图片摘要 | Graphical Abstract
全球气候变暖是当今社会面临的重要问题。土壤-生物炭固碳是一种有潜力的基于自然的固碳解决方案。近年来Lehmann等人多次在Nature上详细介绍并推荐了该技术。针对他提出的土壤-生物炭固碳大规模实施潜力及可行性等问题，近年来，朱利中院士团队致力于研究土壤-生物炭固碳减排的关键影响因素、构建宏观规模化固碳应用情景及估算我国土壤-生物炭固碳减排总体潜力等，为揭示生物炭的环境行为和提高土壤-生物炭固碳减排潜力以促进实现碳中和提供科学依据。近日，他们又揭示了生物炭“土盔甲”的奥秘。今天，就让我们来看一看“土盔甲”有何奥秘，它能为碳封存保驾护航吗？
Global warming is an important issue facing society today. Biochar carbon storage in soils is a potential natural-based solution for carbon sequestration. In recent years, Lehmann and others have repeatedly introduced and recommended this technology in "Nature". In response to the large-scale implementation potential and feasibility of soil-biochar carbon sequestration proposed by him, the team of Academician Lizhong Zhu has been committed to systematic researches (i.e. key influencing factors, macro-scale biochar application scenarios, the overall potential of biochar carbon sequestration in farmland soil in China), which provide scientific basis to maximize the potential of biochar carbon sequestration in soil environment to promote the realization of carbon neutrality. Recently, they have revealed the mystery of biochar "earth armor". Today, let us take a look at the mystery of the "earth armor". Can it promote carbon storage?将不经任何预处理的新鲜生物炭施用到土壤中进行田间老化，一年后随机回收。新鲜生物炭暴露出具有裂纹和通道的褶皱表面（图1a，1c和1e），而老化生物炭表面显示出可观察到更为平滑的覆盖物（图1b和1d）。放大500倍后（图1f），老化的生物炭表面可见附着了许多细颗粒，堵塞了在新鲜生物炭表面上观察到的裂缝和通道（图1e）。去除表面物质后，新鲜和老化的生物炭均显示出丰富的裂纹和孔道（图1g和1h），且形貌并无明显差异。
The fresh biochar exposed a wrinkled surface with cracks and channels (Fig. 1a, 1c, and 1e). In contrast, the aged biochar showed an observable covering on the surface (Fig. 1b). In the image with large magnifications (500 times) (Fig. 1f), the surface of aged biochar was observed to attach with a lot of fine particles, blocking the cracks and channels that were observed on the fresh biochar’s surface (Fig. 1e). After the removal of the surface substances, both the fresh and aged biochar showed a surface with cracks and channels (Fig. 1g and 1h).图1. 生物炭颗粒表面扫描电镜图
Fig. 1. Scanning electron micrographs of fresh biochar and aged biochar
EDS结果显示，老化生物炭表面上的硅（Si）、铝（Al）、铁（Fe）和氧（O）等元素含量明显高于新鲜生物炭，但碳元素含量降低，这与生物炭表面附着了土壤矿物，对碳素测定的稀释效应有关。刮除表面物质后老化生物炭中元素（硅除外）含量与新鲜生物炭元素没有显着差异，表明两种生物炭具有相似的性质，老化生物炭积累的矿物元素主要附着在颗粒表面层。
The SEM-EDS results further indicated that the contents of Si, Al, Fe, and O elements on the surface of aged biochar were significantly increased, as compared to those on fresh biochar which means that the aged biochar was attached with soil minerals (e.g., SiO2). Moreover, the surface contents of soil mineral elements (Si, Al, and Fe) on the aged biochar were decreased after scraping the surface substances.图2. 生物炭表面元素X射线能谱分析图
Fig. 2. EDS images of the biochar’s surface elements
XRD结果支持了老化生物炭上某些矿物质的存在。矿物峰在刮除表面物质的老化生物炭（RBC－B－I和RBC－S－I）中并不存在，表明大多数土壤矿物质聚集在生物炭表面。田间老化后生物炭比表面积显著小于新鲜生物炭（图3b），这与老化后生物炭表面积累了土壤矿物质、阻塞了裂缝和通道相一致（图1d、图2和图3a）。红外结果表明，新鲜生物炭和刮除表面物质层的老化生物炭颗粒中含有一定比例脂肪族碳化合物，然而其在刮除下来的表面物质层（RBC－B－O和RBC－S－O）中并不存在，表明了生物炭表面矿物的覆盖作用（图2、图3a和图3b）或C－H键的氧化作用。氧化试验表明生物炭表面掺杂进矿物以后形成的矿物‑生物炭复合层（即田间老化生物炭颗粒外表层）对化学氧化的抵抗力较高，与老化过程后生物炭上的碳减少和土壤矿物质增加是一致的。化学氧化试验间接证明了老化生物炭上附着的土壤矿物质可以增强生物炭在土壤环境中的抗化学氧化过程。
XRD results further supported the existence of certain minerals on the aged biochar. The surface area of the biochar after the field aging was significantly smaller than the fresh biochar (Fig. 3b), consistent with the mineral accumulation of soil minerals on the surface of the biochar after the field aging, which blocked the cracks and channels (Fig. 1d, 2, and 3a). The discrepancy between the FTIR spectra of interior biochar and the surface substances indicated the high possibility of organo-mineral complexations, which had been widely reported. The oxidation test showed that the aged biochar with composite layer formed has a higher resistance to chemical oxidation than the fresh biochar. The chemical oxidation test indirectly proved that the soil minerals attached to the aged biochar can enhance the anti-chemical oxidation process of the biochar in the soil environment.图3. 生物炭物理化学性质表征
（a）X射线衍射图谱，（b）比表面积，（c）傅里叶红外图谱（d）氧化实验结果。（“去除表面物质的老化生物炭”缩写为“老化生物炭*”）
Fig. 3. Characterization of physicochemical properties of biochar
(a) XRD pattern, (b) SSA, (c) FTIR spectra, and (d) Result of Oxidation experiment. (“Aged biochar*” was abbreviated for “Aged biochar with surface removed”)
老化后生物炭显微维氏硬度值显著增加(P<0.05)，颗粒抗压强度明显提高（荷载峰值和刚度），表明老化生物炭比新鲜生物炭颗粒能够承受更高的机械压力，使其具有相对较低的潜在环境风险。这有利于抑制颗粒在自然环境中的破碎，从而防止内部不稳定物质向外释放。老化导致了生物炭颗粒机械强度增强，可通过影响减少破碎抑制颗粒内不稳定组分的释放，进一步影响生物炭对土壤中CO2或N2O排放的影响以及对土壤微生物群落结构的影响。
The results suggested the improvement of biochar particles’ mechanical strength after the field aging process, which would benefit the sequestration of particle internal structure and substances. The improvement of compressive strength of the aged biochar particles indicates that they might be able to withstand a higher mechanical pressure than the fresh biochar particles, leading to relative lower potential environmental risks, e.g., less fragmentation, less surface carbon loss, and more benefits for the microbial communities in the biochar particles.图4. 机械性能分析
Fig. 4. Mechanical performance analysis
新鲜生物炭对土壤CO2排放没有显著影响，显著减少土壤累积N2O排放；老化生物炭均显著降低土壤的CO2和N2O排放（P＜0.05）；将老化生物炭表面物质刮除以后，老化生物炭对土壤CO2减排作用消失，对土壤N2O减排作用减弱。老化生物炭可抑制土壤CO2排放，可能是由于外表面土壤矿物质与含氧官能团共积累所形成有机-矿物质复合物通过空间位阻稳定了生物炭中的有机碳，降低其对于微生物的有效性；或通过微孔吸附保护锁定微生物所需碳氮源来抑制微生物呼吸作用。该结果表明，老化生物炭的表面物质（含较多有机-矿物复合体）在影响土壤CO2和N2O排放中起重要作用。
Fresh biochar had no significant impact on soil CO2 emissions, and significantly reduced soil accumulated N2O emissions; aged biochar further significantly reduced soil CO2 and N2O emissions (P<0.05); after scraping off the surface material of aged biochar, the soil CO2 emission reduction effect of aged biochar has disappeared while the soil N2O emission reduction effect was weakened. The results indicated that the surface material of the aged biochar (containing more organic-mineral complexes) played an important role in reducing soil CO2 and N2O emissions.图5. 土壤CO2或N2O排放速率或累积排放量
（“去除表面物质的老化生物炭”缩写为“老化生物炭*”）
Fig. 5. The impact of biochar on soil CO2 or N2O emissions
(“Aged biochar*” was abbreviated for “Aged biochar without surface substances”)
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。因此新鲜生物炭使用之前，通过人为或自然的方法去除不稳定组分及构建富含有机-矿物复合体的保护界面，对于增强其在土壤中固碳减排潜力具有重要意义。
These results indicate that soil minerals could accumulate on the biochar during the field aging process, forming organo-mineral complexes, blocking the cracks and channels of the biochar, and improving its mechanical properties. The improved mechanical properties could inhibit the fragmentation of biochar particles, reducing the release of labile fractions from the biochar and the subsequent CO2 and N2O emissions. These findings also indicate that adjusting the mechanical properties of biochar particles to improve their physical stability before adding them into the soil, may be a potential way to better control the release of soil CO2 and N2O emissions.https://www.sciencedirect.com/
science/article/pii/
S0048969721018945
本文内容来自ELSEVIER旗舰期刊Sci Total Environ第782卷发表的论文：
Wang, L., Gao, CC., Yang, K., Sheng, YQ., Xu, J., Zhao, YX., Lou, J., Sun, R., Zhu, LZ., 2021. Effects of biochar aging in the soil on its mechanical property and performance for soil CO2 and N2O emissions, Sci Total Environ 782, 146824.
DOI：https://doi.org/10.1016/j.scitotenv.2021.146824
朱利中，中国工程院院士，浙江大学教授，博士生导师，国家杰出青年基金获得者，973项目首席科学家，英国皇家化学会会士，浙江省特级专家，主持973、863、国家基金重点项目等。担任《环境科学》副主编、《ES&T Engineering》、《Front Environ Sci Eng》、《J Environ Sci》编委等职，曾任亚洲废弃物管理协会副理事长。主要研究方向为污染物多介质界面行为与调控技术，发表SCI收录论文265篇，SCI他引12258次，授权国家发明专利23件，出版4本著作及2本国家级规划教材。主持完成的2项成果分别获国家自然科学二等奖、国家科技进步二等奖；7项成果获教育部、浙江省自然科学/科技进步一等奖，其中第一完成人5项。
在浙江大学获得博士学位，并在浙江大学杭州国际科创中心从事博士后研究。主要研究方向为碳中和背景下土壤-生物炭固碳减排的影响因素及调控机制、场地/农田土壤修复全生命周期碳排放核算、污染物对植物碳汇的影响。以第一作者或共同作者在Science of the Total Environment、Journal of Hazardous Materials等国际期刊发表论文3篇。