On arsenic speciation in the Tagus estuary

• Published in: Netherlands journal of sea research Vol. 22; no. 3; pp. 205 - 212
• Main Author: De Bettencourt, A.M.M.
• Format: Journal Article
• Language: English
• Published: Den Helder Elsevier B.V 01.10.1988; Netherlands Institute for Sea Research
• Subjects: Earth sciences; Earth, ocean, space; Exact sciences and technology
• ISSN: 0077-7579
• DOI: 10.1016/0077-7579(88)90024-5

New evidence is presented pointing to the presence in estuarine waters both of trimethylarsenic forms (TMA) and of an organoarsenical component refractory to the hydride method. Although not previously detected in estuarine and coastal studies, TMA concentrations were measured in the Tagus estuary in August 1984. The results are presented together with total inorganic, monomethyl (MMA) and dimethyl arsenic (DMA) species quantified in the same occasion. Further digestion of a separate water sample gave positive increments for the methylarsenicals (MMA+DMA+TMA), with special relevance for DMA, suggesting the presence of a heavier organo-arsenical, undetectable in undigested samples with our current analytical capabilities. This component seems to be present in concentrations greater than MMA and TMA. That same sample was passed through a molecular fractionation scheme to get indications of the molecular weight of that unknown component. The results suggest a molecular weight of less than 210 although the limitations of the method do not allow a definitive conclusion.