Phytotoxicity of cadmium and barium and derivation of critical limits in soils / Fitotoxidade de cádmio e bário e derivação de lilites críticos em solos

AUTOR(ES)
DATA DE PUBLICAÇÃO

2011

RESUMO

Soil pollution by heavy metals caused by anthropogenic activities is a problem in many countries. Cadmium (Cd) is one of the most hazardous elements due to its relatively high mobility in soils and transfer to plants. The main human exposure pathway to Cd is through the vegetable consumption and depends on the exposure scenario. Thus, defining a critical limit of Cd in soil is necessary. Barium is an earth alkaline element that can be toxic to humans and plants when it is present in the free form (Ba2+). However, only few studies have focused on Ba in soil. Soil characteristics influence Cd and Ba availability for plant uptake. Both metals may affect plant growth and metabolism and cause oxidative stress. The aims of this study were: (i) to compare tropical and temperate datasets to establish critical soil Cd concentrations for the State of São Paulo, Brazil; (ii) to evaluate the influence of liming on Cd availability and accumulation in lettuce in order to calculate site specific critical soil Cd concentrations for two typical tropical soils from the State of São Paulo; (iii) to evaluate the effects of Cd and Ba concentrations on plant growth, lipid peroxidation and activities of antioxidant enzymes in leaves of soybean, grown in tropical soils with contrasting properties. The Cd uptake from the tropical dataset was higher as compared to the temperate dataset. Critical soil Cd concentrations were from 1.7 to 3.2- fold lower when tropical soil data were used. It is suggested that only literature data, regarding Cd in soils and vegetables, from tropical regions should be used for the State of São Paulo to derive critical soil Cd concentrations. Cadmium accumulated linearly in lettuce at soil concentrations up to 12 mg kg-1. In both soils, a slight reduction on Cd uptake was observed as a response to liming. The calculated critical soil Cd concentrations were lower in the Ultisol because of the differences in soil characteristics. Besides, there was a positive correlation with the vegetable consumption rates. Cadmium strongly reduced soybean growth at concentrations from 5.2 mg kg-1, while Ba only slightly reduced at 600 mg kg-1 in the sandy Entisol. The activities of superoxide dismutase, catalase and glutathione reductase were dependent mainly on the soil type: soybean plants grown in the Entisol suffered higher oxidative stress than those grown in the clayey Oxisol and, consequently, responded less to the increase of metal concentrations.

ASSUNTO(S)

estresse oxidativo fitotoxicidade heavy metal human health metal pesado oxidative stress phytotoxicity poluição do solo saúde pública soil pollution soil quality standard. solos - qualidade.

ACESSO AO ARTIGO

Documentos Relacionados