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热带海洋学报

• • 上一篇    

两种测定海洋沉积物中碳酸盐含量的非器测方法对比分析

张强1, 2, 赵中伟1, 苏翔1, 赵璇1, 3, 李伟2   

  1. 1. 边缘海与大洋地质实验室, 中国科学院南海海洋研究所, 广东 广州 511458;

    2. 热带海洋环境与岛礁生态全国重点实验室, 中国科学院南海海洋研究所, 广东 广州 511458;

    3. 中国科学院大学, 北京 100049

  • 收稿日期:2025-07-16 修回日期:2025-09-05 接受日期:2025-09-10
  • 通讯作者: 张强
  • 基金资助:
    广东省基础与应用基础研究基金(2022A1515010932), 国家自然科学基金面上项目(42576068, 42076073), 中国IODP办公室

A comparison of two non-instrumental methodologies for determining carbonate content in marine sediments

ZHANG Qiang1, 2, ZHAO Zhongwei1, SU Xiang1, ZHAO Xuan1, 3, LI Wei2   

  1. 1. Laboratory of Ocean and Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 511458, China;

    2. State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 511458, China;

    3. University of Chinese Academy of Sciences, Beijing 100049, China

  • Received:2025-07-16 Revised:2025-09-05 Accepted:2025-09-10
  • Supported by:

    Guangdong Basic and Applied Basic Research Foundation (2022A1515010932); National Natural Science Foundation of China (42576068, 42076073); IODP-China.

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摘要： 碳酸盐是海洋沉积物中的重要组分, 其含量的准确测定是深入理解全球海洋碳酸盐沉积与溶解特性及碳酸盐系统对气候变化影响规律的重要基础。气量法和质量损失法是测定碳酸盐含量的常用非器测方法, 但两者在海洋沉积物碳酸盐含量测试中的精度与可靠性均未得到系统性评估和验证。本研究通过测定纯碳酸钙标准样品与盐酸溶液反应生成的二氧化碳(CO2)气体体积变化特征, 分析了CO2气体在盐酸溶液中的溶解特性, 发现在常温常压条件下, CO2气体在20ml ~18%盐酸溶液中的溶解比例为0.3~21.5%, 平均~9%。在此基础上, 分别利用气量法和改进后的质量损失法, 对不同碳酸盐含量的配制样品以及深海沉积序列样品开展了碳酸盐含量测试对比分析, 实验结果表明: 受CO2气体在盐酸溶液中溶解的影响, 气量法测定不同配制样品碳酸钙含量时的测量误差为0.3~18.2% (平均~4.4%), 标准偏差为5.4%；而改进后的质量损失法测量碳酸钙含量的误差为0.2~2.4% (平均~1.0%), 标准偏差为1.2%, 其测量准确度和稳定性均高于气量法, 且适应于白云岩化样品的碳酸盐含量测试。进一步将两种方法应用于IODP (International Ocean Discovery Program) U1553井位不同层位碳酸盐含量分析, 并与该井位已有的碳酸盐含量器测数据进行对比, 发现改进后的质量损失法比气量法更能准确地重现该井位的碳酸盐含量变化特征, 证实了质量损失法在深海沉积物碳酸盐含量测定中的可靠性和适应性。

关键词: 碳酸盐, 气量法, 质量损失法, 测量误差, 深海沉积物

Abstract: Carbonates constitute a critical component of marine sediments, and accurate determination of their content is fundamental to understanding global shifts in carbonate deposition and dissolution within the oceans, as well as the influence of carbonate system evolution on climate change. The gasometric method and weight-loss are typical non-instrumental approaches to carbonate quantification; however, the precision and reliability of both techniques in the analysis of marine sediment carbonates remain insufficiently evaluated. This study investigates the solubility characteristics of carbon dioxide (CO2) gas in hydrochloric acid (HCl) solutions, and finds that under typical temperature and pressure conditions, the solubility of CO2 within a 20ml approximately 18% hydrochloric acid solution in the gasometric device ranges from 0.3% to 21.5%, with a mean of 9%. Furthermore, using both the gasometric method and an improved weight-loss method, we conducted a comparative analysis of carbonate content in prepared samples with varying calcium carbonate concentrations, and in a deep-sea sedimentary sequence. The experimental results reveal that, due to CO₂ dissolution in HCl, the gasometric method induces an absolute error in carbonate concentration analysis ranging from 0.3% to 18.2% (mean = 4.4%), with a standard deviation of 5.4%. In contrast, the improved weight-loss method yields errors of only 0.2-2.4% (mean = 1.0%) and a substantially lower standard deviation of 1.2%. These findings indicate that the accuracy and stability of the weight-loss method for carbonate quantification are superior to those of the gasometric method. Moreover, a comparison of carbonate content results obtained by both methods in this study for samples derived from IODP (International Ocean Discovery Program) Site U1553 with those determined by coulometric titration reveals that the improved weight-loss method more accurately reproduces the carbonate content variations observed at Site U1553, further validating its reliability and applicability for determining carbonate content in deep-sea sediments.

Key words: Carbonate, gasometric method, weight-loss method, measurement error, deep-sea sediments