Coexisting Forms of Vanadium in Surface Water Objects (Review)

Resumo

The results of studies of the vanadium content and its coexisting forms in surface water bodies of various regions have been summarized. It has been shown that vanadium concentration in uncontaminated water bodies and rivers does not exceed several μg/L, whereas its concentration in water bodies which are subject to anthropogenic influence or located in the regions of volcanic activity reaches tens to hundreds of μg/L. The ratio of the suspended and dissolved forms of vanadium has been considered. The dissolved form of vanadium generally predominates in water bodies, whereas its migration as a constituent of suspended substances is characteristic of rivers, especially during the spring period. The studies of dissolved vanadium compounds concerning the ratio of its oxidized and reduced forms as well as complexation with dissolved organic matter have been discussed. It has been shown that V(V) dominates in the form of the H₂VO₄^– anion as the most stable form under oxidative conditions of surface waters. Several studies have noted the predominance of V(IV) in the form of oxocation VO²⁺, although it is known as unstable in the natural aquatic environment and is rapidly oxidized to V(V). This process is decelerated in the presence of humic substances which exhibit reducing properties. Anionic, cationic and neutral complexes of vanadium with organic ligands are known. Humic substances play a major part in the complexation as established for certain water bodies of Ukraine. The results of studies on the molecular weight distribution of vanadium complex compounds have been also considered.