Monthly variations of trace elements accumulation and distribution in above- and below-ground biomass of Phragmites australis (Cav.) Trin. ex Steudel in Lake Burullus (Egypt): A biomonitoring application

Abstract

This study was carried out in some natural stands of Phragmites australis (Cav.) Trin. ex Steudel grown in Lake Burullus, a Mediterranean lake in north Egypt, to investigate: (1) the concentration of trace elements in the organs of P. australis, (2) the extent of trace elements mobility from sediment to below-ground organs and within the plant, (3) the organs of P. australis as potential bioindicators for the contamination of the water and sediment by the trace elements, and (4) the amount of trace elements that released back into the surrounding water after decomposition of dead tissues. Above- and below-ground biomass of P. australis, water and sediment were sampled monthly for one year at six sites of Lake Burullus (three sites represent each of the northern and southern parts of the lake) using six randomly distributed quadrats (each of 0.5×0.5m) at each sampling site. The above- and below-ground biomasses of southern sites are significantly higher than that of the northern sites. Above-ground biomass is >2.5 folds of the below-ground biomass in the northern and southern sites. The highest concentration in the below-ground organs is Cu, Fe and Zn; and in the leaf is Cd. The monthly highest values of trace elements are Cu and Fe in February at the beginning of the growing season; and Cd and Zn in January at the end of the growing season. The annual mean of trace element concentrations (inmgkg−1) in P. australis organs ranged from 11.0 to 23.8 for Cd, from 31.0 to 65.6 for Cu, from 34.4 to 97.3 for Zn, and from 505.0 to 2833.0 for Fe. The mean bioaccumulation factor of all trace elements from the sediment to the below-ground organs is greater than unity for all elements with the following sequence: Cd>Fe>Zn>Cu. Cd has the highest translocation factor from the below-ground to the above-ground organs, while Fe has the lowest. Positive linear correlations are detected between the concentrations of all elements (except Cu) in plant organs, water and sediment. The higher translocation factor of Cd in the above-ground organs of P. australis makes it suitable for the phytoextraction of this element from the water and sediment, while the lower translocation factor for Cu, Fe and Zn makes it suitable for their phytostabilization. In conclusion, all the organs of P. australis could act as bioindicators and biomonitors of the examined trace elements.