XRF core scanners as a quick and good screening tool for detecting pollution in sediment cores
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1
University of VIgo, Marine Geosciences Department, Spain
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2
University of Huelva, Geology Department, Spain
The capabilities of X-Ray Fluorescence (XRF) core scanners, to acquire high-resolution geochemical data sets in relatively short time, have made them an increasingly popular geochemical screening tool to study sediment cores for palaeoclimatologic and palaeoceanographic purposes (Peck et al., 2007; Rebolledo et al., 2008). These scanners are able to obtain optical images, X-ray radiographs, and continuous geochemical data with a maximum resolution of 200 µm directly from sediment cores (Croudace et al., 2006). Geochemical results are obtained as peak areas of counts per second that are proportional to element concentrations in the sediment, and thus the assumed semi-quantitative nature of these analyses have hampered the use of this type of instruments to monitor and detect pollution at large; where the availability of a fast screening tool that could substantially cut analytical and time costs will certainly be an advantage.
This study explores the sensitivity of a ITRAX core scanner (Cox Analytical Systems) on sedimentary records from estuarine-like environments in NW (Rías Baixas Galicia) and SW Spain (Ría de Huelva). The Galician Rías Baixas sediments are characterized by high contents of organic matter, but in general terms, are not heavily polluted. We have selected one core in the Marín harbour (Ría de Pontevedra) and another in the intertidal area of San Simón Bay (inner Ría de Vigo), close to a ceramic factory, which is relatively highly polluted by lead. By the contrary, the Ría de Huelva is one of the most polluted areas in western Europe because of the high acid mining activity together with the chemical industries located in its margins. We have selected a core in the Padre Santo Channel in the confluence of the Odiel and Tinto rivers.
ITRAX sensitivity was obtained by establishing equivalences between peak areas and concentrations obtained by traditional analytical techniques such as ICP-MS, ICP-OES and/or conventional XRF of pressed pellets (Fig. 1). Our results show that the ITRAX was able to detect Hg concentrations lower than 0.6 μg g-1, Cd concentrations around 1 μg g-1, and even REE contents such those of Er around 5 μg g-1. Results show good relationships for most of the trace elements. For the rías Baixas sediments only Pb (in San Simón Bay) and Hg (in the Marín harbour) showed concentrations above sediment quality guidelines that could be associated with adverse effects. For Ría de Huelva sediments it was found a coincidence of the REEs maxima with the As, Cu, Pb and Zn maximum peaks confirming their known acid mining origin.
We have also evaluated the suitability of inc/coh, Br/Cl and other element ratios in order to assess the influence of the organic matter variability on the distribution of metals, and to identify salinity and pH changes too. Good correlations were observed between the fraction associated to organic matter and the inc/coh ratio in some of the studied cores. The Cl profile was also useful to show variations in salinity and the marine influence in the sediments.
Our study shows the potential of modern XRF core-scanners such as the ITRAX to perform fast high-resolution and relatively inexpensive measurements to screen and identify pollution in three different coastal environments. Pollution levels can be estimated in a few hours from elements’ peak areas avoiding discrete analysis of the whole core. Organic matter-rich levels associated to higher concentration of toxic metals, can be quickly detected by using the inc/coh ratio in sediments dominated by terrestrial organic matter inputs. Variations in salinity and marine influence can also be detected and some ratios such as Y/Ho profile resulted a good proxy for sediments’ origin.
Acknowledgements
Acknowledgements: Contribution to the IPT- 310000-2010-17 and 10MMA312022PR projects.
References
Croudace IW, Rindby A, Rothwell RG. In: Rothwell R.G. (ed) ITRAX: description and evaluation of a new multi-function X-ray core scanner. New Techniques in Sediment Core Analysis. Geological Society, London, Special Publications 267 (2006). p. 51-63.
Peck VL, Hall IR, Zahn R, Grousset F, Hemming SR, Scourse JD. The relationship of Heinrich events and their European precursors over the past 60 ka BP: a multi-proxy ice-rafted debris provenance study in the North East Atlantic. Quaternary Science Reviews (2007) 26: 862-875.
Rebolledo L, Sepúlveda J, Lange CB, Pantoja S, Bertrand S, Hughen K, Figueroa D. Late Holocene marine productivity changes in Northern Patagonia-Chile inferred from a multi-proxy analysis of Jacaf channel sediments. Estuarine Coastal and Shelf Science (2008) 80: 314-322.
Keywords:
XRF core scanner,
Trace Elements,
estuarine sediments,
Rare Earth Elements,
sediment pollution
Conference:
IMMR | International Meeting on Marine Research 2014, Peniche, Portugal, 10 Jul - 11 Jul, 2014.
Presentation Type:
Oral Presentation
Topic:
OCEANOGRAPHY AND MARITIME TECHNOLOGY
Citation:
Rubio
B,
Rodríguez-Germade
I,
Rey
D,
Borrego
J and
Álvarez-Iglesias
P
(2014). XRF core scanners as a quick and good screening tool for detecting pollution in sediment cores.
Front. Mar. Sci.
Conference Abstract:
IMMR | International Meeting on Marine Research 2014.
doi: 10.3389/conf.fmars.2014.02.00163
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Received:
01 May 2014;
Published Online:
18 Jul 2014.
*
Correspondence:
Prof. Belén Rubio, University of VIgo, Marine Geosciences Department, Vigo, PONTEVEDRA, 36310, Spain, brubio@uvigo.es