Possible role of organic matter in radiocaesium adsorption in soils

The aim of this review is to examine the hypothesis that organic matter decreases the adsorption of radiocaesium on clay minerals. The factors that determine radiocaesium mobility and bioavailability in soil are briefly outlined to show why a relationship between soil organic matter content and enhanced Cs bioavailability is paradoxical. In all the investigations reviewed the ionic compositions of both the solid and the solution phases have been strictly controlled. We show that the addition of organic matter to reference clay minerals causes decreases of up to an order of magnitude in the distribution coefficient of radiocaesium. Similarly, the chemical removal of organic matter from the clay-sized fraction of soil usually leads to an increase in Cs adsorption. We suggest that the nature of the organic matter and its interaction with mineral surfaces are as important as the amount present

Diagenesis as a function of redox conditions in nature : a comparative survey of certain organic and inorganic compounds in a oxic and anoxic Baltic Basin

Sediments from Baltic basins, the relatively well aerated Bornholm Basin and the poorly aerated Gotland Deep, were collected in order to see what effect a relative lack of oxygen at the sediment-water interface has on the diagenesis of organic material deposited in nature. From hydrographic considerations one can assume that the Gotland Deep has a perennial deficiency of oxygen when compared to the Bornholm Basin. This was also shown from the manganese (HARTMANN, 1964) content in the two sediments. Both sediments were also found to have a similar mineral composition and particle size distribution. That they were of a similar age could be shown by the fact that they both had a relatively large amount of organic material (GRIPENBERG, 1955) and similar concentrations of ammonia. Since the two basins have different rates of primary productivity, it was necessary to adjust the quantitative results with a compensating factor. This factor was based upon the pristane, a highly stable hydrocarbon, content, and it was determined that the Bornholm Basin had a primary productivity 1.5 times as high as the Gotland Deep. Quantitatively the lower oxygen concentrations in the Gotland Deep resulted in the preservation of more total soluble amino acids, fatty acids, hydrocarbons, and organic carbon. In addition a greater percentage of the total organic carbon in the Gotland Deep was, in a non-condensed form. Qualitatively no major difference was found in the distribution in the two sediments of the total soluble amino acids (with the possible exception of tyrosine), fatty acids, or hydrocarbons, however unsaturated fatty acids and hydrocarbons showed considerable difference in their qualitative distribution. The low oxygen basin was found also to contain considerable more unsaturated compounds, and its material seemed to have been less influenced by bacteria, as determined by a higher linear/iso fatty acid ratio. A study of the fatty acids and hydrocarbons that were released from the mineral matrix of the sediments by acid digestion, indicates an additional preservative effect in that a still greater degree of unsaturation was present and in that the linear/iso ratios were higher. This preservative effect in the relatively well aerated basin was either less or absent

Preliminary study of the dissolved hydrocarbons and hydrocarbons on particulate material in the Gotland Deep of the Baltic

The quantitative determination of hydrocarbons in nature with either gaschromatography or infrared has several major drawbacks. Therefore a special method was developed. The material obtained by extraction with non-polar solvent was separated on a very short thin layer plate of 10% AgN03 silica gel with hexane as the solvent. The saturated and benzyl hydrocarbons were found near the front, separated from non-hydrocarbon material. An attempt to separate the unsaturated hydrocarbons from non-hydrocarbon material was unsuccessful. The silica gel containing the hydrocarbons was eluted with hexane, and the hydrocarbons were determined in a CHN analyzer. Amounts as small as 1 μg could be determined. Dissolved hydrocarbons and hydrocarbons within particulate matter were determined in the Gotland Deep, a Baltic Basin. An average value of 57.2±4.2 μg C/l as non olefinic, dissolved hydrocarbon was determind, which is about 1,5% of the total dissolved organic carbon. The average of non-olefinic hydrocarbon on particulate material was 1.1±0,75 μg C/l, which is equivalent to 0.8% of the total particulate organic carbon. The ratio of particulate, non-olefinic hydrocarbon to total, particulate organic carbon was the highest at 110 m and lowest at 10 m. The hydrocarbon content had no significant influence on the Corg/N ratios of the particulate material

Effect of organic amendments on herbicide sorption as related to the nature of the dissolved organic matter

It has been assessed the influence of four organic amendments (OA) consisting of two commercial humic amendments (liquid LF and solid SF) from olive-mill wastes, a solid urban waste (SUW), and a sewage sludge (SS) on the sorption properties and leaching potential of simazine and 2,4-D. A sandy soil (TR) and a sandy-clay soil with a relatively high montmorillonite content (A) were treated with the diverse OA. Dissolved organic matter (DOM) was extracted from the amendments, the soils, and the amended soils and studied by fluorescence spectroscopy. A humification index (HIX) was calculated from the fluorescence data. Sorption was determined with the batch technique. Spectroscopical studies revealed that the DOM of the LF differs from the other OA by having a very low ability to absorb and to fluoresce and by its very low HIX values, which indicates that the LF contains large amounts of nonhumified material and consists of small molecules. On the other hand, the SF amendment contains the highest amounts of highly humified material and a large number of carboxylic groups. Amended soils sorbed simazine and 2,4-D to a greater extent than the untreated soils, except in the case of simazine sorption in the LF amended soil A, which had a lower simazine sorption than the original soil. The small molecules of DOM in the LF compete with simazine for montmorillonite sorption sites in soil A. This is not the case for 2,4-D, since this herbicide does not sorb on montmorillonite. In the case of the soil TR, with a lower montmorillonite content, there is no competition between simazine and the LF molecules for sorption sites. Soils amended with the highly humified SF were the best sorbents for simazine but not for 2,4-D, which can be attributed to repulsion between negatively charged 2,4-D molecules and COOgroups, which are more abundant in SF.This project has been supported by Junta de Andalucía through Research group 4092, CICYT through AMB96-0445- CO2-O2, the Deutsher Akademischer Austauschdienst and Ministerio de Educación y Cultura through Acciones Integradas HA98-0072, and by the European Science Foundation within its Groundwater Pollution Program (G-Poll). Municipal treatment plant EMASESA is also acknowledged for providing the sewage sludge.Peer Reviewe