ZINC CONTAMINATION IS AN UNDERESTIMATED RISK TO AMPHIBIANS: TOXICITY EVALUATION IN TADPOLES OF FEJERVARYA LIMNOCHARIS

Aquatic environments are often contaminated with zinc. Amphibian tadpoles are likely to be exposed to high concentrations of zinc present in these environments. We determined the acute and sub-chronic toxicity of ZnCl2 on Fejervarya limnocharis tadpoles under laboratory conditions. The LC50 values of ZnCl2 were found to be 5.81, 4.32, 3.79 and 3.61 mg/L at 24, 48, 72 and 96 h of exposure respectively. Long-term exposure to sub-lethal concentrations of ZnCl2 induced significant mortality in concentration and time dependent manner. Sub-lethal ZnCl2 exposure significantly altered survival, body length and body weight at metamorphosis. Micronucleus test and comet assay indicated the genotoxic potential of ZnCl2. Significant increase in DNA strand break was observed following ZnCl2 exposure equivalent to 1% of the of 24 h LC50 value. The findings indicate possible adverse to tadpoles inhabiting aquatic environments contaminated with zinc. In addition, the findings may be extrapolated to aquatic organisms of similar torphic status.

Sunflower Helianthus annuus for Phytoremediation of Zinc in Hydroponic System

It has been noted that zinc contamination is hazardous which induces researchers seek new means to overcome it. One of the methods is to employ sunflower plant to eliminate zinc in soil. However, there is insufficient information about zinc phytoremediation by sunflower Helianthus annuus in hydroponic system. Hence in this study, a 15-day experiment was conducted using zinc concentrations of 0, 10, 20, and 30 mg/L in a hydroponic system. The effects of zinc concentration on the plant growth (length of root, length of stem and number of leaf), zinc uptake and zinc translocation were evaluated. The findings showed that the plant growth was inhibited, where the zinc concentrations had affected the growth of the sunflower root, length and stem, and the zinc uptake significantly (p<0.05). It was also found that there was a significant variation of root length and zinc uptake in leaves within certain phases statistically (p<0.05). Then the translocation factor was found significant different for the time parameter but not the zinc concentrations (p<0.05). Therefore, this experiment concluded that the sunflower plant was highly tolerant to zinc and able to extract the zinc from contaminated environments. Lastly, this study showed that the sunflower is potential to phytoremediate zinc in a hydroponic system.