Assessment of heavy metal pollution in sediments and their bioaccumulation in phragmites australis frome Nil river (Jijel- Algeria)

The content of heavy metals in sediment and the aquatic plant Phragmites australis (roots and leaves), collected from six different stations along the Nil river, were determined providing information about heavy metals pollution status of this aquatic ecosystem.
The results showed that the abundance of heavy metals measured in the sediments decreased in the order: Fe>Zn>Pb>Cr>Cd. Apart from Cr and Fe, the concentration of heavy metals exceeded the background values. Metals concentrations were found decreasing with the increasing distance from the river mouth, suggesting that anthropogenic inputs, related to agricultural and domestic discharge into the river, are the major sources of heavy metals in the river sediments and aquatic plants.
The assessment of heavy metals pollution was carried out using geoaccumulation index (Igeo) and enrichment factor (EF). According to the mean values of Igeo, the sediment of Nil river is considered as moderately polluted with Pb and Cd, unpolluted to moderately polluted with Zn and unpolluted with Cr and Fe. The mean values of enrichment factor indicate that all stations presented moderate enrichment with Zn, minor enrichment with Cr and moderately to severe enrichment with pb and Cd in three stations.
Regarding the plant samples, the results showed that the concentration of the elements analyzed in Phragmites australis did not exceed the threshold of phytotoxicity.
Mean concentrations of all elements were less in the plants organs compared to the concentrations of the same elements in the corresponding sediment sample. Metals accumulated by P. australis were mostly distributed in root tissues, as shown by the values of translocation factors (TF) which were <1. A positive association between the metal concentrations in P. australis organs and its environment was also found; this suggests that this plant can be used as biological indicator in biomonitoring studies.