Radiocarbon and stable carbon isotopic evidence for transport and transformation of dissolved organic carbon, dissolved inorganic carbon, and CH4 in a northern Minnesota peatland
Radiocarbon and stable carbon isotopic evidence for transport and transformation of dissolved organic carbon, dissolved inorganic carbon, and CH4 in a northern Minnesota peatland
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DOI：
10.1029/1999gb001221
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发表时间：
2000-12-01
影响因子：
5.2
通讯作者：
Rivers, JS
中科院分区：
文献类型：
--
作者：
Chasar, LS;Chanton, JP;Rivers, JS
为了阐明水文和植被在泥炭地地下碳循环中的作用，对阿加西冰湖泥炭地孔隙水溶解有机碳（DOC）、溶解无机碳（DIC）、CH4和泥炭进行了放射性碳值测定。这项工作的主要含义是，泥炭柱内的微生物呼吸速率大于泥炭分解速率。沼泽和沼泽DOC的放射性碳含量相对于固相泥炭都增加了150- 300ppm，这与最近光合作用的DOC向下平流进入泥炭柱一致。DIC和CH4的δ C-14值与深层孔隙水DOC的δ C-14密切相关，表明这一近期植物产物是微生物呼吸的主要底物。在泥炭柱的上1 / 3处，主要以醋酸化产甲烷为主（α = 1.05），随着深度的增加，主要向CO2还原方向转移（α = 1.05 < < 1.08）。上升流地下水对沼泽深处整体DIC池的贡献高达15%。DIC和CH4的C-14值相似，表明产甲烷菌既利用了这一来源的DIC，也利用了原位产生的DIC。在所有深度，孔隙水DIC和CH4的δ C-14值相差小于或等于15‰，相对于DOC， δ C-14的损耗接近100‰，这表明微生物利用了旧基质和现代基质的混合物。CO2还原是沼泽所有深度甲烷生成的主要途径（a = 1.08），地下水对整体DIC的影响可以忽略不计。对于槽位，δ C-14-DIC和δ C-14-CH4在稳定同位素数据表明CO2还原优势的深度近似相等，而当醋酸发酵表明时则不同。
To elucidate the roles of hydrology and vegetation in belowground carbon cycling within peatlands, radiocarbon values were obtained for pore water dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), CH4, and peat from the Glacial Lake Agassiz peatland. The major implication of this work is that the rate of microbial respiration within a peat column is greater than the peat decomposition rate. The radiocarbon content of DOC at both bog and fen was enriched relative to solid-phase peat by similar to 150-300 parts per thousand consistent with the advection of recently photosynthesized DOC downward into the peat column. Fen Delta C-14 values for DIC and CH4 closely track the Delta C-14 of pore water DOC at depth, indicating that this recent plant production was the predominant substrate for microbial respiration. Aceticlastic methanogenesis apparently dominated the upper third of the peat column (alpha = 1.05), shifting toward CO2 reduction with depth (1.05 < < 1.08). Upwelling groundwater contributed as much as 15% of the DIC to the bulk DIC pool at depth in the fen. The similarity of C-14 values for DIC and CH4 suggests that methanogens utilized DIC from this source as well as DIC produced in situ. Bog Delta C-14 values for pore water DIC and CH4 differ by less than or equal to 15 parts per thousand at all depths and are depleted in C-14 relative to DOC by similar to 100 parts per thousand, suggesting microbial utilization of a mixture of older and modern substrate. CO2 reduction was the primary pathway for methanogenesis at all depths in the bog (a = 1.08), and groundwater influence on bulk DIC was negligible. For bath sites, Delta C-14-DIC and Delta C-14-CH4 are approximately equal at depths where stable isotope data indicate a predominance of CO2 reduction and dissimilar when acetate fermentation is indicated.