Carbon fluxes, pCO2 and substrate weathering in a large northern river basin, Canada: carbon isotope perspectives
Carbon fluxes, pCO2 and substrate weathering in a large northern river basin, Canada: carbon isotope perspectives
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DOI：
10.1016/s0009-2541(99)00034-0
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发表时间：
1999-07
期刊：
影响因子：
3.9
通讯作者：
K. Telmer;J. Veizer
中科院分区：
文献类型：
--
作者：
K. Telmer;J. Veizer
渥太华河流域低地碳酸盐支流和高地硅酸盐支流的溶解无机碳（δ13CDIC）同位素组成分别约为-8和-16‰。这表明(1)渥太华河DIC的来源是土壤呼吸和碳酸盐风化，(2)与大气的交换是单向的或体积上不重要的，(3)河内呼吸和光合作用对河流碳收支没有显着影响。接受这些限制，化学和同位素数据被用来重建支流流域的土壤 pCO2。据计算，高地硅酸盐盆地、混合盆地和低地碳酸盐盆地的平均值分别约为 2000、5000 和 30,000 ppm。这些值用作模拟碳通过流域的路径（雨水到土壤水到河水）的输入。渥太华河的碳通量以 DIC 计算为 4.3×1010mol C/a。利用碳同位素，计算出 75% 和 25% 的 Ca2++Mg2+ 通量分别源自碳酸盐和硅酸盐风化，计算出 61% 的 DIC 源自有机呼吸。假设平均呼吸速率为 0.5 mmol C m−2h−1，后者约占流域呼吸碳的 6%。根据扩散模型，渥太华河及其支流向大气中排放的二氧化碳估计为 1.3×1010mol C/a，即 DIC 通量的 30%。
Isotopic composition of dissolved inorganic carbon (δ13CDIC) in the Ottawa River basin is about −8 and −16‰ for lowland carbonate and upland silicate tributaries, respectively. This suggests that (1) the source of DIC to the Ottawa River is soil respiration and carbonate weathering, (2) exchange with the atmosphere is unidirectional or volumetrically unimportant, and (3) in-river respiration and photosynthesis are not significant influences on the river carbon budget. Accepting these constraints, chemical and isotopic data are used to reconstitute soil pCO2for tributary catchments. Averages for upland silicate, mixed, and lowland carbonate basins are calculated to be roughly 2000, 5000, and 30,000 ppm, respectively. These values are used as input to model the pathway of carbon through the watershed—rain water to soil water to river water. The flux of carbon from the Ottawa River as DIC is calculated to be 4.3×1010mol C/a. Utilizing carbon isotopes, 75% and 25% of the Ca2++Mg2+flux is calculated to originate from carbonate and silicate weathering, respectively, and 61% of the DIC is calculated to originate from organic respiration. The latter represents some 6% of respired carbon in the basin, assuming an average respiration rate of 0.5 mmol C m−2h−1. Based on a diffusion model, CO2evasion to the atmosphere from the Ottawa River and its tributaries is estimated to be 1.3×1010mol C/a or 30% of the DIC flux.