PLANT UPTAKE AND DETERMINATION OF ARSENIC SPECIES IN SOIL SOLUTION UNDER FLOODED CONDITIONS

Previous studies have not identified the different As species present in soil systems and determined if effective differences exist between As species with respect to plant parameters such as growth rate and As uptake. This study determined the species and concentrations of As pr esent in soil solution of flooded soils and correlated them to As conc entration, P concentration, and growth rate of plants grown in treated soils. Rice (Oryza sativa L.) was grown in two soils treated with 0, 5, 15, 25, 35, and 45 mg As kg(-1) soil added as either Naarsenate or Na-arsenite. Soil solution samples and plant samples were collected ov er a period of 60 d. The As concentration of rice plants best correlat ed to the mean soil solution arsenate concentration in a Beaumont clay (fine, montmorillonitic, thermic Entic Pelludert) and to the mean soi l solution arsenite concentration in a Midland silt loam (fine, montmo rillonitic, thermic Typic Ochraqualf). in both soils, plant P concentr ation was best correlated to the amount of As added to the soil rather than any soil solution As concentration. Plant weight was best correl ated to the mean soil solution arsenate concentration in both soils. T he rate of As uptake by plants increased as the rate of plant growth i ncreased. Plants grown in soils treated with As had higher rates of As uptake for similar rates of growth when compared with plants in untre ated soils. However, growth per unit of As uptake was higher for plant s in untreated soils than plants in As treated soils.