| Popis: |
Determinations of Zn, Ni, Mn, Cd, Cu, and Fe have been carried out on 51 near-shore and 38 open-ocean surface seawaters from various regions of the World Ocean. The concentrations of the trace metals have been established in the open-ocean waters, and have been used as “baselines” to evaluate trace-metal enhancement in near-shore regions. The factors by which the trace metals are enriched in near-shore regions vary from one element to another and, according to the highest concentration factors found, decrease in the order Zn = Mn > Cd = Cu = Ni. These elements exhibit differences in their distributions between near-shore and open-ocean waters, and they have been divided into two types on this basis: Type I, in which the largest number of samples in both shelf and open-ocean waters lie in the same concentration range. Zinc, cadmium, and copper are Type I elements. Type 2, in which the largest number of samples of near-shore waters lie in a higher concentration range than the largest number of samples of open-ocean waters. Nickel and manganese are Type 2 elements. The concentrations of Mn, Cd and Zn are similar in open-ocean surface waters from the South Atlantic and Indian Ocean, but Cu and Ni have higher concentrations in the former ocean. There is considerable variation in the concentrations of the trace metals in near-shore surface waters from various regions of the World Ocean. These variations are discussed in detail. |
