Copper Speciation in a Collection of Geochemical Reference Materials Using Sequential Extraction and Evaluation of the Validity Using XANES Spectroscopy |
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| Authors: | Atsuyuki Ohta Ran Kubota |
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| Affiliation: | Geological Survey of Japan, AIST, Ibaraki, 305‐8567, Japan |
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| Abstract: | Copper speciation in a collection of Japanese geochemical reference materials (JSO‐1, JLk‐1, JSd‐1, ‐2, ‐3 and ‐4, JMs‐1 and JMs‐2) was achieved by sequential extraction and characterised using X‐ray absorption near‐edge structure spectroscopy. In the first step of the extraction, referred to as the acid fraction, between 1% and 20% total Cu within the reference materials was extracted. Such a result is typically accounted for by absorption of Cu onto clay minerals. However, the presence of Cu sulfate (an oxidation product of chalcopyrite) was observed in some of the stream sediments affected by mining activity (JSd‐2 and JSd‐3) instead. Copper was extracted in the reducible fraction (targeting Fe hydroxide and Mn oxide) (2–49% total Cu). Between 2% and 51% Cu was extracted in the oxidised fraction (targeting sulfides and organic matter). X‐ray absorption near‐edge structure spectroscopy clarified that the reducible fraction consisted of Cu bound to Fe hydroxide, whereas the oxidised fraction was a mixture of Cu bound to humic acid (HA) and Cu sulfide. In the oxidisable fraction, chalcopyrite was the predominant species identified in JSd‐2, and Cu bound to HA was the major species identified in JSO‐1 (a soil sample). |
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| Keywords: | speciation Cu sequential extraction X‐ray absorption near‐edge structure geochemical reference material spé ciation Cu extraction sé quentielle spectroscopie de structure prè s du front d'absorption de rayons X (XANES) maté riel de ré fé rence gé ochimique |
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