Sorption, transport, and degradation of quinoline in unsaturated soil

Sorption, transport, and aerobic biodegradation of quinoline have been studied in a Danish sandy soil. Quinoline is potentially highly biodegradable in soil by means of natural occurring microorganisms. Complete mineralization was observed within 7-10 days in batch experiments independent of pH (comparing pH 5.8 and 7.2). Relative to other creosote compounds (e.g., naphthalene and phenanthrene), low retardation factors were observed (R < 10). The retardation factor (column experiments) was pH dependent with R = 6.9-9.6 at pH 4.6 and R = 4.5-6.5 at pH 7.0. At pH 4.6, R was two to three times lower than estimated from the batch experiments, likely due to nonequilibrium processes. Sorption increased at both pH levels when autoclaving the soil or when using water instead of 0.01 M CaCl(2) as the solution phase. Biodegradation in soil column experiments was in accordance with the batch experiments and was dependent on the residence times (i.e., the retardation factors). The highest degradation was observed at low pH with the highest retardation factor corresponding to the longest residence time. However, even at pH 7.0 where quinoline showed to be the most mobile, the estimated quinoline residence times in the topsoil seem adequate for obtaining complete mineralization under normal Danish weather conditions in the summer period.