Manganese concentration ocean

Sunda, W. G. and Huntsman, S. A. (1986). Relationships among growth rate, cellular manganese concentrations and manganese transport kinetics in estuarine and oceanic species of the diatom Thalassiosira, J. Phycol., 22, 259-270. 

Since the discovery of widespread hydrothermal activity on the seafloor and plumes of altered water in the water column, it has become obvious that circulation of seawater through both high-temperature and low-temperature rocks can add or remove elements, potentially affecting global balances of some elements. For example, dissolved manganese concentrations in open-ocean seawater are as low as 0.2 nanomole per kilogram, but concentrations... 

Grill, E.V. (1982) Kinetic and thermodynamic factors controlling manganese concentrations in oceanic waters. Geochimica et Cosmochimica Acta, 46, 2435-2446. 

Bismuth occurs ia the earth s cmst ia a concentration of approximately 0.1 ppm on the average. Higher concentrations of bismuth occur ia oceanic manganese nodules ia a range of 0.5 to 24 ppm (see Ocean rawmaterials). The next highest concentration of bismuth is found ia siUcic rock at 0.02 to 0.9 ppm (2). 

By far the most important ores of iron come from Precambrian banded iron formations (BIF), which are essentially chemical sediments of alternating siliceous and iron-rich bands. The most notable occurrences are those at Hamersley in Australia, Lake Superior in USA and Canada, Transvaal in South Africa, and Bihar and Karnataka in India. The important manganese deposits of the world are associated with sedimentary deposits the manganese nodules on the ocean floor are also chemically precipitated from solutions. Phosphorites, the main source of phosphates, are special types of sedimentary deposits formed under marine conditions. Bedded iron sulfide deposits are formed by sulfate reducing bacteria in sedimentary environments. Similarly uranium-vanadium in sandstone-type uranium deposits and stratiform lead and zinc concentrations associated with carbonate rocks owe their origin to syngenetic chemical precipitation. 

Average composition of Pacific Ocean nodules (concentrations in wt%) Mineralogical composition of manganese nodules... 

The oceanic distribution of cobalt is similar to that of manganese, although cobalt concentrations are 10-100 times smaller maximum concentrations are 100-300 pM in surface waters, decreasing to 10 pM at depths below 1000 m. As concentrations of cobalt in seawater are so low, it may become biolimiting in open ocean surface waters. 

Manganese and many other trace metals are present in open ocean waters at concentrations in the order of nmol/1 or less, and it is only relatively recently, when adequate contamination control measures have been applied during sampling and measurements, that accurate data have been obtained. 

Graphite-furnace atomic absorption spectrometry, although element-selective and highly sensitive, is currently unable to directly determine manganese at the lower end of their reported concentration ranges in open ocean waters. Techniques that have been successfully employed in recent environmental investigations have thus used a preliminary step to concentrate the analyte and separate it from the salt matrix prior to determination by atomic absorption spectrometry. 

The ready accumulation of plutonium by seaweeds, concentration factors of 10s have been observed (173), is presumably the result of plutonium uptake by the sul-phated polysaccharides which compose part of the cell wall. It is possible that plutonium could concentrate on manganese nodules in the deep ocean since it has been shown that manganese dioxide adsorbs plutonium from water (174). 

Upper panels show vertical profiles of manganese in the North Pacific Ocean at (a) an open-ocean station, (b) a coastal station, and (c) the Mn content of surface water with increasing distance from the California coast. Note the tenfold scale difference in concentration between these diagrams. Source From Landing, W. M., and K. W. Bruland (1980). Earth and Planetary Sciences Letters, 49, 45-56. 

Its concentration in the earth s crust is estimated to he 0.095%. Its average concentration in seawater is 2p,g/L. Manganese also is found in large quantities in deep-sea nodules over the ocean floor at depths of 2.5 to 4 miles. The composition of some common manganese minerals is tabulated helow ... 

Manganese occurs in concentrated form as pyrolusite (Mn02) and man-ganite [MnO(OH)] deposits, and as manganese nodules on the ocean floor. The metal is used in alloys with iron, while MnC>2 is used in dry cells (flashlight batteries ) and as an oxidant in the chemical industry. 

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. 

The nodules are formed by the oxidation and precipitation of iron and manganese. The oxidation of Mn24 is catalyzed by a reaction surface io a tetravalent state that absorbs additional Fe2+ or Mn2+ which, in turn, becomes oxidized. A surface is required and the initial deposition may be of iron oxide, possibly from volcanic or geothermal sources. Proper conditions of pH, redox potential, and metal ion concentration are found in deep ocean waters. The rate of accumulation appears to be very slow. The growth also may be discontinuous, and is estimated at a faster rater rate near the continental margins. 

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