摘要:
纳米二氧化钛(TiO2-NPs)是目前应用最为广泛的纳米材料之一,在城市污水处理厂的出水、污泥以及地表水体中已均有检出,进入到天然湿地和人工湿地中的TiO2-NPs会在湿地生物、基质、水体之间进行迁移转化和归趋。目前针对TiO2-NPs对湿地植物金鱼藻的毒性研究很少。本文采用水培实验方法,研究了不同粒径TiO2对金鱼藻种子发芽和植株生长的影响,解析了TiO2-NPs对金鱼藻的生态毒理效应。研究结果表明:各粒径TiO2-NPs对金鱼藻种子的发芽均具有一定的抑制作用,表现为发芽率、发芽幼苗重量、发芽指数、发芽势和活力指数的降低,且粒径越小、浓度越高对金鱼藻种子发芽的抑制作用越强,4 nm、20 nm和50 nm的TiO2-NPs对金鱼藻种子发芽的半数有效浓度(EC50)分别为1 180、1 520和1 810 mg·L-1。TiO2-NPs对金鱼藻植株的毒害作用表现为叶片失绿发黄、脱落,植株呈萎焉状,并且TiO2-NPs的粒径越小、浓度越高毒害作用越明显。随TiO2-NPs浓度升高,处理后金鱼藻叶片的叶绿素含量和植株体内的Mg含量均降低,丙二醛(malondialdehyde,MDA)含量均升高,而超氧化物歧化酶(superoxide dismutase,SOD)活性则先升高后降低,而且越小粒径的TiO2-NPs对金鱼藻的处理效果越明显。3种粒径的TiO2-NPs均能进入金鱼藻体内,粒径越小、浓度越高进入的量越多。综上表明,TiO2-NPs对金鱼藻种子发芽和植株生长均有一定的抑制作用,且粒径越小、浓度越高抑制作用越强。
关键词:
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纳米二氧化钛
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金鱼藻
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生态毒理
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累积
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分布
Abstract:
Nano titanium dioxide (TiO2-NPs) is one of the most widely used nanometer materials, which has been detected in the effluent of the sewage treatment plant, sludge and the surface water. The NPs will migrate and transform among the wetland biotas, substrate and water body as entering the natural wetland and constructed wetland. At present, there are few studies on the toxicity of TiO2-NPs to the Ceratophyllum demersum. In this study, the effect of TiO2-NPs with different sizes on the seed germination and plant growth of typical constructed wetland plant-C. demersum was explored through hydroponic experiments, and their ecotoxicological effects were also de- termined. The results showed that the seed germination of C. demersum was inhibited after treated by TiO2-NPs with different sizes, and the germination rate, seedling weight, germination index, germination potential and vigor index decreased accordingly. The smaller the particle size or the higher the concentration of the TiO2-NPs was, the stronger inhibitory effects on the seed germination of C. demersum occurred. Moreover, the EC50 of 4 nm, 20 nm and 50 nm TiO2-NPs on the seed germination of C. demersum were determined as 1 180, 1 520 and 1 810 mg·L-1, respectively. The toxic effects of TiO2-NPs on C. demersum were characterized as growth retardation and even stagnation, leaf chlorosis, plant wilting. Moreover, the decreased size or increased concentration of TiO2-NPs could strengthen the aforementioned toxic effects. With the increase of TiO2-NPs concentration, the chlorophyll and Mg content in plant of treated C. demersum decreased, the malondialdehyde (MDA) content increased, while the super- oxide dismutase (SOD) activity increased first and then decreased, and such treatment effect was more obvious as the smaller TiO2-NPs were used. TiO2-NPs with different sizes could enter the C. demersum, and small size or high concentration could favor this entrance. In summary, the seed germination and plant growth of C. demersum was inhibited after treated by TiO2-NPs, and moreover, the smaller the particle size or the higher the concentration of the TiO2-NPs was, the stronger inhibitory effects were detected.
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