The Relation between External and Internal Fluxes

To answer the question how external atmospheric and riverine trace metal inputs are affected by the redox vaiiability of the system, the total external fluxes into the Gotland Basin have been estimated from the sum of riverine input and atmospheric input according to HELCOM (1998). They correspond with 31 nmol/m d for Pb, 3.0nmol/m2d for Cd, 1008 nmol/m d for Zn, and 290nmol/m d for Cu as shown in Table 13.5. 

Internal particulate trace metal fluxes were obtained from an experimental sediment trap flux study (Pohl et al., 2004) (Section 13.4), and internal dissolved trace metal fluxes across the redox interface were considered as estimated above. 

About 25% of Cd, 12% of Cu, and 8% of Zn, which were supplied by rivers and atmosphere, were eliminated by vertical turbulent mixing across the oxic-anoxic interface and subsequent sulfide precipitation. For Pbjiss, the flux at the redox interface was negligible. Comparing the sum of the internal fluxes (dissolved and particulate) in relation to the total 

TABLE 13.5 Comparison of External and Internal Trace Metal Fluxes and Their Relation 

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