Development of Spectrophotometric pH Measurement Capabilities in Estuaries

需要非常精确的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CO2平衡。 经过几十年对一系列随pH值变化而改变颜色的有机分子（称为pH指示剂染料）的仔细化学表征，这种准确性可以用于全浓度海水。 在河流淡水和海水交汇的动态沿海系统中，物理化学和pH值的巨大变化使得非常准确的pH值测量变得困难，并且无法常规获得。该项目的研究人员率先开发了海洋pH指示剂染料，将在测量沿海混合系统pH值所需的更广泛的条件（如温度、盐度）下扩展其化学特性。这项研究的结果将使海洋学家能够以目前不可能的准确度量化河流和海水之间界面处碳化学的变化，缓解pH测量的限制，并大大提高评估沿海系统海水CO2动态的信心。该项目将使研究生和本科生参与实地研究，使他们获得海洋学研究的实践经验，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。PI还计划继续他指导Eckerd学院和当地高中的暑期实习生的历史。目前纯化的磺酞指示染料的特性是高度特异性的，以测量“全强度”公海海水的pH值。 它们目前不足以在盐度低于20的系统中进行非常精确的pH测量。这在所有CO2系统变量（溶解无机碳、总碱度、CO2逸度等）中产生了不确定性。这与平衡计算中的pH值有关，从而阻碍了海洋学家以高度的置信度量化河口CO2动态的能力，这是研究不断变化的沿海碳循环所需的。在河口条件下对磺酞指示染料系列进行的METRONIC表征，结合以前的开放海洋工作，将使研究人员能够在0至40的盐度范围内进行高度精确和准确的pH值测量。将使用表征氢离子交换参数和磺基酞光谱吸光度行为的程序以及获得纯化指示剂的色谱程序进行校准。该项目产生的pH测量新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pH测量，这是天然沃茨准确物理化学表征的重大进步。

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.