生物炭的改性和老化及环境效应的研究进展

Research Progress on Modification and Aging of Biochar and Its Environmental Implications

生物炭是生物质在缺氧或者绝氧条件下通过高温热解后生成的富含碳的固体材料。生物炭作为一种先进的多功能材料,在土壤改良、温室气体减排、污染控制等领域都展现出应用潜力,受到了广泛的关注。研究人员通过改变生物炭的物理和化学性质,开发了多种生物炭改性技术,以提升生物炭的吸附功能。然而,生物炭一旦进入环境后,在生物和非生物的作用下会被老化,其物理和化学性质都会发生变化。随着老化的进行,生物炭逐渐由表面到内部进行降解,苯环结构由大变小,表面含氧官能团增加。这些生物炭的改性、在环境系统中的老化、功能的持久性及在这些动态过程中性质的变化,势必会对其环境效应产生影响。研究表明生物炭氧化程度的加重和表面官能团活性的提升增强了生物炭的吸附能力,促进了生物炭与土壤、植物营养元素和污染物的相互结合,降低了污染物的环境风险。另外的研究指出,老化过程导致生物炭的比表面积和孔体积降低,从而降低了生物炭的吸附能力。同时,老化和改性可能会降低生物炭在环境中的稳定性,导致生物炭的组分(溶解性有机质和溶解性炭黑)和生物炭内源污染物的释放。且由生物炭产生的环境持久性自由基(EPFRs)和短寿命自由基(羟基自由基·OH和超氧阴离子自由基·O^2-)能以自由基途径降解有机污染物。生物炭活化一些无机分子产生的单线态氧(^1 O2)也能以非自由基的途径降解有机污染物。本文对生物炭的改性方法、老化导致的结构变化、老化导致其与化学物质相互作用的不确定性、生物炭与土壤组分的相互作用以及老化生物炭的环境风险方面的研究展开了综述,分析了改性生物炭的老化及其环境效应。最后对生物炭使用后在动态变化过程中的稳定性、功能效果和环境风险等方面提出了展望,强调了生物炭在使用和管理中要充分考虑其性质的动态变化。对生物炭在实际应用领域的深入研究将为其技术管理和评估的建立提供必要的理论基础。

Biochar is a carbon-rich solid material produced by pyrolysis of biomass under anoxic or anaerobic conditions.As an advanced multi-functional material,biochar has shown potential application in the field of soil remediation,greenhouse gas emission reduction and pollution control,which have attracted wide research attention.Various techniques have been developed to modify biochar in order to enhance their adsorption per-formance by changing the physical and chemical properties of biochar.However,when biochar enters the environment,the biological and abiotic processes can change its physical and chemical properties.As aging progresses,biochar is gradually degraded from surface to interior,the size of benzene ring is smaller,and the surface oxygen functional groups are increased.However,it is unknown how these modified biochars persist in the applied systems,let alone their potential environmental implications.Studies have shown that increased oxidation degree and surface functional group of biochar enhance the adsorption capacity of biochar,pro-mote the interaction of biochar with soil components,plant nutrients and pollutants,and thus reduce the environmental risk of pollutants.Other studies have also indicated that the specific surface area and pore volume of biochars are reduced after aging,resulting in their reduction of adsorption capacity.Meanwhile,aging and modification may reduce the stability of biochar in the environment,leading to the release of biochar com-ponents(dissolved organic matter and dissolved black carbon)and endogenous pollutants.Environmentally persistent free radicals(EPFRs)and short life free radicals produced by biochar can degrade organic pollutants by free radical pathway.Singlet oxygen(^1 O2)induced by biochar can also degrade organic pollutants in a non-free radical pathway.This paper reviewed the research progress on the modification of biochar,the structural changes during their aging,the uncertainty of interaction between biochar and chemical substances,the interaction between biochar and soil components,and the environmental risks of the modified and the aged biochar.The aging of modified biochar and its environmental effects were analyzed.Finally,the prospects about stability,functional effects and environmental risks of biochar after being applied are proposed.It is emphasized that the dynamic changes of biochar properties should be fully considered during its use and management.The intensive study on the practical application of biochar will provide the necessary theoretical basis for the establishment of its technical management and evaluation.