The Bioavailability And Risk Assessment Of Copper Oxide Nanoparticles In Soil

With the increasing development of nanotechnology,nanoparticles?NPs?have been applied to various fields,which make them inevitably enter the soil during production,transportation,use and disposal.Copper oxide nanoparticles?CuO NPs?is a promising metal oxide nanoparticles?MeO NPs?that widely used in a range of areas.It can enter the soil through pesticide,fertilizer application,and agricultural use of sludge.CuO NPs interact with soil components to change its morphology and bioavailability.CuO NPs released into the soil will not only be absorbed,transported,and accumulated by plants,then enter the human body through the food chain,but may also be ingested through unintentional pathway such as via mouth and breath to endanger human health.Therefore,in this thesis,the effects of soil properties on the bioavailability of CuO NPs in farmland soil were clarified by using chemical extraction,in vitro simulation experiments,and pot experiments.A preliminary risk assessment of CuO NPs in soil was also performed.The purpose of this study is to provide data support and theoretical basis for scientifically assessing the agro-ecological and health risks of CuO NPs.The important results are as follows:?1?The changing trend of bioavailable Cu content in soil spiked with spherical CuO NPs,as well as comparison with those spiked with CuO BPs and Cu²⁺.The content of DTPA-extracted Cu in soil spiked with spherical CuO NPs increased to equilibrium with time increasing,and the time required to reach the equilibrium of dissolution in acid soil?1 d?was significantly shorter than that in alkaline soil?60 d?.For acidic soils,the content of DTPA-extracted Cu spiked with CuO BPs in gradually increased to equilibrium,while for alkaline soils the change of DTPA-extracted Cu was not significant.The content of DTPA-extracted Cu in soil spiked with Cu²⁺decreased with time increasing.In alkaline soil,the content of bioavailable Cu in the soil treated with Cu²⁺is greater than that of spherical CuO NPs treatment,but there is no significant difference between the two treatments in acid soil.The dissolution rate constant of spherical CuO NPs is 0.33-6.42,and the solubility is 37.1 mg·kg^-1 to 100.1mg·kg^-11 in soil.Correlation analysis shows that with decreasing pH and increasing contents of organic matter,clay,iron and aluminum oxides,the dissolution rate constant and solubility of spherical CuO NPs increase.?2?The bioaccessibility of spherical CuO NPs in soil for the stomach and lung and related influencing factors were researched,and comparison was made with Cu²⁺treatment.In the stomach,the bioaccessibility of spherical CuO NPs and Cu²⁺was not significantly different,ranging from 67%to 95%;in the intestinal fluid,the bioaccessibility of spherical CuO NPs and Cu²⁺ranged from 49%to 74%,which was significantly lower than that in the stomach.The bioaccessibility of spherical CuO NPs in ALF?10.1%-21.2%?was significantly higher than that in Gamble solution?1.2%-3.5%?.Soil properties have no significant effect on the bioaccessibility of spherical CuO NPs and Cu²⁺in gastrointestinal simulants.The bioaccessibility of spherical CuO NPs in the lung is positively correlated with soil CEC and Al_d,and negatively correlated with clay content.The bioaccessibility of Cu²⁺decreased with the increase of soil clay content and pH.In soils with high clay and organic matter content,the bioaccessibility of spherical CuO NPs and Cu²⁺at 90 d aging time was lower than that of 15 d aging.?3?The bioavailability of different forms of copper(CuO NPs,CuO BPs and Cu²⁺)to rape and the influencing factors were clarified.Pot experiments showed that the bioavailability of CuO NPs and Cu²⁺to oilseed rape has a good correlation with DTPA-extracted Cu in soil.In alkaline soil,spherical CuO NPs and Cu²⁺exhibited the greatest impact on the bioavailability of oilseed rape,and spherical CuO NPs may be transported from the roots to the aerial part.In acidic soil,spherical CuO NPs showed the maximum bioavailability to rape,followed by Cu²⁺,and finally CuO BPs and tubular CuO NPs.High concentrations of spherical CuO NPs and Cu²⁺can reduce photosynthesis of oilseed rape,and no negative impact on the absorption of micronutrients was observed.?4?A preliminary assessment on the health risks of CuO NPs in soil was explored.The exposure risk of children are much higher than that of adults for spherical CuO NPs and Cu²⁺via the oral intake route.There is no significant difference in exposure risk of spherical CuO NPs and Cu²⁺.The treatments of 160 mg Cu kg^-1 spherical Cu O NPs and Cu²⁺pose greater risks to human health through ingestion of rapeseed via the food chain pathway.In acid soil,the health risk from spherical CuO NPs are larger than that of Cu²⁺,but there is no significant difference between the two treatments in alkaline soil.