Variability in oxidative degradation of charcoal: Influence of production conditions and environmental exposure
Variability in oxidative degradation of charcoal: Influence of production conditions and environmental exposure
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DOI：
10.1016/j.gca.2011.02.002
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发表时间：
2011-05-01
影响因子：
5
通讯作者：
Apperley, D.
中科院分区：
文献类型：
--
作者：
Ascough, P. L.;Bird, M. I.;Apperley, D.
木炭是黑碳(BC)连续体的关键组成部分，BC是一种顽固的、火灾衍生的多芳香族材料。木炭是古环境数据的重要来源，由于其高的表观环境稳定性，作为潜在的碳汇引起了极大的兴趣。然而，至少某些形式的木炭在相对较短的时间内显然容易受到环境变化和退化的影响。尽管这些过程对木炭在全球生物地球化学中的作用具有重要作用，但人们对它们的了解仍然很少。在这里，我们介绍了一系列木炭样品在酸化重铬酸钾中氧化降解的敏感性的调查结果。这项研究考察了新生产的木炭和暴露在环境条件下长达5万年的木炭。我们比较不同形式的碳在样品之间的比例，特别是关于这些形式的相对耐化学性。这是为了更好地了解影响环境沉积物中木炭的沉积后成岩变化。无论是在样本组内还是在样本组之间，化学成分都有很大的差异。在新生产的木炭中，在300摄氏度生产的材料含有比在摄氏400度生产的木炭更不稳定的碳，这意味着在300-400摄氏度的温度范围内发生了关键的化学变化。暴露在环境沉积条件下的木炭通常由高度羧化的芳香族结构组成，并含有一系列具有不同抗氧化性的碳级分。这些发现表明，相当数量的环境木炭经历了沉积后的成岩蚀变。此外，这些数据强调了使用受控逐步氧化降解作为表征单个木炭样品之间的化学差异的一种方法的潜力。(C)2011爱思唯尔有限公司。保留所有权利。
Charcoal is a key component of the Black Carbon (BC) continuum, where BC is characterized as a recalcitrant, fire-derived, polyaromatic material. Charcoal is an important source of palaeoenvironmental data, and of great interest as a potential carbon sink, due to its high apparent environmental stability. However, at least some forms of charcoal are clearly susceptible to environmental alteration and degradation over relatively short timescales. Although these processes have importance for the role of charcoal in global biogeochemistry, they remain poorly understood.Here we present results of an investigation into the susceptibility of a range of charcoal samples to oxidative degradation in acidified potassium dichromate. The study examines both freshly-produced charcoal, and charcoal exposed to environmental conditions for up to 50,000 years. We compare the proportion of carbon present in different forms between the samples, specifically with respect to the relative chemical resistance of these forms. This was undertaken in order to improve understanding of the post-depositional diagenetic changes affecting charcoal within environmental deposits.A wide range in chemical compositions are apparent both within and between the sample groups. In freshly-produced charcoal, material produced at 300 degrees C contains carbon with more labile forms than charcoal produced at >= 400 degrees C, signifying a key chemical change over the 300-400 degrees C temperature range. Charcoal exposed to environmental depositional conditions is frequently composed of a highly carboxylated aromatic structure and contains a range of carbon fractions of varying oxidative resistance. These findings suggest that a significant number of the environmental charcoals have undergone post-depositional diagenetic alteration. Further, the data highlight the potential for the use of controlled progressive oxidative degradation as a method to characterize chemical differences between individual charcoal samples. (C) 2011 Elsevier Ltd. All rights reserved.