Development of Spectrophotometric pH Measurement Capabilities in Estuaries

需要极其精确的pH值测量，以充分评估海水中无机碳化学的变化，因为它与大气中不断上升的二氧化碳保持平衡。经过几十年对一系列随pH变化而变色的有机分子(称为pH指示剂染料)的仔细化学表征，这种准确性对于全浓度海水是可能的。在河流淡水和海水相遇的动态沿海系统中，物理化学和酸碱度的巨大变化使得酸碱度的极准确测量变得非常困难，而且通常无法获得。该项目的研究人员率先开发了海洋pH指示剂染料，将把它们的化学特性扩展到更广泛的条件范围(例如，温度、盐度)，以测量沿海混合体系中的pH。这项研究的结果将使海洋学家能够以目前无法达到的精度量化河流和海水界面上碳化学的可变性，缓解pH测量的限制，并大大增强评估沿海系统海水二氧化碳动态的信心。这个项目将让研究生和本科生参加实地研究，让他们在海洋研究方面有实践经验，南佛罗里达大学的一名少数民族学生在论文中使用了这项研究的结果。这位PI还计划继续他指导埃克德学院和当地高中暑期实习生的历史。目前对纯化的磺化邻苯二甲酸指示剂的表征高度专一，用于测量‘全强度’开放海洋海水的PH值。它们目前不足以在盐度低于20的系统中进行极其准确的pH测量。这给所有二氧化碳系统变量(溶解无机碳、总碱度、二氧化碳逸度等)带来了不确定性。这与平衡计算中的pH值有关，从而妨碍海洋学家以研究沿海碳循环变化所需的高度信心对河口二氧化碳动态进行量化。在河口条件下对磺化酞类指示剂染料系列进行细致的表征，结合以前的公海工作，将使研究人员能够在盐度从0到40的范围内进行高精度和准确的酸碱度测量。将使用表征磺化邻苯二甲酸氢离子交换参数和光谱吸收行为的程序以及获得纯化指示剂的层析程序进行校准。该项目产生的新的酸碱度测量分析能力将使研究人员和沿海管理专业人员能够在湖泊、河流和混合盐度系统中产生可信的酸碱度测量结果，这是自然水域准确物理化学特征方面的重大进步。

Extremely accurate pH measurements are required to fully evaluate changes of the inorganic carbon chemistry in seawater as it equilibrates with rising atmospheric CO2. After decades of careful chemical characterization of a series of organic molecules that change color with changing pH, called pH indicator dyes, this accuracy is possible for full strength seawater. In dynamic coastal systems where riverine freshwater and seawater meet, large variations in the physical chemistry and pH have made extremely accurate measurements of pH difficult and not routinely available. The researcher on this project, having pioneered the development of oceanic pH indicator dyes, would extend their chemical characterization over the much broader range of conditions (e.g. temperature, salinity) required to measure pH in coastal mixed systems. Results from this research would allow oceanographers to quantify variability in carbon chemistry at the interface between rivers and seawater with accuracy not currently possible, relieving pH measurement constraints and allowing greatly increased confidence in evaluating seawater CO2 dynamics in coastal systems. This project will involve graduate and undergraduate students in field studies, giving them hands-on experience in oceanographic research, with results from this research used by a University of South Florida minority student in a dissertation. The PI also plans to continue his history of mentoring summer interns from Eckerd College and local high schools.Current characterizations for purified sulfonephthalein indicator dyes are highly specific to measure pH values in 'full strength' open ocean seawater. They are not currently adequate for making extremely accurate pH measurements in systems with salinities lower than 20. This creates uncertainties in all of the CO2 system variables (dissolved inorganic carbon, total alkalinity, CO2 fugacity, etc.) that are connected to pH in equilibrium calculations, thus hampering the ability of oceanographers to quantify estuarine CO2 dynamics with the high degree of confidence required to examine changing coastal carbon cycles. Meticulous characterization of the sulfonephthalein indicator dye series across estuarine conditions, combined with previous open ocean work, will allow for researchers to extend highly precise and accurate pH measurements over salinities from 0 to 40. The calibrations will be performed using procedures to characterize the hydrogen ion exchange parameters and the spectral absorbance behavior of sulfonephthaleins, as well as the chromatographic procedures to obtain purified indicators. The new analytical capability for pH measurements generated by this project will enable researchers and coastal management professionals to generate trusted pH measurements in lakes, rivers, and mixed salinity systems, a major advance in the accurate physical chemical characterization of natural waters.