In situ quantitative and visual investigation of the retention of polycyclic aromatic hydrocarbons on the root surface of Kandelia obovata using a microscopic fluorescence spectral analysis method.

A novel approach for in situ determination of individual benzo[a]pyrene (B[a]P), pyrene (Pyr) and anthracene (Ant) on the root surface micro-zone (0.960mm) of Kandelia obovata (K. obovata) was established using a microscopic fluorescence spectral analysis (MFSA) system. The detection limits for the three polycyclic aromatic hydrocarbons (PAHs) were 44.2, 59.7 and 36.3ngg on lateral roots and were 42.8, 62.4 and 39.1ngg on taproots of the K. obovata root micro-zone. Using the established MFSA method, retention of the PAHs on the K. obovata lateral root and taproot surface micro-zone were investigated in situ. The retention of PAHs on the lateral root and taproot surface of K. obovata showed uneven distribution, and both of the retained quantities showed significant differences, which was related to both passive uptake patterns or active uptake patterns of the PAH and the polarity index ((O+N)/C) of the root surface. In addition, increased quantities of retention of the PAHs on both lateral root and taproot surfaces of K. obovata were observed in the order of Ant<Pyr<B[a]P in the presence of graphene oxide (10mgL) for 7 days. The results of this work provided an in situ method for the investigation on the retention of PAHs on plant lateral root and taproot surfaces at the microscopic scale, contributing to the understanding of the mechanisms of plant root uptake of PAHs.