Nickel concentration ocean

Of all the first row transition elements, nickel has received the least attention from oceanographers. Although the vertical profiles of nickel concentration in the oceans exhibit a surface depletion characteristic of nutrients, the surface values remain typically in the 1-5 nM range (Bruland et aL, 1994) (Figure 3), much in excess of the other elements discussed so far. Nonetheless, laboratory data demonstrate that... 

Ammonium pyrrolidine dithiocarbamate (APDC) chelate coprecipitation coupled with flameless atomic absorption provides a simple and precise method for the determination of nanomol kg 1 levels of copper, nickel, and cadmium in seawater. With practice, the method is not overly time-consuming. It is reasonable to expect to complete sample concentration in less than 20 min, digestion in about 4 h, and sample preparation in another hour. Atomic absorption time should average about 5 min per element. Excellent results have been obtained on the distribution of nickel and cadmium in the ocean by this technique. 

A comparison was carried out on the results obtained using ICP-AES and AAS for eight elements in coastal Pacific Ocean water. The results for cadmium, lead, copper, iron, zinc, and nickel are in good agreement. For iron, the data obtained by the solvent extraction ICP method are also in good agreement with those determined directly by ICP-AES. In most of the results the relative standard deviations were 4% for all elements except cadmium and lead, which had relative standard deviations of about 20% owing to the low concentrations determined. 

Correlation plots for the North Pacific Ocean concentration data from Figure 11.14 (a) zinc versus nitrate, phosphate, and silica, (b) cadmium versus nitrate, phosphate, and silica, (c) copper versus nitrate, phosphate, and silica, and (d) nickel versus nitrate, phosphate, and silica. 

Although the nodules vary widely in their composition over the world oceans, metals are concentrated in three distinct types. One type comprises the nickel-copper-iich nodules of the Clarion-Clipperton variety, which is mainly formed in the equatorial regions. Another type, high in cobalt (1% or more) and low in nickel and copper, appears to be most commonly formed on sea mounts. The third type is high in manganese (35% or more), but low in other metals it is known mainly on the eastern side of the Pacific Basin. As of the early 1980s. the most economically attractive were the cobalt-rich nodules. 

Porphyrin complexes can be commonly produced in sparking mixtures. Thus, Hodgson and Baker showed that pyrrole and paraformaldehyde in the presence of copper(II), nickel(II) and vanadyl salts give rise to both free and metal complexes of porphyrins. Tlie most efiective ion for the template reaction is Ni", a result parallelling the observations outlined earlier on the preservation of porphyrin complexes in asphalts, sediments and rocks. It was pointed out that coloured species noticed in earlier experiments were also probably porphyrin coordination complexes. More recently it has been demonstrated that Ni(CN)/ increases the yield of porphyrins in such reactions, as does Fe(CN) . Since these ions were probably present in reasonable concentrations in the primitive oceans, their significance is obvious. 

The zinc content of soil limonite was found to be always greater than that of the soil matrix in Tennessee subsurface soil samples (251), Burns and Fuerstenau (40) determined the occluded heavy metal concentrations in oceanic manganese nodules via an electron probe. They found that nickel and copper occurred in the high manganese bands while cobalt occurred predominantly in the iron rich areas. 

Concentrations of many trace element nutrients (zinc, cadmium, iron, copper, nickel, and selenium) increase with depth in the ocean, similar to increases observed for major nutrients (nitrate, phosphate, and silicic acid) (Figures 2—4). In the central North Pacific, filterable concentrations of zinc and cadmium increase by 80-fold and 400-fold, respectively, between the surface and 1000-m depth. The similarity between vertical distributions of these trace elements and major nutrients indicates that both sets of nutrients are subject to similar biological uptake and regeneration processes. In these processes, both major and trace element nutrients are efficiently removed from surface waters through uptake by phytoplankton. Much of these assimilated nutrients are recycled within the euphoric zone by the coupled processes of zooplankton grazing and excretion, viral lysis of cells, and bacterial degradation of organic... 

---