Volume 28, Issue 4 (July 2005)
New Method to Determine the True Water Content of Organic Soils
The true water content of organic soils is overestimated when the standard oven drying temperature of 110 ± 5°C is used due to some oxidation of the solids, and underestimated when the recommended oven drying temperature of 60°C is used due to some residual pore water remaining in the voids. A new method is presented to identify the precise oven drying temperature for which the mass of the residual pore water exactly balances the loss in the mass of solids due to oxidation. The true water content is calculated on the basis of the specimen dry mass recorded for this oven drying temperature.
A larger error arose when the water content of the test soil (70% organic content) was determined using the specimen dry mass recorded at 60°C rather than the standard drying temperature of 110 ± 5°C. Longer drying times were also required for the dry mass to equilibrate, making it more inconvenient from a practical standpoint. Some oxidation of the organic solids occurred for oven specimen drying above 80°C. The true value of the water content corresponded to an oven drying temperature of 86°C.