[Long-term sorption /desorption behavior of pyrene in soils]

Long-term sorption/desorption behavior of pyrene in six types of soils are investigated. The results show that long-term sorption and desorption entail two phases, including initially rapid process followed by a slow sorption/desorption. When soil organic matter (SOM) content was below 1%, the constant of sorption Kd of dissimilar soils increased with SOM content under different equilibrium time. While clay content played an important role in sorption capacity of the soils as SOM content was below 1%. In long-term sorption experiment, the Kd values of the six soils increased from 35.1% to 557.9%, respectively, with the sorption equilibrium time increased from 2 d to 180 d. Clay influenced significantly on Kd, while the effect of SOM was different, which suggested that the effect of sorption time on Kd of some soils could not be ignored. In long-term desorption experiment, the slow desorption percentages of pyrene from the six soils were in the range of 12.05% - 41.00%, with the tendency that the attribution of slow desorption fraction to desorption process increased with SOM. Ignoring the influence of aging on the sorption/desorption, it indicates that the attribution of SOM to the capacity of irreversible sorption compartment is distinctly higher than that of clay, which is consistent to the attribution of SOM to slow desorption process.