Chromium concentration ocean

In general, the concentration of chromium in ocean water is much lower than that in lakes and rivers. 

Reported concentrations of chromium in open ocean waters range from 0.07 to 0.96 xg/l with a preponderance of values near the lower limit. Methods used for the determination of chromium at this concentration have generally used some form of matrix separation and analyte concentration prior to determination [170-173], electroreduction [174,175] and ion exchange techniques [176,177]. 

High EF values were also noted for Cu (<90-400), Zn (<120-830), and Mn (1-500), with the lower ranges reported for the rural airport site. Iron showed relatively low EF values (< 1 to 30). Vanadium exhibited EF values generally from 1 to 10 with the exception of one event where the value was 68. Concentrations from chromium never exceeded 30 ppb with EF values ranging from 25 to 100. Halogen EF values, when compared to sodium concentrations in the ocean, were generally less than 10 with the exception of iodine. The iodine enrichment is believed not to be anthropogenic but to arise From preferential enrichment from the oceans (7). 

During the 1987-1988 Antarctic Campaign, samples were collected and analyzed from twelve sites at Terra Nova Bay and along the Ross Sea shore. The concentrations of Cr, Cu, Fe and Ni in particulate matter were lower than those found in the Indian sector of the Southern Ocean obtained by a total attack (52). Chromium, Cu and Ni were not site-dependent the Fe concentration was higher... 

Figure 2 Dissolved Cr(VI) (A) and Cr(lll) (B) in the eastern North Pacific Ocean, 23°N, 115°W. (Data from Murray JW, Spell B and Paul B (1983) The contrasting geochemistry of manganese and chromium in the eastern tropical Pacific Ocean. In Wong CS et al. (eds) Trace Metals in Seawater, NATO Conference Services 4 Marine Science vol. 9, pp. 643-668. New York Plenium Press.) (C) Dissolved rhenium in the eastern North Pacific Ocean, 9°46 N, 104°1TW. (Data from Woodhouse OB, Ravizza G, Falkner KK, Statham PJ and Peucker-Ehrenbrink B (1999) Osmium in seawater vertical profiles of concentration and isotopic composition in the eastern Pacific Ocean. Earth and Pianetary Science Letters 173 223-233.)...

Adsorption on manganese oxide, followed by oxidation at the surface, helps considerably to convert Cr(III) into the thermodynamically stable Cr(VI). However, because of the low concentration of suspended MnOa in the oceans, it is not clear whether this catalyzed oxidation is quantitatively more important than the direct oxidation by dissolved oxygen. Thus, chemical speciation of chromium in seawater is still an important issue in marine chemistry. 

On this basis, Bowen states that only in the case of the elements, chromium, copper, lead and tin, would the mean concentration in fresh water rise significantly, while the change in concentration of all elements in ocean water would be immeasurably small. Of these four elements, copper is asserted to be potentially the most dangerous, since the dissolution of the world output of copper in the total mass of fresh water would raise its concentration above the toxic limit for some algae. Mercury must also be considered as a candidate for the distinction of being the most hazardous metal pollutant of the hydrosphere, since it is highly toxic and the amount produced annually is greater than the amount added to the ocean in fresh water (Table 40). 

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