Accumulation of Elements

Although not part of soil, lichens, by virtue of their solubilising action on rocks, contribute to the elemental enrichment of soil. Several studies have identified lichen acids as complexing agents for the iron and aluminium of rocks (95, 96). An examination of the various structures indicates that the basic structure responsible for the chelation is the carboxylic acid group with an orthophenolic group. Grodzinskii (97) has found lichens to be intense accumulators of elements in the uranium-radium, actinouranium and thorium orders. 

Goldschmidt (6) proposed three general methods for the accumulation of elements found in organic matter of coal ... 

The differences between the quantities accumulated in oysters held in filtered vs. nonfiltered water suggest that particles play an important role in the accumulation" of elements. Particles in the water may be living microorganisms, organic detritus, inorganic material, or any combination of the three and may vary in quantity, both with time and location. The role of particles in radionuclide accumulation differed with each radionuclide. In oysters, Co appears to be accumulated primarily from the suspended particulate fraction, whereas appears to be... 

The data on physicochemical forms suggest that this is an important factor in the accumulation of elements. Concentration factors both increased and decreased. George and Coombs (31) reported that complexation to EDTA, humic or alginic acids, or pectin doubled the rates of accumulation and final tissue concentrations in edulis and eliminated a lag period. 

Two of the most important primary biogeochemical processes are the accumulation of elements into the cellular structure of organisms and metabolic changes in the oxidation state of elements leading to the accumulation of oxidized or reduced forms of elements in the external milieu. 

A monitoring study of a repeated, emission-related accumulation of elemental content in H. physodes in western Finland (Halonen et al., 1993) revealed a clear... 

Adsorbed organic compounds can also compete with hydrogen for surface sites or can crack, depositing a residue of elemental carbon. Accumulation of elemental carbon is prevented by ensuring that the feed gas mixture contains adequate steam, thus removing carbon by the reaction C + H2O = H2 + CO [50]. 

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