vi
calcium/potassium, organic matter content, etc. and also weather conditions, plant
species, and land-use practices.
Generally, plant roots are associated with microorganisms, and these links can
have direct or indirect effects on the mobility, availability, and acquisition of elements by plants. The fast uptake of uranium by roots might result due to precipitation of U in the apoplasm as was shown for other heavy metals and also might be
possible due to adsorption of U on the cell wall. Plant cell walls are made up of
cellulose fibers, hemicellulose, pectin, and glycoproteins. It is well-known that the
cell wall also works for root cation exchange capacity (CECR) basically for functional groups of polysaccharides, including carboxyl and galacturonic acid groups
of roots, and, to a minor extent, for phenolic and amine groups. There are two ways
for radionuclides to enter plants: either through the roots or through the stomata
(direct deposition from the atmosphere). Stomatal entry is supposed to account only
for a small fraction of total radionuclide uptake. When a radionuclide enters through
the cuticle layer, it is dynamically transported inside the plant cells through a symplastic pathway and with an exchange mechanism between the phloem and the
xylem.
The peculiarities of plant uptake and translocation of uranium are highly specific
for different types of plants and soil. Soils high in phosphorous content may tend to
suppress uranium uptake in plants. Mobility of U is reduced in finer-textured soils
and those high in organic matter. Plants cannot differentiate isotopes of heavy elements and consequently take up isotopes in the ratios present in soil solution. The
utmost forms of plant-available U in shallow groundwater are soluble carbonate
complexes, with uranium dominantly present in the hexavalent oxidation state.
Generally, the soil-to-plant relocation of elements is often parameterized by the
transfer factor (TF). Basically, the TF is the activity concentration of the radionuclide per unit dry mass in the plants (Bqkg
–1
) divided by the one in the soil (also
given in Bqkg
–1
).
During the past two to three decades, phytoremediation practices became a very
attractive popular alternative to the conventional expensive and energy- and
instrument- intensive, chemical-based restoration techniques of the vast polluted
areas of land and water. Plants are usually resistant to moderate concentrations of
radionuclides. Nevertheless, biosorption to cell walls, extracellular precipitation,
reduced uptake, or amplified efflux are mutual tools from which plants check abiotic stress and also decrease the absorption of metal inflow in cells.
The most remarkable features of this book are interrelated to how U enters the
ecosystem and its translocation from soil to plants and finally into the food chain of
man. Chapters 1–3 deal with the beginning of the nuclear age till now, impact of U
mining on human health, and soil-to-plant transfer of U and its distribution with a
case study on Belarusian soil. Chapters 4 and 5 focus on biogeochemistry of U in
tropical environment and mechanism of U accumulation in agricultural plants.
Chapters 6–8 focus on what are the factors influencing soil-to-plant transfer, its
translocation mechanism, its correlation with other metals, and uptake and phytoremediation approaches. Chapters 9–11 emphasize on the influence of U speciation
on uptake mechanism, epidemiological studies with some modeling, legacy, and
Preface
calcium/potassium, organic matter content, etc. and also weather conditions, plant
species, and land-use practices.
Generally, plant roots are associated with microorganisms, and these links can
have direct or indirect effects on the mobility, availability, and acquisition of elements by plants. The fast uptake of uranium by roots might result due to precipitation of U in the apoplasm as was shown for other heavy metals and also might be
possible due to adsorption of U on the cell wall. Plant cell walls are made up of
cellulose fibers, hemicellulose, pectin, and glycoproteins. It is well-known that the
cell wall also works for root cation exchange capacity (CECR) basically for functional groups of polysaccharides, including carboxyl and galacturonic acid groups
of roots, and, to a minor extent, for phenolic and amine groups. There are two ways
for radionuclides to enter plants: either through the roots or through the stomata
(direct deposition from the atmosphere). Stomatal entry is supposed to account only
for a small fraction of total radionuclide uptake. When a radionuclide enters through
the cuticle layer, it is dynamically transported inside the plant cells through a symplastic pathway and with an exchange mechanism between the phloem and the
xylem.
The peculiarities of plant uptake and translocation of uranium are highly specific
for different types of plants and soil. Soils high in phosphorous content may tend to
suppress uranium uptake in plants. Mobility of U is reduced in finer-textured soils
and those high in organic matter. Plants cannot differentiate isotopes of heavy elements and consequently take up isotopes in the ratios present in soil solution. The
utmost forms of plant-available U in shallow groundwater are soluble carbonate
complexes, with uranium dominantly present in the hexavalent oxidation state.
Generally, the soil-to-plant relocation of elements is often parameterized by the
transfer factor (TF). Basically, the TF is the activity concentration of the radionuclide per unit dry mass in the plants (Bqkg
–1
) divided by the one in the soil (also
given in Bqkg
–1
).
During the past two to three decades, phytoremediation practices became a very
attractive popular alternative to the conventional expensive and energy- and
instrument- intensive, chemical-based restoration techniques of the vast polluted
areas of land and water. Plants are usually resistant to moderate concentrations of
radionuclides. Nevertheless, biosorption to cell walls, extracellular precipitation,
reduced uptake, or amplified efflux are mutual tools from which plants check abiotic stress and also decrease the absorption of metal inflow in cells.
The most remarkable features of this book are interrelated to how U enters the
ecosystem and its translocation from soil to plants and finally into the food chain of
man. Chapters 1–3 deal with the beginning of the nuclear age till now, impact of U
mining on human health, and soil-to-plant transfer of U and its distribution with a
case study on Belarusian soil. Chapters 4 and 5 focus on biogeochemistry of U in
tropical environment and mechanism of U accumulation in agricultural plants.
Chapters 6–8 focus on what are the factors influencing soil-to-plant transfer, its
translocation mechanism, its correlation with other metals, and uptake and phytoremediation approaches. Chapters 9–11 emphasize on the influence of U speciation
on uptake mechanism, epidemiological studies with some modeling, legacy, and
Preface