Information depths of analytical techniques assessing whitefish otolith chemistry

A1 Originalartikel i en vetenskaplig tidskrift (referentgranskad)


Interna författare/redaktörer


Publikationens författare: J-O. Lill,V. Finnäs, Y. Heimbrand, M. Blass, S. Fröjdö, Y. Lahaye, J.M.K. Slotte, J. Nyman, E. Jokikokko, M. von Numers, H. Hägerstrand
Förläggare: Elsevier
Publiceringsår: 2019
Tidskrift: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms


Abstrakt

The elemental composition of otoliths
provides historical information on migration and provenance of fish. Due
to the complex structure of the otoliths, the depth from which the
elemental information originates has to be considered. In this work,
three analytical methods often used to assess otolith chemistry are
compared. The information depths are calculated for µ-XRF and PIXE and
measured for LA-ICP-MS. The information depth in PIXE depends on the
energy of the incident particles and on the element to be analysed while
in XRF it depends mostly on the element to be analysed as the energy of
the incident X-rays usually is high enough to excite atoms at depths of
several hundreds of micrometres. If we assume that the otolith is
exposed to X-rays from a Rh-tube (20.16 keV) about 50% of the detectable
Sr(Kα) X-rays will be emitted from a depth ranging from 0 to 114 µm. In
the case of PIXE with 3 MeV protons the corresponding range is 0–15 µm.
The information depths in LA-ICP-MS were determined by measuring the
depth of the laser-ablated craters or trenches that remained on the
otolith surface. The depths measured with a scanning white light
interferometer (SWLI) were found to be about 40 µm (spots) and 11 µm
(trenches).

The correlation between strontium
concentrations obtained by spot analysis of whitefish otoliths with PIXE
and LA-ICP-MS was excellent (92%), although different spot sizes were
used. A comparison of strontium concentration profiles measured with
µ-XRF and LA-ICP-MS showed that the higher information depth of µ-XRF in
combination with the 52 degree angle of the incident X-rays smoothens
out the sharp edges seen in the LA-ICP-MS profiles. Otoliths from
whitefish captured in the Baltic Sea (n = 30) were analysed in this
comparison of methods. Among these whitefish there are sea spawners,
river spawners and stocked fish with different life history and
different otolith chemistry.


Senast uppdaterad 2020-20-09 vid 06:32