Sediment, mineralization

A significant fraction of lead carried by river water is expected to be in an undissolved form, which can consist of colloidal particles or larger undissolved particles of lead carbonate, lead oxide, lead hydroxide, or other lead compounds incorporated in other components of surface particulate matters from runoff. Lead may occur either as sorbed ions or surface coatings on sediment mineral particles, or it may be carried as a part of suspended living or nonliving organic matter in water. The ratio of lead in suspended solids to lead in dissolved form has been found to vary from 4 1 in rural streams to 27 1 in urban streams (Getzetal. 1977). 

Extracellular enzymes are rapidly sorbed at mineral and humic colloids in soils and sediments. Mineral colloids have a high affinity for enzymes although that is not always synonymous with the retention of their catalytic ability. On the other hand, humic substances have the ability to sorb and sequester enzymes in such a way as to retain their catalytic activity they could also strongly inactivate enzyme activity depending on interaction mechanisms. 

KEYWORDS geochemical mapping, overbank sediment, mineral exploration, energy... 

Stream sediment (mineral sediment, <0.150 mm) Residual soil, upper horizon (topsoil) 0 - 25 cm with out the top organic layer (<2 mm)... 

Stream water Stream sediment (mineral sediment) Residual soil, upper horizon (topsoil) 0 - 25 cm without organic layer Residual soil, lower (C) horizon (subsoil) a 25 cm layer within a depth range of 50 cm - 200 cm Soil samples should represent the dominant soil type of the small catchment. W s T C... 

Since NaOH and NaA102 had no apparent effect on cobalt solubility, it seemed likely that cobalt sorption was increased by these components due to effects they had on the sediment minerals. Studies of the effects of NaOH and NaA102 on the sediment minerals are required to identify possible new mineral phases which might cause increased cobalt sorption. 

Neptunium and plutonium sorption behaviors were remarkably similar, implying that they had similar sorption reactions and solution species. Both NaOH and NaA102 decreased neptunium and plutonium sorption. Several explanations can be offered to rationalize this behavior. First, NaOH and NaAlO, may have reacted with the sediment minerals to yield solids of lower sorptive capacity. Aluminate ion, as an anionic species, also may have competed with the similar neptunate and plutonate anions for sorption sites. Finally, sodium hydroxide may have stabilized the hydrolyzed Np02(0H) and Pu02(0H)2" species in solution, as was shown in the solubility tests, and prevented sorption. Explanation of the effect of NaOH and NaA102 on neptunium and plutonium sorption will require further investigation. 

The presence of either HEDTA or EDTA resulted in significantly lower neptunium and plutonium sorption. Complexation of the neptunium and plutonium by HEDTA and EDTA may have caused the reduced sorption. However, this evidence for complex formation was not consistent with the observations made in the solubility studies (HEDTA increased and EDTA decreased neptunium solubility neither affected plutonium solubility). Thus, HEDTA and EDTA may have decreased neptunium and plutonium sorption through some undetermined effect on the sediment minerals. 

Americium sorption was decreased significantly when HEDTA or EDTA were present. Complexation of americium by these strong chelating agents was responsible for this behavior. Sodium hydroxide increased americium sorption but, again, its effect on americium was probably a manifestation of its effect on the sediment minerals. 

The sorption results suggested that further studies of waste/sediment reactions were required. Sodium hydroxide and aluminate probably altered the sediment minerals and affected the sorption reactions. The complexants HEDTA and EDTA also could have changed the sediment minerals. 

Leaching studies indicate that these radionuclides associated with sediment are not in the form of adsorbed ions, but in the form of discrete minerals, or are partly trapped inside the colloidal hydroxides of Fe and Mn coated on the sediment. Further studies by other leaching agents, such as hydroxylamine hydrochloride, and ammonium oxalate, and by X-ray diffraction and scanning-electron microscopy on sediment minerals will reveal the geochemical status of these radionuclides in the sediment. 

Mackenzie, R.C., 1957b. The illite in some Old Red Sandstone soils and sediments. Mineral. Mag., 31 681-689. 

Christensen, P. B., Rysgaard, S., Sloth, N. P., Dalsgaard, T., and Schwaerter, S. (2000). Sediment mineralization, nutrient fluxes, denitrification and dissimilatory nitrate reduction to ammonium in an estuarine ord with sea cage trout farms. Aquat. Microb. Ecol. 21(1), 73—84. 

Lambert, I.B. and Bubela, B., 1970. Banded sulphide ores the experimental production of monomineralic sulphide bands in sediments. Miner. Deposita, 5 97—102. 

In order to model chemical reactions in a specific system, we need to know the geochemical properties of the aquifer. Any study of fluid/sediment/mineral interactions requires knowledge of both chemical compositions of fluids and mineralogical compositions of the solid matrix. 

Sediment, mineral salts, minor plant debris and wind-transported pollen were carried into the lakes by small local streams, but the majority of the organic material that is in the oil shale came from colonies of algae that thrived in the lakes. 

Wasson, R. J., G. I. Smith D. P. Agrawal, 1984. Late Quaternary sediments, minerals, and inferred geochemical history of Didwana Lake, Thar Desert, India. Palaeogr, PalaeocUm., Palaeoecol. 46 345-372. 

---