【作者】 王琳；

【导师】 杨坤； 朱利中；

【作者基本信息】 浙江大学 ， 环境科学， 2021， 博士

【摘要】 土壤-生物炭固碳是一种耦合了生物炭碳捕获和土壤藏碳的新型固碳技术,主要包含生物炭的生产固碳、土壤温室气体减排和增加植物碳汇等多个方面。生物炭对农田土壤温室气体增减排的影响与生物炭、土壤性质和农业过程等密切相关,迄今不同农业过程对生物炭发挥土壤增减排作用的影响仍存争议。为此,本文探究了不同氮施加量和田间老化对生物炭诱导的农田土壤温室气体增减排的影响;估算了我国农田土壤生物炭固碳减排潜力,以及生物炭引发的土壤增减排对生物炭本身固碳潜力的贡献率,主要研究结果如下:（1）生物炭对土壤温室气体增减排作用随氮肥施加量不同而变化（P<0.05）。当氮肥施加量较低时（50 mg N/kg）,生物炭显著增加土壤CO₂和N₂O排放（P<0.01）;当氮肥施加量较高时（450 mg N/kg）,生物炭对土壤CO₂增排减弱,并显著减少N₂O排放（P<0.01）。当氮施加量较低时,土壤N₂O主要来源于硝化作用,生物炭的不稳定组分促进微生物硝化作用促使N₂O增排、促进微生物化学异养等作用促使CO₂增排;当氮施加量较高时,土壤N₂O主要来源于反硝化作用,生物炭主要通过对氮素的吸附保护来抑制反硝化,促使N₂O减排。（2）田间老化使生物炭表面积累矿物质,形成有机-矿物复合体,从而增强颗粒物理稳定性（如机械强度）,显著减少土壤CO₂和N₂O排放。SEM-EDS,XRD和FTIR等观测表明,田间老化后,生物炭表层矿物质含量显著提高,含氧官能团增多;颗粒抗压强度和表面硬度较老化前均显著提高（P<0.01）。田间老化使生物炭物理稳定性增强,减弱了碎片组分的释放及其对土壤微生物的作用,从而增强固碳减排潜力。（3）农田土壤生物炭的固碳潜力主要由每年可生产生物炭的生物质质量决定,受生物炭对农田土壤温室气体排放的影响较小（约占3%）。保守估算,若从五大类生物质（农业秸秆、林业废物、家禽粪便、污泥及藻类）生产生物炭,我国每年可固定约2.9±0.4亿吨碳（折合减排10.5±1.5亿吨CO₂）。将这些生物炭施入我国农田固碳（按1～2%添加量）,土壤二氧化碳年排放当量(CO_2e=CO₂+25 CH₄+298 N₂O)可减少仅约0.35±1.09亿吨,贡献较小。更多还原

【Abstract】 China’s farmland soil has great potential for carbon sequestration.Soil and biochar system carbon sequestration is a new carbon sequestration technology that combines biochar carbon capture and soil carbon storage.It mainly includes three aspects:biochar carbon sequestration during production process,soil greenhouse gas emission reduction and promotion of plant carbon sinks.The impact of biochar on the increase and emission reduction of greenhouse gases in farmland soil is closely related to biochar,soil properties and agricultural processes,and is a major difficulty in the research.So far,there are still controversies over the soil greenhouse gas emission reduction effects of biochar under the impact of different agricultural processes.Therefore,this paper explores the effects of agricultural practices（nitrogen application amount and field aging）on the increase and emission reduction of greenhouse gas in farmland soil induced by biochar;estimates the farmland soil and biochar system carbon sequestration and emission reduction potential in China,and the contribution rate of the biochar induced soil emission increase or reduction to the biochar carbon sequestration potential during production process.The main research results are as follows:（1）The CO₂ and N₂O mitigation potential of biochar in the soils varied significantly with the amount of nitrogen fertilizer applied（P<0.05）.When the amount of nitrogen fertilizer was low（50 mg N/kg）,biochar significantly increased soil CO₂ and N₂O emissions（P<0.01）;when the amount of nitrogen fertilizer was high（450 mg N/kg）,biochar weakened the soil CO₂ emission increase effect,and significantly reduced N₂O emissions（P<0.01）.When nitrogen input was low,soil N₂O mainly came from nitrification,and the unstable components of biochar promoted microbial nitrification to promote the increase of N₂O,promoted microbial chemical heterotrpphism,etc.to promote the increase of CO₂.When nitrogen input was high,soil N₂O mainly came from denitrification,biochar mainly inhibited denitrification through the adsorption and protection of nitrogen,and promoted N₂O emission reduction.（2）Field aging made the surface of biochar accumulate minerals and form an organic-mineral complex,thereby enhancing the physical stability of the particles（such as mechanical strength）and significantly reducing soil CO₂ and N₂O emissions.The results of SEM-EDS,XRD and FTIR together shown that after field aging,biochar surface mineral element content significantly increased,with some oxygen-containing functional groups increased simultaneously.The physical stability（compressive strength and surface hardness）of the particles were significantly improved compared with those biochars pre-aging（P<0.01）.Field aging enhanced the physical stability of biochar,weakened the release of debris components and their effects on soil microorganisms,thereby enhancing the potential for carbon sequestration and emission reduction.（3）The carbon sequestration potential of biochar in farmland soil was mainly determined by the biomass mass that could produce biochar each year,and the impact of biochar on the greenhouse gas emission of farmland soil was small（about 3%on average）.It was conservatively estimated that if biochar was produced from five types of biomass（agricultural straw,forestry waste,poultry manure,sludge and algae）,China could fix about 290±40 million tons of carbon（equivalent to reducing emissions of 1050±150million tons of CO₂）every year.When these biochar were applied to farmland in China（at the addition amount of 1～2%）for carbon sequestration,the annual carbon dioxide-equivalent(CO_2e)emission from farmland soil（under the macroscopic background）could be reduced by about 35±109 million tons,compensating relatively small proportion of the carbon sequestration potential of biochar.更多还原