The influence of humic acid on the toxicity of nano‐ZnO and Zn²⁺ to the Anabaena sp.

Abstract

This study explored the effects of humic acid (HA) on the toxicity of ZnO nanoparticles (nano-ZnO) 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 EC50 (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, EC50 of nano-ZnO increased to 1.15 ± 0.04 mg/L and EC50 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-ZnO had more damage to the cell membrane than Zn(2+) did, which could be proven by the malondialdehyde content in Anabaena sp. cells. © 2014 Wiley Periodicals, Inc. Environ Toxicol 30: 895-903, 2015.

Isotopically Labeled Nanoparticles at Relevant Concentrations: How Low Can We Go? The Case of CdSe/ZnS QDs in Surface Waters

“…ZnO at 100 ppb-163 ppm, QDs at 60-3600 ppb). 26,27,29,[51][52][53] Finally, this method does not require the commonly employed feature (e.g. optical emission) for fluorescent ENPs such as QDs, which photoluminescent properties can easily be quenched.…”

Tracing multi-isotopically labelled CdSe/ZnS quantum dots in biological media

“…To summarize our results for the QD-LOQs, the mean values of the QD-LOQs for Cd and Zn are 15 and 3132 ppt, respectively. These values are lower than the typical concentrations used in ENP dissemination and toxicity studies (ppb-ppm level) 18,[33][34][35] . Indeed, coherent to our previous findings in the case of aquatic matrices, the QD-LOQs found on average previously were also lower by about 3 to 6 orderof magnitudes than those in the aforementioned studies.…”

“…Based on our findings, isotopic labelling of ENPs coupled with HR-ICP-MS will enable researchers to work at ENP concentrations lower than the usual range of concentrations used in ENP studies related to their fate, behavior, and toxicity (e.g. QDs at 60-3600 ppb) 33,34 . In addition, this method does not require the use of specific ENP characteristics (e.g.…”

A comparison of fate and toxicity of selenite, biogenically, and chemically synthesized selenium nanoparticles to zebrafish (Danio rerio) embryogenesis

“…Interestingly, the presence of recalcitrant components of EPS such as humic-like acids can reduce the bioavailability of contaminants to organisms due to the increased electrostatic repulsion (Lundqvist et al, 2010;Tang et al, 2015). A decrease in the selenium uptake by plant roots due to interactions between selenite and fulvic acids was reported (Wang et al, 1996), and it was suggested that association of selenium with organic matter in aquatic environments may play an important role in the mobility and bioavailability of selenium.…”