Fast Spectrophotometric Method as Alternative for CuO Oxidation to Assess Lignin in Soils with Different Tree Cover

Given the ongoing climate change, estimating the amount of less degradable plant compounds that can be stored in the soil, such as lignin, is a topic of primary importance. There are few methods applicable to soils for the determination of lignin, such as the copper oxide (CuO) oxidation method (CuOL). Acetyl bromide spectrophotometric lignin (ABSL) could be a valid alternative providing information that is less detailed compared to CuOL, but it offers data on the bulk amount of lignin and may offer a valid, fast, and cheap alternative to the CuO method. The aim of this work was to compare ABSL with the CuO method on several soils receiving plant residues from different trees. Mineral soil samples from 0 to 10 cm depth were obtained from a former agricultural site in northern Italy (Brusciana, Tuscany), where different tree plantations were established 22 years ago. The plantations were white poplar and common walnut, which were also intercropped with other species such as hazelnut, Italian alder, and autumn olive. Soil samples under these plantations were also compared to soil under an adjacent agricultural field. In general, the amount of lignin in the afforested stands was approximately double than in the agricultural field as determined by either method. The two methods returned a largely different scale of values due to their different mechanisms of action. The acid-to-aldehyde ratio of syringyl structural units highlights that forest plantation provides a plant input material that is more slowly oxidatively degraded compared to arable soil. A linear mixed model proved that ABSL performed well in relation to CuOL, especially when considering the random variation in the model given by the plantation field design. In conclusion, ABSL can be considered a valid proxy of soil C pool derived from structural plant component, although further analyses are needed.

Phenolic Compounds as Unambiguous Chemical Markers for the Identification of Keystone Plant Species in the Bale Mountains, Ethiopia

: Despite the fact that the vegetation pattern and history of the Bale Mountains in Ethiopia were reconstructed using pollen, little is known about the former extent of Erica species. The main objective of the present study is to identify unambiguous chemical proxies from plant-derived phenolic compounds to characterize Erica and other keystone species. Mild alkaline CuO oxidation has been used to extract sixteen phenolic compounds. After removal of undesired impurities, individual phenols were separated by gas chromatography and were detected by mass spectrometry. While conventional phenol ratios such as syringyl vs. vanillyl and cinnamyl vs. vanillyl and hierarchical cluster analysis of phenols failed for unambiguous Erica identification, the relative abundance of coumaryl phenols (>0.20) and benzoic acids (0.05—0.12) can be used as a proxy to distinguish Erica from other plant species. Moreover, a Random Forest decision tree based on syringyl phenols, benzoic acids (>0.06), coumaryl phenols (<0.21), hydroxybenzoic acids, and vanillyl phenols (>0.3) could be established for unambiguous Erica identification. In conclusion, serious caution should be given before interpreting this calibration study in paleovegetation reconstruction in respect of degradation and underground inputs of soil organic matter.

Testing of Purification and Purity Control System High Temperature Helium Loop

Helium purification system as a part of the HTHL and helium purification methods for future HTR or GFR reactors was tested in the series of experiments. The experiments were aimed (among others) to operation of CuO unit, which is part of the helium purification system. This unit is used for converting some minor impurities in helium coolant (namely H2 and CO) to compounds, which can be easily removed on molecular sieve adsorbents (H2O, CO2). The CuO oxidation capabilities were tested at several temperatures (100, 150, 200 and 250°C) for helium containing different impurities. Final oxidation products were removed by molecular sieves after stabilization of gas composition inside the HTHL. The CuO oxidizer bed showed good performance in H2 and CO oxidation. The overall oxidation efficiency is highly dependable on CuO bed temperature.

Autohydrolysis and aqueous ammonia extraction of wheat straw: effect of treatment severity on yield and structure of hemicellulose and lignin

Pseudo-lignin accumulation in wheat straw autohydrolysis was revealed by relative double detection high-performance size-exclusion chromatography and confirmed by CuO oxidation.

Interaction of CO with CuO and CuO/graphene: Reactions Mechanism and the Formation of CO2

CuO/graphene oxygen carrier models were built to investigate the reaction stoichiometry mechanism between the fuel gas CO and oxygen carrier CuO. The results show that the energy barrier of the single metal oxide CuO oxidation CO is 127.17kJ/mol, while energy barrier is only 42.64 kJ/ mol for the CuO/graphene. From the point view of chemical reaction dynamics, the oxidation activity of CuO/graphene much higher than single-metal oxide CuO, which indicate that graphene can improve the reaction performance of oxygen carrier. And analysis results for the oxidation of fuel gas CO has an important understanding of the process of scientific significance, and will promote the fundamental understanding and applications of the oxygen carrier CuO.