氮、硫元素在生物炭制备和老化过程中的形态变化及其环境效应

Biochar is recognized as a kind of new functional materials because of its unique and multi- functions. It has attracted a great deal of research attention in the application areas of environmental remediation, soil restoration and carbon sequestration. Previous investigators have emphasized that the geochemical behaviors of carbon element in biochars greatly control greenhouse gas emissions, which is why biochar production is beneficial in controlling global warming. Researches on biochars mostly focused on bio-geochemical behavior of carbon. It should be noted that nitrogen and sulfur elements may also have greenhouse effect. In most cases, researchers tend to focus on carbon fixation in biochars without noticing the behavior of nitrogen and sulfur elements. Therefore, the speciation change of nitrogen and sulfur in these biomasses during biochar production and aging are not investigated, let alone the related environmental implications. We thus propose that during the anaerobic pyrolysis process of biomass, nitrogen and sulfur will be released partially in the form of gas. Meanwhile parts of the sulfur and nitrogen will be fused into the heterocyclic structures as well as functional groups connected with benzene rings in biochars. These nitrogen and sulfur containing components in biochar will play important roles in the removal of heavy metals, because of the strong electrostatic interactions or complexation. This study will extensively investigate the elemental behavior of nitrogen and sulfur in biomass during pyrolysis and aging. The kinetics as well as the compositions of the released gas will be investigated, with a special emphasis on nitrogen and sulfur-contained compositions. With this new information, we will be able to fully evaluate the functions of biochars in greenhouse gas control. The efficiency of heavy metal retention by the residual nitrogen and sulfur in biochar particles will be systematically analyzed. This study is aimed at understanding nitrogen and sulfur behavior as well as the related environmental implications. This line of work will provide a new angle to fully evaluate the environmental significance of biochars.

生物炭作为一类新型功能材料并由于其特殊、多元的功能价值而得到越来越多的关注，它在环境修复、土壤改良等方面都展现出极大的应用潜力，而且生物炭中的碳元素，以及氮、硫元素的地球化学行为在温室气体排放控制中起到了不可估量的作用。但研究者往往以富碳的生物质作为主要的研究对象，理解其中碳的行为和功效，忽略了生物炭中氮、硫元素的行为和功能。本研究提出对生物质制备生物炭过程中氮、硫形态变化及其相关环境效应进行系统性的研究，探明在生物炭制备、老化过程中，氮、硫元素的形态变化，识别这些过程中含氮、硫气体释放的类型和动力学，全面评估生物炭各元素对温室效应的贡献。分析生物炭固体颗粒中的氮、硫元素与重金属的相互作用，包括生物炭内源重金属的形态变化、外源重金属的沉淀、吸附等。本研究将为理解生物炭中氮、硫元素的固定、释放机理，及与之关联的环境效应提供理论支持，为废弃生物质的资源化利用提供重要的科学理论支撑。

生物炭中的炭、氮和硫元素在环境地球化学过程中起到不可估量的作用，但其氮硫元素行为及功能往往被研究者忽略。本项目以不同污泥和畜禽粪便生物质来源制备的生物炭为研究对象，在生物质热解制备生物炭和模拟其在环境中老化过程中，利用元素分析、比表面积分析、扫描电镜、火焰原子吸收光谱仪、傅里叶红外光谱分析、X射线光电子能谱、气相色谱质谱联用仪、离子色谱仪、电子顺磁波普仪等表征分析方法，测定不同来源生物炭的元素组成、形态和表面官能团、持久性自由基及热解释放气体组成和排放量，针对生物炭物理化学性质变化及与重金属相互作用机理，氮硫元素和金属形态在制备过程中的迁移转化规律及生态风险评估，生物炭表面持久性自由基状况，内源金属对氮元素迁移转化和表面持久性自由基稳定性的作用等诸多问题展开研究。研究结果表明，污泥生物炭中灰分（无机矿物）含量高，对生物炭性质起关键作用并决定其对重金属的吸附，影响表面持久性自由基强度和种类，促进氮的迁移转化；生物炭热解制备过程中产生的主要氮硫气体有污染效应，内源重金属随热解温度升高有向稳定的残渣态转化趋势；老化后不同污泥生物炭中都有一定量金属溶出，但重金属溶出风险小。研究结果揭示了氮硫元素和内源金属在污泥和畜禽粪便生物炭制备和老化过程中的环境行为和功效，为系统认识生物炭制备和老化过程中的环境效应，深入理解该类生物碳施用过程的动态风险奠定基础。