Summary:
This present study is part of the Master of Science (MsC) titled "Applied
Environmental Geology" of the National University of Athens.
Selenium belongs to metalloids with characteristic chemical and physical
properties which are intermediate metals and non-metals, which occurs at 4
oxidation states: selenate (6+), selenite (2+), selenide (2-) and elemental
form (0).
Selenium is characterized by a wide range of applications in industry, mainly
in elemental form. It finds application in improving the machinability and
porosity in steel, the discoloration and staining glass, it is used as catalyst
in chemical reagents, lubricants and medicaments. Because of its unique
properties of the semiconductor, the high purity selenium is used in
xerography, in photoelectric cells, rectifiers and solar cells.
The antioxidant capacity of selenium makes it essential to human health. Trace
amounts of selenate or sodium selenite are added to poultry feed, pigs, cattle
and dairy cattle, in order to secure the daily nutritional requirements in
selenium.
Because the mobility and uptake of selenium by plants and animal organisms are
significantly determined by soil factors that contribute to bioavailability,
the cultivation of two plant species (alfalfa and lettuce) in acidic and
alkaline environment in order to study the soil acidity as one of the most
critical indicators of interaction between soil solution and plant species, was
the main subject of this study.
Cultivation was carried out in a greenhouse under controlled environmental
conditions, of the Agricultural University of Athens. In these cultivations was
added selenium (sodium selenate Na2SeO4 1 M) in two installments stages,
concentration 5 ppm each one, with an interval of about two months to
investigate the selenium absorption by plant tissue suitable for human and
animal use.
The plant samples were separated according to their soil growth substrate, in
acidic and alkaline environment. In order to the better comparison between
selenium values in soil and plant tissues, as well as to achieve reliable
results, all samples of two cultivations contain samples as controls and
replicates. The measurements, which are derived from soils and plant tissues,
showed remarkable selenium absorption difference depending on the crop.
Specifically, the cultivation of clover (shoots and roots) scored the highest
selenium levels in acidic soil conditions, contrary to the seedlings of
lettuce, which absorbed bioavailable selenium in alkaline conditions.
By combining the experimental procedure and selenium values, which were
determined in all the samples of plants, showed that the acidic soil substrate
is suitable for the absorption of selenium in the cultivation of clover. In
contrast to the clover, the cultivation of lettuce plants, showed that optimal
range field pH values are the alkaline range, to achieve higher selenium
accumulation performance.
Keywords:
Selenium, Trifollium, Lettuce, Bioaccumullation, pH
