The role of pHT measurements in marine CO2-system characterizations
The role of pHT measurements in marine CO2-system characterizations
复制标题
DOI：
10.1016/s0967-0637(99)00031-x
复制
发表时间：
1999-11-01
影响因子：
2.4
通讯作者：
Millero, FJ
中科院分区：
文献类型：
--
作者：
Byrne, RH;McElligott, S;Millero, FJ
分光光度法 pH(T) 测量通常会产生约 +/- 0.0005 pH(T) 单位的不精确度。这种不精确度相当于总氢离子浓度的不精确度为 +/- 0.1%（其中 pH(T) = -log[H+]，且 [H+](T) 等于 [H+] + [HSO4-]）。在这种精度水平下，pH(T) 测量为其他 CO2 系统参数（CO2 逸度、总无机碳、总碱度）的质量控制评估提供了重要工具。对于本工作中考虑的大数据集，使用测量的 pH(T) 和总无机碳计算的 CO2、逸度和总碱度分别具有 0.15 和 0.1% 量级的相对精度。通过pH(T)和盐度归一化碱度计算的总无机碳的精度约为0.02%或更好。在这项工作中，使用 NOAA 1992 年北方秋季赤道太平洋 (EqPac) 数据集表明，通过 pH(T) 计算的 CO2 系统变量可用于提高直接测量参数的精度和准确度。通过本工作中描述的程序，1992 年 NOAA 数据集的初始版本中发现了重大问题，并且数据集得到了极大的改进。此外，在这项工作中，我们根据 pH(T) 的变化、分配给 tris 海水缓冲液的值以及磺酞 pH(T) 指示剂校准的相应变化，重新审视 CO2 系统热力学一致性问题。作为间甲酚紫的 pK 增加 +0.0047 的主要结果，CO2 逸度计算和测量与 NOAA 1992 年北方秋季 EqPac 数据集非常一致。我们还注意到，这是由于 NOAA 1992 年北方秋季数据集中使用的滴定剂酸浓度的重新分配所致。测量的总碱度与根据总碳和 pH(T) 计算的总碱度非常一致。 (C) 1999 Elsevier Science Ltd. 保留所有权利。
Spectrophotometric pH(T) measurements can routinely be obtained with an imprecision on the order of +/- 0.0005 pH(T) units. This level of imprecision is equivalent to an imprecision in total hydrogen ion concentration of +/- 0.1% (where pH(T) = -log[H+], and [H+](T) congruent to [H+] + [HSO4-]). At this level of precision, pH(T) measurements provide an important tool in quality control assessments of other CO2-system parameters (CO2 fugacity, total inorganic carbon, total alkalinity). CO2, fugacities and total alkalinities calculated using measured pH(T) and total inorganic carbon, for the large data set considered in this work, have relative precisions on the order of 0.15 and 0.1%, respectively. The precision of total inorganic carbon calculated via pH(T), and salinity-normalized-alkalinity is on the order of 0.02% or better. In this work, using the NOAA 1992 boreal autumn Equatorial Pacific (EqPac) dataset, it is shown that CO2-system variables calculated via pH(T) can be used to enhance both the precision and accuracy of directly measured parameters. Through the procedures described in this work significant problems were revealed in the initial version of the 1992 NOAA dataset, and the dataset was greatly improved. Additionally, in this work, we revisit CO2-system thermodynamic consistency issues in view of changes in the pH(T), values assigned to tris seawater buffers and consequential changes in the calibration of sulfonephthalein pH(T) indicators. As the principal result of a +0.0047 increase in the pK of meta cresol purple, CO2 fugacity calculations and measurements are in very good agreement for the NOAA 1992 boreal autumn EqPac dataset. We note, as well, that due to a reassignment of the titrant acid concentration used in the NOAA 1992 boreal autumn dataset. measured total alkalinities are in good agreement with total alkalinities calculated from total carbon and pH(T). (C) 1999 Elsevier Science Ltd. All rights reserved.