From surface discrimination to incorporation into the bulk: XAFS observations of trace metals in calcite

Conference · Wed Dec 31 04:00:00 EST 1997

OSTI ID:560056

Reeder, R J; Lamble, G M ^[1]

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1. SUNY, Stony Brook, NY (United States)

The existence of multiple surface sites on (1014) calcite surfaces causes a strongly selective uptake of divalent trace metals (e.g., Co, Zn, Cd, Pb, Ba) during layer growth, resulting in a spatially segregated distribution of metals in the crystal. Questions arise about whether differential incorporation results in a unique or multiple bulk environments. XAFS spectroscopy was undertaken for individual metals (Co, Zn, Pb, and Ba) to determine local coordination in the bulk. Despite the range of ion sizes and differences in surface-controlled incorporation, all ions have octahedral local coordination environments. This is surprising for Ba, which is {approximately}40% larger than Ca and does not favor sixfold coordination. No metal clustering is found; surface clustering may be unlikely during growth. We conclude that structural differences between surface sites, which cause differential incorporation, do not persist as metals are buried in the near surface by growth.

• OSTI ID: 560056
• Report Number(s): CONF-970443--
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
54 ENVIRONMENTAL SCIENCES
CALCITE
ENVIRONMENTAL TRANSPORT
GEOCHEMISTRY
METALS
POLLUTANTS
SPECTRA
SURFACE PROPERTIES
TRACE AMOUNTS