Voltammetric tools for trace element speciation in fresh waters: methodologies, outcomes and future perspectives

Environmental context Trace elements are ubiquitous in natural waters where their levels are highly variable depending on natural factors and anthropogenic pollution. The chemical form of the element determines its behaviour in the environment and whether it is likely to pose a risk to environmental and human health. This paper focuses on elemental forms in freshwater systems: it reviews analytical methods, gathers available data, and assesses trends, needs and open issues in this field. Abstract Research in voltammetric speciation methods has been mainly driven by the research interests of the oceanographic scientific community and methods were subsequently adapted to freshwater conditions. Nonetheless, different processes, variability of geological, chemical, biological and ecological settings on the one side, and different human land and water uses on the other imply specific needs and a strong shift in concerns for inland waters in terms of investigated analytes. This review paper focuses on speciation of trace elements in freshwater by voltammetric techniques, giving information on and a critical assessment of the state of the art in this field. Methods determining covalently bound substituents, redox species and element forms differing in the nature of their complexed substituents were considered, according to the IUPAC definition of species. Three relevant topics are discussed: an overview of existing voltammetric speciation methods, with emphasis on practical features; current knowledge in the field of trace element speciation in freshwater bodies, organised by element and matrix; and future perspectives and needs for freshwater speciation studies. As a general outcome, a complete picture of trace element speciation in freshwater matrices is far from being achieved.