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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >Effect of nutrient enrichment on δ~(13C)H_4 and the methane production pathway in the Florida Everglades
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Effect of nutrient enrichment on δ~(13C)H_4 and the methane production pathway in the Florida Everglades

机译：营养物质富集对佛罗里达大沼泽地δ〜（13C）H_4和甲烷生成途径的影响

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摘要

Water Conservation Area 2A in the Florida Everglades is characterized by a nutrient gradient with high levels in the north from agricultural runoff and more oligotrophic conditions in the southern interior. Based on laboratory incubations and field studies, we found that the relative importance of methane (CH_4) production mechanisms shifted along this gradient, with a greater contribution due to hydrogenotrophic methanogenesis at higher nutrient levels. The relative contributions of hydrogenotrophic and acetoclastic methanogenesis were determined from laboratory experiments and verified with field results. In the lab the relative contributions of the two pathways were determined fromthe differences in CH_4 production rates in soil collected fromsites along the nutrient gradient that was incubated with and without an inhibitor of acetoclastic methanogenesis (methyl fluoride, CH_3F). In the nutrient-poor soil, most of the CH_4 was formed via acetate fermentation and only 25% came from hydrogenotrophic methanogenesis. At the nutrient-impacted site CH_4 was produced at fourfold higher rates and the proportion of CH_4 produced via hydrogenotrophic methanogenesis increased to 50%. Isotopic fractionation factors for hydrogenotrophic and acetoclastic methanogenesis were calculated from the soil incubations and applied to δ~(13)C-CO_2 and δ~(13)C-CH_4 measured in pore water from the same transect. The trend of increased hydrogenotrophic relative to acetoclastic CH_4 production along the nutrient-impacted gradient was mirrored in the field data, which produced similar results to the lab incubation work, with up to 23% of the CH_4 produced fromhydrogenotrophic methanogenesis at the nutrient-poor site and nearly half at the nutrient-impacted site.
机译：佛罗里达大沼泽地水源保护区2A的特点是北部的营养物梯度较高，其农业径流的水平较高，而南部内部的营养营养状况则较差。基于实验室培养和现场研究，我们发现甲烷（CH_4）生成机制的相对重要性沿该梯度变化，这归因于营养水平较高时的氢营养甲烷化作用。通过实验室实验确定了氢营养和产甲烷分解甲烷生成的相对贡献，并得到了现场结果的证实。在实验室中，根据沿土壤养分梯度从现场采集的土壤中CH_4产生速率的差异确定了这两种途径的相对贡献，其中土壤中的营养梯度是在有和没有乙酰破伤性甲烷生成抑制剂（甲基氟，CH_3F）的条件下孵育的。在营养贫瘠的土壤中，大多数CH_4是通过醋酸盐发酵形成的，只有25％来自氢营养型甲烷生成。在受营养物影响的位点，CH_4的生成速率提高了四倍，并且通过氢营养型甲烷生成生成的CH_4的比例增加到50％。从土壤培养中计算出氢营养和乙酰碎屑甲烷生成的同位素分馏因子，并将其应用于同一样地的孔隙水中测得的δ〜（13）C-CO_2和δ〜（13）C-CH_4。沿田间数据反映了相对于乙酰破损CH_4产生的营养养分梯度而言，氢养分增加的趋势，其结果与实验室孵化工作相似，在营养贫乏的地方，高达23％的CH_4是由氢养分甲烷化产生的。在营养影响部位接近一半。

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