Study of the Effect of Adsorbed Species on the Elemental Composition of Pristine Ash, Ash –Soil, and Soils after the Soufrière Hill Volcanic Eruption.

During volcanic activity gases and many volatile substances are removed from the atmosphere by either chemical reaction, or as wet or dry deposits, or adsorbed on to the pristine ash surface. Further, occurrence of rainfall can result in the potential rapid release of heavy loadings on to soils and water bodies. The short term leaching of materials from the pristine un-weathered ash may be due to the enrichment of materials that originated from plume gases and not from the glass in the ash.  High temperature volcanic ejecta either in the form of ash or particulate matter deposition has a tendency to impact the soil surface. Weathering at high temperatures can be rapid but the concentrations of materials released may not pose as big a hazard as the adsorbed materials leached from the surface of ash. Impact assessment has been carried out by detailed chemical analysis using a variety of extractants to determine the major element components in the exposed and unexposed ash. Results indicate the presence of high concentrations in the order of Al> Ca>Fe>Na> Mg > K> Mn.  Comparative trace metal concentrations in ash and ash soil, and soil indicate that metal contamination would be very minimal due to ash deposition. Moreover depending on the pH of the ash, ash soil and soils, the amount of  adsorbate reaches a maximum and then appears to fall. It is understood that exposed ash usually has a tendency for the leaching and therefore would affect the water sources as well as on the plants in terms of questionable nutrient quality and quantity. Implications of high Al concentrations in the ash pose a toxicity problem for vegetation in the region