STRENGTHS AND LIMITATIONS OF PROPOSED RESEARCH 



Strengths. Sediments are the natural integrators of carbon-cycle processes in the sea, providing 

 time-averaged information on particle transport and deposition which is free from assumptions 

 about the behavior of artificial particle collectors. Thus sediment chronologies are the natural (and 

 perhaps the only reliable) techniques for assessment of the long- term (years - millennia) rates 

 of carbon burial and its impact on atmospheric C0 2 . 



Limitations. Along most of the Atlantic margin of North America long-term sediment 

 accumulation rates do not exceed a few tens of centimeters per 1000 years. Such rates provide 

 little resolution of modern trends in sediment accumulation. Indeed, in many places bioturbation 

 has mixed the sedimentary record of the last two centuries, the period of most critical human 

 impact on the carbon cycle, into sediments deposited during the last 1000- 2000 years. Thus 

 inferences from sediments as to the recent past are often more model-dependent than one would 

 like. In addition, sedimentary geochemistry and radiochemistry are labor-intensive, and very little 

 of the labor can be performed at sea. 



STATUS OF RESEARCH 



Relative to our expectations, we are currently sample-rich and data-poor; this resulted 

 from our spending a month at sea in year two, rather than the five days for which we had 

 planned. We have made good progress on screening analyses of our several hundred samples: 

 we have loss-on-ignition for all, gamma spectrometry on most, scattered grain-size measurements 

 (emphasizing % mud). We are presently implementing carbonate analysis, and as we will use 

 the same samples for multiple measurements, this will carry through to most of the remaining 

 wet-chemical and radiochemical analyses. The aforementioned analyses we regard as "screening" 

 for 14-C, in that the data are needed either to assess the feasibility of 14-C determination (LOI 

 or % organic C, % carbonate C) or to place 14-C data in context. 



Our samples for 14-C analysis are stored frozen from the time of collection. Advice of 

 colleagues that these samples should be freeze-dried, rather than oven-dried, for 14-C analysis 

 has been borne out in preliminary comparisons of carbon contents in sample splits dried by both 

 methods. Lacking access to a conventional freeze-drying apparatus, we have assembled one from 

 parts, and we are systematically freeze-drying samples for 14-C analysis. Our large samples 

 require 1-2 days to freeze-dry. Dried samples are again stored frozen. 



Planning for, executing, and curating and screening samples from, our cruises has left too 

 little time in the laboratory, and the 14-C line is still not operational. We plan final 

 modifications of the combustion train for early this summer. Then we will begin synthesizing 

 and counting benzene. Again, however, we are committed to substantial field work for which 

 we did not plan: the Gyre cruise in June- July (16 days) affords an opportunity to sample 

 Chesapeake Bay; a NOAA/DOE-funded submersible in August provides access to the seafloor, 



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