Description
The purpose of this LOI is to study the production method of a new radiotracer, within the
framework of the REMO/ ClimOcean project, dedicated to developing a novel methodology for
monitoring the effects of climate change on marine species using radioisotopes. Radio tracer
applications are essential instruments in evaluating the changes in some key biological processes,
e.g. primary production, growth and calcification rates. This knowledge is also essential for the risk
assessment of coastal ecosystems and the management of the stock of commercial species and to
understand the responses of organisms to pH changes. Radiotracers are used to study the main
changes of biological processes in selected marine organism (mollusks, crustaceans, seagrasses
etc.), e.g. calcifications using 41,45Ca.
The REMO/ClimOcean project aims monitoring the adaptation of marine species to Climate Change. Goal is the study of
the influence of the acidification of the seas and oceans on the growth of various species of coral,
bivalves and echinoderms, as they are organisms that build their skeleton or their shell through the
production of calcium carbonate. The uptake of isotopes of Ca (41Ca, 45Ca) into the exoskeleton is
used to determine the growth of those species, exposed to present and time projected (50-100
years) climatic conditions. Isotopic composition is determined by direct determination of the
emitted radiation (45Ca) or by the mass measurements performed with accelerator mass
spectrometry (41Ca). In the first case (45Ca) self-absorption of the radiation in the exoskeleton
represent a serious limitation for precise assessment of the growth rate. In the second case, since
successive measurements on the same individuum are not possible, genetic variability is affecting
the results.
A new radio tracer of potential interest is 85Sr, having a similar chemistry to Ca and with a half-life
of 64.849 D, compatible with the animal growth. The complementarity here is that, being a
gamma emitter, it allows a determination of the growth of the animal not affected by
the uncertainties discussed above, potentially allowing measurements without removing the animal
from water.
85Sr could be produced using the SPES cyclotron through the reaction 85Rb(p,n) 85Sr. The
production cross section is relatively large, being at 11.5 MeV of 794.6 mb. The idea is to use the 40
MeV proton beam of SPES, degrade it to the required energy using an appropriate Pb foils
(thicknesses 2mm), and direct it onto a target of pressed RbCl.
Therefore, with the starting of the operation/tests of the SPES cyclotron, we propose a short
exploratory run in which we test the 85Sr production at energies close to the maximum production
cross section (with the intention to minimize the contaminants).
Assuming an intensity of the proton beam of about 10 micrAmp, we estimate that about 2 day
of irradiation would be sufficient.
