Black (pyrogenic) carbon in soils and waters: a fragile data basis extensively interpreted

Gerke, Jörg

doi:10.1186/s40538-019-0151-6

Cited by 26 publications

(10 citation statements)

References 68 publications

(154 reference statements)

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“…The effects of forest fires on SOM can vary widely depending on factors such as fire intensity and duration, and the amount and flammability of biomass added to the soil (Zimmerman et al 2017;Gerke 2019). An additional intrinsic fire effect on SOM is the immediate decrease in microbial biomass on the soil surface due to the death of most living organisms at temperatures between 50 and 120 °C (Vazquez et al 1993;Neary et al 1999).…”

Section: Introductionmentioning

confidence: 99%

Effects of fire on soil organic matter in northern Amazonian forest fragments

et al. 2022

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Forest fires incorporate pyrogenic organic matter into the soil, affecting the characteristics of soil organic matter (SOM) due to its high aromaticity, increasing its renewal time. However, the factors that control the concentration of pyrogenic organic matter and its chemical composition and structure are still little known. Forest fragments dispersed in a savanna matrix of the northern Brazilian Amazon are frequently impacted by fires, which can affect the composition of SOM within the fragments. The aim of this study was to analyse the chemical composition of SOM in the border and interior of six forest fragments in the Roraima savanna, in the northern Brazilian Amazon. Soil samples were collected at 10-cm intervals up to 1 m in depth at the border and in the interior of each fragment. Soil organic material concentration was determined with 10% HF solution and its elemental composition, thermogravimetric index, and 13C CPMAS NMR spectroscopic analysis were determined. There was no significant difference in the aromaticity index between border and interior. The concentration of alkyl C structures between border (22 to 25%) and interior (19 to 29%) indicated the occurrence of medium-intensity fires in the study area. The thermogravimetric analysis showed no significant difference in the thermal stability of SOM between border and interior. Our results showed no pronounced difference in SOM quality up to 1 m depth between the border and the interior of the evaluated forest fragments, indicating that this compartment is stable throughout the fragments.

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Section: Introductionmentioning

confidence: 99%

Effects of fire on soil organic matter in northern Amazonian forest fragments

et al. 2022

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“…Another common misconception is that the methods employed by wildfire researchers (BPCA, chemothermal oxidation, and others) detect pyrogenic molecules (i.e., BC) in environmental matrices. There is an expanding literature raising awareness that “BC methods” in fact do not measure fire-derived residues, but detect a certain type of structures (ConAC) in the analyzed sample. ,, In light of our findings, assuming that BPCA (and other) methods quantify BC would lead to major overestimations of environmental reservoirs and fluxes of “true” fire-derived carbon . This is especially notable for soils, where the non-pyrogenic process of soil formation (soil humification) produces ConAC, with biomass oxidation being a key process.…”

Section: Resultsmentioning

confidence: 72%

“…It must be noted that the aromaticity of soils (and of other types of environmental samples) depends on the concentrations of monoaromatics, polyaromatics, and ConAC. Thus, caution should be exercised to not assume that organic matter aromaticity comes exclusively from ConAC . While our ancillary characterizations suggest the production of non-condensed aromatics, such as polyphenols (Figures S2 and S4), quantitative methods, such as lignin-phenol quantification, are needed to discern the extent of which oxidation (via Fenton or other pathways) drives the natural organic matter aromaticity to increase.…”

Section: Resultsmentioning

confidence: 97%

Potentially Massive and Global Non-Pyrogenic Production of Condensed “Black” Carbon through Biomass Oxidation

Goranov,

Chen,

Duan

et al. 2024

Environ. Sci. Technol.

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With the increased occurrences of wildfires worldwide, there has been an increase in scientific interest surrounding the chemistry of fire-derived "black" carbon (BC). Traditionally, wildfire research has assumed that condensed aromatic carbon (ConAC) is exclusively produced via combustion, and thus, ConAC is equated to BC. However, the lack of correlations between ConAC in soils or rivers and wildfire history suggests that ConAC may be produced non-pyrogenically. Here, we show quantitative evidence that this occurs during the oxidation of biomass with environmentally ubiquitous hydroxyl radicals. Pine wood boards exposed to iron nails and natural weather conditions for 12 years yielded a charcoal-like ConAC-rich material. ConAC was also produced during laboratory oxidations of pine, maple, and brown-rotted oak woods, as well as algae, corn root, and tree bark. Back-of-the-envelope calculations suggest that biomass oxidation could be producing massive non-pyrogenic ConAC fluxes to terrestrial and aquatic environments. These estimates (e.g., 163−182 Tg-ConAC/year to soils) are much higher than the estimated pyrogenic "BC" fluxes (e.g., 128 Tg-ConAC/year to soils) implying that environmental ConAC is primarily non-pyrogenic. This novel perspective suggests that wildfire research trajectories should shift to assessing non-pyrogenic ConAC sources and fluxes, developing new methods for quantifying true BC, and establishing a new view of ConAC as an intermediate species in the biogeochemical processing of biomass during soil humification, aquatic photochemistry, microbial degradation, or mineral−organic matter interactions. We also advise against using BC or pyrogenic carbon (pyC) terminologies for ConAC measured in environmental matrices, unless a pyrogenic source can be confidently assigned.

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“…Increasing concerns about the priming effects by biochar have greatly improved our understanding of the flux of OC in amended soils. However, the effects of biochar on the molecular composition and speciation changes of native OC in soil, which are critical to fully assess the potential and viability of biochar application as a C sequestration strategy, remain largely unexplored. , This is largely due to the analytical difficulties in distinguishing the speciation of native OC in soil and OC from biochar and the long-term nature associated with OC speciation changes in the environment. The chemical complexity and spatial heterogeneity of SOC challenge the most advanced analytical techniques and impede our understanding of OC turnover in soil environments .…”

Section: Effect Of Biochar On C Cycling In Soilmentioning

confidence: 99%

Carbon Sequestration Strategies in Soil Using Biochar: Advances, Challenges, and Opportunities

Luo

Wang

et al. 2023

Environ. Sci. Technol.

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Biochar, a carbon (C)-rich material obtained from the thermochemical conversion of biomass under oxygen-limited environments, has been proposed as one of the most promising materials for C sequestration and climate mitigation in soil. The C sequestration contribution of biochar hinges not only on its fused aromatic structure but also on its abiotic and biotic reactions with soil components across its entire life cycle in the environment. For instance, minerals and microorganisms can deeply participate in the mineralization or complexation of the labile (soluble and easily decomposable) and even recalcitrant fractions of biochar, thereby profoundly affecting C cycling and sequestration in soil. Here we identify five key issues closely related to the application of biochar for C sequestration in soil and review its outstanding advances. Specifically, the terms use of biochar, pyrochar, and hydrochar, the stability of biochar in soil, the effect of biochar on the flux and speciation changes of C in soil, the emission of nitrogen-containing greenhouse gases induced by biochar production and soil application, and the application barriers of biochar in soil are expounded. By elaborating on these critical issues, we discuss the challenges and knowledge gaps that hinder our understanding and application of biochar for C sequestration in soil and provide outlooks for future research directions. We suggest that combining the mechanistic understanding of biochar-to-soil interactions and long-term field studies, while considering the influence of multiple factors and processes, is essential to bridge these knowledge gaps. Further, the standards for biochar production and soil application should be widely implemented, and the threshold values of biochar application in soil should be urgently developed. Also needed are comprehensive and prospective life cycle assessments that are not restricted to soil C sequestration and account for the contributions of contamination remediation, soil quality improvement, and vegetation C sequestration to accurately reflect the total benefits of biochar on C sequestration in soil.

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Black (pyrogenic) carbon in soils and waters: a fragile data basis extensively interpreted

Cited by 26 publications

References 68 publications

Effects of fire on soil organic matter in northern Amazonian forest fragments

Effects of fire on soil organic matter in northern Amazonian forest fragments

Potentially Massive and Global Non-Pyrogenic Production of Condensed “Black” Carbon through Biomass Oxidation

Carbon Sequestration Strategies in Soil Using Biochar: Advances, Challenges, and Opportunities

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