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两类纳米材料的特性及其污染复合体系的生物效应与影响机制
Alternative TitleCombined Biological Effects and Impact Mechanism of Manufactured Nanomaterials and Other Contaminants: Role of the Propreties of Nanomaterials
苏宇
Subtype博士
Thesis Advisor王东升
2014-05
Degree Grantor中国科学院研究生院
Place of Conferral北京
Degree Discipline环境科学
Keyword碳纳米管 纳米二氧化钛 结构特性 界面反应 生物效应 Carbon Nanotubes (Cnts) Titanium Dioxide Nanoparticles (Ntio2) Structural Property Interfacial Reaction Biological Effects
Abstract    随着纳米技术的高速发展,纳米产品的生产和使用与日俱增,势必会有越来越多的人工纳米材料(MNMs)进入环境。然而,与当前MNMs的商品化进程相比,人们现有的认知还不足以应对如何减轻MNMs潜在的环境影响。本文围绕“环境过程对MNMs的环境健康与安全的影响”这一重要的科学问题,选择目前研究和使用较为广泛的两种MNMs——单壁碳纳米管(SWCNTs)和纳米二氧化钛(nTiO2)为研究对象,为理解结构特性对两类MNMs的生物累积性的影响,以及MNMs对环境污染物的生物蓄积性和生物可利用性的影响展开了细致的研究工作。
    首先,研究了表面修饰对SWCNTs的生物累积性的影响。结果表明表面修饰可改变SWCNTs的表面电荷属性和影响其在水中的聚集沉降行为。经混酸氧化处理,SWCNTs的缺陷程度增强,表面含氧官能团总量增加6.1倍,表面带负电荷(-63.3±3.5mV);聚乙二醇(PEG)包覆使SWCNTs表面从中性(-1.9±0.6 mV)变为荷负电(-46.1±1.4 mV)。随着SWCNTs分散稳定性的改善,大型蚤对表面修饰后的SWCNTs的摄食和累积明显增加,从4.65±0.70 μg/mg增至6.64±0.15 μg/mg(PEG包覆)和8.84±2.19 μg/mg(混酸氧化)。
    进一步研究了水中SWCNTs共存对菲的生物累积性的影响。结果表明SWCNTs对菲的生物累积水平的影响与SWCNTs的累积量以及SWCNTs对菲的吸附量有关。水中SWCNTs共存时,大型蚤体内菲的累积量增加了1.1-2.1倍,且在净化阶段,大型蚤体内菲的剩余量也增加了10.7-32.3倍。此外,在生物体内这部分菲会从SWCNTs中释出,与水中SWCNTs对菲的可逆吸附结果一致。SWCNTs共存时,日本青鳉肠中菲的累积量显著增加且全身累积量增加了2.1倍(72 h)。较含有相同浓度溶解态菲的单一体系而言,SWCNTs和菲预先达到吸附平衡的复合体系暴露72 h,青鳉肝和脑中菲的含量分别增加了6.4-48倍和20-34倍。进一步分析推断这部分多余的菲来自青鳉肠中累积的SWCNTs上吸附的菲。因此,SWCNTs的结构性质既会影响两种水生生物对SWCNTs的摄取和累积,也会影响SWCNTs对菲的吸附和解吸,继而影响SWCNTs与菲共存的复合体系暴露下生物体内菲的累积和分布。
    研究了nTiO2在污泥中的形态转化对其生物累积性的影响。结果表明污泥滤液中溶解性微生物副产物类有机物含量高(DOC为22.5-26.3 mg/L)且离子强度大(电导率为54.1-55.5 μS/cm)可使nTiO2脱稳,随着nTiO2粒径从79±2 nm增至129±6 nm,污泥滤液中nTiO2的吸光度A500下降20%。同时在污泥生物质的吸附作用下,nTiO2被污泥去除且大多数nTiO2不易释出。介污泥传播到土壤,暴露初期赤子爱胜蚓对nTiO2的摄取量显著减少,nTiO2的累积量也相应地降低。
    最后,研究了nTiO2对污泥中金属的生物累积性的影响。结果表明以污泥为土壤中重金属的污染源,添加nTiO2将显著降低蚯蚓体内金属Cu和Ni的累积量。暴露28 d后,蚯蚓体内Cu和Ni的生物累积因子(BAF)分别从2.34±0.20和0.18±0.03降至1.32±0.19和0.16±0.01。虽然在污泥中加入nTiO2会降低金属Zn的可交换态和碳酸盐结合态的含量,但是蚯蚓体内Zn的累积量并未受到影响。同样地,纳米二氧化钛对污泥中Cu和Ni的赋存形态没有明显的影响,却会降低这两种金属的BAF。由此,基于化学提取方法评价nTiO2对污泥中金属赋存形态的影响并不能有效预测nTiO2对污泥中金属的生物累积性的影响。
Other Abstract    Rapid development and application of nanotechnology and its related products will increase the release of manufactured nanomaterials (MNMs) into the environment. However, currently, MNMs are being incorporated into a broad range of commercial products at a rapid rate, which is outpacing the development of knowledge and regulations to mitigate their potential environmental impacts. The environmental process would have great impacts on the environmental health and safety effects of MNMs, and therefore this dissertation mainly focused on the issue. Two representative MNMs--single-walled carbon nanotubes (SWCNTs) and titanium dioxide nanoparticles (nTiO2) were used, and a series of experiments were conducted for better understanding the properties of MNMs on their own bioaccumulation and bioavailability as well as co-existed environmental contaminants.
    First of all, the effects of surface modification on the bioaccumulation of SWCNTs by Daphnia magna were studied. The results showed that surface modification could change
the surface charge of SWCNTs and have impact on the aggregation and precipitation behaviors of SWCNTs. suspensions. With treatment by strong acid, the oxidized SWCNTs had more defects and 6.1 times higher oxygen-containing groups, accordingly, this type of SWCNTs were negatively charged (-63.3±3.5 mV). As a result of coating by polyethylene glycol (PEG), the surface charge of SWCNTs was altered from neutral (-1.9±0.6 mV) to negative (-46.1±1.4 mV). With increase in the stability of SWCNT suspensions, the uptake and accumulation of the oxidized and the PEG-coated SWCNTs by D. magna were increased from 4.65±0.70 μg/mg to 6.64±0.15 and 8.84±2.19 μg/mg, respectively.
    In addition, the impacts of the presence of SWCNTs on the bioaccumulation of phenanthrene by D. magna in aqueous phase were investigated. The results demonstrated that the biological uptake of SWCNTs and the adsorption of  phenanthrene on SWCNTs could have effects on the bioaccumulation of phenanthrene by D. magna. In the presence
of SWCNTs, the contents of phenanthrene in D. magna were enhanced by 1.1-2.1 times during the exposure period, and the residual phenanthrene concentrations in D. magna were increased by 10.7-32.3 times. Moreover, the potential release of phenanthrene from SWCNTs in Japanese medaka was observed, which was consistent with the reversible
adsorption of phenanthrene on SWCNTs in batch experiments. The coexistence of SWCNTs facilitated the accumulation of phenanthrene in the intestine of fish and therefore
enhanced the whole-body phenanthrene concentration by 2.1 fold after exposure for 72 h. Meanwhile, 6.4-48 and 20-34 times higher phenanthrene concentrations were measured in
the liver and brain of fish after exposure to the two mixtures, respectively, when comparing with the phenanthrene alone treatment with equal concentration of soluble phenanthrene.
The extra phenanthrene was from the SWCNTs-associated phenanthrene that accumulated in the intestine. As mentioned above, the properties of SWCNTs could affect the uptake and accumulation of SWCNTs by the two aquatic organisms as well as the adsorption of phenanthrene on SWCNTs, which subsequently influence the retention of phenanthrene that associated with the carbon nanotubes.
    Furthermore, transformation of nTiO2 in sewage sludge and its impacts on the bioaccumulation of nTiO2 by earthworm (Eisenia fetida) in soils simulating land application of sludge-borne nTiO2 were studied. The results showed that the filtrate samples of the sludge containing high concentrations of soluble microbial by-product-like organic matter (DOC 22.5-26.3 mg/L) and high ion strength (conductivity 54.1-55.5 μS/cm)could result in destabilization of nTiO2. With an increase in the diameter of nTiO2 (from 79±2 to 129±6 nm) after incubation for 24 h, the formed larger-sized aggregates were
unstable in the sludge filtrate as absorbance at 500 nm was decreased by 20% within 120 min. The formation of nTiO2 aggregates and association with biomass together contributed
to the removal of nTiO2 by the sludge and hindered the release of nTiO2 from the matrix.Both the bioaccumulation factor (BAF) of titanium and in vivo imaging whole-body distribution of Alizarin red S-labeled nTiO2 showed that the bioaccumulation of these nanoparticles was in a low level, and pre-interaction with sludge caused significant reduction in BAF of titanium by earthworms comparing to soil treatments directly amended with nTiO2.
    At last, the influences of nTiO2 on the bioaccumulation of heavy metals originated from sewage sludge by E. fetida were investigated. The results demonstrated that taking sewage sludge as the sources of heavy metals-contaminated soils, amendment with nTiO2 could decrease the bioaccumulation of copper and nickel by earthworms. After exposure for 28 days, the BAF values for copper and nickel were decreased from 2.34±0.20 and 0.18±0.03 to 1.32±0.19 and 0.16±0.01, respectively. However, the results were inconsistent with the impacts of nTiO2 amendment on the speciation of heavy metals of the sludge by chemical sequential extraction process. Although the exchangeable fraction and the fraction bound to carbonates of zinc were decreased by the amended nTiO2, the BAF of zinc was insignificantly affected. Similarly, the speciations of copper and nickel were unaffected with amendment of nTiO2, but the BAF values of these two metals were significantly decreased. Therefore, the effects of nTiO2 on the bioaccumulation of heavy metals in the sludge could not be effectively predicted through the chemical sequential extraction methods.

Document Type学位论文
Identifierhttp://ir.rcees.ac.cn/handle/311016/13469
Collection环境水质学国家重点实验室
Recommended Citation
GB/T 7714
苏宇. 两类纳米材料的特性及其污染复合体系的生物效应与影响机制[D]. 北京. 中国科学院研究生院,2014.
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