The influence of natural organic matter (NOM) on the desorption kinetics of pyrene and naphthalene from quartz

The influence of natural organic matter (NOM) on the desorption kinetics of pyrene and naphthalene adsorbed on quartz was examined in batch experiments. Online determination of the concentration of the polycyclic aromatic hydrocarbons (PAH) in the aqueous phase was performed using fluorescence detection. Desorption experiments were done in a Completely Mixed Batch Reactor (CMBR) using PAH loaded quartz as model soil. A diluted pyrophosphate extract and a water extract of a well characterized soil, water of a bog lake (Hohlohsee, Black Forest), and deionized water were used as aqueous phases. The experimental data were fitted to two mathematical models: (1) an empirical model and (2) the diffusion film model. Both models were able to describe the concentration profile of the dissolved PAH quite well. Whereas the desorption rate of naphthalene decreased in the presence of NOM, no significant influence of NOM on the desorption kinetics of pyrene was observed. In this context, neither the origin nor the concentration of the different NOM had a significant impact on the values obtained.