Evaluation of the synergistic effects of chromium and lead during the process of phytoremediation with watercress (Nasturtium officinale) in an artificial wetland

Heavy metal pollution has increased over the years due to its different applications. Different plant species have been evaluated to bioaccumulate heavy metals; watercress is a species with phytoremediation capacity. However, there is little information on the synergy that occurs when two metals in the medium are present and condition their accumulation in plants. The objective of this research was to evaluate the synergistic effect on the simultaneous accumulation of Pb and Cr (VI) in watercress. We used a batch system and an artificial wetland to evaluate the behavior of metals in the presence of watercress, quantifying at the end of each experiment the cumulative concentration in stems, leaf, and root. The highest concentration of both metals occurred in the root section (Pb>Cr). As the presence of Cr (VI) in solution increases, the plant absorbs more metal, and combination with Pb the tolerance index is increased and the translocation factor decreases. Within the constructed wetland the percentage of total Pb and Cr removal was >99.9 % (100 mg L-1) and 95% (28.5 mg L-1) respectively. The results show the presence of effects of environmental, physical and chemical interactions that determine the capacity of bioaccumulation of the metals evaluated in watercress.