Porewater evidence for a dynamic sedimentary iron cycle in salt marshes. [Spartina alterniflora]

Journal Article · Sun Jan 01 04:00:00 EST 1984 · Limnol. Oceanogr.; (United States)

DOI:https://doi.org/10.4319/lo.1984.29.1.0047· OSTI ID:6631749

Giblin, A E; Howarth, R W

Dynamic transformations of iron occur seasonally at Great Sippewissett Marsh, Massachusetts. Small changes in the dissolved iron concentration in prewater represent only a small fraction of the iron involved in transformation reactions during the year. During the growing season, salt marsh grasses oxidize the sediment, and a large percentage of sedimentary pyrite is converted to an oxidized iron mineral. Over the fall and winter there is a net increase in pyrite as the grass is anaerobically decomposed. When oxidation rates in summer are high enough to neutralize the alkalinity produced by sulfate reduction and substantially lower the pH, oxidized iron minerals become increasingly soluble and iron levels in the porewater increase. If large amounts of soluble iron are lost by tidal flushing, iron availability may limit pyrite formation in later years. Sulfide concentrations in the porewater would then increase, leading to depressed growth of Spartina alterniflora. For most of the year the porewaters of Great Sippewissett were undersaturated with respect to all iron monosulfide minerals and supersaturated with respect to pyrite (FeS/sub 2/). Thus pyrite formation at Great Sippewissett probably occurs directly by reaction of polysulfides with iron and not by reactions of FeS with elemental sulfur. Porewaters were always undersaturated with respect to manganese minerals. Porewaters taken from marshes at Sapelo Island, Georgia, in fall were supersaturated with respect to pyrite at all depths and appear to be saturated for iron monosulfides below 12 cm at all sites.

• Research Organization: Boston Univ. Marine Program, Woods Hole, MA
• OSTI ID: 6631749
• Journal Information: Limnol. Oceanogr.; (United States), Journal Name: Limnol. Oceanogr.; (United States) Vol. 29:1; ISSN LIOCA
• Country of Publication: United States
• Language: English

Related Subjects

510200* -- Environment
Terrestrial-- Chemicals Monitoring & Transport-- (-1989)
54 ENVIRONMENTAL SCIENCES
ANAEROBIC CONDITIONS
AQUATIC ECOSYSTEMS
CHALCOGENIDES
CHEMICAL ANALYSIS
CHEMICAL REACTIONS
DECOMPOSITION
ECOSYSTEMS
ELEMENTS
FEDERAL REGION I
GRASS
GROWTH
IRON
IRON COMPOUNDS
IRON SULFIDES
MANGANESE
MASSACHUSETTS
METALS
MINERAL CYCLING
MINERALS
NONMETALS
NORTH AMERICA
PH VALUE
PLANT GROWTH
PLANTS
PYRITE
REDOX REACTIONS
SEDIMENTS
SULFIDE MINERALS
SULFIDES
SULFUR
SULFUR COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
USA
WETLANDS