FIRST INVESTIGATION ON BIOACCUMULATION POTENTIALITY OF LEMNA GIBBA L. FOR HEAVY METAL POLLUTION IN LEBANESE FRESH WATERS

摘要

Addressing heavy metal pollution is considered among the most serious challenges of fresh water bodies. Floating macrophytes such as Lemna gibba (duckweed species) have a great potential in the bioaccumulation of heavy metals alleviating these contaminants. This research aimed to characterise the quality of water habitat and to evaluate the natural bioaccumulation potential of native L. gibba growing naturally in polluted surface water bodies in Lebanon. A set of physiochemical properties with chlorophyll a (Chl a) and levels of heavy metals i.e. Cu, Cr, Zn, Ni, Cd, Mn, Pb and As were determined in seven surface water bodies with high relative abundance of L. gibba in order to have a minimum understanding of its habitat. Findings revealed mineralization, phosphates, Chl a, turbidity, As, Cd and Mn levels that exceed international limit values. Statistical analysis with PCA revealed three components with strong loadings of phosphates, nitrates, turbidity, total hardness, Mg hardness, Cl~- and pH. On the other hand, bioaccumulation factors (BAFs) of tested heavy metals were also determined in plant tissues using AA. Values of BAFs ranged between 35.25 and 1068 and followed the descending order of Zn＞Cu＞Mn＞Ni＞Pb＞As＞Cd＞Cr indicating high accumulation capacity of heavy metals. Strong associations between the BAFs of As, Mn and Ni on one side and the factor scores of physiochemical variables on the other side were observed. This study confirms the ability of L. gibba to efficiently accumulate a large span of heavy metals prevailing in the Lebanese water bodies, and therefore its potentiality to be used effectively in the reduction of pollutants. Additional investigations are required to check the efficiency of this macrophyte for in situ phytoremediation of local aquatic environments contaminated by the anthropogenic activities.