Quantification of potential methane emissions associated with organic matter amendments following oxic-soil inundation

[摘要] Methane ( CH 4 ) emissions are a potent contributor to global warming, and wetlands can be a significant CH 4 source. In a microcosmstudy, we evaluated how the practice of amending soils with organic matter as part of wetland restoration projects may affect CH 4 productionpotential. Organic amendments including hay, manure, biosolids, composted yard waste, and wood mulch were evaluated at three different levels. Using1  L glass microcosms, we measured the production of biogenic gases over 60  d in two soils designated by texture: a sandy loam (SL)and a sandy clay loam (SCL). Fresh organic amendments increased CH 4 production, leading to potentially higher global warming potential andwetland C loss, and CH 4 production was more pronounced in SL. We observed biogenic gas production in two sequential steady-statephases: Phase 1 produced some CH 4 but was mostly carbon dioxide ( CO 2 ), followed by Phase 2, 2 to 6 weeks later, with higher totalgas and nearly equal amounts of CH 4 and CO 2 . If this is generally true in soils, it may be appropriate to report CH 4 emissions in the context of inundation duration. The CH 4 from the SCL soil ranged from0.003–0.8  cm 3 kg - 1 d - 1 in Phase 1 to 0.75–28  cm 3 kg - 1 d - 1 inPhase 2 and from SL range from 0.03–16  cm 3 kg - 1 d - 1 in Phase 1 to 1.8–64  cm 3 kg - 1 d - 1 inPhase 2. Adding fresh organic matter (e.g., hay) increased concentrations of ferrous iron ( Fe 2+ ), whereas in some cases composted organicmatter decreased both Fe 2+ concentrations and CH 4 production. Methanogenesis normally increases following the depletion ofreducible Fe; however, we observed instances where this was not the case, suggesting other biogeochemical mechanisms contributed to the shift ingas production.

[学科分类] 大气科学