Arsenate in freshwater

Concentration and chemical forms of arsenic in freshwater environment have been reviewed in detail by the present author . When comparing freshwater and marine organisms in the natural environment, there seems to be a clear difference in the total arsenic concentration, which in freshwater organisms is lower than in marine organisms. Trimethyl-, dimethyl- and monomethylarsenic compounds were detected in freshwater organisms whose chemical structure in vivo have not been confirmed . 

Arsenate and arsenite are major forms of arsenic in freshwater and terrestrial plants. 

Freshwater algae have been little studied compared with their marine counterparts, but their pattern of arsenic compounds appears to be similar (15,70). Arse-nosugars are present as major or significant compounds (only compounds 1 and 2 in Fig. 2 have been reported so far). Arsenate can also be a major arsenical in freshwater algae, and small amounts of dimethylarsinate and methylarsonate have also been reported. Arsenite has not been detected. 

Chemical structures of the arsenic compounds in marine organisms have been confirmed in many cases, but very few chemical species of arsenic in freshwater organisms have been found. Arsenic transformation via the freshwater food chain has rarely been reported. This chapter focuses on the toxicity of arsenicals and the biotransformation of arsenic in the freshwater organisms. 

Bebbington, G.N., N.J. Mackay, R. Chvojka, R.J. Williams, A. Dunn, and E.H. Auty. 1977. Heavy metals, selenium and arsenic in nine species of Australian commercial fish. Austral. Jour. Mar. Freshwater Res. 28 277-286. 

May, T.W. and G.L. McKinney. 1981. Cadmium, lead, mercury, arsenic, and selenium concentrations in freshwater fish, 1976-77 — National Pesticide Monitoring Program. Pestic. Monit. Jour. 15 14-38. 

May, T.W. and G.L. McKinney. 1981. Cadmium, lead, mercury, arsenic, and selenium concentrations in freshwater fish, 1976-77 — National Pesticide Monitoring Program. Pestic. Monitor. Jour. 15 14-38. McDonald, L.J. 1986. Suspected lead poisoning in an Amazon parrot. Canad. Vet. Jour. 27 131-134. McLean, R.O. and A.K. Jones. 1975. Studies of tolerance to heavy metals in the flora of the rivers Ystwyth and Clarach, Wales. Freshwater Biol. 5 431 -444. 

Marine algae transform arsenate into nonvolatile methylated arsenic compounds such as methanearsonic and dimethylarsinic acids (Tamaki and Frankenberger 1992). Freshwater algae and macrophytes, like marine algae, synthesize lipid-soluble arsenic compounds and do not produce volatile methylarsines. Terrestrial plants preferentially accumulate arsenate over arsenite by a factor of about 4. Phosphate inhibits arsenate uptake by plants, but not the reverse. The mode of toxicity of arsenate in plants is to partially block protein synthesis and interfere with protein phosphorylation — a process that is prevented by phosphate (Tamaki and Frankenberger 1992). 

In studies of the concentrations of arsenic, bromine, chromium, copper, mercury, lead and zinc in south-eastern Lake Michigan, it was shown that these elements concentrated near the sediment water interface of the fine-grained sediments. The concentration of these elements was related to the amount of organic carbon present in the sediments (161). However, it was not possible to correlate the concentration of boron, berylium, copper, lanthanum, nickel, scandium and vanadium with organic carbon levels. The difficulty in predicting the behaviour of cations in freshwater is exemplified in this study for there is no apparent reason immediately obvious why chromium and copper on the one hand and cobalt and nickel on the other exhibit such variations. However, it must be presumed that lanthanium might typify the behaviour of the trivalent actinides and tetravalent plutonium. 

Nicholas, D.R., Ramamoorthy, S., Palace, V. et al. (2003) Biogeochemical transformations of arsenic in circumneutral freshwater sediments. Biodegradation, 14(2), 123-37. 

The New Hampshire Department of Health and Human Services is determining blood mercury concentrations and related freshwater fish consumption, studying speciated arsenic in urine, and analyzing phthalates in urine and PBDEs in serum and breast milk (APHL 2004, 2006). In 2004, New Hampshire received about 300,000 to support its biomonitoring program (APHL 2004). 

Kuroiwa, T., Ohki, A., Naka, K. and Maeda, S. (1994) Biomethylation and biotransformation of arsenic in a freshwater food chain green alga (Chlorella vulgaris) — shrimp (Neocaridina denticulata) — Killifish (Oryzias latipes). Appl. Organomet. Chem., 8, 325-333. 

R. Tukai, W. A. Maher, I. J. McNaught, M. J. Ellwood, M. Coleman, Occurrence and chemical form of arsenic in marine macroalgae from the east coast of Australia, Austr. Mar. Freshwat. Res., 53 (2002), 971-980. 

Z. Slejkovec, Z. Bajc, D. Z. Doganoc, Arsenic speciation patterns in freshwater fish, Talanta, 62 (2004), 931-936. 

---