Abstract
The objective of this study was to determine the effect of zinc, copper and cadmium on phytomass and grain production and to evaluate indirectly the adsorbent effect of bentonite clay by determining the accumulation of these heavy metals in bean plants. The study consisted of three separate experiments (one for each cation) with the application of three doses of bentonite (0, 30 and 60 t ha-1) in pots containing separately 50 mg of Zn; Cu and Cd kg-1 of soil, with three replicates. Thus, each experiment consisted of 9 experimental units. In each one, a bean plant was cultivated and after 65 days, samples of leaves, stems, roots and grains were collected. Afterwards, the samples were dried, weighed, grinded and the concentrations of Zn, Cu and Cd were determined. The phytomass of leaves of the plant growing on the soil with Zn, the Zn concentration in the whole plant and the Cd concentration in the leaves, stem and grains were significantly influenced by the bentonite application. Zn and Cd concentration in leaves, stem and grains decreased with the application of bentonite, indicating a positive effect of the clay application to the soil on the adsorption of these metals, decreasing the availability for plants. Zn was the most accumulated element in the plant, followed by Cd and Cu. The Zn, Cu and Cd accumulation in the plant obeyed the following sequence: stem > leaves > grains > roots; roots > stem > grains > leaves; roots > stem > leaves > grains, respectively.
Highlights
The accelerated increase of population, city urbanization, industrial and technological development, indiscriminate use of fertilizers, soil amendments has contributed to the increase of heavy metals in the soil and water (Rangel et al, 2006; Cunha et al, 2008).The use of contaminated soils and water is more worrying, when they are used for agriculture and horticultural products and harvested parts of these plants are consumed by humans, because plants are the main entry of the heavy metals in the food chain (Alcarde & Rodella, 2003)
The objective of this study was to determine the effect of zinc, copper and cadmium on phytomass and grain production and to evaluate indirectly the adsorbent effect of bentonite clay by determining the accumulation of these heavy metals in bean plants
The data show that the soil utilized in the study was not contaminated by these heavy metals
Summary
The use of contaminated soils and water is more worrying, when they are used for agriculture and horticultural products and harvested parts of these plants are consumed by humans, because plants are the main entry of the heavy metals in the food chain (Alcarde & Rodella, 2003) Heavy metals, such as zinc (Zn), copper (Cu) and cadmium (Cd), frequently accumulate in the surface layer of the soil (0–20 cm), called the “agricultural layer”, making these elements available to the roots and accumulated in the plant, reaching toxic levels when present in high concentrations. The low cost and high availability of these materials (Chui, 2005; Lacin et al, 2005) and their adsorption properties has caught the attention for its use as an alternative adsorbent material. Lacin et al (2005) has shown that bentonite is highly efficient for the removal of zinc ions and adsorption of toxic heavy metal cations such as Cu, Cd and Pb
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