Effects of soil organic matter heterogeneity on equilibrium sorption by soils and sediments (The)

2021 ◽  
Author(s):  
Baohua Xiao
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Equilibrium Sorption ◽  
Soils And Sediments

The aqueous geochemistry of metals in the weathering environment: strengths and weaknesses in our understanding of speciation and process

2003 ◽  
Vol 67 (2) ◽  
pp. 235-246 ◽  
Author(s):  
C. D. Curtis
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Recent Work ◽  
Metal Speciation ◽  
Soil Profiles ◽  
Metal Release ◽  
Aqueous Geochemistry ◽  
Organic Complex ◽  
Soils And Sediments ◽  
Different Climates

Soil profiles developed in different climates and physical settings are highly variable in structure, in mineralogy, in the local biosphere and in the compositions of the soil gas and water phases. Discussion of metals in ‘the weathering environment’ needs to acknowledge and address this diversity.The thermochemical methods developed by Pourbaix (1949) and Garrels and Christ (1965) remain useful predictors of metal speciation and solubility but the approach is valid only for processes involving carbonates, sulphides, hydroxides and similar minerals in soils and sediments. Almost no primary silicates are thermodynamically stable: they spontaneously decompose to non-equilibrium solid products with metal release determined by kinetics.Hydrolysis constants for aquo-complexes are useful indicators of metal speciation, mobility and availability. Recent work on soluble soil organic matter confirms that the active ligands are overwhelmingly oxygen based: phenols, carboxylic acids, alcohols. Many of these molecules compete very effectively with aquo-complexes to form strong metal chelates and appear to be responsible for substantial Al and Fe mobilization within and translocation down soil profiles.It is important to note also that strong clay mineral/organic matter associations (clay-organic complex) will fix metals as a consequence of the same chelation reactions (in this case removing them from solution - retardation).

scholarly journals The Fate of Glyphosate in Soil and Water: A Review

2021 ◽  
Vol 7 (SpecialIssue) ◽  
pp. 389-399
Author(s):  
Suwardji Suwardji ◽  
‪I Made Sudantha
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Phosphate Adsorption ◽  
Suspended Material ◽  
Soil Sediment ◽  
Soils And Sediments ◽  
Soil Evidence ◽  
Soil Constituents ◽  
Soil And Water

The fate of glyphosate in soil and water is dependent on the properties of glyphosate and its envoronement. Behaviour of glyphosate in soil, sediment and water is strongly influenced the way by which it can be adsorbed by soils, sediments, and suspended material in water. The role of soil organic matter, clay mineral, and amorphous minerals on the adsorption of glyphosate depends primarily on the nature and properties of the soil itself and the properties of glyphosate. Environmental factors have some influence on sorption and degradation of glyphosate. Glyphosate is rapidly inactivated in soil, is in part due to adsorption. Some soil properties have been identified strongly influence adsorption of glyphosate, such as clay minerals, composition of cations in exchangeable site of clay and organic matter, unoccupied phosphate adsorption site, degree of humification, and soil pH. Adsorption limits the availability of glyposate for microbial degradation. The sorbed glyphosate is not directly available to microorganisms in soil. Evidence also suggests that not only a strongly sorbed compound such as paraquat but also weakly sorbed compounds such as flumetsulam and picloram can persist for long periods when they are sorbed by soil constituents. This suggests that the interaction between sorption and biodegradation should be considered in predicting the fate of pesticides in soils and sediments.

Soil Organic Matter

1962 ◽  
Vol 54 (5) ◽  
pp. 470-470
Author(s):  
T. M. McCalla
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter
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