Minerals colloids

G. Stotzky, Influence of soil mineral colloids on metabolic processes, growth, adhesion and ecology of microbes and virus. Interaction of Soil Minerals and Natural Organics and Microbes (P. M. Huang and M. Schnitzer, eds). Special Publication Number 17, Soil Science Society of America, Madison, Wl, 1986, pp 305-428. 

Products of this type seem to protect the humus from rapid incorporation into new biological processes. Additional factors that appear to be associated with the accumulation of organic matter in Mollisols are high exchange capacities, saturation with calcium, an abundance of mineral colloids and a high content of minerals of the smectite group (Fenton, 1983). 

Influences of Mineral Colloids on Soil Organic Matter... 

Mineral Colloid-Organic Substance-Microorganism Interactions... 

Metal oxides have a significant role in influencing physical, chemical, and biological properties of soils. They may exist as ciystalline minerals, as short-range ordered (SRO) mineral colloids, or as surface coatings on clay minerals and organic matter. Organic compounds influence the formation, transformation, and surface properties of these metal oxides. The SRO A1... 

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. 

Mineral colloid-enzyme interactions have been documented (e.g., Theng 1979 Bums 1986 Naidja et al. 2000 Bums and Dick 2002). Besides cation-exchange reactions, adsorption of enzymes by mineral colloids may proceed through ionic, covalent, hydrophobic, hydrogen bonding, and van der Waals forces. When enzymes are adsorbed on mineral colloids, changes in the tertiary structures (i.e., the folding of the helix or... 

In the majority of cases, minerals in topsoils are partially covered with organic materials, especially humic substances, which are to a large extent microbially resistant. The most common mode of mineral colloid-organic material-microorganism interactions may be depicted as follows (Theng and Orchard 1995) ... 

Microbial activity can also be stimulated by mineral colloids through their ability to sorb metabolites that would otherwise have an adverse effect on microbial growth (Filip et al. 1972 Filip and Hattori 1984) This may be due to the toxicity of metabolites, and their feed back repression and, encouraging competitors. Predictably, montmorillonite (CEC —100 cmol kg-1 and specific surface of 800 m g 1) is more effective than kaolinite and finely ground quarts. Other substances, such as antibiotics and pesticides that are toxic to some microorganisms, can also be adsorbed by the surfaces of mineral colloids (Theng and Orchard 1995 Dec et al. 2002). 

Mineral Colloid-Organic Substance-Microorganism Interactions in Relation to Soil Structural Stability... 

Guggenberger G, Haider KM (2002) Effect of mineral colloids on biogeochemical cycling of C, N, P, and S in soil. In Huang PM, Bollag J-M, Senesi N (eds) Interactions between soil particles and microorganisms. Impact on the terrestrial... 

Bioavailability of Metals, Nonmetals and Xenobiotics Immobilized on Soil Components, (4) Distribution and Activity of Biomolecules in Terrestrial Systems, (5) Interactions between Soil Microbial Biomass and Organic Matter/Nutrient Transformations, and (6) Impact of Interactions among Soil Mineral Colloids, Organic Matter and Biota on Risk Assessment and Restoration of Terrestrial Ecosystems. There were 2 plenary lectures, 9 invited speakers, 36 oral presentations and 45 posters. Dr. N. Senesi from University of Bari, Italy, presented an IUPAC lecture entitled Metal-Humic... 

It is reasonable to assume that clay colloids exhibit a similar surface chemistry as clay which is sorbed, bonded, or precipitated in the stationary solid phase. Mineral colloids may be formed when precipitation or dissolution generate particles which are resistant to settling. These particles maybe formed by any number of conditions whereby the solubility of a particular solute is exceeded or a stable solid is disrupted mechanically [21,24]. 

The amphiphilic nature of dissolved humic substances (DHS) lends them the ability to associate with both hydrophobic organics and polar or ionic species [62-64]. Inorganic ions or mineral colloids in solution will interact with the electrically active surface of humic material in solution or in the solid phase according to the same bonding forces which lead to the association between SP0M and the solid mineral matrix. Humic matter in water is associated with... 

Clay minerals behave like Bronsted acids, donating protons, or as Lewis acids (Sect. 6.3), accepting electron pairs. Catalytic reactions on clay surfaces involve surface Bronsted and Lewis acidity and the hydrolysis of organic molecules, which is affected by the type of clay and the clay-saturating cation involved in the reaction. Dissociation of water molecules coordinated to surface, clay-bound cations contributes to the formation active protons, which is expressed as a Bronsted acidity. This process is affected by the clay hydration status, the polarizing power of the surface bond, and structural cations on mineral colloids (Mortland 1970, 1986). On the other hand, ions such as A1 and Fe, which are exposed at the edge of mineral clay coUoids, induce the formation of Lewis acidity (McBride 1994). 

The mineral phase. Mineral colloids are composed of layered silicates and amorphous metal hydroxides. The two basic building layers of the silicates are (i) a tetrahedral silicon dioxide layer modified by occasional substitution by Al and (ii) an octahedral A1 oxyhydroxide layer with occasional substitution by Mg2+, or... 

There is a need to resume studies of soil saccharides and peptides. These can compose as much as 30-40% (when account is taken of the compositions of humin materials). Much is known about how polysaccharides of known structures interact with soil colloids, but it has not been possible as yet to know in sufficient detail the structures of the polysaccharides that persist in the soil. Hence we do not know the mechanisms of their binding to soil mineral colloids. The same applies for the peptide materials, though it is clear that polysaccharides and peptides have important roles in soil structure formation and stabilization. 

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