圖片摘要 | Graphical Abstract
全球氣候變暖是當今社會面臨的重要問題。土壤-生物炭固碳是一種有潛力的基于自然的固碳解決方案。近年來Lehmann等人多次在Nature上詳細介紹并推薦了該技術。針對他提出的土壤-生物炭固碳大規(guī)模實施潛力及可行性等問題，近年來，朱利中院士團隊致力于研究土壤-生物炭固碳減排的關鍵影響因素、構建宏觀規(guī)?；?span style="font-size: 15px;outline: 0px;box-sizing: border-box;color: rgb(82, 146, 88);overflow-wrap: break-word !important;">固碳應用情景及估算我國土壤-生物炭固碳減排總體潛力等，為揭示生物炭的環(huán)境行為和提高土壤-生物炭固碳減排潛力以促進實現(xiàn)碳中和提供科學依據(jù)。近日，他們又揭示了生物炭“土盔甲”的奧秘。今天，就讓我們來看一看“土盔甲”有何奧秘，它能為碳封存保駕護航嗎？
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?將不經(jīng)任何預處理的新鮮生物炭施用到土壤中進行田間老化，一年后隨機回收。新鮮生物炭暴露出具有裂紋和通道的褶皺表面（圖1a，1c和1e），而老化生物炭表面顯示出可觀察到更為平滑的覆蓋物（圖1b和1d）。放大500倍后（圖1f），老化的生物炭表面可見附著了許多細顆粒，堵塞了在新鮮生物炭表面上觀察到的裂縫和通道（圖1e）。去除表面物質后，新鮮和老化的生物炭均顯示出豐富的裂紋和孔道（圖1g和1h），且形貌并無明顯差異。
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).圖1. 生物炭顆粒表面掃描電鏡圖
Fig. 1. Scanning electron micrographs of fresh biochar and aged biochar
EDS結果顯示，老化生物炭表面上的硅（Si）、鋁（Al）、鐵（Fe）和氧（O）等元素含量明顯高于新鮮生物炭，但碳元素含量降低，這與生物炭表面附著了土壤礦物，對碳素測定的稀釋效應有關。刮除表面物質后老化生物炭中元素（硅除外）含量與新鮮生物炭元素沒有顯著差異，表明兩種生物炭具有相似的性質，老化生物炭積累的礦物元素主要附著在顆粒表面層。
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.圖2. 生物炭表面元素X射線能譜分析圖
Fig. 2. EDS images of the biochar’s surface elements
XRD結果支持了老化生物炭上某些礦物質的存在。礦物峰在刮除表面物質的老化生物炭（RBC－B－I和RBC－S－I）中并不存在，表明大多數(shù)土壤礦物質聚集在生物炭表面。田間老化后生物炭比表面積顯著小于新鮮生物炭（圖3b），這與老化后生物炭表面積累了土壤礦物質、阻塞了裂縫和通道相一致（圖1d、圖2和圖3a）。紅外結果表明，新鮮生物炭和刮除表面物質層的老化生物炭顆粒中含有一定比例脂肪族碳化合物，然而其在刮除下來的表面物質層（RBC－B－O和RBC－S－O）中并不存在，表明了生物炭表面礦物的覆蓋作用（圖2、圖3a和圖3b）或C－H鍵的氧化作用。氧化試驗表明生物炭表面摻雜進礦物以后形成的礦物?生物炭復合層（即田間老化生物炭顆粒外表層）對化學氧化的抵抗力較高，與老化過程后生物炭上的碳減少和土壤礦物質增加是一致的。化學氧化試驗間接證明了老化生物炭上附著的土壤礦物質可以增強生物炭在土壤環(huán)境中的抗化學氧化過程。
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.圖3. 生物炭物理化學性質表征
（a）X射線衍射圖譜，（b）比表面積，（c）傅里葉紅外圖譜（d）氧化實驗結果。（“去除表面物質的老化生物炭”縮寫為“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”)
老化后生物炭顯微維氏硬度值顯著增加(P<0.05)，顆?？箟簭姸让黠@提高（荷載峰值和剛度），表明老化生物炭比新鮮生物炭顆粒能夠承受更高的機械壓力，使其具有相對較低的潛在環(huán)境風險。這有利于抑制顆粒在自然環(huán)境中的破碎，從而防止內(nèi)部不穩(wěn)定物質向外釋放。老化導致了生物炭顆粒機械強度增強，可通過影響減少破碎抑制顆粒內(nèi)不穩(wěn)定組分的釋放，進一步影響生物炭對土壤中CO2或N2O排放的影響以及對土壤微生物群落結構的影響。
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.圖4. 機械性能分析
Fig. 4. Mechanical performance analysis
新鮮生物炭對土壤CO2排放沒有顯著影響，顯著減少土壤累積N2O排放；老化生物炭均顯著降低土壤的CO2和N2O排放（P＜0.05）；將老化生物炭表面物質刮除以后，老化生物炭對土壤CO2減排作用消失，對土壤N2O減排作用減弱。老化生物炭可抑制土壤CO2排放，可能是由于外表面土壤礦物質與含氧官能團共積累所形成有機-礦物質復合物通過空間位阻穩(wěn)定了生物炭中的有機碳，降低其對于微生物的有效性；或通過微孔吸附保護鎖定微生物所需碳氮源來抑制微生物呼吸作用。該結果表明，老化生物炭的表面物質（含較多有機-礦物復合體）在影響土壤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.圖5. 土壤CO2或N2O排放速率或累積排放量
（“去除表面物質的老化生物炭”縮寫為“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”)
田間老化使生物炭表面積累礦物質，形成有機-礦物復合體，從而增強顆粒物理穩(wěn)定性（如機械強度），顯著減少土壤CO2和N2O排放。因此新鮮生物炭使用之前，通過人為或自然的方法去除不穩(wěn)定組分及構建富含有機-礦物復合體的保護界面，對于增強其在土壤中固碳減排潛力具有重要意義。
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
本文內(nèi)容來自ELSEVIER旗艦期刊Sci Total Environ第782卷發(fā)表的論文：
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
浙江大學環(huán)境與資源學院
浙江大學杭州國際科創(chuàng)中心
朱利中，中國工程院院士，浙江大學教授，博士生導師，國家杰出青年基金獲得者，973項目首席科學家，英國皇家化學會會士，浙江省特級專家，主持973、863、國家基金重點項目等。擔任《環(huán)境科學》副主編、《ES&T Engineering》、《Front Environ Sci Eng》、《J Environ Sci》編委等職，曾任亞洲廢棄物管理協(xié)會副理事長。主要研究方向為污染物多介質界面行為與調(diào)控技術，發(fā)表SCI收錄論文265篇，SCI他引12258次，授權國家發(fā)明專利23件，出版4本著作及2本國家級規(guī)劃教材。主持完成的2項成果分別獲國家自然科學二等獎、國家科技進步二等獎；7項成果獲教育部、浙江省自然科學/科技進步一等獎，其中第一完成人5項。
在浙江大學獲得博士學位，并在浙江大學杭州國際科創(chuàng)中心從事博士后研究。主要研究方向為碳中和背景下土壤-生物炭固碳減排的影響因素及調(diào)控機制、場地/農(nóng)田土壤修復全生命周期碳排放核算、污染物對植物碳匯的影響。以第一作者或共同作者在Science of the Total Environment、Journal of Hazardous Materials等國際期刊發(fā)表論文3篇。