Beijing Key Laboratory of Farmland Soil Pollution Prevention and Remediation, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China.
Beijing Key Laboratory of Farmland Soil Pollution Prevention and Remediation, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China.
Sci Total Environ. 2021 Feb 20;756:144058. doi: 10.1016/j.scitotenv.2020.144058. Epub 2020 Nov 26.
Biochar has been widely applied to remediate the heavy metal-polluted soils, whereas biochar aging can induce the changes of the biochar physic-chemical properties. Afterwards, the bioavailability of heavy metals (BHM) will vary in soils which likely increase the unstable fractions of heavy metals and the following environmental risks. To explore the biochar aging effects on the BHM changes in responses to the variation of experimental conditions and biochar properties, a meta-analysis for the literatures published before May 2020 was conducted. A sum of 257 independent observations from 22 published papers was obtained. The results from the analysis of boosted regression tree showed that the soil pH was the most important factor influencing the BHM changes in biochar amended soil, followed by soil texture, aging time and biochar pyrolysis temperature. The results of this review showed that the BHM was decreased by 16.9%, 28.7% and 6.4% in weakly acid soil (pH 6.00-6.99), coarse- and medium-textured soils, respectively, but increased by 149% and 121% in the alkaline (pH > 8.00) and fine-textured soils. The BHM declined in the soils amended with biochar pyrolyzed at relative high temperature (> 500 °C), and increased during aging in soils amended with biochar pyrolyzed at relatively low temperature (401-500 °C). In terms of diverse immobilized heavy metals, only bioavailable Zn in soil decreased after aging. However, there was no significant changes in Cd, Cu and Pb's bioavalability. Besides, the BHM was decreased by 18.6% within the short-term (less than one year) biochar aging, while showed inverse trend during the longer aging processes. Besides, the application of lignin-enriched biochar may counteract the positive effects of the biochar aging on BHM. Our works may promote the interpretation of the interference factors on the BHM changes and filled the research gaps on biochar aging process in soils.
生物炭已广泛应用于修复重金属污染土壤，而生物炭老化会引起生物炭理化性质的变化。随后，重金属的生物可利用性（BHM）将在土壤中发生变化，这可能会增加重金属的不稳定部分及其随后的环境风险。为了探索生物炭老化对响应实验条件和生物炭特性变化的 BHM 变化的影响，对截至 2020 年 5 月之前发表的文献进行了荟萃分析。从 22 篇已发表的论文中获得了 257 个独立观测值的总和。增强回归树分析的结果表明，土壤 pH 是影响生物炭添加土壤中 BHM 变化的最重要因素，其次是土壤质地、老化时间和生物炭热解温度。本综述的结果表明，在弱酸性土壤（pH 6.00-6.99）、粗质地和中质地土壤中，BHM 分别减少了 16.9%、28.7%和 6.4%，但在碱性（pH>8.00）和细质地土壤中分别增加了 149%和 121%。在高温（>500°C）下热解的生物炭添加的土壤中，BHM 下降，而在低温（401-500°C）下热解的生物炭添加的土壤中，BHM 在老化过程中增加。就不同的固定重金属而言，只有土壤中生物可利用的 Zn 在老化后减少。然而，Cd、Cu 和 Pb 的生物可利用性没有明显变化。此外，在短期内（不到一年）生物炭老化过程中，BHM 减少了 18.6%，而在较长的老化过程中则呈现相反的趋势。此外，富木质素生物炭的应用可能会抵消生物炭老化对 BHM 的积极影响。我们的工作可能会促进对干扰因素对 BHM 变化的解释，并填补土壤中生物炭老化过程的研究空白。
