Arsenic Concentrations in Marine Samples

Although there had been earlier reports (1-3) of the presence of arsenic in marine samples, the first comprehensive study was presented by Jones (4) in 1922. He examined marine algae collected from British coastal waters, reporting concentrations of arsenic and information on its extraction with water and ethanol. He referred to the arsenic as organic arsenic and, perhaps somewhat mischievously, remarked that the reputed medicinal properties of some algae may be due to their organic arsenic content. 

In work related to the human toxicology of arsenic, Cox (5) noted that within 24 hours after a person eats fish, arsenic can be measured in the urine at levels normally indicative of chronic arsenic poisoning. The subsequent study of Chapman (6) in 1926 established the occurrence of high levels of arsenic in a wide range of marine organisms. Arsenic concentrations in seawater were also reported at this time (7). Over the ensuing years there followed only infrequent reports (e.g., 8) on arsenic in marine samples until the late 1960s. Renewed interest 

Type Location (no. of species) Arsenic concentration (mg/kg wet or dry wt. as shown) Range Mean Ref. 

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Tables I to III provide a summary of some representative data for total arsenic concentrations in sediments, marine algae, and marine animals. There can be considerable variation in the arsenic levels in these samples, in contrast to the levels in seawater, which are reasonably uniform in the world s oceans at about 0.5-2 p.g/liter (9,10). For sediments, there is perhaps a tendency for arsenic concentrations to be lower in samples from coastal regions and estuaries compared with deep-sea sediments. Industrial discharges of arsenic-enriched effluents can, however, result in arsenic contamination of near-shore sediments (11,12). Arsenic concentrations in marine algae are generally considerably higher in brown algae than in either red or green algae. Reasons...

The chemical form of arsenic in marine environmental samples is of interest from several standpoints. Marine organisms show widely varying concentrations of arsenic [4-6] and knowledge of the chemical forms in which the element occurs in tissues is relevant to the interpretation of these variable degrees of bioaccumulation and to an understanding of the biochemical mechanisms involved. Different arsenic species have different levels of toxicity [7] and bioavailability [8] and this is important in food chain processes, while physicochemical behaviour in processes such as adsorption onto sediments also varies with the species involved [9]. It has... 

Fish are known to accumulate arsenic and a study carried out in 1998 found appreciable quantities of total arsenic in all samples analysed.15 The mean concentration of arsenic in samples of fresh marine fish landed in UK ports in 1995-1997 ranged between 1.9 mg/kg and 8.4 mg/kg. An earlier survey found that fish that live on or close to the sea bed, such as plaice, dabs, flounders and skate, tend to have higher levels of arsenic than other fish,24 and this was confirmed by the later work, where the highest level was found in plaice. Arsenic levels in shellfish show more variation, ranging from 1.3 mg/kg to 30 mg/kg. High levels are frequently found in crab, in which the white meat generally contains more arsenic than the brown meat. Lobsters contained similar levels of arsenic to crabs, with the highest levels found in pink shrimps. 

The concentrations of the three arsenicals (75-77) were determined in 37 marine organisms comprising algae, crustaceans, bivalves, fish and mammals by high-performance liquid chromatography/inductively coupled plasma mass spectrometry (HPLC/ICPMS) [170]. All three organoarsenics, which occurred at pg/kg concentrations, were detected in 25, 23 and 17 of the 37 samples analyzed, respectively. The limits of detection were 2-3 pg/kg dry mass. The data illustrate that all three compounds are common minor constituents in practically all marine samples. 

A second arsenic betaine, trimethylarsoniopropionate (Figure 6 F6-21), was first found in a fish sample, " and has subsequently been shown to occur widely in marine animals, albeit generally at low concentrations.A new trimethylarsonioriboside (Figure 6 F6-22) was also found as a trace constituent in several gastropod species, and as a much more significant arsenic component in the intestine of fish and invertebrates. 

Few investigations on arsenite oxidation in the marine environment have been published (15,16). Andreae (15) found lower concentrations of arsenite in surface water samples than in deep water samples from the Pacific Ocean. He found arsenite concentrations in surface waters in the range of 0.15-0.01 parts per billion (ppb), whereas below 400 m he found the average concentration to be 7.9 parts per thousand (ppt). He attributed this difference in concentration between surface and deep water to biological uptake and transport. Andreae s measurement of an observed ratio of As(V)/As(III) in deep water of 2.5 x 10 indicated to him a thermodynamic disequilibrium, because at equilibrium the expected ratio was 10 based on a pE of 8.0 and standard activity coefficients of the two arsenic species in seawater. The observed ratio would be expected at a pE of 2.0. Andreae... 

Arsenic has a relatively high concentration in seawater (when compared with many other trace elements see Table 12-1) and is not present at high levels in materials used in the construction of ships, marine equipment, and samplers. Therefore, the problem of sample contamination is much less severe for this element and its species than for many other trace elements. Clean room facilities are not required for arsenic species determination. Care should, however, be taken in the laboratory to avoid the possibility of contamination resulting from the preparation and handling of standards. 

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