Carbonate chemistry of groundwater from Tropical Tower Karst in South Thailand

Abstract

Waters from tropical tower karst in an area with no seasonal variations in temperature show marked variations in their dissolved carbonate chemistry. Saturation indices for calcite and dolomite indicate that most samples are saturated to supersaturated with these solids. Calculated log PCO•. values for the waters give a mean of -2.12 + 0.41. Measured PCO•. values for the soil atmosphere and soil leachates give a mean log PCO•. of-1.43 + 0.07. The wide variation of springwater PCO•. is best explained by a predominantly closed system evolution from the initial PCO•. of the soil. • Now at School of Environmental Sciences, University of East outcrop; dolomitized areas do, however, occur around Krabi Anglia, Norwich England. ' on the eastern edge of the outcrop. The exterior faces of the Copyright (D 1978 by the American Geophysical Union. towers are extensively covered with thick tufa deposits: Paper number 8W0268. 961 •

Soil carbon dioxide and weathering potentials in tropical karst terrain, peninsular Malaysia: A preliminary model

“…If, for example, the actual COz concentration with which recharge water equilibrates is several times higher than the MAXCOz values used in the model, either because samples extracted from diffusion wells are unrepresentative or because COz in the ground air of the unsaturated zone (Atkinson, 1977) is much higher than in the soil, then weathering might be occurring under closed system conditions. Since the measured C 0 2 concentrations are very similar to those obtained by different sampling methods in other tropical karst soils (Nicholson and Nicholson, 1969;Miotke, 1974;Trudgill, 1977;Pitman, 1978;Sweeting, 1979), the soil COz data would appear reliable. The significance of ground air in the Malaysian outcrops remains to be established.…”

“…Samples were extracted by syringe from diffusion wells and CO, was measured using a GallenkampLloyd gas analyser (details in Crowther, 1982b). At all 13 sites slope profiles were surveyed along two or three 30 m sections using a 1 m pantometer (Pitty, 1968), and soil depth was determined by auger at the end of each 1 m segment ( Figure 3). One deep soil profile was examined in detail and, as part of an ecological study, tree girths (> 15cm breast height) were recorded within a 300-900m2 rectangular plot and litterfall was measured.…”

“…Mean CO, concentrations (% by volume) in the six karst soils. Range given in parentheses CO, and rainfall during a wide range of pre-set antecedent periods, using the method outlined by Pitty (1966).…”

Geochemistry of the Floridan aquifer system in Florida and in parts of Georgia, South Carolina, and Alabama

“…Many papers attempt to relate the total C02 dissolved in ground water to the C02 of the soil zone in recharge areas because of the effects C02 equilibria exert on both rock dissolution (for example, Thrailkill, 1968;Langmuir, 1971;Shuster and White, 1972;Long and Saleem, 1974;Drake and Wigley, 1975;Harmon and others, 1975 Trainer and Heath, 1976;Pitman, 1978) and the carbon isotope content of ground water (for example, Pearson and Hanshaw, 1970;Rightmire and Hanshaw, 1973;Deines and others, 1974;Fritz and others, 1978;Pearson and others, 1978;Rightmire, 1978). Drake and Wigley (1975) derived a general relation between soil PC02 and soil zone temperature which explained the PC02 in calcium-carbonate-saturated ground water that had evolved under essentially "closed system" conditions.…”

A world model of soil carbon dioxide

“…The Sulawesi value is based on 29 measurements of soil PCO, in hillslopes on limestone and in alluvial plains (McDonald, 1976). The Thailand value is the average of 10 measurements made by Pitman (1978) over a five-day period in August 1976.…”