Abiotic humification, dominated by catalytic oxidation, is one of the critical mechanisms for organic carbon preservation in nature. However, the effects of biochar catalysis on abiotic humification have not yet been elucidated. This study investigated the catalytic power of biochar from walnut shells at different temperatures (300 °C, 600 °C, and 900 °C) for the abiotic transformation of hydroquinone (HQ) as a representative polyphenol. All the biochar samples catalyzed HQ polymerization, resulting in the formation of humic polymers such as fulvic acids (FAs) and humic acids (HAs). Light and oxygen promoted HA formation. HO•was detected in the BC600–HQ reaction system, and HO•quenching resulted in a 41.22% decrease in HA production, indicating that HO•plays a major role in the oxidative polymerization. In the proposed pathway for the abiotic humification, biochar active sites and generated reactive oxygen species accept an electron from HQ, resulting in oxidation to (semi)quinone radicals, which subsequently undergo cleavage or a coupling reaction to form the oligomerized products. Under BC600 catalysis, the weight-average molecular weight (Mw) of the reaction products of HQ, glucose, and glycine reached 14,449 Da. These findings provide new insights into the application potential of biochar for promoting soil carbon sequestration.
This study presents the first comprehensive investigation on an easily neglected biogeochemical process of phenolic endocrine-disrupting chemical (EDC) capture and carbon sequestration by seagrass detritus. The results showed that Zostera marina L. detritus captured nonylphenol (NP) and bisphenol A (BPA) with high efficiency (>90%) and enhanced organic carbon sequestration in marine ecosystems. Under various seawater-sediment scenarios (pure seawater, nonburial, and burial systems), phenolic EDC rerelease rates were low (<20%), while total organic carbon (TOC) stocks increased by 21.5%–28.8% in EDC-treated groups compared to controls. Kinetic analyses revealed that NP and BPA were rapidly captured onto heterogeneous active sites of the detritus surface, with capture efficiency influenced by the physicochemical properties of contaminants, environmental factors, and the specific characteristics of the detritus. Laser scanning confocal microscopy (LSCM) and density functional theory (DFT) were employed to investigate synergistic mechanisms between phenolic EDCs and carbon at cellular and molecular levels. The lipids mediated NP sequestration through hydrophobic interactions with lipid-rich sites (such as phospholipids), while polysaccharides facilitated BPA binding via electrostatic interactions, highlighting their crucial roles in capturing phenolic EDCs. These findings reinforced the importance of seagrass meadows in capturing emerging contaminants and storing carbon in marine ecosystems.
Continuous straw returning is widely encouraged for augmenting soil organic carbon (SOC) in arable lands. However, the magnitude of changes in net SOC related to native SOC mineralization and new SOC development upon fresh straw incorporation remains elusive, particularly in soils after continuous straw returning with different strategies. To address this, soil that had undergone nine years of straw returning with different strategies (NS, non-straw returning; DS, direct straw returning; IS, indirect straw returning) was incubated with fresh 13 C-labeled straw for 45 days. Fresh straw incorporation stimulated native SOC-derived CO 2 emission in DS soil, which in turn promoted straw-derived CO 2 emission in IS soil. Overall, the amounts of newly developed SOC from straw (2.41–2.59 g C/kg soil) overcompensated for the native SOC losses (0.91–1.37 g C/kg soil) by mineralization, and led to net C sequestration in all treatments. No obvious difference was found in the amounts of SOC sequestrated from straw between the DS and NS soils, while the amount of native SOC mineralization increased by 40–50% in the DS soil relative to other treatments, thus resulting in lower net C sequestration in the DS soil (1.21 g C/kg soil) than IS and NS soil (1.43 and 1.65 g C/kg for IS and NS soil, respectively). Spearman's correlation analyses indicated a significant ( p < 0.01 ) and positive correlation between SOC contents and native soil C mineralization, while the soil microbial index played a greater role in influencing fresh straw sequestration ( p < 0.01 ). In conclusion, the DS soil showed a weaker effect on SOC sequestration than IS after 9 years of practices, upon fresh straw incorporation. This difference may be attributed to the magnitude of native SOC mineralization in the soil. Besides the straw-C input rate, results emphasize that native soil C protection should be also considered in long-term SOC sequestration practices.
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