ABSTRACT
This chapter examines considerations relevant to the reduction of selected trace metals in treatment marshes. For many of the trace metals, information is very scarce or absent. That is because they have heretofore not been the subjects of regulatory concern in treatment marshes, although these are sometimes the concern for treatment wetlands dealing with industrial or mine source waters. The spectrum of commonly measured trace metals is represented by the databases for urban runoff systems (Table 13.1). Those urban wetlands remove about half the total metal concentrations, excepting nickel; but are not as effective at reducing dissolve metal concentrations. Metals reduction in urban wetlands. Systems Events Inlet (µg/L) Outlet (µg/L) Removal Total Iron 18 404 692 278 60% Lead 47 763 7.07 2.25 68% Nickel 10 113 4.39 2.20 50% Zinc 61 1,075 49.0 21.0 57% Copper 51 975 8.24 4.00 51% Cadmium 32 508 0.34 0.20 41% Chromium 13 170 4.18 1.50 64% Arsenic 4 25 1.20 1.00 17% Dissolved Iron 5 115 52 64 -23% Lead 15 199 0.98 0.82 16% Nickel 4 17 1.80 2.30 -28% Zinc 24 466 22.6 12.0 47% Copper 22 469 4.51 3.20 29% Cadmium 7 90 0.20 0.12 40% Chromium 4 41 1.00 1.00 0% Source: Clary et al. (2017b).
