生物炭中溶解性炭黑在红壤中的吸附稳定及其效应

Dissolved black carbon (DBC), the soluble fraction of biochar, manure and waste bio-refineries, is an important constituent of dissolved organic matter pool. Biochar, the incomplete combustion product of organic materials, has attracted a great deal of attention because it is stable in soils and beneficial in improving soil fertility, sequestering carbon and alleviating soil pollution. Biochar also contains a large number of DBC. The dissolution and transport of DBC will inevitably lead to some new processes in the environment with the wide application of biochars. For example, DBC is an important adsorbent for organic contaminants due to its relatively condensed structure compared to common dissolved organic matter, and at the same time, abundant oxygen-containing functional groups such as -OH, C-O, C-O-C. DBC will change the environmental behaviors and transport of these contaminants. Meanwhile, DBC could interact with the exposed inorganic minerals when it enters into red soils. Unfortunately, how this process affects the stability of DBC in red soil, the effect on the properties and function of red soil are not clear. This work is thus specifically designed to study the adsorption, stability and environmental effects of DBC from biochar in red soils. DBC is extracted from biochars derive from different biomass and under a range of well-defined combustion conditions. The effect of parent biomass types for the composition and properties of DBC, and the change of the properties for DBC in complex red soil system are described. Benzene polycarboxylic acid (BPCA) molecular marker method is used to describe the properties of DBC in the chemical oxidation experiments of DBC-inorganic mineral complexes process. According to this basis, the interaction between DBC and inorganic minerals could be studied. We emphasize the effect of this interaction on the stability of DBC in red soils, and discuss the regulation of the properties for red soils which affect by the adsorption of DBC on inorganic mineral particles surface. The environmental effects of DBC after adsorption will be discussed according to the surface potential of soil particles, redox ability, interaction characteristics of contaminants and soils. Traditional batch sorption/degradation experiments are used to study the environmental behaviors of organic contaminants that affect by the changes of properties for red soils. This study will deepen the scientific understanding of the improvement of soils by biochars, and provide further information to apply biochar widely in red soils.

虽然生物炭颗粒本身与土壤颗粒没有相互作用，其中的溶解性炭黑（DBC）溶出以后，在矿物颗粒上吸附、稳定，从而实质上改善土壤团聚体的形成，这个过程可能是理解生物炭对土壤系统，特别是对红壤影响的关键，但是还没有得到研究者的关注。本研究拟从DBC的吸附稳定及这个过程的效应进行深入的研究，拟从不同母源生物质、不同条件下制备的生物炭中提取DBC，深入研究DBC与无机矿物颗粒之间的相互作用，理解相对常规溶解性有机质而言，DBC较高的稠环度特征对其吸附特征的影响，揭示不同类别无机矿物对DBC各组分的分级吸附特征；在对DBC-无机矿物复合体的化学氧化实验中，引入生物标记物方法对DBC特性进行动态描述，重点阐述DBC吸附后的稳定性特征；从土壤颗粒表面电位、氧化还原能力、与污染物相互作用特征等角度，对DBC吸附稳定后的效应进行剖析。本研究将加深生物炭改良土壤的科学理解，为生物炭在红壤中的大规模应用奠定理论基础。

本研究针对生物炭施入土壤后，溶出的DBC与红壤中的无机矿物相互作用形成有机-无机复合体的作用机制及其环境效应、DBC发生光老化、化学老化后对有机污染物相互作用展开相关研究。从该研究得到DBC中的芳香性组分会优先选择性地吸附在n-Al2O3表面，憎水性作用、p/π-π作用、氢键作用是两者的复合机制。选取诺氟沙星和菲作为研究对象，诺氟沙星主要通过π-π电子供受体、静电吸引作用、H键等吸附在DBC-n-Al2O3复合体上，而菲在复合体上的吸附机理主要是憎水性作用、π-π作用和p/π-π作用。此外，生物炭施入土壤后，其中溶出的DBC会发生光老化和化学老化，DBC光老化后其芳香性增加、憎水性增强，而DBC化学老化后，1% H2O2 DBC的含氧官能团含量、芳香组分、憎水性比原始DBC和2% H2O2 DBC的高。从光老化和化学老化后DBC的性质变化及其与菲的荧光猝灭曲线得到两种方式老化后的DBC与菲的相互作用机制是憎水性作用和π-π作用。综上，本研究证明了生物炭施入土壤后，溶出的DBC在红壤中的无机矿物颗粒上吸附稳定后形成有机-无机复合体，这个过程是理解生物炭对红壤影响、红壤中碳稳定以及成土过程的关键。此外，本项目从DBC吸附后的稳定性特征、DBC-无机矿物形成的复合体吸附污染物的机制、光老化和化学老化后的DBC对污染物的相互作用机制等角度，对DBC吸附稳定后的效应进行剖析，为生物炭在改良土壤中的环境效应及其在红壤中的大规模应用提供理论数据和技术支撑。