tailieunhanh - Handbook of Plant Nutrition - chapter 21

Vanadium. The transition element vanadium exists mostly in the 3, 4, and 5 oxidation states (Table ), with the 4 and 5 states predominating under oxidizing conditions in the normal soil acidity of below pH 8 (1,2). Vanadium, with many other heavy metals, is released by anthropogenic activity. | 7 1 2006 7 33 AM Page 585 2 1 Vanadium David J. Pilbeam and Khaled Drihem University of Leeds Leeds United Kingdom CONTENTS Historical .585 Growth Effects .586 Growth Stimulation .586 Vanadium in Plant Acknowledgment .594 References .594 HISTORICAL The transition element vanadium exists mostly in the 3 4 and 5 oxidation states Table with the 4 and 5 states predominating under oxidizing conditions in the normal soil acidity of below pH 8 1 2 . Vanadium with many other heavy metals is released by anthropogenic activity and its concentration has been steadily increasing in the environment. A study on peat dating back 12 370 years from a bog in Switzerland indicated a large increase in inputs of vanadium since the industrial revolution 3 . Analysis of herbarium specimens of 24 species of vascular plants and 3 bryophytes collected over many years in Spain has shown a large increase in leaf vanadium concentrations particularly since the 1960s 4 . In soils the main source of vanadium is from the burning of coal and the subsequent addition of fly ash and bottom ash. In 1988 this ash contributed 11 to 67 X 106kg V yr 1 to soils 25 of the total vanadium deposited 5 . Agricultural and food wastes contributed 3 to 22 X 106kg yr and atmospheric fallout added to 21 X 106kg yr . TABLE Oxidation States of Some Important Species of Vanadium Species Formula Oxidation State Vanadous V2 2 Vanadic V3 3 Vanadyl VO2 4 Pervanadyl VO3 V OH 4 5 Metavanadate VO3 5 585 7 1 2006 7 33 AM Page 586 586 Handbook of Plant Nutrition Total atmospheric fallout in a typical year in recent times 1983 resulted mainly from the burning of oil in electricity generation estimated to be 6960 to 52 200 X 103kg and from industrial and domestic combustion of oil 30 150 to 141 860 X 103kg 5 . Of the 15 heavy metals considered in that study vanadium was the highest to be emitted .