PRINCIPAL 



INVESTIGATOR(S) Ken O. Buesseler 



Department of Marine Chemistry and Geochemistry 

 Woods Hole Oceanographic Institution 

 Woods Hole, MA 02543 



PROJECT TITLE DETERMINATION OF PARTICULATE ORGANIC CARBON 



FLUXES USING THORIUM-234 



AMOUNT OF FUNDING FY 1994: $0 K (This project is not currently funded within 



OMP) 



SUMMARY OF GOALS 



The goal is to quantify the vertical flux of particulate organic carbon from the surface 

 ocean. 



SPATIAL AND TEMPORAL SAMPLING SCALES 



The vertical particle flux will vary with season and location on the same scale as the 

 biology and particle resuspension fluxes. Since 234 Th has a 24 day half-life, its distribution at any 

 one time will reflect the net effect of scavenging and particle export over a period of a couple 

 of months. To make a reasonable 234 Th budget off of Hatteras, one would hope to have sampling 

 opportunities every other month, perhaps on a spatial scale equivalent to the 24 stations along 

 2-3 off shelf transects and one along shelf line identified in previous OMP documents. 



METHODS AND PLATFORMS 



Thorium can most efficiently be sampled using in-situ pumps. In JGOFS, we reduced the 

 sample load considerably combining water from multiple depths into a "vertically integrated" 

 average 234 Th activity, for example from the 0-100m layer. One could also sample from an 

 underway surface pump for mixed-layer 234 Th activities. A separation into dissolved and 

 particulate phases is made with in-line filtration, and POC/PON are determined as well. 



STRENGTHS AND LIMITATIONS OF PROPOSED RESEARCH 



Strengths include the ability to quantify particle export fluxes on spatial and temporal 

 scales equivalent to the biology and physics of the region. The measurement is relatively easy, 



21 



