Acid Release from an Acid Sulfate Soil Sample Under Successive Extractions with Different Extractants

摘要

An acid sulfate soil sample was successively extracted with deionized water, 1 mol L-1 KCI and 0.000 5rnmol L-1 Ca(OH)2 solutions. The results showed that only very small amounts of acidity were extracted rnby deionized water, possibly through slow jarosite hydrolysis. Acid release through jarosite hydrolysis was rngreatly enhanced by Ca(OH)2 extraction at the expense of the added OH- being neutralized by the acid rnreleased. Successive extraction of the sample with KCI removed the largest amounts of acidity from the rnsample. However, it is likely that the major form of acidity released by KC1 extraction was exchangeable rnacidity. The results also show the occurrence of low or non charged A1 and Fe species in water and Ca(OH)2rnextracts after first a few extractions. It appears that such a phenomenon was related to a decreasing EC rnvalue with increasing number of extractions.