Effect of the bentonite application on the cadmium mobility in an Argisol

Abstract

Aiming to evaluate the effect of doses of bentonite (0, 30 and 60 t ha -1 ) in the mobility of cadmium on an Argisol, tests of mobility in soil columns with different cadmium concentrations (50, 250 and 450 mg kg -1 of soil) and steady state flux, were conducted, determining its flux density and percolation velocity. The cadmium was dislocated by pulse, the solution containing the cadmium initially infiltrated into the soil for a given time period and afterwards the soil was lixiviated with distilled water. Leachates were collected every 10 minutes during 80 minutes of water percolation. The solutions percolated, expressed in pore volumes, were 6.33, 2.28 and 1.93 for the 0, 30 and 60 t ha -1 of bentonite, respectively, being one pore volume equal to 1.22 cm 3 . The concentration of cadmium was measured by atomic absorption spectrophotometry. At the end of the experiment, the columns were dismounted and the concentrations of cadmium in the soil at different depths (0-10, 10-20, 20-30 e 30-40 cm) were also determined. The results showed that the flux density and velocity of water percolation of the water solution were significantly reduced by the addition of bentonite to the soil. The levels of cadmium in the soil did not affect these mobility parameters. Increasing doses of bentonite favored the adsorption of cadmium in the soil.Keywords: heavy metal, miscible displacement, clay mineral. Efeito da aplicação de bentonita na mobilidade de cádmio em Argissolo RESUMOObjetivando-se avaliar o efeito da aplicação de doses de bentonita (0, 30 e 60 t ha -1 ) na mobilidade do cádmio num Argissolo, realizaram-se ensaios de mobilidade do referido metal em colunas de solo com diferentes concentrações de cádmio (50, 250 e 450 mg de kg -1 de solo) submetidas a lixiviação num regime saturado, determinando-se a densidade do fluxo e a velocidade de fluxo. O cádmio foi deslocado por pulso, isto é, a solução contendo o cádmio inicialmente infiltrou no solo por um determinado tempo quando então a lixiviação foi continuada com água destilada. Lixiviados foram coletados a cada 10 minutos durante 80 minutos de percolação. As soluções percoladas, expressas em volume de poros, foram 6,33; 2,28 e 1,93 para os tratamentos de bentonita de 0, 30 e 60 t ha -1 sendo um volume de poros igual a 1,22 cm 3 . As concentrações de cádmio determinadas por espectrofotometria de absorção atômica. Ao final dos ensaios, as colunas foram desmontadas e as concentrações de cádmio no solo a diferentes profundidades (0-10, 10-20, 20-30 e 30-40 cm), foram também TITO, G. A.; CHAVES, L. H. G.; GUERRA, H. O. C. Effect of the bentonite application on the cadmium mobility in an Argissol. Ambi-Agua, Taubaté, v. 7, n. 2, p. 18-29, 2012