Dissolved vanadium in rivers: effects of silicate weathering

New measurements of vanadium in 15 small California catchments as well as s ome tributaries of the Mississippi River are presented here, These measurem ents complement previously published fluvial vanadium data and allow a re-e xamination of prior conclusions about the geochemistry of vanadium in river s. The data suggest a best estimate of the fluvial flux of dissolved vanadi um to be 0.52 Gmol year(-1), though considerable uncertainty remains in thi s number. Dissolved vanadium in rivers appears to be derived largely from t he weathering of silicate rocks which leads to a general correlation betwee n dissolved V and Si in rivers. However, rock type can modify this basic co rrelation as can solubility limits on Si. The nature of the erosional regim e may play some role in modifying fluvial V/Si ratios, but the effect is we ak enough to be obscured by other factors. Fluvial vanadium transport is al so potentially affected both by organic matter (through complexation and re duction) and by the effects of oxygen depletion in lakes, reservoirs and fr esh water sediments. However, these factors require additional study. The d evelopment of methodology to determine vanadium redox speciation in the fie ld would aid the further understanding of the processes affecting the trans port of this element through the environment. (C) 2000 Elsevier Science B.V . All rights reserved.