It has been observed previously at Gelang Patah that bubbling air through water from the ponds can raise the pH fairly rapidly and thus could possibly be of value in ameliorating effects of acidification. The consultants conducted bubbling experiments using water from Ponds 23 and 29 and from the stream opposite Main Gate I (Table 6). In all three cases pH increased appreciably, while alkalinity and iron were not affected significantly, despite the visual appearance of improved water clarity. The cause of the pH increase is due to reduction of the partial pressure of carbon dioxide (pCO2) in the initial water samples by about an order of magnitude to reach equilibrium with atmospheric pCO2 (300 to 400 × 10-6 atmospheres). The dissociation constants appropriate for computing pCO2 in Gelang Patah waters are summarized in Table 7, along with calculations for each of three bubbling experiments. The initial pCO2 values are much greater than atmospheric pCO2 because of microbial production of CO2 as organic compounds in sediments and waters are oxidized. Such values are typical of streams and shallow ponds throughout the world.
