Natural oxidation of black carbon in soils: Changes in molecular form and surface charge along a climosequence
Natural oxidation of black carbon in soils: Changes in molecular form and surface charge along a climosequence
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DOI：
10.1016/j.gca.2008.01.010
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发表时间：
2008-03-15
影响因子：
5
通讯作者：
Engelhard, Mark H.
中科院分区：
文献类型：
--
作者：
Cheng, Chih-Hsin;Lehmann, Johannes;Engelhard, Mark H.
本工作的目的是研究长期自然氧化作用下黑碳(BC)分子形态和表面电荷的变化，以及气候和土壤因素对BC氧化的影响。从加拿大魁北克到美国佐治亚州的11个历史木炭高炉遗址收集了黑色C，并与使用重建的历史窑新生产的BC进行了比较。结果表明，与新的BC或培养一年的BC相比，历史BC样品在土壤中130年后被大量氧化。BC自然氧化的主要变化包括：(1)元素组成随氧气的增加而变化(0)从新BC的7.2%增加到历史BC的24.8%，C从90.8%下降到70.5%；(2)含氧官能团的形成，特别是羧基和酚官能团的形成；(3)12个月后表面正电荷的消失和表面负电荷的演化。尽管暴露时间显著增加了BC的自然氧化，但年平均温度(MAT)与BC氧化(O/C比，r=0.83；P<；0.01)呈显著正相关，说明每单位MAT增加BC氧化87毫摩尔·kg~(-1)C~(-1)。这种长期的氧化在BC表面比整个颗粒更明显，并且对MAT的增加的反应是7倍。我们的结果还表明，BC的氧化比非BC的吸附更重要。因此，BC的自然氧化可能在BC对土壤生物地球化学的影响中起着重要作用。(C)2008爱思唯尔有限公司。保留所有权利。
The aim of this work was to investigate changes in molecular form and surface charge of black carbon (BC) due to long-term natural oxidation and to examine how climatic and soil factors affect BC oxidation. Black C was collected from 11 historical charcoal blast furnace sites with a geographic distribution from Quebec, Canada, to Georgia, USA, and compared to BC that was newly produced (new BC) using rebuilt historical kilns. The results showed that the historical BC samples were substantially oxidized after 130 years in soils as compared to new BC or BC incubated for one year. The major alterations by natural oxidation of BC included: (1) changes in elemental composition with increases in oxygen (0) from 7.2% in new BC to 24.8% in historical BC and decreases in C from 90.8% to 70.5%; (2) formation of oxygen-containing functional groups, particularly carboxylic and phenolic functional groups, and (3) disappearance of surface positive charge and evolution of surface negative charge after 12 months of incubation. Although time of exposure significantly increased natural oxidation of BC, a significant positive relationship between mean annual temperature (MAT) and BC oxidation (O/C ratio with r = 0.83; P < 0.01) explained that BC oxidation was increased by 87 mmole kg C-1 per unit Celsius increase in MAT. This long-term oxidation was more pronounced on BC surfaces than for entire particles, and responded 7-fold stronger to increases in MAT. Our results also indicated that oxidation of BC was more important than adsorption of non-BC. Thus, natural oxidation of BC may play an important role in the effects of BC on soil biogeochemistry. (C) 2008 Elsevier Ltd. All rights reserved.