Large-scale biochar field trials have been conducted worldwide to test for “carbon negative strategy” in the event of carbon credit and if other subsidies become enacted in the future. Once amended to the soil, biochar engages in complex organo-mineral interactions, fragmentation, transport, and other aging mechanisms exhibiting interactions with treatments including the irrigation and fertilizer application. As a result, quantitative tracing of biochar carbon relying on the routinely measured soil parameters, e.g., total/particulate organic carbon, poses a significant analytical uncertainty. This study utilized two biochar field trial sites to calibrate for the biochar carbon structure and quantity based on the infrared- and fluorescence-based chemometrics: (1) slow pyrolysis biochar pellets on kaolinitic Greenville fine sandy loam in Georgia and (2) fast pyrolysis biochar powder on Crider silt loam in Kentucky. Partial least squares-based calibration was constructed to predict the amount of solvent (toluene/methanol)-extractable fluorescence fingerprint (290/350 nm excitation and emission peak) attributed to biochar based on the comparison with the authentic standard. Near-infrared-based detection was sensitive to the C–H and C–C bands, as a function of biochar loading and the particulate organic carbon content (< 53 μm) of the bulk soil. Developed chemometrics could be used to validate tarry carbon structures intrinsic to biochar additives, as the impact of biochar additives on soil chemical properties (pH, electric conductivity, and dissolved organic carbon) becomes attenuated over time.

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荧光和近红外化学计量学检测生物碳

在全球范围内已经进行了大规模的生物炭田间试验，以测试是否存在碳信用以及将来是否会实施其他补贴的“碳负战略”。一旦被改良到土壤中，生物炭便会参与复杂的有机矿物质相互作用，破碎，运输和其他老化机制，这些机制与包括灌溉和施肥在内的各种处理相互作用。结果，依赖于常规测量的土壤参数（例如，总/颗粒有机碳）对生物炭碳的定量追踪带来了显着的分析不确定性。这项研究基于基于红外和荧光的化学计量学，利用两个生物炭现场试验站点对生物炭的碳结构和数量进行校准：（1）在佐治亚州的高岭土格林维尔细砂质壤土上缓慢地热解生物炭颗粒，（2）在肯塔基州的Crider粉砂壤土上快速地热解生物炭粉末。基于与真实标准品的比较，构建了基于偏最小二乘的部分校准，以预测可归因于生物炭的溶剂（甲苯/甲醇）可提取的荧光指纹（290/350 nm激发和发射峰）的量。基于近红外的检测对C–H和C–C波段敏感，这是生物炭含量和大块土壤中颗粒有机碳含量（<53μm）的函数。随着生物炭添加剂对土壤化学性质（pH，电导率和溶解的有机碳）的影响随着时间的推移而减弱，已开发的化学计量学可用于验证生物炭添加剂固有的焦油状碳结构。