摘要
摘要
环境持久性自由基（PFRs）作为一种新型的环境风险物质广泛存在于不同环境介质或材料中，包括大气颗粒物、土壤矿物、天然有机质、以及碳质材料等。黑炭作为生物质或化石燃料不完全燃烧产生的碳质材料（包括生物炭、烟灰、焦炭等），分布于大气、土壤、沉积物、水体等自然环境中。黑炭的来源不同，其理化性质和结构特性不同，所携带的PFRs的特性也存在明显的差异。特别是PFRs的类型、稳定性和反应活性直接影响到其潜在的环境行为和生态风险。因此，本论文以生活源黑炭（如烟灰）和工业源黑炭（如焦炭、生物炭）为研究对象，结合电子顺磁共振波谱仪、傅里叶变换红外光谱、电子扫描电镜等光谱学手段，在明确不同来源的黑炭颗粒上PFRs与活性氧自由基丰度的差异的基础上，研究了黑炭上PFRs的形成过程，反应性和稳定性，揭示了黑炭上PFRs的稳定性和活性之间的关系，并为评估PFRs在碳质材料中的环境行为提供了有价值的信息。所得主要结论如下：
（1）不同来源黑炭颗粒上PFRs的丰度与类型不同。不同原料燃烧产生的烟灰颗粒上PFRs的丰度不同，以木材为原料产生的烟灰PFRs丰度大于以煤为原料产生的烟灰，其PFRs浓度达到1017 spins/g，PFRs主要类型为含氧官能团的碳中心自由基。焦炭颗粒上PFRs的浓度可达1018 spins/g，其类型为以碳为中心的自由基。以木质素为原料制备的生物炭上PFRs浓度达到1018 spins/g，不同温度制备的生物炭PFRs类型
和丰度不同，但总的来说，生物炭3种类型的自由基均存在，即以碳为中心的自由基、以氧为中心的自由基和带有含氧官能团的碳中心自由基。影响黑炭PFRs浓度与类型的因素包括：热解条件（特别是温度）、含氧官能团的类型（如酚羟基）、以及热解原料的类型。
（2）不同来源黑炭颗粒诱导产生活性氧（Reactive oxygen species，ROS）类型及丰度不同。烟灰ROS类型主要为•OH和1O2，；焦炭只有浓度较低的•OH；生物炭主要为•OH和O2●-。黑炭上ROS的形成主要是由其携带的活性物质（包括PFRs）与环境小分子物质（如O2和H2O）发生电子传递（氧化还原）反应生成，但不同介质上ROS的产生途径有一定的差异。生物炭表面ROS的产生主要是由碳质材料中较不稳定的PFRs引起的，ROS与PFRs的浓度呈正相关，即反应性较高的PFRs易诱导ROS的形成，同时，生物炭上酚羟基参与到ROS的形成。
（3）碳质颗粒上各类PFRs与ROS的稳定性不同。不同材质烟灰PFRs在光照和水中稳定性较弱，易发生反应，在土壤中较为稳定。通过生物炭上各类自由基稳定性的分析可以发现，以氧为中心的PFRs最为稳定，衰减速率最小，以
西北农林科技大学硕士学位论文
碳为中心的PFRs衰减速率较大。碳质颗粒上的ROS稳定性取决于不稳定的PFRs 转化能力。
（4）碳质颗粒上不稳定的PFRs是产生•OH促使生物炭表面吸附态多环芳烃降解的主要贡献者。不稳定的PFRs作为一种电子供体传递电子给活化剂产生ROS，甚至在不添加活化剂的情况下产生•OH诱导有机污染物的转化。
通过对不同来源黑炭PFRs与反应活性的研究，本文明确了PFRs在黑炭介质中的产生途径与衰减特性，为认识黑炭颗粒上PFRs的环境化学行为提供坚实的科学依据，同时为黑炭PFRs的稳定、转化、降解等环境行为与效应提供有效的理论支持。
关键词：黑炭；持久性自由基；活性氧；稳定性；反应性
ABSTRACTA
ABSTRACT
Environmental persistent free radicals (PFRs) as a new type of environmental risk substances widely exist in different environmental media or materials, including atmospheric particulate matter, soil minerals, natural organic matter, and carbonaceous materials. Carbonaceous materials (including biochar, soot, coke, etc.) produced by incomplete combustion are distributed in the natural environment such as the atmosphere, soil, sediment, and water bodies. The source of black carbon is
different, its physical and chemical properties and structural characteristics are different, and the characteristics carried by PFRs also have obvious differences. In particular, the types, stability and reactivity of PFRs directly affect their potential environmental behavior and ecological risks. Therefore, this paper takes life source black carbon (such as soot) and industrial source black carbon (such as coke and biochar) as the research objects, combining electronic paramagnetic resonance spectrometer, fourier transform infrared spectroscopy, scanning electron microscope and other spectroscopy means. Based on the differences in the abundance of PFRs and active oxygen radicals on black carbon particles from different sources, the formation process, reactivity and stability of PFRs on black carbon were studied, and the relationship between the stability and activity of PFRs on black carbon was found and provided valuable information for evaluating the environmental behavior of PFRs in carbonaceous materials. The main conclusions are as follows:
(1) The concentrations and types of PFRs on black carbon particles from different sources are different. The abundance of PFRs on the soot particles produced by different raw materials are different. The abundance of soot produced by wood as raw material is greater than that produced by coal. The concentration of PFRs reaches 1017 spins/g, and the main type of PFRs are carbon-centered free radicals with oxygen-containing functional groups. The concentration of PFRs on coke re
ached 1018 spins/g, and the main type of PFRs was carbon-centered free radicals. The concentration of PFRs on biochar prepared with lignin as raw material reaches 1018 spins/g. The types of biochar PFRs prepared at different temperatures are different, but in general, all three types of free radicals of biochar exist, namely carbon-centered free radicals, oxygen-centered free radicals and carbon-centered free radicals with oxygen-containing functional groups. The main reasons for the different concentrations and types of black carbon PFRs are: pyrolysis conditions (especially temperature), types of oxygen-containing
西北农林科技大学硕士学位论文
functional groups (such as phenolic hydroxyl groups), and types of pyrolysis raw materials.
(2) Different types of black carbon particles induce different types and abundances of reactive oxygen species (ROS). The types of soot ROS produced by rural households are mainly •OH and 1O2; coke has only a very low concentration of •OH; biochar is mainly •OH and O2●-. The formation of ROS on black carbon is mainly caused by the electron transfer (redox) reaction between the active substances (PFRs) and small environmental substances (O2 and H2O), but the generation of ROS on different media are different. The generation of ROS on the surface of biochar is mainly caused by the unstable
PFRs in carbonaceous materials. The concentration of ROS is positively correlated with the concentration of PFRs. That is, the PFRs with higher reactivity can easily induce the formation of ROS, and at the same time, the phenolic hydroxyl groups on biochar participate in the formation of ROS.
(3) The stability of various PFRs and ROS on carbonaceous particles are different. PFRs of different materials are weak in light and water, easily react and stable in soil. Through the analysis of the stability of various free radicals on biochar, it can be found that the oxygen-centered PFRs are the most stable and the attenuation rate is the smallest, and the carbon-centered PFRs have a larger attenuation rate. The stability of ROS on carbonaceous particles depends on the conversion ability of unstable PFRs.
(4) The unstable PFRs on carbonaceous particles are the main contributors to the production of •OH to promote the degradation of adsorbed polycyclic aromatic hydrocarbons on the surface of biochar.Unstable PFRs as an electron donor to transfer electrons to the activator to generate ROS, and even produce •OH to conversion of organic pollutants without adding an activator.
By studying the PFRs of black carbon and reactivity from different sources, this article clarifies the generation path and attenuation characteristics of PFRs in black carbon media, which provides a solid
scientific basis for understanding the environmental chemical behavior of PFRs on black carbon particles, and provides effective theoretical support for the stabilization, transformation and degradation of PFRs in black carbon and other ecological environmental behavior and effects.
KEY WORDS:Black Carbon; Persistent free radicals; Reactive oxygen species;
Stabilization; Reactivity
目录
目录
摘要............................................................................................................................ I ABSTRACT ................................................................................................................. I II 第一章绪论. (1)
1.1 研究背景 (1)
1.1.1 环境持久性自由基的概念与分类 (1)
1.1.2 环境持久性自由基的产生方式及影响因素 (1)
1.1.3 环境持久性自由基的环境稳定性及毒理效应 (2)
1.1.4 黑炭持久性自由基的反应活性及环境稳定性 (4)
1.2 研究目的及意义 (6)
1.3 研究内容 (6)
1.4 技术路线 (8)
第二章材料与方法 (9)
2.1 烟灰的采集及基本理化性质分析 (9)
2.1.1 烟灰的采集 (9)
2.1.2 烟灰的基本理化性质分析 (9)
2.1.3 烟灰的稳定性实验设计 (9)
2.2 焦炭的采集及基本理化性质分析 (10)
2.2.1 焦炭的采集 (10)
2.2.2 焦炭降解菲的实验设置 (10)
2.3 生物炭的制备及基本理化性质分析 (11)
2.3.1 生物炭的制备 (11)
2.3.2 生物炭的基本理化性质分析 (11)
2.3.3 生物炭降解菲的实验设置 (11)
reactive oxygen species是什么意思2.4 黑炭稳定性自由基与活性的测定方法 (12)
2.4.1 持久性自由基的测定 (12)
2.4.2 活性氧的检测 (12)
2.4.3 黑炭老化试验处理 (12)
第三章烟灰持久性自由基特征及反应活性 (14)
3.1 烟灰的结构特性 (14)
3.1.1 元素分析 (14)
3.1.2 表面形态分析 (15)