Collaborative Research: Black Carbon Remineralization in the Environment: Physical and Chemical Controls

知识价值：直到最近人们才意识到，热原碳或黑碳（BC）可以构成土壤和沉积物中有机碳的很大一部分。因此，在地质时间尺度上，BC是作为碳汇和氧源的全球碳循环的一个重要但鲜为人知的部分。此外，BC可能是土壤肥力的重要成分，控制着有机污染物的命运，并且，作为木炭，通常用于14C测年，并在古环境和考古研究中用于重建火灾频率和人类职业记录。由于黑碳的化学结构和在地圈中的寿命长，它通常被认为是生物和化学惰性的。然而，考虑到它通过生物质燃烧产生的估计速率，它也必须以相当大的速率（100-1000年？）虽然最近的研究记录了短期微生物培养中可测量的降解率，但对于不同BC形式的降解率范围或控制微生物利用率的化学和物理变量知之甚少。此外，虽然一些研究表明，活性有机物（OM）的存在可能会促进BC的降解，但其他研究则认为BC可以保护OM免受微生物分解。本研究探讨了BC、OM和微生物之间的关系，重点研究了化学和物理因素对土壤中BC降解的相对重要性。科学计划：提出的一系列综合实验室BC-微生物培养、OM吸附实验和野外土壤研究将为了解BC在环境中的循环提供强有力的理论基础。这些实验的材料将包括国际BC指导委员会推荐的BC参考材料和PI在一系列受控温度和氧化条件下通过燃烧各种木材和草产生的BC。这些材料的表面化学将通过13C-NMR（官能团）和电位滴定（表面电荷）在实验室和现场培养前后进行表征，并通过CO2吸附法（比常用的N2吸附法改进）表征表面形态（内外表面积和孔径分布和体积）。这些参数中的每一个都将与微生物降解率有关，微生物降解率是通过实验室中二氧化碳的演变来测量的，微生物降解率是通过在巴西热带土壤中测量的BC损失和团聚体形成来测量的。此外，培养/吸附实验将用于确定不稳定的OM引发的潜力。以增强BC的降解和OM吸附，以隔离和保存BC内的活性有机碳。更广泛的影响：所产生的数据将对努力确定BC的组成和结构，建立最合适的分析方法的科学家社区具有重要价值，并且还将提供关于这一知之甚少的全球碳循环组成部分的生物地球化学循环的关键信息。这些结果也将对那些考虑将BC作为土壤修复、改良和大气碳固存工具的人具有实用价值。为了在传统科学文献之外广泛传播，研究结果将发布在积极讨论BC应用的网站和列表服务上。PI还将与采用或考虑BC技术的商业部门进行交互。这一提议代表了PI（一个没有NSF资助的早期职业科学家）的新方向，以及PI和共同PI以及另外四个合作者（包括巴西的一个）的新合作。它包括要求三名研究生（佛罗里达大学2名，佛罗里达州立大学1名）和两名本科生的全部或部分支持。该项目的成果将纳入教师培训讲习班和公开讲座。

Intellectual Merit: It has only recently been realized that pyrogenic carbon, or black carbon (BC), can make up a significant fraction of the organic carbon in soils and sediments. As such, BC is an important but poorly understood portion of the global carbon cycle that serves as a carbon sink and oxygen source over geological time-scales. Further, BC may be an important ingredient for soil fertility, controls the fate of organic contaminants, and, as charcoal, is commonly used for 14C dating and in paleoenvironmental and archeological studies to reconstruct fire-frequency and human occupation records.Black Carbon has generally been regarded as biologically and chemically inert due to its chemical structure and longevity in the geosphere. However, considering its estimated production rate by biomass combustion, it must also turnover at considerable rates (100-1000 years?). While recent studies have recorded measurable degradation rates in short-term microbial incubations, little is known as to the range of degradation rates that occur with different BC forms, or the chemical and physical variables that control rates of microbial utilization. Further, while some studies suggest that the presence of labile organic matter (OM) may enhance BC degradation, others would have BC serve to protect OM from microbial decomposition. The proposed study examines the relationships between BC, OM, and microbes with a focus on examining the relative importance of chemical and physical factors on BC degradation in soils.Science Plan: The series of integrated laboratory BC-microbial incubations, OM adsorption experiments and field-based soil studies proposed will provide a strong theoretical foundation for understanding the cycling of BC in the environment. Materials for these experiments will include both BC reference materials recommended by the International BC Steering Committee and BC produced by the PI by combustion of a variety of wood and grasses under a range of controlled temperature and oxygenation conditions. The surface chemistry of these materials will be characterized before and after lab and field incubations by 13C-NMR (functional groups) and potentiometric titration (surface charge), and the surface morphology (external and internal surface area and pore size distribution and volume) by CO2 sorptometry (an improvement over commonly used N2 sorptometry). Each of these parameters will be related to rates of microbial degradation measured via CO2 evolution in the laboratory, and BC loss and aggregate formation measured in tropical soils in Brazil. In addition, incubation/adsorption experiments will be used to determine the potential for labile OM ?priming? to enhance BC degradation and for OM adsorption to sequester and preserve labile organic carbon within BC.Broader Impacts: The data generated will be of great value to the community of scientists struggling to identify the composition and structure of BC, establish the most appropriate methods of analysis, and will also provide critical information on the biogeochemical cycling of this poorly understood component of the global carbon cycle. The results will also be of practical value to those considering BC as a tool for soil remediation, amelioration, and atmospheric carbon sequestration. For wide dispersal beyond the conventional scientific literature, findings will be posted on websites and list-serves that are actively discussing BC applications. The PI will also interface with the commercial sector employing or considering BC technologies.This proposal represents a new direction for the PI, an early career scientist with no prior NSF funding, and a new collaboration for the PI and co-PI as well as for four additional collaborators including one in Brazil. It includes a request for full or partial support of three graduate (2 at UF, 1 at FSU) and two undergraduate students. Results of this project will be incorporated into a teacher training workshop and public lectures.