Four methods on determination of organic- and inorganic-carbon in soils and sediments from calcareous region have been compared and evaluated. The methods were Walkley-Black procedure (i.e. potassium dichromate oxidization, chemical titration with ferrous sulfate) for organic carbon associated with pressure-calcimeter determination for inorganic carbon, weight–loss-on-ignition for organic and inorganic, Thermogravimetric method, Vario max CNS Autoanalyzer either reduced the reduction temperature to determine organic carbon and subtracted inorganic carbon from the total obtained with normal temperature, and determined the total, and organic carbon with subsamples removed inorganic carbon by HCl fumigation, respectively. The result displayed that Walkley-Black procedure provided an accurate determination for organic carbon in soils but not in sediments; Weight-loss-on-ignition provided an accurate estimation on organic carbon at 475 °C to 500 °C, and for inorganic carbon at 800 °C; Thermogravimetric method displayed a quantitative "fingureprint" in weight loss for both organic and inorganic carbon on certain samples but mostly needs some experiences to interpret the data; CNS autoanalyzer either removed inorganic C via HCl fumigatoin or reduced reduction temperature displayed a good estimation only on soil samples. With cost effectiveness, simplicity and accuracy, weight-loss-on-ignition method at 500 °C for organic C and 800 °C for inorganic C simultaneous determinations is highly recommended for both soil and sediment samples in a calcareous region.
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