Abstract:
Heavy metal pollution of fresh and marine aquatic system has increased linearly since the beginning of industrial revolution. For decontamination purpose, several aquatic macrophytes are considered as good accumulators of heavy metals and other toxic contaminants. This study investigated cadmium accumulation by water lettuce (Pistia stratioties), watercress (Nastutium officinale) and pennywort (Cetella asiatica). Plants were exposed to different levels of cadmium (0, 5, 10, 15 and 20 mg/L) to evaluate accumulation and its physiological effects. Plant samples were examined by atomic absorption spectroscopy for accumulated heavy metal contents. Cadmium accumulation in all macrophytes increased with the increase in metal concentrations in solution. Metal accumulation in shoots of N. officinale and C. asiatica was considerably higher than roots and vicversa in P. stratioties. Macrophytes treated with 20 mg/L died, in the mid of exposure period of 21 days, and highest accumulation was shown as 17.8. 68.7 and 67.3 mg/kg, of dry weight at 15mg/L of cadmium concertation by P. stratiotes, N. officinale and C. asiatica, respectively. Results also showed that all the studied macrophytes were cadmium accumulator with BCF >1. N officinale and C. asiatica are able to translocate metal into the aerial parts. This hydroponic study revealed the reduction in chlorophyll content and plant biomass upon exposure to cadmium. Plant oil generation capacity also decreased with increase in cadmium level. Furthermore, XRF results of extracted oil showed the absence of cadmium up to 10 mg/L. Keeping in view the results obtained from the study, these macrophytes have a potential to accumulate cadmium from growing medium and can be used for the treatment of contaminated water, and may also off-set the costs through bio-oil production.
