硅稳定同位素用于大气颗粒物和二氧化硅纳米颗粒的来源分析

发布时间：2019-06-14 00:48

【摘要】：二氧化硅纳米颗粒作为生产量和使用量最大的纳米材料,其毒理学效应逐渐引起了人们的关注,前人的研究指出,来自天然源与来自人为源的二氧化硅纳米颗粒具有不同的毒理学效应。但是,目前还没有方法能够有效甄别二氧化硅纳米颗粒的来源。本文表征了天然源和人为源二氧化硅颗粒的形貌、晶体结构和氧硅比等基本信息。经过大量样品的测定发现,人为源与天然源二氧化硅颗粒中硅稳定同位素分布范围差异明显,δ~（30）Si(‰)= 0.08可作为人为源和天然源的区分阈值。此外,4个不同厂家生产的二氧化硅颗粒的硅稳定同位素分布范围较窄,具有同位素指纹识别特征。说明在一定情况下,可以通过二氧化硅颗粒的硅天然稳定同位素的差异实现对不同厂家来源的甄别。来自同一工厂,原料相同,合成工艺不同的二氧化硅纳米颗粒硅同位素分布也存在明显差异,说明不同合成工艺造成了不同程度的同位素分馏,这为通过硅同位素分布来甄别二氧化硅颗粒不同合成工艺提供了理论基础。实验结果说明,硅稳定同位素可以作为甄别二氧化硅纳米颗粒的来源的有利工具。近几十年来,随着我国工业化与城市化进程的日益推进,大气污染现象呈现出愈发严峻的态势。李克强总理在2017年的政府工作报告中特别指出中国目前大气污染的严峻性,亟需加强对大气灰霾成因与防治措施的研究。因此,对于灰霾的来源及其成因的进一步研究有利于减少大气污染对于人体健康的影响,这已成为目前一段时期内一项极其迫切的任务。目前,已有一些大气溯源模型可用来解析大气颗粒物(PM)的来源,但这些方法大多基于多元素浓度信息,需要多种仪器设备才能实现,结果争议也比较大。在本研究中,我们基于硅元素的普遍存在性,利用天然硅稳定同位素组成作为一种新的示踪剂,对大气PM的来源进行了研究。我们用电感耦合等离子体质谱仪(inductively coupled plasma mass spectrometry,ICP-MS))和多接收器电感耦合等离子体质谱仪(multicollector inductively coupled plasma mass spectrometry,MC-ICP-MS)等仪器对 2015 年 12月北京地区不同粒径的大气颗粒物样品(TSP和PM_（2.5）)进行了硅浓度和硅稳定同位素组成的测量,并计算出硅比重(硅元素占PM重量的比重)。研究发现,随着污染程度的增加,PM_（2.5）中硅浓度和硅比重不断下降,而硅稳定同位素却保持相对稳定,既验证了颗粒物粒径不断增大的过程,同时也证明了在灰霾形成的过程中,大气颗粒物一次来源对灰霾的贡献比重不断减小。因此,2015年12月北京地区大气颗粒物爆发性增长,主要来自二次颗粒物的贡献。
[Abstract]:As the most widely produced and used nanomaterials, the toxicological effects of silica nanoparticles have gradually attracted people's attention. previous studies have pointed out that silica nanoparticles from natural sources and from artificial sources have different toxicological effects. However, at present, there is no method to effectively identify the source of silica nanoparticles. In this paper, the morphology, crystal structure and oxygen-silicon ratio of natural and artificial silica particles have been characterized. Through the determination of a large number of samples, it is found that the distribution range of silicon stable isotopes in silicon dioxide particles from artificial source and natural source is obviously different, and 未 ~ (30) Si (per thousand) can be used as the threshold for distinguishing artificial source from natural source. In addition, the stable isotopic distribution of silicon in silica particles produced by four different manufacturers is narrow and has the characteristics of isotopic fingerprint recognition. It is shown that under certain circumstances, the discrimination of different sources of silicon can be realized by the difference of natural stable isotopes of silicon dioxide particles. From the same factory, the raw materials are the same, and the silicon isotopic distribution of silica nanoparticles with different synthesis processes is also obviously different, which indicates that different synthesis processes result in different degrees of isotopic fractionation, which provides a theoretical basis for identifying different synthesis processes of silica particles by silicon isotope distribution. The experimental results show that silicon stable isotopes can be used as a useful tool to identify the source of silica nanoparticles. In recent decades, with the development of industrialization and urbanization in China, the phenomenon of air pollution is becoming more and more serious. In his 2017 government work report, Premier Li Keqiang pointed out the seriousness of air pollution in China and the urgent need to strengthen the study on the causes and prevention measures of atmospheric haze. Therefore, further study on the source and causes of haze is helpful to reduce the impact of air pollution on human health, which has become an extremely urgent task in a period of time. At present, some atmospheric traceability models can be used to analyze the source of atmospheric particulate matter (PM), but most of these methods are based on multi-element concentration information and need a variety of instruments and equipment to achieve it, and the results are controversial. In this study, based on the universal existence of silicon elements, the source of atmospheric PM was studied by using natural silicon stable isotopic composition as a new tracer. The silicon concentration and stable isotopic composition of atmospheric particulate samples (TSP and PM_) with different particle sizes in Beijing in December 2015 were measured by inductively coupled plasma mass spectrometer (inductively coupled plasma mass spectrometry,ICP-MS) and multi-receiver inductively coupled plasma mass spectrometer (multicollector inductively coupled plasma mass spectrometry,MC-ICP-MS), and the specific gravity of silicon (the proportion of silicon to the weight of PM) was calculated. It is found that with the increase of pollution degree, the concentration of silicon and the specific gravity of silicon in PM_ (2.5) continue to decrease, while the stable isotopes of silicon remain relatively stable, which not only verifies the process of increasing particle size, but also proves that the contribution of atmospheric particles to haze decreases during the formation of haze. Therefore, the explosive growth of atmospheric particles in Beijing in December 2015 mainly comes from the contribution of secondary particles.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X513

【相似文献】