Maria Odete Torres

Effects of heavy metals on the growth and mineral composition of a nickel hyperaccumulator

Abstract Alyssum pintodasilvae Dudley is a nickel (Ni) hyperaccumulator endemic to serpentine soils of north‐east Portugal. In one experiment, the effects of cadmium (Cd), chromium (Cr), copper (Cu), Ni, lead (Pb), and zinc (Zn) on the growth and mineral composition of this species were evaluated. The growth of A. pintodasilvae, measured by dry matter accumulation, was not influenced by the presence of Cr, Cu, Pb, Ni, or Zn in the soil, but Cd applications led to significant decreases in dry matter yield. The addition of heavy metals to the soil resulted in increased uptake and translocation by A. pintodasilvae but only Ni was accumulated to high levels. In a second experiment, two cuts of A. pintodasilvae, grown on a Ni‐enriched soil, were compared. Nickel concentrations were higher in the second cut, suggesting the possibility of continued growth and harvest of this plant to detoxify Ni‐contaminated soils.

Effect of polyacrylate polymers with different counter ions on the growth and mineral composition of perennial ryegrass

Abstract Enhanced plant growth following the application of hydrophilic polymers has been assumed to result from increased water supply. However, little attention has been paid to the contribution of counter ions to plant nutrition or to their effects on soil characteristics, such as pH, that might influence plant growth and nutrient availability. We investigated the effects of polyacrylate polymers with different counter cations, sodium (Na+) and potassium (K+) or NH4 +, on some characteristics of an acid soil, and on dry matter accumulation, water use efficiency, and the mineral composition of perennial ryegrass. Addition of polymers to the soil enhanced plant growth to a greater extent than did liming. The presence of the Na‐polymer or the Na—NH4 +‐polymer resulted in the greatest biomass accumulations by perennial ryegrass. Evapotranspiration was greatest in the soil amended with the Na‐polymer and similar in soils amended with the Na K‐polymer or the Na NH4 +‐polymer. Total plant dry matter was corre...

REMEDIATION OF SANDY SOIL ARTIFICIALLY CONTAMINATED WITH CADMIUM USING A POLYACRYLATE POLYMER

Soil pollution with toxic metals has become an important social and environmental challenge. When the polluted area is large and the site poses little immediate risk to health or environment, in situ remediation technologies can be envisaged. Here we used a polyacrylate polymer to immobilize cadmium (Cd) in a sandy soil artificially contaminated with the metal. Growth of perennial ryegrass in pots with 9.5 kg of soil was stimulated in polymer-amended soil. Even in pots with the highest levels of Cd, growth was much less impaired than in pots without polymer. Shoot Cd concentrations were smaller in the plants cultivated in the amended soil. Because water soluble Cd was considerably reduced in the contaminated polymer-amended soil, the effect of the polymer on plant growth was attributed to the decrease of Cd concentration in soil solution.

A preliminary spatial-temporal study of some soil characteristics in the calcareous massif of Sicó, Portugal

The mountainous massif of Sicó, in the centre of Portugal, is an extensive area composed of calcareous Jurassic formations. Hillside calcareous soils, with high pH, present chemical restrictions to support plant growth and are subjected to important erosion processes leading to their degradation if not protected by vegetation. In a first year of study some soil physicochemical characteristics have been measured in some geo-referenced locations of a larger design experiment and an exploratory spatial analysis has been performed. The objective of this study was to present some suggestions in order to give sustainable phosphorus fertiliser recommendations aiming to establish pastures in these soils and thus support traditional livestock activity. Ten years apart, those soil characteristics have been measured again in the same locations and comparisions have been made. The objective was to understand the variability of the soil properties under study in order to better adequate the fertiliser soil management regarding the area restoration.

Lead uptake and distribution in legume species grown on lead-enriched soils

Soils can be progressively enriched with lead due to the application of sewage sludge and city refuse or from aerial deposition. Lead incorporated into soils is usually precipitated or tightly bound to colloidal materials and presents low availability to plants. Even so, plants grown on these soils can take up and accumulate increasing amounts of lead. Lead translocation is very restricted, so that roots contain lead at greater concentrations than above-ground tissues. However, translocated lead can be sufficient to be harmful to the animals that eat those plants. In the present work, we studied lead uptake and distribution in lupins (Lupinus spp.) and berseem (Trifolium alexandrinum L.) grown in nutrient solutions or on soils that were enriched with lead. Lead uptake varied with the external lead concentration, the soil cation-exchange capacity and the plant species. Regression equations were determined for each experiment and compared. The results showed that translocation was restricted in both species, where lead accumulated in roots could represent over 95% of the total lead content. Berseem plants presented higher lead concentrations, both in roots and shoots, than lupins.