Lake Pavin History, geology, biogeochemistry, and sedimentology of a deep meromictic maar lake

© Springer International Publishing Switzerland 2016 205
T. Sime-Ngando et al. (eds.), Lake Pavin, DOI 10.1007/978-3-319-39961-4_12

The Iron Wheel in Lac Pavin: Interaction

with Phosphorus Cycle

Vincent Busigny, Didier Jézéquel, Julie Cosmidis,

Eric Viollier, Karim Benzerara, Noah J. Planavsky,

Patrick Albéric, Oanez Lebeau, Gérard Sarazin,

and Gil Michard

Abstract

Lac Pavin is a crater lake, characterized by water column stratification, with oxygenated

shallow waters lying above anoxic and ferruginous deep waters. In the deep waters, ferrous

iron, Fe(II)aq, is the main dissolved cation, with concentrations up to 1 mM. Iron is effi-

ciently confined below the oxic-anoxic boundary due to the formation of insoluble ferric

iron species, Fe(III)s, by oxidation with O 2 and other oxidants (e.g., NO 3 −, Mn(IV)). The

Fe(III)s particles settle down and are reduced in the anoxic waters and at the lake bottom by

reaction with organic matter to soluble Fe(II)aq. It then diffuses upward in the water column

and finally is re-oxidized to Fe(III) at the redox boundary. This process, known as the “iron

wheel”, is described in the present paper that reviews available data for dissolved and par-

ticulate matter in the water column, settling particles collected by sediment traps and sedi-

ment cores. Detailed analyses for some major and trace element concentrations, along with

iron speciation and isotope composition, high-resolution microscopy, and geochemical

modeling provide a picture of biogeochemical cycling in this Fe-rich aqueous system. At

Lac Pavin the P and Fe cycles are tightly coupled. Orthophosphate is sorbed onto Fe oxy-

hydroxides and/or precipitated as Fe(II)-Fe(III)-phosphates at the redox interface, confining

P ions in the deep anoxic waters. Deeper in the water column, particulate Fe concentrations

progressively increase due to Fe(II) phosphate (vivianite) formation. In the sediment, Fe is

buried as various ferrous minerals, such as vivianite, pyrite and siderite.

Keywords

Anoxic • Ferruginous • Lake • Pavin • Meromictic • Iron • Phosphate • Sulfide • Manganese

• Biogeochemical cycle

V. Busigny (*) • D. Jézéquel • E. Viollier • G. Sarazin
G. Michard
IPGP (Institut de Physique du Globe de Paris), Sorbonne Paris
Cité, Univ. Paris Diderot, UMR 7154 CNRS,
1 rue Jussieu, 75005 Paris, France
e-mail: [email protected]

J. Cosmidis
Department of Geological Sciences, University of Colorado,
Boulder, CO, USA

K. Benzerara
Institut de Minéralogie, de Physique des Matériaux, et de
Cosmochimie (IMPMC), Sorbonne Universités, UPMC Université
Paris, 6, CNRS UMR 7590, MNHN, IRD UMR 206, Paris, France

12

N.J. Planavsky

Department of Geology and Geophysics, Yale University,

New Haven, CT, USA

P. Albéric

ISTO (Institut des Sciences de la Terre d’Orléans), Observatoire

des Sciences de l’Univers en région Centre, UMR 7327 (CNRS-

Université d’Orléans-BRGM),

1A rue de la Férollerie, 45071 Orléans Cedex 2, France

O. Lebeau

Institut de Physique du Globe de Paris, Sorbonne Paris Cité,

Université Paris Diderot, UMR 7154 CNRS, Paris, France