Resumo

MENDEZ, Juan Carlos  e  BERTSCH, Floria. Total content and nutrients availability in two samples of ash eject by the Turrialba Volcano, Costa Rica in January 2010. Agron. Costarricense [online]. 2011, vol.35, n.2, pp.97-104. ISSN 0377-9424.

In January 2010, at a distance of approximately 10 km from the main crater, 2 samples of ashes ejected by the Turrialba Volcano, Costa Rica, were collected with the objective of analizing their total content of elements, and the percentage available in the short time. To analyze the total amount of elements, both samples were digested with HNO3 (70%), and the elements were determined by Atomic Emission Spectroscopy Plasma (ICP), while and to determine the amount of “immediately available” elements in the samples, KCl (1N) and Modified Olsen extractants were used. Moreover, to study the ashes' solubility in water, sample 1 was dissolved at 3 different pH (4, 5.5 and 6.7), and with 4 agitation times (0, 0.5, 4 and 24 h), with 3 repetitions in each case. After each agitation time the Electrical Conductivity and the pH of the resulting solution were determined, and the amount of elements dissolved in the solution was analyzed by ICP. The total average contents present in the ashes were, from higher to lower amounts, Fe (13 300), Ca (8700), Mg (2300), K (750), S (700), P (450), Mn (79), Zn (38), Cu (33) and B (31) mg.kg-1. As to the immediate availability in the extractant solution in relation to total content, Fe was only 0.2% available, and for the rest of the elements the percentages were: 8-11% for Ca, 0.5% for Mg, 6-15% for K, 10-13% for S, 2-7% for P, 0-3% for Mn, 2-7% for Zn, and 0-3% for Cu. In the analyses of water solubility no presence of P, Zn, Cu, or Mn was detected at any initial water pH or agitation time. For the rest of the elements, except for K which showed no defined tendency, significant increases in the amount dissolved in water were shown with increases in agitation time at the 3 different initial pH of water. Also, the dissolved ash showed a “buffer” effect since, regardless of the initial water pH, the solution pH increased to around 6.7 under all conditions

Palavras-chave : Volcanic ashes; solubility; Turrialba Volcano; nutrient availability; Andisols.

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