Effect of nutrient enrichment on δ13CH4 and the methane production pathway in the Florida Everglades
Effect of nutrient enrichment on δ13CH4 and the methane production pathway in the Florida Everglades
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DOI：
10.1002/jgrg.20122
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发表时间：
2014-07
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影响因子：
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通讯作者：
M. Holmes;J. Chanton;H. Bae;A. Ogram
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文献类型：
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作者：
M. Holmes;J. Chanton;H. Bae;A. Ogram
佛罗里达大沼泽地的水源保护区2A的特征是营养梯度，北部农业径流量高，南部内陆贫营养状况较好。基于实验室培养和实地研究，我们发现，甲烷（CH 4）生产机制的相对重要性转移沿着这一梯度，更大的贡献，由于氢营养产甲烷在更高的营养水平。通过室内实验确定了氢营养型和乙酸裂解型甲烷生成的相对贡献，并与现场结果进行了验证。在实验室中，这两种途径的相对贡献，确定从土壤中收集的站点沿着营养梯度，与和不与抑制剂乙酸裂解甲烷（甲基氟，CH 3F）培养的CH 4生产率的差异。在养分贫乏的土壤中，大部分CH 4是通过乙酸发酵形成的，只有25%来自氢营养甲烷生成。在受营养物影响的地点，甲烷的产生率高出四倍，通过氢营养甲烷生成产生的甲烷比例增加到50%。从土壤培养物中计算氢营养型和乙酸裂解型甲烷生成的同位素分馏因子，并将其应用于在同一样带的孔隙水中测量的δ 13 C-CO2和δ 13 C-CH 4。在田间数据中反映了沿养分影响梯度的氢养甲烷相对于乙酸裂解甲烷产量沿着增加的趋势，这产生了与实验室培养工作相似的结果，在养分缺乏的地点，氢养甲烷产生的甲烷高达23%，在养分影响的地点，近一半。
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 (CH4) 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 from the differences in CH4 production rates in soil collected from sites along the nutrient gradient that was incubated with and without an inhibitor of acetoclastic methanogenesis (methyl fluoride, CH3F). In the nutrient‐poor soil, most of the CH4 was formed via acetate fermentation and only 25% came from hydrogenotrophic methanogenesis. At the nutrient‐impacted site CH4 was produced at fourfold higher rates and the proportion of CH4 produced via hydrogenotrophic methanogenesis increased to 50%. Isotopic fractionation factors for hydrogenotrophic and acetoclastic methanogenesis were calculated from the soil incubations and applied to δ13C‐CO2 and δ13C‐CH4 measured in pore water from the same transect. The trend of increased hydrogenotrophic relative to acetoclastic CH4 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 CH4 produced from hydrogenotrophic methanogenesis at the nutrient‐poor site and nearly half at the nutrient‐impacted site.