Collaborative Research: Collection, Testing, and Intercalibration of New Trace Metal Consensus Seawater Samples

About This Grant

Reliable concentration measurements of chemical elements require careful quality control. Part of this quality control depends on the use of reference materials of known concentration to assess the accuracy of measurements and intercalibrate between laboratories. For trace element concentration analyses of seawater, the supply of reference materials has become exhausted in recent years. This project aims to collect large samples of water from the Pacific Ocean and Gulf of Mexico to be used as a new set of reference materials. Trace metal concentrations will be measured by several experts using different methods and conditions. The concentration values will be compared against one another, and a consensus value will be developed by these experts using state-of-the-art statistics. The remainder of these large-volume water sample will be stored for distribution to the scientific community in the future. These consensus materials are expected to improve the quality and accuracy of seawater trace metal concentration data over the next decade. Several students will participate in the three research cruises and receive training on trace metal sampling and intercalibration studies. The project also provides support for an early career scientist. The primary objective of this project is to improve the quality of trace metal data in the ocean over the next decade through optimized methodologies and well-studied consensus samples that can be used to assess accuracy. Samples will be collected from the surface and 1000 m at Station ALOHA, which brackets common ranges of open ocean dissolved metal concentrations. In addition, two surface stations in the Gulf of Mexico that have lower salinities and higher organic content due to the influence of the Mississippi River outflow will be used to test the boundaries of sample storage and analytical intercalibration. Samples will be collected and homogenized within large volume tanks and dispensed into 500mL bottles for archiving and distribution to the community. These samples will be analyzed initially by fifteen laboratories worldwide for a suite of trace metal concentrations, to address two goals. First, the data will be compared statistically, via a collaboration with an expert statistician from the National Institutes of Standards and Technology, to calculate consensus concentration values for each element. This consensus concentrations will be reported on the GEOTRACES website, and the statistical best practices will be published. Second, this network of collaborators will explore common intercalibration issues that have arisen over the last decade by utilizing a range of analytical methodologies and conditions. The primary scientific impact of this project will be a set of well-studied consensus samples that can be used to monitor the accuracy of trace metal analyses of seawater over the next decade. This project will support one early-career scientist, one PhD student from the University of Southern California, and 5-15 graduate and/or undergraduate students from Texas A&M University who will participate in the staging and collection of samples from these expeditions. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.