Manganese in sediments

The coordinative environment of manganese in sediment-trap material was evaluated with EXAFS spectra recorded at the Mn K-edge. Figure 7 shows the radial distribution function (RDF) around Mn atoms of a sediment-trap sample. The RDFs of pyrochroite, manganite, Na-bimessite, todorokite, and vemadite are also shown. A comparison of EXAFS data with results from X-ray diffraction (XRD) is shown in Table III for all three oxidation states of manganese. 

Lynn, D. C. and Bonatti, E. (1965). Mobility of manganese in diagenesis of deep-sea sediments. Marine Geol. 3,457-474. 

Mahan K.I., Foderaro T.A., Garza T.L., Martinez R.M., Maroney G.A., Trivisonne M.R., Willging E.M. Microwave digestion techniques in the sequential extraction of cadmium, iron, chromium, manganese, lead and zinc in sediments. Anal Chem 1987 59 938-945. 

Most of the zinc introduced into aquatic environments is sorbed onto hydrous iron and manganese oxides, clay minerals, and organic materials, and eventually is partitioned into the sediments (USEPA 1987). Zinc is present in sediments as precipitated zinc hydroxide, ferric and manganic... 

Van Cappellen, P. Wang Y. 1996. Cycling of iron and manganese in surface sediments a general theory for the coupled transport and reaction of carbon, oxygen, nitrogen, sulfur, iron and manganese. American Journal Sciences, 296, 197-243. 

The processes described and their kinetics is of importance in the accumulation of trace metals by calcite in sediments and lakes (Delaney and Boyle, 1987) but also of relevance in the transport and retention of trace metals in calcareous aquifers. Fuller and Davis (1987) investigated the sorption by calcareous aquifer sand they found that after 24 hours the rate of Cd2+ sorption was constant and controlled by the rate of surface precipitation. Clean grains of primary minerals, e.g., quartz and alumino silicates, sorbed less Cd2+ than grains which had surface patches of secondary minerals, e.g., carbonates, iron and manganese oxides. Fig. 6.11 gives data (time sequence) on electron spin resonance spectra of Mn2+ on FeC03(s). 

Departures from idealized redox zonation can also result from temporal shifts in sedimentation rates and in the depth of the oxic zone. Some examples are provided in the next section using iron and manganese as case studies. These elements are particularly useful as records of past changes in sedimentation rates because they respond to local redox conditions by undergoing postdepositional migration. 

This material focuses on the redox dynamics of manganese in the sediments of the... 

Arsenic contaminants may be found in the aquatic and terrestrial environments as a result of anthropogenic inputs and weathering of primary materials. It is known (e.g., Oscarson et al. 1983 Tournassat et al. 2002) that in such environments, manganese oxides like birnessite (b-MnO ) directly and rapidly oxidize As(III) to As(V). However, As(III) oxidation can be inhibited in sediments when additional natural materials lead to coating of MnO by CaC03 (Oscarson et al. 1983). 

Samples of the red clay having uniform physical and chemical characteristics were provided by G. R. Heath of the University of Rhode Island. The samples were obtained from core LLUU-GPC-2, collected on October 11, 1976, at 30° 20.9 n, 157° 50.85 w, water depth 5821 meters, and are representative of the smectite-rich region of the red clays which occurs in the sediment at depths below about ten meters. In this region, the sediment appears to contain about five to six percent by weight leachable iron and manganese in the form of hydrous oxides. The remaining material appears to be dominated by iron-rich smectite and lesser, varying amounts of phillipsite (2). The results of a semi-quantitative (precision in data is within a factor of 2) elemental analysis... 

All measured profiles of sulfate reduction in sediments indicate that much sulfide production and, by inference, oxidation occurs in permanently anaerobic sediments (78, 73, 90,101). The two most likely electron acceptors for anaerobic sulfide oxidation are manganese and iron oxides. Burdige and Nealson (151) demonstrated rapid chemical as well as microbially catalyzed oxidation of sulfide by crystalline manganese oxide (8-Mn02), although elemental S was the inferred end product. Aller and Rude (146) documented microbial oxidation of sulfide to sulfate accompanied by reductive dissolution... 

Andrews (4) showed that fine-grained particulate contaminants (arsenic, cadmium, copper, lead, and zinc in sediment less than 0.016 mm in diameter) decreased downstream from the source and that the distribution could be explained solely by mixing of mill tailings with uncontaminated floodplain sediment. Work by Brook and Moore (5) and Moore et al. (6) showed that the sediments were enriched in arsenic, cadmium, copper, manganese, lead, and zinc. They also found that the contaminants were carried mostly in the reducible and oxidizable phases (operationally defined). 

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