Iron Isotopes in Acid Mine Drainage: Extreme and Divergent Fractionation between Solid (Schwertmannite, Jarosite, and Ferric Arsenate) and Aqueous Species.
Environ Sci Technol
; 56(24): 18060-18068, 2022 12 20.
Article
en En
| MEDLINE
| ID: mdl-36442144
Examination of stable Fe isotopes is a powerful tool to explore Fe cycling in a range of environments. However, the isotopic fractionation of Fe in acid mine drainage (AMD) has received little attention and is poorly understood. Here, we analyze Fe isotopes in waters and Fe(III)-rich solids along an AMD flow-path. Aqueous Fe spanned a concentration and δ56Fe range of â¼420 mg L-1 and + 0.04 at the AMD source to â¼100 mg L-1 and -0.81 at â¼450 m downstream. Aqueous As (up to â¼33 mg L-1) and SO42- (up to â¼2000 mg L-1), like aqueous Fe, decreased in concentration down the flow-path. X-ray absorption spectroscopy indicated that downstream attenuation in aqueous Fe, As, and SO42- was due to the precipitation of amorphous ferric arsenate (AFA), schwertmannite, and jarosite. The Fe(III) in these solids displayed extreme variability in δ56Fe, spanning +3.95 in AFA near the AMD source to -1.34 in schwertmannite at â¼450 m downstream. Similarly, the isotopic contrast between solid Fe(III) precipitates and aqueous Fe (Δ56Feppt-aq) dropped along the flow-path from about +4.1 to -1.1. The shift from positive to negative Δ56Feppt-aq reflects divergence between competing equilibrium versus kinetic fractionation processes.
Palabras clave
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Arseniatos
/
Compuestos Férricos
Idioma:
En
Revista:
Environ Sci Technol
Año:
2022
Tipo del documento:
Article
País de afiliación:
Australia
Pais de publicación:
Estados Unidos