Carbon isotope fractionation of dissolved inorganic carbon (DIC) due to outgassing of carbon dioxide from a headwater stream
Carbon isotope fractionation of dissolved inorganic carbon (DIC) due to outgassing of carbon dioxide from a headwater stream
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DOI：
10.1002/hyp.6833
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发表时间：
2008-07-01
影响因子：
3.2
通讯作者：
Boyer, Elizabeth W.
中科院分区：
文献类型：
--
作者：
Doctor, Daniel H.;Kendall, Carol;Boyer, Elizabeth W.
在美国佛蒙特州的Sleepers River Research流域，研究了溶解无机碳（δ C-13-DIC）的稳定同位素组成，作为径流生成过程的潜在示踪剂。下游取样显示，从流源到下游约0.5 km的出口堰，Δ C-13-DIC增加3-5%，同时pH值增加，PCO 2降低。从融雪期间收集的下游样带数据中观察到，过量PCO 2（流PCO 2归一化为大气PCO 2）减少的Δ C-13-DIC增加2.4 +/- 0.1份/千份/对数单位。同位素分馏DIC由于CO2脱气，而不是与大气CO交换，可能是主要原因增加三角洲C-13-DIC值下游时，PCO 2的地表淡水超过大气CO2浓度的两倍。虽然CO2放气导致流三角洲C-13-DIC值的普遍增加，局部地下水渗入流的点被确定为三角洲C-13-DIC的减少和DIC浓度的增加叠加在一般下游趋势的溪流。此外，融雪，早春和夏季之间的比较表明，DIC是从浅层地下水流路在融雪，并取代了更大比例的DIC来自土壤CO2在早春生长季节。因此，尽管从CO2释气的影响，三角洲C-13的DIC可以是一个有用的指示地下水添加到源头流和示踪剂的碳动态集水区。版权所有（c）2007约翰威利父子有限公司。
The stable isotopic composition of dissolved inorganic carbon (delta C-13-DIC) was investigated as a potential tracer of streamflow generation processes at the Sleepers River Research Watershed, Vermont, USA. Downstream sampling showed delta C-13-DIC increased between 3-5% from the stream source to the outlet weir approximately 0.5 km downstream, concomitant with increasing pH and decreasing PCO2. An increase in delta C-13-DIC of 2.4 +/- 0.1 parts per thousand per log unit decrease of excess PCO2 (stream PCO2 normalized to atmospheric PCO2) was observed from downstream transect data collected during snowmelt. Isotopic fractionation of DIC due to CO2 outgassing rather than exchange with atmospheric CO, may be the primary cause of increased delta C-13-DIC values downstream when PCO2 of surface freshwater exceeds twice the atmospheric CO2 concentration. Although CO2 outgassing caused a general increase in stream delta C-13-DIC values, points of localized groundwater seepage into the stream were identified by decreases in delta C-13-DIC and increases in DIC concentration of the stream water superimposed upon the general downstream trend. In addition, comparison between snowmelt, early spring and summer seasons showed that DIC is flushed from shallow groundwater flowpaths during snowmelt and is replaced by a greater proportion of DIC derived from Soil CO2 during the early spring growing season. Thus, in spite of effects from CO2 outgassing, delta C-13 of DIC can be a useful indicator of groundwater additions to headwater streams and a tracer of carbon dynamics in catchments. Copyright (c) 2007 John Wiley & Sons, Ltd.