CHROMIUM AND LEAD UPTAKE BY ALFALFA AND ORCHARD GRASS

Abstract

The effluent of the sewage treatment plant of the City of Aguascalientes contains chromium and lead. This effluent is used to irrigate alfalfa (Medicago sativa) and orchard grass (Dactylis glomerata). The present study was carried out to evaluate the uptake of both metals by the two mentioned species. Plots were sown with alfalfa and orchard grass and irrigated with solutions containing 6, 12 or 24 mg L-1 of chromium, and 5, 10 or 20 mg L-1 of lead when seedlings were three weeks old. The irrigation treatments were repeated every two weeks, during 4 months. Soil and plants samples were collected at different growth stages and digested with nitric acid for chromium and lead determination. Metals in solution were determined by atomic absorption spectrophotometry. Chromium uptake by orchard grass was higher than by alfalfa, and uptake was a function of the amount applied. Chromium content of orchard grass roots was twice that of the aboveground portion, however, in alfalfa, this ratio was closer to equality. Lead uptake by these species was less than that of chromium. Orchard grass accumulated more lead in the roots than in the above ground portion, however, the opposite was true in the case of alfalfa.