Role of Nanoparticles in Controlling Arsenic Mobilization from Sediments near a Realgar Tailing

Microcosm experiments were conducted to investigate the mechanism of microbial-mediated As mobilization from high arsenic tailing sediments amended with nanoparticles (NPs). The addition of SiO₂ NPs could substantially stimulate arsenic mobilization in the sodium acetate amendment sediments. However, the addition of Fe₂O₃ and Fe₃O₄ NPs restrained arsenic release because these NPs resulted in Fe–As coprecipiate. Moreover, NP additions in sediments amended with sodium acetate as the electron donor clearly promoted microbial dissimilatory iron reduction. Nearly 4 times the Fe­(II) (11.67–12.87 mg·L^–1) from sediments amended with NPs and sodium acetate was released compared to sediments amended with only sodium acetate (3.49 mg·L^–1). Based on molecular fingerprinting and sequencing analyses, the NP additions could potentially change the sediment bacterial community composition and increase the abundance of Fe­(III) and As­(V) reduction bacteria. Several potential NP-stimulated bacteria were related to <i>Geobacter</i>, <i>Anaeromyxobacter</i>, <i>Clostridium</i>, and <i>Alicyclobacillus</i>. The findings offer a relatively comprehensive assessment of NP (e.g., Fe₂O₃, Fe₃O₄, and SiO₂) effects on sediment bacterial communities and As mobilization.