• • In-situ ecological risk: ≥97.83% of sediment samples posed moderate or higher potential ecological risk under both national and Yunnan background values; Hg and Cd were dominant contributors, with Hg exhibiting higher risk, underscoring the necessity for dredging to mitigate internal pollution.
• • Ex-situ agricultural risk: 95.65% of sampling points were unacceptable for both paddy and other agricultural uses; pollution intensity order was Cd>Cu>Zn>As>Cr, with Cd showing the highest pollution coefficient, indicating that sediment unsuitable for in-situ risk may still require treatment before agricultural reuse.
• • Ex-situ construction risk: For Class I construction land, As was the sole target pollutant with 93.48% of points unacceptable, while Class II land was fully acceptable; this distinction is critical for cost-effective remediation and land-use planning.
• • Vertical stratification: The polluted layer exhibited 11.58% higher Hg and 24.19% higher Cd potential ecological risk coefficients, and 43.27% higher comprehensive potential ecological risk index than the transition layer; pollution coefficients for Cd, Zn, Cu, and As increased by 123.02%, 6.3%, 4.1%, and 41.02%, respectively, confirming the need for layer-specific dredging and treatment.