Toxic Effects And Ecological Risks Of Copper And Copper Oxide Nanoparticles On Soil And Brassica Chinensis L.

Nanomaterials are widely used in production and life due to their unique physical and chemical properties.With the development of science and technology,nanomaterials are gradually industrialized on a large scale.In this process,they will inevitably enter the ecological environment and have toxic effects on the environment.And it is transmitted and accumulated in the food chain,which will eventually have a negative effect on the human.In this study,Cu nanomaterials（Cu NPs）and Cu O nanomaterials（Cu O NPs）were used as the research objects,Tianjin farmland soil was used as the test soil to explore their effects on soil respiration intensity,enzyme activity and microbial diversity.Brassica chinensis L.was used as the test plants,the effects of Cu NPs and Cu O NPs on the germination,biomass,antioxidant enzyme activity,Cu accumulation,and cytotoxicity of B.chinensis L.were studied.The research is expected to provide a theoretical basis for the soil ecological risk assessment and plant safety control of Cu NPs and Cu O NPs.The main results of this thesis are as following:Using soil static culture experiments,the effects of Cu NPs and Cu O NPs on soil respiration intensity,antioxidant enzyme activity and microbial community structure were studied.The results showed that the soil CO₂ accumulation was inhibited to varying degrees after adding Cu NPs and Cu O NPs,and compared with the control,it was reduced by 1.3%-5.3%and 2%-4.5%,respectively.Cu NPs inhibited the activities of soil urease,dehydrogenase,alkaline phosphatase and catalase.Compared with the control,they decreased by 29.4%-82.9%,8.4%-62.1%,35.8%-76.2%and15.7%-47.1%,respectively.The inhibition of Cu O NPs on four soil enzyme activities was-2.4%-29.1%,4.2%-58.9%,16.0%-39.4%and-6.5%-47.1%,respectively.After adding Cu NPs,the total phospholipid fatty acid（PLFA）content of the soil decreased by 19.1%-32.7%compared with the control.The Cu NPs treatment had an effect on gram-positive bacteria PLFA,gram-negative bacteria PLFA,and actinomycete,and the number of fungi PLFA,arbuscular mycorrhizal fungi PLFA,anaerobic bacteria PLFA,and eukaryotic PLFA caused varying degrees of inhibition.The ratio of gram-positive bacteria to gram-negative bacteria（G+/G-）and fungi/bacteria（F/B）decreased overall.Soil microbial ecology index（Shannon,Simpson and Pielou index）,cluster analysis（Cluster analysis）,principal component analysis（Principal component analysis）showed that the addition of Cu NPs had a negative impact on the diversity of soil microbial communities.The treatment of Cu O NPs increased the total soil PLFA,bacterial PLFA,gram-positive PLFA,gram-negative PLFA,fungi PLFA and eukaryotic PLFA content and F/B ratio firstly and then decreased,decreased the amount of soil fungi PLFA,actinomycetes PLFA,arbuscular mycorrhizal fungi PLFA,and anaerobic bacteria PLFA.Ecological index,cluster analysis and principal component analysis showed that Cu O NPs had a certain impact on the structure of soil microbial community.Paper culture experiments were used to study the effects of Cu NPs and Cu O NPs on seed germination,root and shoot elongation,seedling Cu accumulation,root cell microscopic characteristics and seedling physiological and biochemical characteristics of Brassica chinensis L.The results showed that the three material treatments with different concentrations had no significant effect on the seed germination rate（p>0.05）.The root and shoot elongation of B.chinensis L.seedling increased firstly and then decreased with the increase of Cu NPs,Cu O NPs and Cu SO₄concentrations.The inhibition rate of root elongation was 10.7%-59.9%,-15.7%-33.62%and-1.6%-32.8%,and the promotion rate of shoot elongation was-15.8%-9.1%,0.7%-3.9%and-12.6%-2.3%,the seedling dry weight decreased-6.5%-35.2%,-2.1%-3.9%and-3.1%-15.9%.Transmission electron microscopy showed that the addition of 10 mg?L^-1 Cu NPs resulted in a relatively common plasmolysis in root cells and high-density accumulations were observed,the structure of root cells under the treatment of Cu O NPs was complete,and no damage was observed,the mitochondria of the root cells were slightly damaged,and the parenchyma cells showed serious plasmolysisthe under Cu SO₄ treatment.Compared with the control group,the activity of superoxide dismutase（SOD）in Brassica chinensis L.seedlings decreased by 4.5%-64.0%,and the reduction of peroxidase（POD）reached 17.0%-59.3%.（CAT）activity is not significant under Cu NPs treatment（p>0.05）.Under the treatment of Cu O NPs,the SOD activity of seedlings was significantly increased by 3.0%-28.8%,while the effects of CAT and POD were not significant（p>0.05）.The SOD and POD activities of B.chinensis L.seedlings were significantly increased,with the maximum increase of 96.0%and 21.7%,and the CAT activity decreased by-17.1%-27.2%under Cu SO₄.The effects of Cu NPs,Cu O NPs and Cu SO₄ on biomass,photosynthetic rate and enzyme activity of B.chinensis L.were studied by hydroponic experiments.The results showed that other treatments inhibited the photosynthetic rate to varying degrees except Cu O NPs.Compared with the control,the fresh weights of root and shoot of B.chinensis L.under Cu O NPs treatment were significantly increased by 22.0%and 26.0%,respectively.The fresh weights of root and shoot of B.chinensis L.decreased by 31.2%and 36.5%under Cu NPs treatment,respectively.Compared with the control,the SOD activity in above-ground part of B.chinensis L.without any Cu treatment decreased by 6.1%,and the root enzyme activity increased by 16.0%.After adding Cu NPs,the activity of SOD increased by 4.0%in the above-ground part and 46.4%in the underground portion.Cu O NPs decreased SOD activity by 9.8%and 27.7%,respectively.No Cu addition and Cu O NPs addition had no significant effect on CAT activity in the B.chinensis L.underground portion,while CAT activity increased by 25.3%and 38.4%under Cu NPs and Cu SO₄ treatments.Compared with the control group,the POD activity in the underground portion of the B.chinensis L.without any Cu treatment significantly increased by 57.1%,and the POD activity in the above-ground part decreased by 36.8%,but there was no significant difference with the control.The POD activities in the above-ground and under-ground parts of B.chinensis L.under 10 mg·L^-1 Cu NPs treatment increased by 252.9%and 198.8%,respectively.Cu O NPs had no significant effect on POD activity.Except for the APX activity increased in the B.chinensis L.under-ground part by Cu SO₄ treatment,other treatments decreased the activity of APX in the under-ground part by 54.4%,9.4%and 1.0%,respectively,compared with the control.All treatments increased the APX activity in above-ground parts.The hydroponic experiment was conducted to study the characteristics of Cu accumulation and nutrient elements in seedling and mature stage of B.chinensis L.under different treatments.The results showed that Cu accumulation in B.chinensis L.seedlings increased with the increase of Cu NPs,Cu O NPs and Cu SO₄ concentrations.Cu accumulation was the highest under Cu NPs treatment,and the lowest under Cu O NPs treatment.Cu accumulated more in the root of B.chinensis L.,and the Cu accumulation in the above-ground part of B.chinensis L.increased by 240.8%,45.1%and258.6%under Cu NPs,Cu O NPs and Cu SO₄ treatments,respectively.No Cu treatment and 10 mg·L^-1 Cu O NPs addition had an effect on the Cu accumulation in the under-ground part of B.chinensis L.,but there was no significant difference compared with the control group（p<0.05%）.Under different treatment conditions,Cu was more accumulated in the cell soluble components,followed by the cell wall,the lowest content in the organelles.Cu NPs reduced the content of K,Ca,Mg and Mn in the B.chinensis L.root,and the content of Ca,Mg,Fe and Mn in the shoot part.Cu SO₄reduced Ca and Mg content of shoot part,K and Mg content of root part.Cu O NPs increased the K,Mg,Zn,Mn in the B.chinensis L.shoot part,and Ca,Mg,Fe in the root part.