1,721,021 research outputs found
Chemical Processes Affecting the Mobility of Heavy Metals and Metalloids in Soil Environments
No full textThe mobility, bioavailability, and toxicity of metal(-
loid)s are influenced by their interactions with phyllosilicates,
organic matter, variable charge minerals, and microorganisms.
Physicochemical processes influencing the chemistry of metal(-
loid)s in soil environments include sorption/desorption, solution
complexation, oxidation-reduction, and precipitationdissolution
reactions. In particular, the sorption/desorption reactions
of metal(loid)s on/from soil sorbents are influenced by pH,
nature of soil components, and presence and concentrations of
cations and inorganic anions. In recent years, many extraction
tests have been used for assessing trace elements mobility and
phytoavailability. Chemical speciation of toxic elements may be
achieved by spectroscopic analyses (XAS), which provide information
about oxidation state, symmetry, and identity of the
coordinating ligand environment, and possible solid phases
Biogeochemical processes at soil-root interface
No full textRhizosphere is a microsite where interactions among roots, microorganisms, soil constituents (minerals and
organic matter), and soil solution take place. Biomolecules produced by plants and microorganisms and soil
organic substances are involved in many biogeochemical processes at soil-root interface such as: a) weathering
of clay minerals and release of Al and Fe, b) formation of nanoprecipitates and organo-mineral complexes, c)
sorption/desorption of cations and anions on/from soil colloids and d) bioavailability of nutrients and pollutants.
Many exudates form strong complexes with Fe and Al ions, retard or inhibit their hydrolytic reactions and
promote the formation of noncrystalline or short-range ordered Al and Fe nanoprecipitates. The so-called iron
plaques, present on many wetland plant roots, are Fe(III)-oxyhydroxides (mainly ferrihydrite). These precipitates
may interact with biopolymers (proteins, polysaccharides, DNA, RNA and so on), phyllosilicates, soil organic
substances as well as microorganisms forming organo-mineral complexes. Root exudates play a vital role on the
sorption/desorption of nutrients and pollutants at soil-root interface. The processes, which affect the sorption
of cations and anions on sorbents present in the rhizosphere are particularly complex, being sorption of cations
quite different from that of anions. Root exudates usually inhibit the sorption of anions, but may promote or
inhibit the sorption of cations. They may desorb, at least partially, nutrients and pollutants previously sorbed
on soil components, promoting their bioavailability for plants and microorganisms. Finally, some plants release
chelating organic ligands able to complex metals (e.g. Al) which become less toxic. Many factors control these
processes, for example; pH, nature and concentration of the biomolecules present in the rhizosphere, nature of
sorbent and sorbate, reaction time
Spatial distribution, speciation and availability to plants and human beings of potentially toxic metals in soil from an automobile-battery recycling plant.
No full textMobilità e biodisponibilità di contaminanti metallici in un suolo agricolo interessato da sversamento di fanghi industriali
No full textIndagini geochimiche e saggi di biodisponibilitá-bioaccessibilitá di elementi potenzialmente tossici in suoli agricoli e industriali contaminati
No full textEffetto della fertilizzazione con acidi umici o composti inorganici sulla disponibilità dell'arsenico nel suolo e suo assorbimento da parte di piante di carota (Daucus carota L.) irrigate con acque contaminate
No full textChemical speciation to assess bio-availability, bio-accessibility and geochemical forms of potentially toxic metals (PTMs) in polluted soils (Chapter 10).
No full text
Nature, mineralogy and reactivity of aluminun-, iron(III)- and mixed iron(III)-aluminum-arsenate coprecipitates
No full textBeneficial effects of phosphorus fertilization, arbuscular mycorrhizal and saprophyte fungi on the growth of Cichorium envidia grown in arsenic contaminated soils
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