Cores 11 through 26 by Gary B. Dr - University of Illinois at Urbana ...

animals leave waste behind, small insects, worms, and microorganisms die in the soil. The remains areincorporated into the soil column. In each core except cores 12 and 16 the highest total carbon contentoccurred inn the uppermost sample and it was almost entirely organic carbon. The range of total carboncontent was 0.05 to 3.38 %, inorganic carbon content ranged from 0.01 to 2.31 %, and organic carbonranged from 0.01 to 2.52 %. The total carbon content in cores 12 and 16 followed the same pattern as inmost of the other cores except that the highest total carbon content occurred in the lowermost sample andwas mostly inorganic, or carbonate carbon. A secondary maximum was observed in the total C contentof core 15 in the fourth sample from the top. It is noted that the clay-size content and the content of traceelements associated with clay minerals also reached maxima in the same sample. The inorganic carbonin most of the cores was low and relatively invariant with depth, however, in a few cores (19, 20, 23, and25) there were noticeable variations in carbon content. Limestone might have been applied to the fieldprior to collecting core 19, which resulted in relatively high inorganic carbon and calcium contents in theuppermost sample.CONCLUSIONSThe contents of several trace elements, including chromium, copper, rubidium, vanadium, and zinc werestrongly correlated with the content of clay-sized particles. Each of these metals is easily sorbed byvarious clay minerals. As the colloidal-sized clay minerals migrate downward through the soil column,any elements attached to the clay particles are also transported.The sand-plus-silt content is an indicator of the amount of silica in a sample. There is a similar relationshipbetween clay and alumina content.Indications of differences in chemical composition between modern and ancient buried soils were seen incores 25 and 26, in which the silica content was higher and the alumina content lower in the samples fromthe modern soil than in those from the buried soil.As more cores are analyzed and more data become available, we expect that some regional trends in soilcomposition may emerge. Presently, the data are too few to make such inferences reliably. With moredata we may be able to distinguish between various mechanisms for the addition and removal of material.For example, we noted the possible input of Pb content to the surface from particulate matter carried anddeposited by wind versus the increase in content due to weathering.REFERENCESAllen, B. L. and B. F. Hajek, 1989, Mineral occurrences in soil environments, in Dixon, J. B. and S. B.Weed, eds., Minerals in Soil Environments, Second Edition, SSSA Book Series: 1, Soil ScienceSociety of America, Madison WI, 1244 p.Baas Becking, L. G. N., I. R. Kaplan, and D. Moore, 1960, Limits of the natural environment in terms ofpH and oxidation-reduction potentials, J. Geol., v. 68, p. 243-284.Barnett, M. O., L. A. Harris, R. R. Turner, R. J. Stevenson, T. J. Henson, R. C. Melton, and D. P. Hoffman,1997, Formation of mercuric sulfide in soil, Environ, Sci, Technol., v.31, p. 3037-3043.Birkeland, P. W., 1999, Soils and Geomorphology, Third Edition, Oxford University Press, New York, 430p.24