Geochemical Effects of Organic-Rich Swamp Effluents from the Okefenokee Swamp-Marsh Complex of Southern Georgia
J. Helmut Reuter, Kevin C. Beck, 1977. "Geochemical Effects of Organic-Rich Swamp Effluents from the Okefenokee Swamp-Marsh Complex of Southern Georgia ", Interdisciplinary Studies of Peat and Coal Origins, P. H. Given, A. D. Cohen
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The Okefenokee swamp-marsh complex of southern Georgia is losing upward of 1011 g per year of humic matter as a result of surface drainage.. The loss of these highly stable polymers amounts to ~50 g per m2 per year. Because net accumulation of peat is <100 g per m2 per year, this loss could have a significant effect on the eventual petrography of the coal which could result from Okefenokee eats.
The waters leaving the swamp, notably those of the Suwannee River, carry a load of 70-100 mg/1 dissolved humic substances. These are characterized by high total acidity (>10 meq/g) and a high carboxyl content (<6 meq/g). Number average molecular weights range from ~S00 to ~5000. Elemental composition and spectral properties resemble those of soil humic substances. The organic matter contributes more than 0.4 meq/1 of acidic functional groups to the low ionic strength swamp effluents, thus controlling pH and providing anions for electrical charge balance. The presence of salicylic acid sites in the humic polymers allows the formation of strong metal chelates, in addition to other complexing reactions, which explains the linear correlation between organic carbon and iron.
During periods of high discharge from the headwaters of the Suwannee, the effect of the dissolved humic matter extends to the mouth of the river, as evidenced by concentrations of 40 mg/1 organic carbon and a slow gradual increase of pH downstream to ~6.7. During periods of low discharge the karst waters from the downstream limestone terrains dominate. The organic carbon concentrations are as low as 10 mg/1, and pH values increase sharply from 4.2 to 7.2 immediately after entering the karst region.
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This publication represents the proceedings, of a symposium on The Geology, Paleobotany, Geochemistry, and Microbiology of Peats." The symposium was held during the Annual Meeting of the Geological Society of America and associated societies, which took place in Miami, 18-20 November, 1974, and was jointly sponsored by the Coal Geology Division of the Society and the Organic Geochemistry Division of the Geochemical Society. Fourteen papers were presented, and nine are included in this publication. Five authors elected to make other arrangements for publishing their work; but the abstracts of these five papers, as submitted for inclusion in Abstracts with Programs, volume 6, number 7, 1974, are included here for completeness. Peats are of interest to scientists in a variety of disciplines: coal geology, organic geochemistry, soil science, plant ecology, the general ecology of food chains, agronomy, and environmental studies. Workers in many of these fields contributed to this symposium, but it is perhaps fair to say that the central unifying core is the consideration of peat as the precursor of coal. From a broad and general earth science point of view, peats and coals are of special interest because (a) such sediments contain higher concentrations of organic matter than any other common sedimentary deposits, and (b) in most peat beds and coal seams, the greater part of the organic matter and part of the mineral matter are autochthonous in the strictest sense, so that the many biological and chemical fossils that they contain are valid indicators of the organisms from which the organic matter was derived or of the environment of deposition. By contrast, although the reservoir and source rocks of petroleum do contain chemical fossils indicating their origin, reservoir rocks at least, cannot, of their nature, contain relevant fossils in the ordinary biological sense.