Marine conditions

Aggressive environments include marine conditions and particularly industrial atmospheres containing high concentrations of acid gases such as sulphur dioxide rain washing is benehcial in both environments, while dampness and condensation alone can accentuate the rate of attack in the presence of chlorides and acidic sulphates. 

Porter, F. C., Aluminium Sprayed Steel in Marine Conditions , Engineer, Lond., 211, 906 (1961)... 

Variable results have been reported with this pigment and an examination of its inhibitive action has led to the conclusion that under rural and marine conditions, where the pH of the rain-water is above 5, it behaves as an inert pigment owing to its limited solubility. However, in industrial and urban areas, where the pH of the rain-water may be in the region of 4 or lower, it is converted into the more soluble monohydrogen phosphate. This reacts in the presence of oxygen, with the steel surface to form a mixture of tribasic zinc and ferric phosphates, which being insoluble protects the steel from further attack. 

These equations identify the dominant source and loss processes for HO and H02 when NMHC reactions are unimportant. Imprecisions inherent in the laboratory measured rate coefficients used in atmospheric mechanisms (for instance, the rate constants in Equation E6) can, themselves, add considerable uncertainty to computed concentrations of atmospheric constituents. A Monte-Carlo technique was used to propagate rate coefficient uncertainties to calculated concentrations (179,180). For hydroxyl radical, uncertainties in published rate constants propagate to modelled [HO ] uncertainties that range from 25% under low-latitude marine conditions to 72% under urban mid-latitude conditions. A large part of this uncertainty is due to the uncertainty (la=40%) in the photolysis rate of 0(3) to form O D, /j. 

While methylmercury occurs naturally in tlie environment, it is reasonable to expect that methylmercury levels have increased in modem times as a result of increased inorganic mercury concentrations. Whether methylmercmy concentrations have increased to a similar extent as inoiganic mercuiy is not known. It is clear, however, that elevated fish mercuiy concentrations can currently be found in remote lakes, rivers, reservoirs, estuaries, and marine conditions, typically in predators such as sportfish at the top of food webs. As of 2003, 45 states had fish consumption advisories related to mercuiy, and 76% of all fish consumption advisories in the United States were at least partly related to mercury (USEPA 2004a). The number of advisories is increasing with time, although this is due at least partly to more sites being sampled (Wiener et al. 2003). 

Fatty Acid Esters. Defoamers that are more environmentally acceptable than convential products are based on fatty acid esters of hydroxy alcohols, such as sorbitan monooleate [1908] or sorbitan monolaurate in combination with diethylene glycol monobutyl ether as a cosolvent [451]. These defoamer compositions are as effective as conventional materials, for example, those based on acetylenic alcohols are less toxic, especially to marine organisms, and are readily biodegradable. The defoamer compositions are used in water-based hydrocarbon well fluids during oil/gas well drilling, completion, and workover, especially in marine conditions. 

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. 

This is an on-going project aimed at examining the T/D characteristics of metals and alloys in a marine medium in seven- and twenty eight-day tests. The data obtained to date on seven-day tests of cuprous oxide (Cu20) and nickel metal powder (Ni) provides useful comparisons with those reported earlier for the freshwater OECD 203-based media at pH 6 and 8 (Skeaff Hardy 2005) and insight into the behaviour of metal-bearing substances used in commerce under marine conditions of the T/DP. The data supports an approach directed to the eventual adaptation, validation and application of the OECD T/DP to marine systems for the purposes of marine hazard classification of metals, metal compounds and alloys. 

Note (a) BCF is hioconcentration factor, NOEC is no-observed effect concentration. (b) For marine environmental risk assessment, half-life data in freshwater sediment can be overruled by data obtained under marine conditions. (c) Substances are classified when they fulfil the criteria for all three inherent properties for P, B and T. However, there is certain flexibility for instance in cases where one criterion is marginally not fulfilled but the others are exceeded considerably. (d) R48 Danger of serious damage to health by prolonged exposure. ... 

Exposure under marine conditions is a particular case which can be especially complex. Apart from irradiance levels and temperatures being different, where the water has significant effect the frequency and duration of immersion can be critical. A standard for marine exposure of plastics is being developed as ISO 15314 [14]. 

The Siluro-Devonian Tobique-Chaleurs Zone (TCZ) of New Brunswick is host to several relatively small Zn-Pb Cu-Ag sulfide deposits and occurrences that are all spatially associated with Early Devonian felsic volcanic and related sedimentary rocks (Fig. 1). The sulfide mineralization occurs as veins, veinlets and replacements of rock units that had high primary permeability (e.g., flow top breccias). Massive bedded sulfides that are typical of many modern and ancient VMS deposits are not present however, their absence is not surprising given the relatively shallow oxidizing marine conditions at that time therefore, the TCZ deposits belong to that part of the VMS family formed beneath the seafloor. This study was undertaken to assess the nature of the felsic volcanic host rocks and their control on mineralization. 

Sources of Sulfur in Coal and Oil. The major coal beds of eastern North America are of Pennsylvanian age. During that time, there was a constantly fluctuating sea level across flat lowlands over the North American interior. Coal was formed just before the onset of marine conditions, so that coal swamp forests occurred on broad lands along or near the sea shore. Thicker sections accumulated on the more rapidly subsiding Illinois and Forest City basins and in the Appalachia fireland basin (14). 

Isolation and culture of putative symbiotic microorganisms to obtain the bioactive metabolites isolated from the invertebrate-microbe assemblages has been particularly problematic. It has been estimated that only 1% of marine microbes can be isolated and fermented using techniques modified to approximate marine conditions. However, to address this problem, several groups have used differential fractionation or flow cytometric techniques to separate populations of extracellularly associated microorganisms from invertebrate host cells. Chromatographic and spectroscopic analyses of the enriched cell fractions have been used to determine which cell type is producing the compounds. The assumption is that the metabolites are produced in the cell types in which they are detected. 

Both field and laboratory observations are consistent with the idea that dissolution can proceed faster than precipitation in carbonate sediments (also see Pytkowicz, 1971 Berner et al., 1978 Moulin et al 1985 Burton and Walter, 1987), and that the pore waters reach steady-state ion activity products close to those of the most unstable phase (dissolution processes will be discussed later in this chapter). Carbonate ion may be "pumped" down to values at saturation with less soluble phases, as dissolution of the more soluble material eventually causes its removal. However, the persistence of high magnesian calcites in sediments for long periods of time indicates that this process does not involve a large amount of mass transfer under normal marine conditions. 

Unconformity-related deposits are found near principal unconformities. Examples include the ore bodies at Quff Lake, Key Lake, and Rabbit Lake in northern Saskatchewan, Canada, and in the Alligator Rivers area in northern Australia. Sandstone deposits are contained in rocks that were deposited under fluvial or marginal marine conditions. The host rocks nearly always contain pyrite and organic plant matter. The sediments are commonly associated with tuffs. Unoxidized deposits of this type consist of pitchblende and coffinite in arkasoic and quartzitic sandstones. Upon weathering, secondary minerals such as camotite, tuyamunite, and uranophane are formed. More information on these and other uranium deposit types is available (1). 

Neurotoxic events linked to cyanobacteria are not limited to freshwater or marine conditions. For example, there is growing evidence that the neurological condition amyotrophic lateral sclerosis-parkinsonism-dementia complex (ALS-PD) is caused by consumption of p-methylaminoalanine (BMAA). BMAA is found in cyanobacteria which grow in the tissues of plants and is possibly biomagnified in the food chain in areas affected by ALS-PD. 

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