TY - JOUR
T1 - Impacts of cryogenic sampling processes on iron mineral coatings in contaminated sediment
AU - Hua, Han
AU - Yin, Xin
AU - Renno, Maria Irianni
AU - Sale, Thomas C.
AU - Landis, Richard
AU - Dyer, James A.
AU - Axe, Lisa
N1 - Publisher Copyright:
© 2020 Elsevier B.V.
PY - 2021/4/15
Y1 - 2021/4/15
N2 - This study focused on comparing iron mineral coatings found in contaminated sediments from a cryogenic (Cryo Core) core versus an Anaerobic Core (collected under oxygen-free and ambient conditions). After thawing the Cryo Core in an oxygen-free glovebox, a suite of analyses was applied on sediments from both cores: pH, redox potential, X-ray fluorescence (XRF), X-ray diffraction (XRD), and field-emission scanning electron microscopy (FESEM) with energy dispersive X-ray analyzer (EDX). Among the iron minerals identified, crystalline pyrite was found throughout the Cyro Core sediment samples, which is in contrast to that observed for the Anaerobic Core. Moreover, mackinawite and greigite that were ubiquitous in the Anaerobic Core were not observed in Cryo Core samples. To better understand why the metastable minerals were not present, a freeze/thaw process was simulated on Anaerobic Core samples using a liquid‑nitrogen quench with surface coatings characterized by FESEM/EDX. In these quenched samples, mackinawite was no longer observed, and in its place was pyrite. In addition, both greigite and pyrite were found to be unique morphologically after quenching. Dissolution and re-precipitation of iron sulfide coatings during the freeze/thaw process appears to affect the geochemistry of the pore water through two main mechanisms of freeze-concentration and freezing potential.
AB - This study focused on comparing iron mineral coatings found in contaminated sediments from a cryogenic (Cryo Core) core versus an Anaerobic Core (collected under oxygen-free and ambient conditions). After thawing the Cryo Core in an oxygen-free glovebox, a suite of analyses was applied on sediments from both cores: pH, redox potential, X-ray fluorescence (XRF), X-ray diffraction (XRD), and field-emission scanning electron microscopy (FESEM) with energy dispersive X-ray analyzer (EDX). Among the iron minerals identified, crystalline pyrite was found throughout the Cyro Core sediment samples, which is in contrast to that observed for the Anaerobic Core. Moreover, mackinawite and greigite that were ubiquitous in the Anaerobic Core were not observed in Cryo Core samples. To better understand why the metastable minerals were not present, a freeze/thaw process was simulated on Anaerobic Core samples using a liquid‑nitrogen quench with surface coatings characterized by FESEM/EDX. In these quenched samples, mackinawite was no longer observed, and in its place was pyrite. In addition, both greigite and pyrite were found to be unique morphologically after quenching. Dissolution and re-precipitation of iron sulfide coatings during the freeze/thaw process appears to affect the geochemistry of the pore water through two main mechanisms of freeze-concentration and freezing potential.
KW - Cryogenic coring
KW - FESEM
KW - Iron sulfide coatings
KW - Surface mineral coating characterization
KW - XRD
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U2 - 10.1016/j.scitotenv.2020.142796
DO - 10.1016/j.scitotenv.2020.142796
M3 - Article
C2 - 33092846
AN - SCOPUS:85092896605
SN - 0048-9697
VL - 765
JO - Science of the Total Environment
JF - Science of the Total Environment
M1 - 142796
ER -