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BEHAVIOUR OF PLUTONIUM AND AMERICIUM IN THE MARINE ENVIRONMENT

Objective

THE GOAL OF THE PROJECT IS TO STUDY THE PROCESSES CONTROLING THE DISTRIBUTION OF RADIOACTIVE AND HEAVY METALS POLLUTANTS IN THE COASTAL MARINE ENVIRONMENT.
IT WILL BE ESTABLISHED THE DISTRIBUTION AT SEA OF PU AND AM AND IT WILL BE DETERMINED THE INVENTORIES OF THESE RADIONUCLIDES ON THE CONTINENTAL SHELF, THE CONTINENTAL SLOPE AND ON THE DEEP OCEAN FLOOR. FROM DIFFERENCES IN INVENTORIES IN THE THREE DEPTH REGIMES IT IS EXPECTED TO MAKE CLEAR THE CAUSES OF THE EXPECTED INVENTORY DECREASES IN DEEPER WATER. PARTICULARLY IT WILL BE INVESTIGATED THE ROLE THAT PARTICLE POPULATIONS PLAY IN REMOVING PU AND AM FROM SEAWATER.
ALSO IT IS EXPECTED TO ESTABLISH THE CORRESPONDENCE IN BEHAVIOUR OF PU AND AM WITH HEAVY METALS THAT ARE, LIKEWISE, PARTICLE REACTIVE. THROUGH STATISTICAL TREATMENTS OF THE DISTRIBUTIONS OF THE POLLUTANTS IT WILL BE SPECIFIED WHICH HEAVY METALS BEHAVE LIKE THE TRANSURANICS AND WHICH DO NOT.
The behaviour of radionuclides and, in particular, transuranides in sea water has been studied in several sea areas. Radionuclide concentrations generally decrease as water depth increases. There is a an increase at the south of Almanzora river mouth and a decrease along the coast (this fact could be due to better scavenging of radionuclides by the particulate matter coming from the river or to a radionuclide input which took place in the Almanzora river). The radionuclide concentrations were similar to those found in other Mediterranean areas except in one small area located south of Almanzora river mouth. Heavy metals show a constant distribution over the shelf and slope and an increment close to a minerals treatment plant (Portman).
IN THE FOLLOWING, DETAILED PROPOSED ACTIVITIES ARE DESCRIBED:
A. SAMPLING OF SEDIMENT CORES
SEDIMENT CORES WILL BE RAISED BETWEEN CABO DE GATA AND CABO DE PALOS FROM THE CONTINENTAL SHELF, CONTINENTAL SLOPE AND OCEAN FLOOR NEAR THE BASE OF CONTINENTAL SLOPE. THE CORES WILL BE TAKEN ON TWO SAMPLING LINES OFFSHORE FROM THE COAST AND ALSO ON LINES NEAR THE TWO CAPES. IT WILL BE OBTAINED SAMPLES FROM DIFFERENT DEPTHS.
THE CORES, 18 CM DIAMETER AND 40 CM LENGHT, WILL BE COLLECTED AND EXTRUDED WITH A RECENTLY DESIGNED BOX CORER-EXTRUDER PARTICULARLY SUITABLE FOR MARINE POLLUTION STUDIES. THEY WILL BE SECTIONED INTO THE 1 CM INCREMENTS. THE DIMENSIONS OF CORE ARE ENOUGH TO HAVE SUFFICIENT MATERIAL FOR THE REQUIRED ANALYSES AND TO RETRIEVE THE ENTIRE HISTORY OF THE IMPACT OF MAN-MADE RADIOACTIVITY.
B. CHEMICAL ANALYSES
IT IS PLANNED TO ANALYSE THE SEDIMENT CORES FOR PU-239/240, PU-238, AM-241, CS-137 AND PB-210. SPECIFICALLY, THE SEPARATION OF AM AND PU IN THE ENVIRONMENT IN RESPONSE TO THEIR CHEMICAL DIFFERENCES IS NOT WHOLLY UNDERSTOOD AND CAN BE INVESTIGATED THROUGH THE CHANGING AM/PU RATIOS. CS-137 WILL BE MEASURED BECAUSE OF ITS PRESENCE IN FALLOUT. RATIOS OF PU/CS AND AM/CS CAN BE COMPARED AS A GUIDE TO DISTINGUISHING BETWEEN THE SOURCES OF THE TRANSURANICS IN THE REGION. THIS QUESTION WILL BE INVESTIGATED MORE THROUGHLY BY MEASURING PU ISOTOPE RATIOS BY MASS SPECTROMETRY IN A FEW SAMPLES CAREFULLY SELECTED. PB-210 WILL BE MEASURED TO CALCULATE SEDIMENTATION RATES FROM THE EXCESS OF THIS RADIONUCLIDE IN THE UPPER LAYERS OF THE SEDIMENT CORES.
IT WILL BE DEVOTED OF THE ATTENTION TO DEMONSTRATING THAN THE RESULTS ARE ACCURATE AND INTERCOMPARABLE THROUGH THE EXCHANGE OF SAMPLES BETWEEN PARTICIPANTS, THE ANALYSIS OF CERTIFIED STANDARDS AND, IF NECESSARY, THE EXCHANGE OF METHODS.
IT IS ALSO PLANNED TO MEASURE A SUITE OF STABLE HEAVY METALS BY ATOMIC ABSORPTION SPECTROMETRY (FE, MN, PB, HG AND CR), SPECIFICALLY THE FRACTION ASSOCIATED WITH HYDROUS FE AND MN OXIDE COATINGS ON THE SURFACE OF SEDIMENT PARTICLES (TREATMENT OF THE SEDIMENT WITH HYDROXYLAMINE HYDROCHLORIDE AND CITRATE-DITHIONATE).
C. SUPPORTING MEASUREMENTS
IN ORDER TO HAVE A BEARING ON GEOCHEMICAL INTERPRETATION OF THE DATA AND TO ESTABLISH THE GEOLOGICAL SETTING IN THE STUDY AREA, IT WILL BE STUDIED VARIOUS PARAMETERS INCLUDING GRAIN SIZE ANALYSIS, GRAIN MINERALOGY AND POROSITY MEASUREMENTS IN THE SEDIMENTS. IN PARTICULAR IT IS ACCEPTED THAT POROSITY IS CLOSELY CORRELATE WITH PU CONCENTRATIONS IN SURFACE LAYERS OF THE SEDIMENTS.
IT IS ALSO PROPOSED TO STUDY THE SEASONAL CYCLE PARTICLE POPULATIONS IN WATER SAMPLES COLLECTED FROM THE SURFACE AND NEAR BOTTOM AT EACH OF SEVERAL STATIONS LOCATED ON FIVE LINES AT DEPTH CONTOURS OF 10M, 25M, 50M, 100M AND 200M, BETWEEN THE TWO ABOVE MENTIONED CAPES. THE MOST RECENT RESEARCH SUGGESTS THAT PARTICLE CONCENTRATIONS IN THE SEA LARGELY CONTROL THE REMOVAL TO THE SEDIMENTS OF PU AND OTHER PARTICLE REACTIVE POLLUTANTS.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

JUNTA DE ENERGIA NUCLEAR
Address
Avenida Complutense 22
28040 Madrid
Spain