The Toxic Effect Of Nanoscale Zinc Oxide And Nanoscale Titanium Dioxide On Chlorella Vulgaris Under Different Nutrient Conditions

Nanoscale zinc oxide and nanoscale titanium dioxide are important components of synthetic nanomaterials.In recent years,they have been widely used.In the widespread application of nano-ZnO and nano-TiO₂,they will inevitably be released into the environment,and eventually into the ocean,thereby posing a potential threat to marine life.Other physical and chemical factors in the ocean,such as nutritional conditions,may affect the toxic effects of nanomaterials on marine life,and different types of nanomaterials may also interact.However,there is still a lack of research in this area.This subject compared the toxic effects of nano-ZnO and nano-TiO₂ on Chlorella vulgaris under different nutritional conditions to assess their ecological risks.Results were as follows:1.Within the experimental concentration range,the growth inhibition effect of nano-ZnO and nano-TiO₂ on C.vulgaris was related to the exposure concentration and nutritional conditions.As the increase of exposure concentration,the growth inhibitory becomed stronger;oligotrophic condition enhanced the toxicity of nano-ZnO and weakened the toxicity of nano-TiO₂.5 mg/L of nano-TiO₂ reduced the growth inhibition of nano-ZnO.Under eutrophic condition,10 mg/L of nano-ZnO inhibited the growth of C.vulgaris;under oligotrophic condition,5 mg/L of nano-ZnO inhibited the growth of C.vulgaris.There was a certain antagonistic effect between nano-ZnO and nano-TiO₂.2.Under two nutritional conditions.,nano-ZnO reduced the chlorophyll a content of C.vulgaris,nano-TiO₂ have no significant effect on the chlorophyll a content of C.vulgaris;nano-ZnO and nano-TiO₂ induced the Fv/Fm,Y(II),NPQ decreased,q P increased.Under oligotrophic condition,nano-ZnO completely decomposes the chlorophyll b of C.vulgaris.Oligotrophic condition exacerbated the destruction of C.vulgaris photosynthesis system by nano-ZnO and nano-TiO₂.3.Under two nutritional conditions,the changes of biochemical indicators of nano-ZnO and nano-TiO₂ on C.vulgaris were differently.Under eutrophic condition,10 mg/L nano-ZnO increased the MDA content of C.vulgaris by 35.76%,and the oligotrophic condition increased by 64.52%.Intensify the damage of nano-ZnO to the membrane system.Under eutrophic condition,100 mg/L of nano-TiO₂ increased the MDA content of C.vulgaris by 256.51%,and oligotrophic condition increased by 62.09%.It was speculated that oligotrophic can alleviate the damage of nano-TiO₂ to the membrane system.Under eutrophic condition,the SOD activity of the 2 control groups were 6.27 and 3.60 times of the oligotrophic control groups.It was speculated that nutritional stress was the main factor affecting SOD activity.Compared with eutrophic condition,AKP and ACP activity of oligotrophic condition was increased,it speculated that oligotrophic induced phosphatase synthesis.4.TEM images showed that showed that nano-ZnO caused significantly wall separation of C.vulgaris,and chloroplasts and thylakoids were blurred;nano-ZnO and nano-TiO₂ increased the amount of starch granules and lysosomes in C.vulgaris cells.Both nanomaterials caused damage to cell structure of C.vulgaris.