Vanadium speciation and cycling in coastal waters

Different chemical species of dissolved vanadium, V (IV) and V (V), were measured in the water column of the Long Island Sound (LIS), from the East River to the Atlantic boundary during spring and summer conditions. Our preliminary results showed seasonal and spatial changes in total dissolved V and its redox speciation along LIS. Levels of both V species were high in summer (V (IV), 2.2 ± 1.7 nM; V (V), 22.4 ± 3.9 nM), and low in spring (V (IV), 1.4 ± 1.4 nM; V (V), 11.1 ± 2.6 nM). A V-salinity mixing plot suggests a non-conservative behavior of total dissolved V (and V (IV)) during estuarine mixing.Dissolved V (IV) occurred mostly in western LIS, accounting for 15–25% of the total dissolved V pool in summer hypoxic bottom waters of that region. In spring, V (IV) accounted for up to 40% of the total dissolved V pool in western LIS, likely from sewage inputs. Dissolved V (IV) was also measured near the Quinnipiac, Housatonic and Connecticut rivers (accounting for 10–20% of the total dissolved in summer), suggesting a local source of the reduced V (likely desorption from surficial sediments and resuspended particles). A positive trend between V (IV) and large size phytoplankton biomass suggests that levels of reduced V may be influenced by biological activity.