Temperature effect on the partitioning of Polycyclic Aromatic Hydrocarbons between natural organic carbon and water

The influence of temperature on KDOC was quantified for fluoranthene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, benzo[ghilperylene and indeno[1,2,3-cd]pyrene using the gas-purge technique and natural dissolved organic carbon from lake Ketelmeer, the Netherlands. Sorption of PAHs to DOC decreased with increasing temperature over a temperature range of 16 to 45°C. ΔH° values ranged from −18.3 kJ.mol−1 for fluoranthene to −40.6 kJ.mol−1 for benzo[ghi]perylene. A temperature decrease of 10°C lead to an average increase of KDOC with 60%. The partition coefficients (KPOC and KDOC) for sorption to particulate and dissolved organic carbon from the same lake were also determined. Log KPOC-values ranged from 5.4 ± 0.3 for fluoranthene to 6.8 ± 0.3 for indeno[1,2,3-cd]pyrene and are in agreement with previously published values. Log KDOC- values ranged from 5.18 ± 0.07 for fluoranthene to 6.86 ± 0.03 for indeno[1,2,3-cd]pyrene, which is higher than previously reported for natural DOC. The data support the linear relationship between log KPOCpoc and log KDOC with a slope of nearly one. The effect of the temperature and PAH sorption to DOC influenced fate calculations for these components. For compounds with low volatilization rates and high sorption partition coefficients such as the PAHs used in this study, sorption to DOC has a large influence on mobility in porous systems. The influence of temperature is relatively small.