“…Understanding the mobility and fate of naturally or anthropogenically sourced trace metals in surface waterseither as contaminants, nutrients or otherwise -is important for a range of environmental applications, including environmental monitoring of rivers (Pestana et al, 1997;Gerritse et al, 1998), predicting the persistence and fate of contaminants (Rate et al, 2000;Balistrieri and Blank, 2008), and geochemical exploration (McHugh, 1988;Benedetti and Boulëgue, 1991;Graham et al, 2015). Investigating controls on metal mobility may also assist understanding of processes occurring on longer time-scales, and, when combined with metal records in sediments, can provide insights into the history of a catchment (Gerritse et al, 1998;Dill, 2008).…”