Monitoring of V(IV) and V(V) in Etnean drinking-water distribution systems by solid phase extraction and electrothermal atomic absorption spectrometry E. Veschetti ⁎ , D. Maresca, L. Lucentini, E. Ferretti, G. Citti, M. Ottaviani Istituto Superiore di Sanità, Department of Environment and Primary Prevention, Viale Regina Elena, 299-00161 Rome, Italy Received 14 January 2006; received in revised form 2 May 2006; accepted 7 May 2006 Available online 21 July 2006 Abstract Monitoring activities carried out since 1994 showed the presence of significant levels of vanadium in drinking waters delivered in a lot of Etnean towns. The highest vanadium concentration was found in ground waters collected in the drainage gallery Ciapparazzo located on the Northwestern flank of Mt. Etna in Bronte's area (Catania, Italy). This drainage gallery, with a flow rate of near 500l s - 1 , is an important water source for several towns of the Etnean province. On account of different toxicological behaviours of V(IV) and V(V), which are the only possible oxidation states in aqueous media, a research project was set up to evaluate the ratio between their concentrations before and after disinfection treatments (chlorination or UV irradiation). Data were acquired in the most representative sites of the drainage gallery and the distribution network to evaluate the effect of residence times and disinfection treatments on possible species interconversion. The average total concentration of vanadium was 165 μgl - 1 . Speciation analyses performed by solid phase extraction of both species followed by furnace atomic absorption spectrometric determination of V(IV) eluates revealed that the latter was the predominant species (90–100%) in untreated waters. Moreover, among the two disinfecting treatments applied by the water supplier, only sodium hypochlorite altered the species ratio and determined an instant increase of near 20% in V(V) relative concentration. No significant effect was observed as residence time varied in the drainage gallery or in the distribution systems. Other physico-chemical and chemical parameters (i.e. pH, E H , water temperature, electrical conductance, dissolved oxygen as well as major and minor inorganic cations and anions) were determined in the collected water samples to evaluate if they are proper or not for interconversion of the two V species. Redox potential of the water was also correlated to the percentage of V(IV). © 2006 Elsevier B.V. All rights reserved. Keywords: Vanadium; Speciation; Etna; Drinking water networks; SPE; ETAAS 1. Introduction Vanadium is a trace element of ubiquitous distribution that constitutes about 0.02% of the Earth's crust. It can exist in many oxidation states from - 1 to +5 and in a number of oxyanionic and oxycationic forms [1,2]. The multiple oxidation states, ready hydrolysis and polymerization confer a level of complexity to its chemistry well above that of many other transition metals. Vanadium dissolves in natural waters as vanadyl and vanadate ions [3]. The coexistence of these species depends on pH, redox potential and ionic strength of the aqueous system [4–7]. Food is the main source of exposure for general population with an estimated daily dietary intake of 10–63 μg [8]. Vanadium concentration in ground and surface waters is largely dependent on geographical location; typical values range from 1 to 6 μgl - 1 in unpolluted areas [9,10]. Therefore, drinking water contribu- tion to V ingestion is generally negligible except where relative high concentrations of the element (usually 40–100 μgl - 1 ) have been recorded mainly as an effect of the presence of volcanic rocks [9,10]. Vanadium at levels observed is seawaters (0.2–29 μgl - 1 ) was shown to be an essential element for normal cell growth of some lower organisms [11–13]. Although no specific functional role has been discovered in higher animals [14], its salts can interact with a number of enzymatic systems. As a consequence of these interactions, it is capable of sustaining diverse physiological activities ranging from antitumorigenicity [15– 20], mitogenicity [21–24], and inhibition of key metabolic enzymes such as phosphoglucomutases and others [25–27]. It is generally known to have insulin-mimetic activity demonstrated Microchemical Journal 85 (2007) 80 – 87 www.elsevier.com/locate/microc ⁎ Corresponding author. E-mail address: enrico.veschetti@iss.it (E. Veschetti). 0026-265X/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.microc.2006.05.005