Does pyrite oxidation contribute to the acidification of tropical peat? A case study in a peat swamp forest in Central Kalimantan, Indonesia

The chemical properties of peat pore water in the basin of the Sebangau River and Lahei district, Central Kalimantan, Indonesia, were studied. We analyzed major ions, pH, electrical conductivity (EC) and redox potential (Eh) of the peat pore water with reference to their vertical profile. We evaluated the contribution of sulfates to the acidification of peat by including data from Furen mire, eastern Hokkaido, Japan. The coastal peat of Furen mire and the peat in Paduran in the lower basin of the Sebangau River included extraordinarily high concentrations of sulfates (>1000 mg/l) compared to the peat in the middle and upper basins of the river (<10 mg/l). High concentrations of sulfates, however, did not lead to a low pH for the peat. The present findings suggest that the acidification of the peat pore water is subject to the production of organic acids originating from peat decomposition, rather than the production of sulfuric acid produced by pyrite oxidation in the underlying mineral sediments.