Short-term enhancement effect of nitrogen addition on microbial degradation and plant uptake of polybrominated diphenyl ethers (PBDEs) in contaminated mangrove soil

Effects of nitrogen (N) addition on the microbial degradation and uptake of a mixture of BDE-47 and -209 by Aegiceras corniculatum, a typical mangrove plant species were investigated. At the end of 3-month experiment, a significant dissipation of BDE-47 was observed in the planted soil, and this dissipation, particularly in rhizosphere soil, was significantly accelerated by the frequent addition of N in the form of ammonium chloride. The removal percentage of BDE-47 in the rhizosphere soil without N addition was 47.3% and increased to 58.2% with N. However, the unplanted soil only removed less than 25% BDE-47, irrespective to N supply. The N addition in planted treatments significantly increased soil N content, urease and dehydrogenase activities, and the abundances of total bacteria and dehalogenating bacteria, leading to more microbial degradation of BDE-47. The N addition also enhanced the root uptake and translocation of PBDEs to above-ground tissues of A. corniculatum. These results suggested that N addition could enhance the phytoremediation of BDE-47-contaminated soil within a short period of time. Different from BDE-47, BDE-209 in all contaminated soils was difficult to be removed due to its persistence and low bioavailability.