The Influence of Humic Acid on the Toxicity of Nano-ZnO and Zn~(2+) to the Anabaena sp.

摘要

This study explored the effects of humic acid (HA) on the toxicity of Zn~(2+)O nanoparticles (nano-Zn~(2+)O) and Zn~(2+) to Anabaena sp. Typical chlorophyll fluorescence parameters, including effective quantum yield, photosynthetic efficiency and maximal electron transport rate, were measured by a pulse-amplitude modulated fluorometer. Results showed that nano-ZnO and Zn~(2+) could inhibit Anabaena sp. growth with the EC_(50) (concentration for 50% of maximal effect) of 0.74 ± 0.01 and 0.3 ± 0.01 mg/L, respectively. In the presence of 3.0 mg/L of HA, EC_(50) of nano-ZnO increased to 1.15 ± 0.04 mg/L and EC_(50) of Zn~(2+) was still 0.3 ± 0.01 mg/L. Scanning electron microscopy observation revealed that HA prevented the adhesion of nano-ZnO on the algae cells due to the increased electrostatic repulsion. The generation of intracellular reactive oxygen species and cellular lipid peroxidation were significantly limited by HA. Nano-Zn~(2+)O had more damage to the cell membrane than Zn~(2+) did, which could be proven by the malondialdehyde content in Anabaena sp. cells.