提高海水pH测量准确度的定标方法研究

Research on a Calibration Method for Improving the Accuracy of Seawater pH Measurements

pH是海洋碳循环体系的重要参数之一,测量海水pH的标准方法有电极法和分光光度法,其中电极法已应用到海水pH的现场原位测量中,但准确度相对较低,限制了其在碳循环体系中的应用。文中采用人工海水pH标准缓冲溶液代替传统的NBS标准缓冲溶液对pH电极进行定标,探索了提高海水pH测量准确度的方法,并以分光光度法为标准方法,进行了实验研究和分析比对。结果表明:采用人工海水缓冲溶液定标后,电极法测量结果与分光光度法的测量结果偏差明显减小,测量准确度显著提高。该人工海水标准缓冲溶液可应用到pH传感器的现场标定中,从而提高海水pH现场测量的准确度,为海洋碳循环、海洋酸化等研究提供更为准确的基础数据。

pH is regarded as one of the most important parameters indicating the state of ocean carbon cycle system. The electrode method and spectrophotometry method are standard methods for seawater pH measurements. Currently,the electrode method has been applied to in-situ pH measurement, but with relatively low accuracy, which have restricted its application in the context of carbonate system. To improve the accuracy of the electrode method, a series of experimental research and analysis has been carried out by the pH electrode calibrated with synthetic seawater pH buffer solution instead of traditional NBS standard buffer solution, and with the spectrophotometric method as a standard method. The results show that the measurement error between the electrode method and spectrophotometry method has been significantly reduced, and the accuracy considerably improved using the electrode calibrated with synthetic seawater buffer. Therefore, the synthetic seawater standard buffer is expected to replace the traditional NBS buffer, and is employed for calibrating the pH electrode sensor, thus enhancing the accuracy of the pH measurements as well as presenting more accurate results for the marine carbon cycle.