Fengming Xi

水泥是全球用量最高、用途最广的建筑材料之一, 同时水泥生产也是人为活动碳排放的重要来源之一. 水泥材料中的碱性化合物能缓慢吸收周围环境中的CO₂发生碳化反应, 形成特殊的碳汇效应. 中国是水泥生产与消费大国, 科学系统核算中国水泥碳汇量并明确其对碳中和的贡献值得深入探讨. 通过构建水泥全生命周期碳汇核算综合分析模型, 发现1930~2021年中国水泥碳汇量不断增长, 到2021年高达426.77Mt CO₂(95%置信区间CI: 317.67~874.33Mt CO₂), 相当于中国年陆地碳汇的8.10%~45.40%, 全球陆地碳汇的2.51%~4.54%, 是全球碳循环中不可忽视的重要因素. 在此期间, 水泥的累积碳吸收量约为7.06Gt CO₂(95% CI: 5.22~9.44Gt CO₂), 抵消了同期水泥工业过程排放(13.91Gt CO₂, 95%CI: 12.44~17.00Gt CO₂)的50.7%. 其中, 水泥砂浆对碳吸收贡献最大, 占总量的65.64%. 从生命周期的角度看, 使用阶段的水泥材料碳吸收量占比最高(90.03%). 水泥碳汇核算模型不仅提高了水泥行业碳核算的准确性, 而且为中国乃至全球碳中和评估提供了科学依据. 水泥材料及其废弃物的未来吸收潜力巨大, 应进一步加强水泥材料的生态效益, 加速水泥及其废弃物的CO₂封存技术研发和产业化进程, 助力中国早日实现碳中和目标.

The main contributor to the greenhouse gas (GHG) footprint of the cement industry is the decomposition of alkaline carbonates during clinker production. However, systematic accounts for the reverse of this process – namely carbonation of calcium oxide and other alkaline oxides and/or hydroxides within cement materials during cements' life cycles – have only recently been undertaken. Here, adopting a comprehensive analytical model, we provide the most updated estimates of CO₂ uptake by cement carbonation. The accumulated amount of global CO₂ uptake by cements produced from 1930 to 2021 is estimated to be 22.9 Gt CO₂ (95 % confidence interval, CI: 19.6–26.6 Gt CO₂). This amount includes the CO₂ uptake by concrete, mortar, construction waste and kiln dust, accounting for 30.1 %, 58.5 %, 4.0 % and 7.1 % respectively. The cumulative carbon uptake by cement materials from 1930 to 2021 offsets 55.1 % of the emissions from cement production (41.6 Gt CO₂, 95 % CI: 38.7–47.2 Gt CO₂) over the same period, with the greater part coming from mortar (58.5 % of the total uptake). China has the highest cement carbon uptake, with cumulative carbonation of 7.06 Gt CO₂ (95 % CI: 5.22–9.44 Gt CO₂) since 1930. In addition, the carbon uptake amounts of the USA, EU, India and the rest of the world took 5.0 %, 23.2 %, 5.6 % and 34.8 % separately. As a result of rapidly increased production in recent years, over three-quarters of the cement carbon uptake has occurred since 1990. Additionally, our results show little impact by the COVID-19 pandemic on cement production and use, with carbon uptake reaching about 0.92 Gt CO₂ (95 % CI: 0.78–1.10 Gt CO₂) in 2020 and 0.96 Gt CO₂ (95 % CI: 0.81–1.15 Gt CO₂) in 2021. Our uniformly formatted and most updated cement uptake inventories provide coherent data-based support for including cement carbon uptake into future carbon budgets from the local to global scale. The latest version contains the uptake data till 2021, showing the global uptake's increasing pattern and offering more usable and relevant data for evaluating cement's carbon uptake capacity. All the data described in this study are accessible at https://doi.org/10.5281/zenodo.7516373 (Bing et al., 2023).

The main contributor to the GHG footprint of the cement industry is the decomposition of alkaline carbonates during clinker production. However, systematic accounts for the reverse of this process – namely carbonation of calcium oxide and other alkaline oxides/hydroxides within cement materials during cements’ life cycle have only recently been undertaken. Here, adopting a comprehensive analytical model, we provide the most updated estimates of CO₂ uptake by cement carbonation. The accumulated amount of global CO₂ uptake by cements produced from 1930 to 2021 is estimated to be 22.9 Gt CO₂ (95 % Confidence interval, CI: 19.6–26.6 Gt CO₂). This amount includes the CO₂ uptake by concrete, mortar, and construction waste and kiln dust. The cumulative carbon uptake by cement materials from 1930 to 2021 offsets 55.1 % of the emissions from cement production (41.6 Gt CO₂, 95 % CI: 38.7–47.2 Gt CO₂) over the same period, with the greater part coming from mortar (58.5 % of the total uptake). China has the highest cement carbon uptake, with cumulative carbonation of 7.06 Gt CO₂ (95 % CI: 5.22–9.44 Gt CO₂) since 1930. As a result of rapidly increased production in recent year, over three-quarters of the cement carbon uptake has occurred since 1990. Additionally, our results show little impact of the COVID-19 pandemic on cement production and use, with carbon uptake reaching about 0.92 Gt CO₂ (95 % CI: 0.78–1.10 Gt CO₂) in 2020 and 0.96 Gt CO₂ (95 % CI: 0.81–1.15 Gt CO₂) in 2021. Our uniformly formatted and most updated cement uptake inventories provide coherent data support for including cement carbon uptake into future carbon budgets from the local to global scale. The latest version contains the uptake data till 2021, showing the global uptake increasing pattern and offering more usable and relevant data for evaluating cement’s carbon uptake capacity. All the data described in this study are accessible at https://doi.org/10.5281/zenodo.7516373 (Bing et al., 2023).

A substantial amount of CO₂ is released into the atmosphere from the process of the high-temperature decomposition of limestone to produce lime. However, during the lifecycle of lime production, the alkaline components of lime will continuously absorb CO₂ from the atmosphere during use and waste disposal. Here, we adopt an analytical model describing the carbonation process to obtain regional and global estimates of carbon uptake from 1930 to 2020 using lime lifecycle use-based material data. The results reveal that the global uptake of CO₂ by lime increased from 9.16 Mt C yr⁻¹ (95 % confidence interval, CI: 1.84–18.76 Mt C) in 1930 to 34.84 Mt C yr⁻¹ (95 % CI: 23.50–49.81 Mt C) in 2020. Cumulatively, approximately 1444.70 Mt C (95 % CI: 1016.24–1961.05 Mt C) was sequestered by lime produced between 1930 and 2020, corresponding to 38.83 % of the process emissions during the same period, mainly contributed from the utilization stage (76.21 % of the total uptake). We also fitted the missing lime output data of China from 1930 to 2001, thus compensating for the lack of China's lime production (cumulative 7023.30 Mt) and underestimation of its carbon uptake (467.85 Mt C) in the international data. Since 1930, lime-based materials in China have accounted for the largest proportion (about 63.95 %) of the global total. Our results provide data to support including lime carbon uptake into global carbon budgets and scientific proof for further research of the potential of lime-containing materials in carbon capture and storage. The data utilized in the present study can be accessed at https://doi.org/10.5281/zenodo.7896106 (Ma et al., 2023).

Because of the alkaline nature and high calcium content of cements in general, they serve as a CO₂-absorbing agent through carbonation processes, resembling silicate weathering in nature. This carbon uptake capacity of cements could abate some of the CO₂ emitted during their production. Given the scale of cement production worldwide (4.10 Gt in 2019), a life-cycle assessment is necessary to determine the actual net carbon impacts of this industry. We adopted a comprehensive analytical model to estimate the amount of CO₂ that had been absorbed from 1930 to 2019 in four types of cement materials, including concrete, mortar, construction waste, and cement kiln dust (CKD). In addition, the process CO₂ emission during the same period based on the same datasets was also estimated. The results show that 21.02 Gt CO₂ (95 % confidence interval, CI: 18.01–24.41 Gt CO₂) had been absorbed in the cements produced from 1930 to 2019, with the 2019 annual figure mounting up to 0.89 Gt CO₂ yr⁻¹ (95 % CI: 0.76–1.06 Gt CO₂). The cumulative uptake is equivalent to approximately 55 % of the process emission based on our estimation. In particular, China's dominant position in cement production or consumption in recent decades also gives rise to its uptake being the greatest, with a cumulative sink of 6.21 Gt CO₂ (95 % CI: 4.59–8.32 Gt CO₂) since 1930. Among the four types of cement materials, mortar is estimated to be the greatest contributor (approximately 59 %) to the total uptake. Potentially, our cement emission and uptake estimation system can be updated annually and modified when necessary for future low-carbon transitions in the cement industry. All the data described in this study, including the Monte Carlo uncertainty analysis results, are accessible at https://doi.org/10.5281/zenodo.4459729 (Wang et al., 2021).

The effect of greenhouse soil management on soil aggregation and sesquioxides cycling should be evaluated to maximize the benefits of solar greenhouses rationally. The aggregation process of long-term greenhouse soil management and the influence of aggregate-associated sesquioxides on this process were investigated. Wet-sieving method was used to determine aggregate size distribution. Sesquioxide forms were also determined. The aggregates stability decreased and a similar trend for the stability of microaggregates was observed. The macroaggregate stability in 5 years of greenhouse age was statistically significantly lower than those in other ages. Compared to free and complex oxides, amorphous oxides had the closest relationships with mineral-associated organic carbon and soil aggregation. These results indicated that amorphous oxides were effective in binding aggregates and contributed significantly to macro- and micro- aggregate stability.

This paper presents a study of the relationship between phosphorus fractions and phosphorus release in the presence of manure. Dynamic changes in the characteristics of total phosphorus in surface water are simulated by waterlogged incubation. The study was carried out by comparing sterilized and non‐sterilized treatments to analyze the effect of manure on the dynamics of phosphorus (P) release from soil. Experimental results show that manure application in paddy soil can significantly increase the content of phosphorus fractions (p < 0.05). The concentration of total phosphorus in surface water also increased during incubation. The regression coefficients of moderately resistant organic phosphorus (B = 0.066), occluded P (O‐P) (B = 0.012), and calcium phosphate (Ca‐P) (B = −0.034) are significantly linear, which suggests possible contributions to total phosphorus. Path analysis indicates that the direct effect of Ca‐P on P loss curbs the release of P; the indirect effect of Ca‐P via O‐P and moderately resistant organic phosphorus involved promotion of P loss. The presence of microorganisms promoted transformation of phosphorus forms; for example, Ca‐P can transform into O‐P and moderately resistant organic phosphorus.