Spatial variations of scavenging rates within the central and northern Adriatic Sea: Use of U-Th disequilibria

Conference · Mon Apr 01 04:00:00 EST 1996

OSTI ID:231454

Hamilton, T ^[1]; Heilmann, J ^[2]; Fowler, S; Miquel, J C ^[3]

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1. Lawrence Livermore National Lab., CA (United States)
2. Danish Inst. for Fisheries and Marine Research, Charlottenlund (Denmark)
3. IAEA Marine Environment Lab., Monaco (Monaco)

Dissolved and particulate concentrations of {sup 234}Th, {sup 210}Pb and {sup 210}Po were measured in surface waters of the central and northern Adriatic Sea. The half-lives and biogeochemistry of {sup 234}Th (t{sub 1/2} = 24.1 days), {sup 210}Po (t{sub 1/2} = 138.4 days) and {sup 210}Pb (t{sub 1/2} = 22.3 years) are ideal for studying particle dynamics in the upper water column. It has been observed that the residence time of dissolved {sup 234}Th with respect to removal on biogenic particles is inversely proportional to primary productivity and may be used to predict export from or new production in the euphotic zone. Model-derived {sup 234}Th fluxes can also be used to help validate sediment trap collections in the upper water column. The aim of the present study was to gain an insight into the intensity and variability of active scavenging and particle removal processes in the central and northern Adriatic Sea. This semi-enclosed sea is strongly influenced by fresh water runoff from rivers carrying large quantities of dissolved nutrients and suspended particles. These inputs of nutrients and suspended particles are expected to give rise to large biological and biogeochemical gradients across the Continental Shelf and offer a range of environments for studying particle scavenging and removal processes. The authors have examined the relationships between {sup 234}Th scavenging rates and residence times of dissolved and particulate phases as a function of other physical and biological parameters (primary productivity, POC, chlorophyll, C/N and total suspended matter). Particular reference is made to the two contrasting environments of the Adriatic--a eutrophic zone near the Po River outflow and in the largely oligotrophic waters of the Jabuka Pit.

• Research Organization: Lawrence Livermore National Lab., CA (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 231454
• Report Number(s): UCRL-JC--123865; CONF-9604139--2; ON: DE96010833
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
ADRIATIC SEA
CONTAMINATION
HALF-LIFE
LEAD 210
POLONIUM 210
RADIATION MONITORING
RADIOECOLOGICAL CONCENTRATION
REMOVAL
THORIUM 234