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Applications of Analytical Chemistry to Oceanic Carbon Cycle Studies Summary Understanding the chemical composition and processes of the ocean is of great importance because of a major role played by the ocean in regulating changes in the global environment. The ocean interacts with the atmosphere and land masses through complex cycles of biogeochemical and hydrological processes. To understand oceanic processes a range of measurements are required, from the poles to the equator as well as from the ocean surface to deep-ocean sediments. New techniques that allow precise measurements rapidly over extensive global areas and over a long term are needed to acquire information relevant to global change studies. Ocean scientists tend to rely on well-established techniques when making measurements, in order to maintain the compatibility of new data with data collected in the past. Measurement science is one of the most active fields of chemistry today. Advances in microelectronics, computers, and sensing devices have accelerated the development of measurement instruments and techniques. Many of these innovations could be used for ocean measurements, although some of the new methods are not well known to ocean scientists. The use of new techniques of analytical chemistry for ocean science applications is impeded by limited interactions between ocean scientists and analytical chemists. Significant technical innovations will be required to make many of the new techniques amenable to the ocean environment, however. A group of analytical chemists and ocean scientists was brought together by the Committee on Oceanic Carbon of the National Research Council (NRC) Ocean Studies Board to identify techniques of analytical chemistry
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Applications of Analytical Chemistry to Oceanic Carbon Cycle Studies that could be used in ocean science. This report highlights the state of the art of measurement technologies offering new promise for ocean measurements. In particular, the group focused on new techniques for measuring seawater analytes that are important for understanding key aspects of the ocean's role in the global carbon cycle. The committee also noted other seawater analytes whose improved measurement would contribute to a better understanding of ocean processes. The report does not encompass all areas of chemical oceanography; instead, it highlights a subset of the possible measurements that could be useful for obtaining improved understanding of the global carbon cycle. The report focuses on in situ measurements of dissolved analytes in seawater that might not be feasible in the near future but could play an important role in global ocean observations of the future. The committee believes that the most difficult problem is in designing sensors of the desired selectivity, stability, and sensitivity for dissolved analytes in the open ocean. The committee acknowledges that the particulate flux of carbon out of the euphotic zone, the transformation of particles, and sedimentation and diagenesis on the seafloor are important processes that need to be understood for a full characterization of the ocean carbon system. However, the focus on dissolved analytes was selected because one objective of this report is to interest analytical chemists in applying their techniques to ocean studies. Furthermore, some of the sensor techniques discussed in this report may be modified and engineered for in situ measurements of dissolved species in pore waters of sediments. This report identifies technical hurdles and opportunities and discusses the role that government and academia can play in overcoming the nontechnical barriers to successful research, development, and transfer of these technologies to the ocean science community. Major conclusions and recommendations, discussed in detail at the end of this report, fall into two major categories, the role of the federal government and the role of academic scientists. Achievement of the recommendations will require cooperative activities between the federal government, industry, and academia (NRC, 1992). SUMMARY OF RECOMMENDATIONS Among the variety of techniques that could be developed for ocean measurements in the future, research and development in several areas seems to hold promise to improve capabilities for ocean measurements, including long-term remote, profiling, and shipboard sensors. The report specifies the priority analytes that must be measured to improve our understanding of the ocean's role in the global carbon system. The committee recommends that resources be made available to attract specialists in synthetic or
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Applications of Analytical Chemistry to Oceanic Carbon Cycle Studies ganic chemistry and polymer materials to develop systems that rely on selective reactions (recognition chemistry) for ocean measurements. Biosensors are becoming available for a variety of analytes and could contribute to ocean measurement techniques. Other research areas that will undoubtedly improve measurement capabilities include electrode and sensor design and mathematical techniques for experimental optimization. New measurement techniques are now available because of advances in microcomputer control and analysis. Development of microcomputer-based in situ instruments is another area of great potential for control of sampling, analysis, and communication by remote instruments. The report describes the attributes of an ideal in situ sensor. Research will be required to improve these characteristics for sensors that will be deployed on long-term remote moorings or autonomous vehicles. The constraints listed are less applicable for profilers, for which speed of the measurement, selectivity, and reversibility are more important. New techniques must be compared extensively with existing methods, so that the continuity of time-series observations and their quality will be assured. Development and long-term maintenance of relevant standards and calibrants are needed to assure data continuity and are an integral part of the long-range global observations that represent the backbone of global change studies. The Federal Government's Role The federal government must take the lead in supporting the research and development effort for ocean instrumentation because the government, through its agencies, is the beneficiary and ultimate consumer of most ocean measurements. Regardless of the approaches taken, it is clear that a considerable investment of time and resources will be required to develop the arsenal of chemically selective and stable host compounds that will be required to measure all the key oceanic species via in situ chemical sensor technology. Relevant standards and calibrants are vital to the ability of chemical oceanographers to make analytical measurements of quality high enough to be useful for studies of global change. The committee recommends that agencies supporting new ocean measurement technology, such as the Department of Energy, the National Science Foundation, the National Oceanic and Atmospheric Administration, the National Institute of Standards and Technology, and the Office of Naval Research, devote a portion of their budgets to support development and maintenance of standards and calibrants. Finally, the federal government could ensure that resources are available for instrument development. A major premise of this report is that improved ocean instrumentation will be necessary to acquire the data neces-
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Applications of Analytical Chemistry to Oceanic Carbon Cycle Studies sary to evaluate global change. The committee recommends that the federal government take steps to expedite instrument development. There are a range of approaches that might be taken, some of which could be accomplished by reprogramming existing funding rather than allocation of new fiscal resources. One possible step would be to establish research buoys and vessels that would serve primarily as test platforms for instrumentation. The time frame for instrument development often exceed the duration of research grants. Therefore another step to improve the instrument development process would be for federal agencies to devote some of their instrument development funds of long-term (7 to 10 years) grants and to maintain instrument engineering groups. The Role of Academic Scientists The committee chose to categorize analytes into groups with different levels of priority for measurement in the mid-term future; priorities are based on the committee's charge "to recommend new technologies for the measurement of carbon dioxide and other biologically important elements and compounds." In order to promote interdisciplinary activities between oceanographers and analytical chemists, the committee recommends that oceanographers identify a limited number of analytes on which analytical chemists can focus. This report lists analytes that are most important for studies of the ocean carbon cycle; development of techniques and instrumentation for these analytes is a priority for such studies. As new techniques become commonplace and new information is gathered, it is possible that a reprioritization of the analytes will be necessary, with a concentration of resources to solve the most important remaining measurement problems. The committee recognizes that successful implementation of a development effort for ocean instrumentation requires extensive ongoing transfer of information and opportunities between the ocean science and analytical chemistry communities. The committee recommends a multipronged approach to disseminating information to the chemistry community in general and the analytical chemistry community in particular. In addition, the committee believes that an effort should be undertaken to apprise both the public and undergraduate and graduate students of the opportunities in this field. A number of potential vehicles for accomplishing these goals are discussed in the recommendation section.
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