Marine environment oxygen

In the marine environment oxygen and hydrogen isotope compositions of pore waters may be inherited from ocean water or inflnenced by diagenetic reactions in the sediment or nnderlying basement. Knowledge of the chemical composition of sedimentary pore waters has increased considerably since the beginning of the Deep-Sea-Drilling-Project. From numerous drill sites, similar depth-dependent trends in the isotopic composition have been observed. 

In rusting, the initial corrosion product of iron is ferrous hydroxide. Reacting with oxygen and water, it forms higher oxides, mainly hydrated ferric oxide and magnetite. Rust formed in industrial or marine environments contains corrosion-promoting salts and is particularly dangerous. Rust is not considered a satisfactory base over which to paint and it too must be removed. 

Mercury point sources and rates of particle scavenging are key factors in atmospheric transport rates to sites of methylation and subsequent entry into the marine food chain (Rolfhus and Fitzgerald 1995). Airborne soot particles transport mercury into the marine environment either as nuclei for raindrop formation or by direct deposition on water (Rawson etal. 1995). In early 1990, both dimethylmercury and monomethylmercury were found in the subthermocline waters of the equatorial Pacific Ocean the formation of these alkylmercury species in the low oxygen zone suggests that Hg2+ is the most likely substrate (Mason and Fitzgerald 1991 Figure 5.1). 

Fig. 3. The shapes of oxygen isotope zones associated with alteration about sub-volcanic intrusive complexes in a sub-marine environment reflect the local strain, yet still retain zoning systematics. Sizes of intrusions and high-temperature zones correlate approximately with total district tonnage of VMS...

Carbonate sediments deposited in shallow marine environments are often exposed to the influence of meteoric waters during their diagenetic history. Meteoric diagenesis lowers 8 0- and 8 C-values, because meteoric waters have lower 8 0-values than sea water. For example. Hays and Grossman (1991) demonstrated that oxygen isotope compositions of carbonate cements depend on the magnitude of depletion of respective meteoric waters. 5 C-values are lowered because soil bicarbonate is C-depleted relative to ocean water bicarbonate. 

Oxygen isotopic composition of ferric oxides from recent sod, hydrologic, and marine environments. Geochim. Cosmochim. Acta 64(13) 2221-2231... 

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