Highly efficient stabilization of arsenic in the contaminated sediments of Jiehe River by schwertmannite to inhibit arsenic release into overlying water.

Arsenic (As) represents the most typical associated element in gold mines, with As pollution frequently observed in regions of intensive gold mining activities, especially in Zhaoyuan City, renowned as the "Gold Capital" of China. In this study, schwertmannite (Sch), an iron oxyhydroxysulfate mineral with unique channel structure renowned for its As adsorption and stabilization capabilities in aqueous and soil systems, was synthesized and applied to evaluate its efficacy in stabilizing As for gold mining-impacted sediments. Besides, the functional mechanisms of Sch in mediating the redistribution and persistent immobilization of As in the sediments of Jiehe River in Zhaoyuan city were also explored. Stability assessments were performed on three distinct As-contaminated sediments sampled from real sediments of Jiehe River in Zhaoyuan city. After adding Sch into the sediments, acetic acid extractable As in the sediments were decreased by 72.9 %-87.2 % over 84 days, with less than 5 % of As being released into the water. Throughout the 84-day experimental period, As concentration in the overlying water of the sediments amended with Sch remained consistently below 50 μg/L, a limited value of surface water environmental quality standards regulated by China. Additionally, As incorporation hindered the phase transformation of Sch and improved the stability of Sch. This study provides a promising approach for the in-situ remediation of As-contaminated riverine sediments.