Tuesday, November 14, 2006

Phosphorus forms in Volcanic Ash and Soil from Montserrat Island, West Indies.

Thilini Ranatunga, Kamala Bhat, Robert Taylor, and Zachary Senwo. Alabama A&M University, "Dept of Plt & Soil Sci, PO Box 1208", "Dept of Plt & Soil Sci, PO Box 1208", Normal, AL 35762, United States of America

Eruption of the Soufriere Hills volcano located in Montserrat Island, West Indies may have potential impacts on the soil and plant environment of Montserrat.  Preliminary studies on the volcanic ash and soils from regions highly affected by the volcano indicate ash and soil (beneath ash) to be rich in phosphorus (P). Thus, a preliminary investigation was carried out to identify and quantify various forms of P present in ash and soil samples collected from “Exclusion Zone” of Montserrat Island.  Plant-available P was extracted from ash and soil using different P extractants such as  Mehlich-I, Mehlich-III, Troug [(NH4)2SO4/H2SO4], Morgan (CH3COONa/CH3COOH)and Bray (NH4F/HCl). Highest amount of P was extracted by the Troug extractant followed by Mehlich I, Bray, and Mehlich III extractants. Results from these extractions indicate presence of high amounts of Ca-bound P in ash as well as soils beneath ash. In addition, ash deposited during the first major eruption (1997) was found to contain relatively high levels of plant-available P compared to recently deposited ash (2005).  Water soluble P in ash was relatively low compared to plant-available forms indicating P in ash samples may occur either adsorbed and/or co-precipitated onto the ash particle surfaces. Plant-available P may also be present as calcium phosphate minerals in ash. Sequential P fractionation was also carried out on these samples using water, NaHCO3, NaOH, and HCl.