The effect of initial metal concentration and exposure time on the ability of Salvinia minima (Salviniaceae) to absorb lead (Pb) from contaminated water

Over the years, progressive anthropogenic activities have resulted in the increased contamination of the environment with toxic heavy metals, which pose a serious threat to human health. In response to this pressing issue, phytoremediation has become an emerging alternative to conventional engineering procedures due to its low-cost budget as well as its eco-friendly purpose. In this study, samples of Salvinia minima were incubated for certain periods at increasing concentrations of Pb(NO3)2 (0 ppm, 4 ppm, 8 ppm and 12 ppm) in order to determine the effects of initial metal concentration and contact time on the lead-uptake capacity of S. minima. Results showed that heavy metal uptake increases proportionally to the level of initial metal concentration as well as the length of contact time. When high initial metal concentration was paired with long exposure to the metal, plant absorption was greatly increased. The highest efficiency for lead uptake was observed in the 4 ppm treatment, which increased independently of prolonged exposures to the metal. However, extensive exposure of the plant to high metal concentrations rendered low percentage of metal absorption in plant tissues. The higher the initial metal concentration, the earlier a decrease in absorption will be encountered as seen in the decrease in percent lead-uptake of 8 ppm and 12 ppm treatment during the 6th and 4th day, respectively. Possible explanations could be that long exposures to such high metal stress damaged plant physiology and metabolism of heavy metals, or lead to the shortage of heavy metal binding to adsorption sites on the plant surface due to saturation. A 2-Way ANOVA test concluded that the initial metal concentration and exposure time individually had a significant effect on the amount of lead absorbed by the plant, and that there existed a strong additive relationship between the 2 factors