Sediment/water and octanol/water equilibrium partitioning of volatile organic compounds: temperature dependence in the 2–25°C range

• Published in: Water research (Oxford) 1999-07, Vol.33 (10), p.2424-2436
• Main Authors: Dewulf, J., Van Langenhove, H., Graré, S.
• Format: Article
• Language: English
• Subjects: Applied sciences; Biological and physicochemical phenomena; Biological and physicochemical properties of pollutants. Interaction in the soil; EPICS; Exact sciences and technology; Natural water pollution; octanol/water partitioning; Pollution; sediment/water partitioning; Soil and sediments pollution; sorption; volatile organic compounds (VOCs); Water treatment and pollution
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/S0043-1354(98)00460-6

The sediment/water ( K d) and octanol/water ( K ow) equilibrium partitioning coefficients have been investigated for volatile chlorinated and monocylic aromatic hydrocarbons in the 2 to 25°C temperature range. The equilibrium partitioning in closed systems (EPICS) method has been optimized to measure both equilibrium partitioning coefficients. Sediment/water equilibrium partitioning for a riverine sediment (organic carbon fraction 4.12%) proved to increase with increasing temperature, showing changes in enthalpy between 2.5 and 12.8 kJ·mol −1. A statistical approach showed that for 5 out of 12 compounds investigated this temperature dependence is significant at α=0.05. Next, the temperature dependence of the octanol/water equilibrium partitioning was investigated for 8 compounds. The octanol/water equilibrium partitioning coefficients increased with increasing temperature for all compounds, except for toluene. Changes in enthalpies of this process proved to be between −1.0 and 5.2 kJ·mol −1. However, the temperature dependence of this process was statistically not significant ( α=0.05). The log K d–log K ow relationship showed correlation coefficients between 0.89 and 0.90 at 2.3, 6.2, 18.6 and 25.0°C ( n=8). Slopes of the linear regression increased with increasing temperature. This was explained by the higher temperature dependence of sediment/water equilibrium partitioning process for compounds with higher K d coefficients.