three Gorges Reservoir, providing a foundation for future management efforts.