ASSESSING THE BLANK CARBON CONTRIBUTION, ISOTOPE MASS BALANCE, AND KINETIC ISOTOPE FRACTIONATION OF THE RAMPED PYROLYSIS/OXIDATION INSTRUMENT AT NOSAMS
ASSESSING THE BLANK CARBON CONTRIBUTION, ISOTOPE MASS BALANCE, AND KINETIC ISOTOPE FRACTIONATION OF THE RAMPED PYROLYSIS/OXIDATION INSTRUMENT AT NOSAMS
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DOI：
10.1017/rdc.2017.3
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发表时间：
2017-02-01
期刊：
影响因子：
8.3
通讯作者：
McNichol, Ann P.
中科院分区：
文献类型：
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作者：
Hemingway, Jordon D.;Galy, Valier V.;McNichol, Ann P.
我们估计在典型的Ramped PyrOx（RPO）分析（150-1000 ℃; 5 ℃ × min（-1））过程中的空白碳质量为（3.7 +/-0.6）μ g C，Fm值为0.555 +/-0.042，Δ C-13值为（-29.0 +/-0.1）份/千VPDB。此外，我们提供了RPO Fm和Δ C-13空白校正的方程，包括相关的误差传播。通过比较RPO质量加权平均值和独立测量的环境样品和标准参考物质（SRM）汇编的整体δ C-13值，我们观察到RPO仪器内的δ C-13消耗量较小但一致（平均体积：μ = -0.8/1000; +/-1 sigma = 0.9/1000; n = 66）。相比之下，因为它们根据定义进行了分级校正，所以质量加权平均Fm值准确地匹配本体测量（平均-本体：mu = 0.005; +/- 1 sigma = 0.014; n = 36）。最后，我们发现，在碳酸盐SRM峰之间不存在显着的样品内δ C-13变异性，表明RPO分析期间质量依赖性动力学同位素分馏最小。这些数据最好通过0.3-1.8 J x mol（-1）的含C-13和含C-1 - 2的化合物之间的活化能差异（（13- 1 - 2）Δ E）来解释，表明空白和质量平衡校正的RPO Δ C-13值准确地将碳源同位素信号保留在1-2份/千份内。
We estimate the blank carbon mass over the course of a typical Ramped PyrOx (RPO) analysis (150-1000 degrees C; 5 degrees C x min(-1)) to be (3.7 +/- 0.6) mu g C with an Fm value of 0.555 +/- 0.042 and a delta C-13 value of (-29.0 +/- 0.1)parts per thousand VPDB. Additionally, we provide equations for RPO Fm and delta C-13 blank corrections, including associated error propagation. By comparing RPO mass-weighted mean and independently measured bulk delta C-13 values for a compilation of environmental samples and standard reference materials (SRMs), we observe a small yet consistent delta C-13 depletion within the RPO instrument (mean-bulk: mu = -0.8 parts per thousand; +/- 1 sigma = 0.9 parts per thousand; n = 66). In contrast, because they are fractionation-corrected by definition, mass-weighted mean Fm values accurately match bulk measurements (mean-bulk: mu = 0.005; +/- 1 sigma = 0.014; n = 36). Lastly, we show there exists no significant intra-sample delta C-13 variability across carbonate SRM peaks, indicating minimal mass-dependent kinetic isotope fractionation during RPO analysis. These data are best explained by a difference in activation energy between C-13- and C-12-containing compounds ((13-12)Delta E) of 0.3-1.8 J x mol(-1), indicating that blank and mass-balance corrected RPO delta C-13 values accurately retain carbon source isotope signals to within 1-2 parts per thousand.