FitorremediaÃÃo de arsÃnio: disponibilidade do metalÃide no solo e seu acÃmulo em girassol e mamona. / Arsenic phytoremediation: metalloid forms in soils and its accumulation in plants.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

The increasing accumulation of arsenic (As) in soils and water bodies has caused increasing concern about human and animal exposure to this metalloid in the environment. As a result, studies assessing the bioavailability of arsenic by different soil extractants and the effect of phosphorus (P) upon this metalloidâs availability, combined with research comparing plant performance in terms of biomass production and As removal from contaminated soil and water are necessary not only to assess the risk of As entry into the food chain, but also to help with the development of remediation strategies for contaminated areas. Phytoextraction is among the alternatives that can be used for remediation of contaminated areas, and is characterized by the concentration of a contaminant in plant shoots, followed by its removal from the contaminated area. The objectives of this work were: (1) to quantify the production of biomass and accumulation of As in castor bean plants grown in nutrient solution aiming to evaluate the plantâs phytoextracting potential as well its tolerance to this metalloid; (2) to assess the tolerance of sunflower and castor bean plants in two soils contaminated with As, to compare the removal of As by these species and to determine As bioavailability as estimated by different soil extractants (tridestilled water, ammonium sulfate, ammonium phosphate, ammonium oxalate + oxalic acid, organic acids mixture, Mehlich-1 and USEPA 3051A; and, (3) to evaluate the effect of phosphorus upon arsenic availability to sunflower (Helianthus annus) grown in two As-contaminated soils, comparing their biomass production and As accumulation capacities. Greenhouse experiments were conducted with plants grown in pots containing a nutrient solution amended with increasing doses of As (0, 10, 50, 100, 250, 500 and 5000 Âg L-1), as well as in two soils with different clay and organic matter content, amended with 0, 35, and 150 mg As dm-3 soil. Shoot and roots dry matter production as well as arsenic and nutrient tissue concentrations and contents were measured at the end of the experiments (35 days). Arsenic availability to plants was also evaluated by different soil extractants. The results showed that increasing As concentration in the nutrient solution causes a reduction in dry matter production of castor bean roots and shoots, but does not cause severe phytotoxicity symptoms. Arsenic concentrations were higher in roots compared to shoots. The addition of As in the nutrient solution does not affect the accumulation of nutrients. Castor bean and sunflower plants do not show characteristics of phytoextracting plants, but could be used for phytostabilization of As-contaminated areas. We could not recommend any of the tested extractants due to poor correlations found between soil As with either As concentration/content in plants or dry matter production. Increasing P doses decreased As adsorption and, consequently, a higher solubility of the metalloid in the soil. The addition of a molar P/As ratio of 3.23 in a Typic Oxisol and 13.76 in an Entisol caused an increase on As removal by sunflower grown in As-contaminated soils, indicating that the application of P could be used to maximize the efficiency of this species for remediation of As-contaminated areas.

ASSUNTO(S)

remediaÃÃo do solo plantas oleaginosas extratores quÃmicos contaminaÃÃo do solo ciencia do solo

ACESSO AO ARTIGO

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