Effects of nitrogen on the removal of dibutyl phthalate from surface water in the presence of Potamogeton crispus L.

Abstract

Experiments in 5 surface waters with different levels and compositions of nitrogen were performed to investigate the effects of nitrogen on the removal of dibutyl phthalate (DBP) from surface water in the presence of Potamogeton crispus L., a submerged aquatic plant. The removal of DBP using P. crispus with (Group A) and without (Group B) associated microorganisms was studied and compared with that in the non-autoclaved surface water samples (Group C). The first-order rate constants for DBP loss from the aqueous medium in Groups A, B, and C were in the range of 0.016–0.227d−1, 0.008–0.112d−1 and 0.015–0.204d−1, respectively, and were mostly in the order of Group A>Group C>Group B. In Group B, a positive link between NO3−-N concentration and rate constant for DBP loss, as well between NO3−-N concentration and plant activity (chlorophyll a, soluble protein and nitrate reductase) was found. In addition, at the end of 10-day incubation, only small amount of DBP taken up by P. crispus was retained in P. crispus, which was no more than 11.5%, suggesting that DBP in P. crispus was mostly degraded. Different from Group B, rate constant for DBP loss in Group C increased with the increase of total inorganic N (TIN) concentration. The rate constants for DBP loss in Group A were 5.9–45.9% higher than those in Group C, and the enhancement was significantly related to the NO3−-N:TIN ratio. The most possible reason is that surface waters with higher NO3−-N:TIN ratio facilitate the activity of P. crispus, and consequently, removal of DBP in the presence of P. crispus is more significantly enhanced.