Abstract:
Varieties of mangrove plants are investigated in phytoextraction potentiality of
probable toxic elements considering the different regions of the world which are
controlled by the prevailing environmental and climatic conditions. Yet, the eastern
coastal environments of Sri Lanka are rich in natural vegetation, a very few studies
have been carried out to investigate the phytoextraction potentiality of Sri Lankan
mangrove species. The present study aimed to estimate the phytoextraction potentiality
of selected six heavy metals in readily available mangrove species (Avicennia marina)
in Batticaloa Lagoon and Uppar Lagoon of the eastern coast of Sri Lanka. A batch
experiment was conducted considering the concentrations of As, Cd, Cr, Cu, Ni and Pb
in three similar extent plants in each lagoon. The root sediments and plant parts
including roots, stem below water, stem above water and leaves were considered in
order to identify the above trace metal concentrations using Inductively Coupled
Plasma Mass Spectrometry. The average toxic element concentrations in sediments are
in the order of Cr (58.97 ppm)> Ni (39.20 ppm)> Cu (25.57 ppm)> Pb (10.56 ppm)>
As (0.95 ppm)> Cd (0.14 ppm). The content of Ni is above the Effect Rage -Low
(ERL) in marine sediments indicating its rare adverse effects on biodiversity whereas
other elements are below the ERL values. The concentration of considered toxic metals
in different parts of Avicennia marina shows higher values in stem parts for Cd and Pb
while all other elements show that in roots. The Bio Concentration Factor (BCF) of
below water plant parts (roots and stem) were in order of Cr > As > Ni > Cu > Pb > Cd
indicating significant phytoextraction potentiality for the study area compared to the
previous studies in different regions of the world. The root to leave translocation factors
(TF) are in order of Pb (0.97)> Cu (0.91)> Ni (0.74)> As (0.69)> Cd (0.68)> Cr (0.54)
indicating the high capacity of Avicennia marina to store the metals. Hence, the present
study recommends the applications of Avicennia marina in soil remediation from non
essential toxic elements such as Pb, Cd and As for Sri Lankan coastal environments.
