How To Measure Dissolved Organic Matter In Seawater

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9402859 SHARP The measurement of dissolved organic carbon (DOC) has garnered renewed importance recently. This parameter is used by geochemists, biological oceanographers, and physical oceanographers in studies of global elemental fluxes and studies of ecosystem elemental cycling. In the past, DOC distributions were thought to show little variation in the ocean and to represent refractory remnants of biological activity. They were considered poorly measured parameters of little importance. Demonstrations in the past 10 years of apparently much higher concentrations in the ocean and large variations with depth caused considerable interest and excitement in the importance of DOC, especially in relation to ocean-atmosphere carbon interactions. With many analysts trying to measure DOC, controversy arose because of differences in reported concentrations as large as an order of magnitude. The principal investigator of this renewal proposal has been involved for the past two years with an attempted solution of the controversy; working closely with a steering committee and with a number of experienced analysts funded for routine DOC measurements in the Joint Global Ocean Flux Study. In a coordinator and referee role, he has been able to get agreement among analysts and variations are more on the order of +7.5% instead of the previous +100% or more. This agreement on analysis has come from careful attention to analytical blanks, method standardization, and carbon dioxide peak measurement, not from preconceived ideas of concentrations and distribution. A broad community DOC analytical comparison is now underway with participation by about 70 analysts from the United States and 17 other countries. The effort of the renewal proposal will: 1.) Complete the DOC community comparison; 2.) Make available reference materials to keep broad community standardization for DOC analyses; and 3.) Carry out research on collection and preservation of samples to avoid sporadic rapid changes in DOC concentrations from microbial activity. The large number of analysts interested and willing to participate in the methods comparisons plus a larger number who are not directly involved but who have been in contact with the principal investigator, indicates the interest in the international oceanographic and limnological communities and the urgency to complete the proposed project.