EnvironmentAsia (Jul 2009)
Investigation of Organic Carbon using Rapid Dichromate Oxidation in Comparison with Dry Combustion Techniques among Three Groups of Two Different Sizes of Soils
Abstract
The purpose of this research was to compare two methods for the determination of organic carbon (OC)—rapid dichromate oxidation technique and dry combustion technique, in three groups of two different sizes of agricultural soils in Thailand. Fifty four soils collected from 3 provinces—Nakorn Pathom, Samut Sonkhram, and Samut Sakhon were classified as followed; 26 clays, 12 clay loams, and 16 medium loams. The selected soil sizes were <65 μm representing the metal-studied soil size and <212 μm representing the general purpose studied soil size. The statistical comparison of OC between the two methods indicated that using rapid dichromate oxidation technique—(Walkley-Black method) gave significantly less amounts of OC in clay and clay loam for soil size < 65 μm, but for soil size <212 μm, the amounts of OC in clay were significantly less than those obtained from dry combustion technique. This implied that the amounts of OC associated to the soil particle size differently. In this study, the smaller of the soil particles the more underestimation of the amounts of OC were obtained by using rapid dichromate oxidation techniques. Therefore, we introduce new correction factors for the rapid dichromate oxidation technique: 1.37, 1.37, and 1.46 for clay and clay loam of soil size < 65 μm and clay of soil size < 212 μm, respectively.
