近年來，浙江大學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、構建宏觀規模化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，為揭示生物炭的環境行為和提高土壤-生物炭固碳減排潛力以促進實現碳中和提供科學依據。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？

圖片摘要 | Graphical Abstract

導讀 | Introduction

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、構建宏觀規模化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，為揭示生物炭的環境行為和提高土壤-生物炭固碳減排潛力以促進實現碳中和提供科學依據。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. Bio 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-bio carbon sequestration proposed by him, the team of Academician Lizhong Zhu has been committed to systematic researches (i.e. key influencing factors, macro-scale bio application scenarios, the overall potential of bio carbon sequestration in farmland soil in China), which provide scientific basis to maximize the potential of bio carbon sequestration in soil environment to promote the realization of carbon neutrality. Recently, they have revealed the mystery of bio "earth armor". Today, let us take a look at the mystery of the "earth armor". Can it promote carbon storage?

圖1.生物炭顆粒表面掃描電鏡圖

Fig. 1.Scanning electron micrographs of fresh bio and aged bio

2. 生物炭顆粒表面元素組成

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 bio were significantly increased, as compared to those on fresh bio which means that the aged bio was attached with soil minerals (e.g.,SiO2). Moreover, the surface contents of soil mineral elements (Si, Al, and Fe) on the aged bio 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 bio’s surface elements

3. 生物炭礦物組成、吸附性、官能團及抗氧化性

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境中的抗化學氧化過程。

XRD results further supported the existence of certain minerals on the aged bio. The surface area of the bio after the field aging was significantly smaller than the fresh bio (Fig. 3b), consistent with the mineral accumulation of soil minerals on the surface of the bio after the field aging, which blocked the cracks and channels (Fig. 1d, 2, and 3a). The discrepancy between the FTIR spectra of interior bio and the surface substances indicated the high possibility of organo-mineral complexations, which had been widely reported. The oxidation test showed that the aged bio with composite layer formed has a higher resistance to chemical oxidation than the fresh bio. The chemical oxidation test indirectly proved that the soil minerals attached to the aged bio can enhance the anti-chemical oxidation process of the bio 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 bio

(a) XRD pattern, (b) SSA, (c) FTIR spectra, and (d) Result of Oxidation experiment. (“Aged bio*” was abbreviated for “Aged bio with surface removed”)

4. 生物炭顆粒機械性能

老化后生物炭顯微維氏硬度值顯著增加(P<0.05)，顆粒抗壓強度明顯提高（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境風險。這有利于抑制顆粒在自然環境中的破碎，從而防止內部不穩定物質向外釋放。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不穩定組分的釋放，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 bio 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 bio particles indicates that they might be able to withstand a higher mechanical pressure than the fresh bio 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 bio particles.

圖4.機械性能分析

Fig. 4. Mechanical performance analysis

5. 生物炭對土壤CO2或N2O排放的影響

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 bio had no significant impact on soilCO2emissions, and significantly reduced soil accumulatedN2Oemissions; aged bio further significantly reduced soilCO2andN2Oemissions (P<0.05); after scraping off the surface material of aged bio, the soilCO2emission reduction effect of aged bio has disappeared while the soilN2Oemission reduction effect was weakened. The results indicated that the surface material of the aged bio (containing more organic-mineral complexes) played an important role in reducing soilCO2andN2Oemissions.

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 bio on soilCO2orN2Oemissions

(“Aged bio*” was abbreviated for “Aged bio without surface substances”)

總結 | Conclusions

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 bio during the field aging process, forming organo-mineral complexes, blocking the cracks and channels of the bio, and improving its mechanical properties. The improved mechanical properties could inhibit the fragmentation of bio particles, reducing the release of labile fractions from the bio and the subsequentCO2andN2Oemissions. These findings also indicate that adjusting the mechanical properties of bio particles to improve their physical stability before adding them into the soil, may be a potential way to better control the release of soilCO2andN2Oemissions.