Purification and Calibration of Indicators for Measurement of Seawater pH

化石燃料燃烧产生的不断增加的大气二氧化碳极有可能导致显著的全球变暖(IPCC，2007)。大气中二氧化碳含量上升的另一个较少讨论的方面是海洋酸化。最近(2006年)对沿152W的1991年北太平洋断面的重新调查发现，水柱上部200米的PH值变化约为0.025个PH值单位(Byrne等人，在PREP中)。这种变化很重要，因为pH对溶液的形态和生物有效性、表面化学(包括活细胞的表面化学)、矿物的溶解(包括钙质生物的溶解)以及氧化和还原动力学都有很大的影响。凭借0.0004个pH单位的机载精度，分光光度测量提供了一种在短期和长期范围内快速而准确地监测酸化的方法。自1990年以来，分光光度法在海洋和河口pH分析中得到了广泛的应用。然而，由于指示剂染料中存在不同浓度的杂质，因此pH指示剂的校准可能变得不可靠。根据指示剂的来源(制造商)的不同，杂质可能会导致高达0.01个单位的pH值差异。因此，比较从不同实验室获得的海水PH值结果是有问题的。在这个项目中，南佛罗里达大学的研究人员将表征不同pH指示剂的杂质，并对指示剂进行提纯。提纯的指标将作为标准参考材料，并将提供给研究界。提纯的指示剂将通过实验进行仔细的重新表征(平衡常数和摩尔吸光度比的测量)，以提供真正的无校准测量。最佳提纯程序的公布将使研究人员能够提纯自己的指示剂。使用校准的pH标准物质也将使研究人员能够纠正以前用不纯试剂获得的数据。就更广泛的影响而言，该项目将把研究生教育作为关键优先事项。USF海洋科学学院在创新少数群体参与研究生研究和教育方面有着很好的记录。首席调查员担任两名少数民族学生的首席顾问。海洋科学学院有面向高中生和本科生的外展项目。PI成功地让参与研究和出版的本科生参与其中。拟议的项目还将促进少数民族学生、本科生和研究生的机会。

It is highly probable that the ever-increasing atmospheric CO2 from fossil fuel burning will lead to substantial global warming (IPCC, 2007). A less-discussed aspect of rising atmospheric CO2 is ocean acidification. A recent reoccupation (2006) of a 1991 North Pacific transect along 152 W revealed pH changes in the upper 200 meters of the water column on the order of 0.025 pH units (Byrne et al., in prep). Such changes are important because pH has a very strong influence on solution speciation and bioavailability, surface chemistry (including that of living cells), mineral solubility (including that of calcareous organisms), and oxidation and reduction kinetics. With on-board precision on the order of 0.0004 pH units, spectrophotometric measurements offer a quick and precise means of monitoring acidification on both short and long-term scales. Since 1990 spectrophotometric pH measurements have been widely used in oceanic and estuarine pH analysis. However due to the presence of impurities, at variable concentrations in indicator dyes, the calibrations of pH indicators can become unreliable. Depending on the source (manufacturer) of an indicator, impurities can cause pH differences as large as 0.01 units. As such, comparison of seawater pH results obtained from different labs is rendered problematic. In this project, researchers at the University of South Florida will characterize the impurities of different pH indicators and purify the indicators. The purified indicators will serve as standard reference materials and will be made available to the research community. Purified indicators will be carefully re-characterized experimentally (measurements of equilibrium constants and molar absorbance ratios) to provide truly calibration-free measurements. Publication of the optimal purification procedures will allow researchers to purify their own indicators. Use of calibrated pH reference materials will also allow researchers to correct data that had been obtained previously with impure reagents. In terms of broader impacts, this project will feature graduate student education as a key priority. The USF College of Marine Science has a strong record of innovative minority participation in graduate student research and education. The principal investigator serves as principal advisor to two minority students. The College of Marine Science has outreach programs for both high school students and undergraduates. The PI has successfully involved participating undergraduate students in both research and publication. The proposed project will also promote opportunities for minority students, undergraduate students, and graduate students.