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Rapid Simulation of Decade-Scale Charcoal Aging in Soil: Changes in Physicochemical Properties and Their Environmental Implications.

Xiao ChenXiaodong GaoPingfeng YuLeonardo SpanuJessica HinojosaShuqi ZhangMingce LongPedro J J AlvarezCaroline A Masiello
Published in: Environmental science & technology (2022)
In situ aging can change biochar properties, influencing their ecosystem benefits or risks over time. However, there is a lack of field verification of laboratory methods that attempt simulation of long-term natural aging of biochar. We exploited a decade-scale natural charcoal (a proxy for biochar) aging event to determine which lab-aging methods best mimicked field aging. We oxidized charcoal by ultraviolet A radiation (UVA), H 2 O 2 , or monochloramine (NH 2 Cl), and compared it to 10-year field-aged charcoal. We considered seven selected charcoal properties related to surface chemistry and organic matter release, and found that oxidation with 30% H 2 O 2 most representatively simulated 10-year field aging for six out of seven properties. UVA aging failed to approximate oxidation levels while showing a distinctive dissolved organic carbon (DOC) release pattern. NH 2 Cl-aged charcoal was the most different, showing an increased persistent free radical (PFR) concentration and lower hydrophilicity. All lab oxidation techniques overpredicted polycyclic aromatic hydrocarbon release. The O/C ratio was well-correlated with DOC release, PFR concentration, surface charge, and charcoal pH, indicating the possibility to accurately predict biochar aging with a reduced suite of physicochemical properties. Overall, our rapid and verified lab-aging methods facilitate research toward derisking and enhancing long-term benefits of biochar application.
Keyphrases
  • organic matter
  • heavy metals
  • anaerobic digestion
  • risk assessment
  • radiation therapy
  • room temperature
  • nitric oxide