Role of colloidal biochar in metals sequestration and transport

生物质炭是植物通过火自然热解的产物，通过人为热解多种类型的生物质用于农业土壤改良、碳封存和水处理技术。虽然生物质炭在物理和化学性质方面得到了很好的研究，但它的相当一部分由纳米颗粒热解碳(NPC)组成。很少有研究调查NPC的性质，在这些研究中，只有少数几个对NPC的表面化学和对水和土壤中发现的金属和养分的反应性有了了解。为了解决这个问题，这个研究计划建议从各种类型的生物质产生的生物炭中提取NPC，包括木材、木材、草、污水污泥和城市垃圾--并彻底表征它们的组成、表面化学和对水物种的反应性。利用湿化学和光谱方法，将开发表面络合模型，以在广泛的环境条件下预测金属和营养物质与NPC的结合。了解生物炭在环境中的老化和NPC在环境中的降解也是预测其表面反应性的关键考虑因素。使用上面讨论的同一组生物炭，将对散装生物炭应用湿干加速老化，以模拟长达100年的老化。从这些陈年生物炭的时间序列中提取的NPC用于限制NPC表面化学随时间的差异--对于了解金属和营养物质结合的变化以及NPC通过含水层的运输至关重要。每年野火产生的生物炭中有相当一部分(高达32%)最终被输送到海洋，其中大部分通过河流和溪流。因此，我们还将进行光氧化实验，以模拟阳光对NPC功能和活性增加的影响。通过将这些研究路线与现有的全球热源碳产生限制相结合，我们的目标是限制NPC在水文流域和全球海洋中的金属和营养物质运输中的作用，包括现在和过去的地质历史。森林火灾发生在泥盆纪，并在白垩纪和早二叠世至中二叠世达到顶峰，当时大气中的氧气水平可能高达35%。在这些条件下，NPC可能在向河口输送水生物种方面发挥了相当大的作用--即使与粘土和浮游微生物相比也是如此。如果NPC是营养物质和生物必需金属的源或汇，它可能通过限制或促进微生物的生长，对河口的初级生产力产生了直接而深远的影响。这反过来又会直接影响细胞与其他颗粒物质(如粘土、氢氧化铁和黑碳)的絮凝程度，沉积物的形成，最终影响我们今天观察到的海相岩石记录的地球化学。

Biochar a product of the natural pyrolysis of plants by fire, and via anthropogenic pyrolysis of numerous types of biomass for use in agricultural soil amendment, carbon sequestration, and water treatment technologies.  While biochar is well-studied in terms of its physical and chemical properties, a considerable fraction of it is comprised of nanoparticulate pyrogenic carbon (NPC).  Few studies have investigated the nature of NPC, and of those, only a handful have developed an understanding of the surface chemistry and reactivity of NPC towards metals and nutrients found in water and soils.  To address this gap, this research program proposes to extract NPCs from biochars produced from numerous types of biomass - including wood, grasses, sewage sludge, and municipal waste - and thoroughly characterize their composition, surface chemistry, and reactivity towards aqueous species.  Using wet chemical and spectroscopic approaches, surface complexation models will be developed to predict metals and nutrients binding to NPC across a wide range of environmental conditions.  Understanding the aging of biochar and degradation of NPCs in the environment is also a critical consideration in predicting their surface reactivity.  Using the same set of biochars discussed above, wet-dry accelerated aging will be applied to the bulk biochars to simulate up to 100 years of aging, and NPCs extracted from a time series of these aged biochars used to constrain differences in NPC surface chemistry over time - critical to understanding changes in metals and nutrients binding, and NPC transport through aquifers.  A considerable fraction (as much as 32%) of the annual wildfire-produced biochar is ultimately transported to the oceans, much of this via rivers and streams.  For this reason, we will also conduct photooxidation experiments to simulate the effect of sunlight on increased functionality and reactivity of NPC.  By combining these lines of inquiry with existing constraints on global pyrogenic carbon production, we aim to constrain the role of NPC in metals and nutrients transport in hydrologic catchments and to the global oceans, both in the present and in the geologic past.  Forest fires emerged in the Devonian and peaked in the Cretaceous and early to middle Permian, when atmospheric oxygen levels may have reached as high as 35%.  At these conditions, NPC may have had a considerable role - even as compared to clays and planktonic microorganisms - in the transport of aqueous species to estuaries.  If NPC is a source or sink of nutrients and bioessential metals, it may have had a direct and profound impact on primary productivity in estuaries by limiting or promoting the growth of microorganisms.  This, in turn, would have a direct effect on the degree of flocculation of cells with other particulate matter such as clays, iron oxyhydroxides, and black carbon, the formation of sediments, and ultimately the geochemistry of the marine rock record we observe today.