“…Zinc, Cd, Cu, Pb, and Hg sulfides were confirmed to precipitate at contaminated sites rich in natural organic matter. These include freshwater canal and river sediments, wetlands, soils, and flooded mines (Sobolewski, 1996;Gammons and Frandsen, 2001;Large et al, 2001;Sonke et al, 2002;Moreau et al, 2004;Myagkaya et al, 2016;Ciszewski et al, 2017;Lazareva et al, 2019;Mantha et al, 2019;Quevedo et al, 2020). Experimental studies confirm the importance of organic matter in facilitating metal sulfide formation and persistence in water fluctuating systems (Lau and Hsu-Kim, 2008;Weber et al, 2009;Hofacker et al, 2013;Hoffmann et al, 2020).…”