Trace metal budget

Pohl, C., Hennings, U., Peterson, I., Singel, H., 1998. Trace metal budget, transport, modification and sink in the transition area between the Oder and Peene rivers and the southern Pomeranian Bight. Marine Pollution Bulletin, 36(8), 598-616. 

FIGURE 13.9 Trace metal budget (t/a) for Pb, Cd, Zn, and Cu in the surface water of the Eastern Gotland Basin. 

The residence times in Box 6.3 are based on riverwater being the only input of ions to the oceans. This is a simplification as there are also inputs from the atmosphere and from hydrothermal (hot water) processes at mid-ocean ridges (Fig. 6.7). For major ions, rivers are the main input, so the simplification in Box 6.3 is valid. For trace metals, however, atmospheric and mid-ocean ridge inputs are important and cannot be ignored in budget calculations (Section 6.5). 

The higher concentrations of some trace metals, like Zn, Cu, Ni, and Pb, in snowmelt waters in comparison with rain waters is possibly related to the elevated content of solid particles in snow. The deposition fluxes are less important in the biogeochemical mass budget of elements in Southern ecosystems, than in northern Forest ecosystems. 

Catchment acidification has been invoked to explain increases in the catchment contribution of Mn in Sweden (Renberg, 1985) and Fe in Norway (Davis et al., 1983). Enhanced supply of Al due to catchment acidification is also reported (White Gubala, 1990). The export of trace metals is demonstrated in acidified parts of Sweden, where stream water concentrations of Cd and Zn are enhanced in acidified areas (Johansson et al., 1995). In a study of catchment and lake budgets in the highly acidified area around Sudbury, Ontario, Dillon et al. (1988) found that the acidified catchments were sources for Al, Mn and Ni, but sinks for Cu and Zn. An enhanced supply from the catchment is supported by lake sediment studies for Al and Zn, but not for Pb. 

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