COMPARISON OF WATER AND DILUTE ACID TREATMENT ON ORGANIC AND INORGANIC CHEMISTRY OF LEACHATE FROM ORGANIC-RICH HORIZONS OF AN ACID FOREST SOIL

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Abstract
We examined the organic and inorganic chemistry of leachate produced by treating organic-rich horizons of an acid forest soil with distilled-deionized water or with water acidified to pH 3 with H2SO4. Each soil horizon imparted considerable free and total acidity to the distilled-deionized water through the solubilization of organic matter. The amount and acidic nature of solubilized organic matter was a function of horizon. The amounts of Ca, Mg, and Al in solution were related to the amount of organic matter solubilized. After extensive leaching, material from the Oi horizon was allowed to equilibrate with water, which resulted in considerable further solubilization of organic matter and inorganic constituents and acidification of solution. Leaching with pH 3 H2SO4 produced complex changes in both the organic and inorganic composition of leachate. The amount of Al solubilized was related to soluble organic matter, depending upon the horizon leached. Although it is generally considered that soil organic matter buffers against strong acid additions only by exchange of bases and aluminum for H+, our results indicate that a number of other mechanisms related to the solubilization of soil organic matter also act to consume H+.