CLOVER AND CRESS AS INDICATOR SPECIES OF IMPACTS FROM LIMED SEWAGE-SLUDGE AND LANDFILL WASTE-WATER LAND APPLICATION

This study evaluated the performance of cress and clover as bioindicat ors to evaluate the impact of limed sewage sludge and landfill wastewa ter application on soil. The use of these two species, and the subsequ ent parameters measured, were also compared for their effectiveness in evaluating potential effects. Sewage sludge was added to the soil at a rate of 23 mg ha(-1) and also at twice this dose. Wastewater was add ed at a level of 2 and 10% of the soil volume. Germination rate, heigh t increase per week and final dry biomass were measured for both speci es. Heavy metal (Cd, Pb, Fe, Cu, Ni, and Zn) concentration was determi ned only for the shoot and root of clover. In general, the results sho wed that, compared to the control, the overall performance improved fo r plants exposed to both treatments. However, plants appeared to respo nd better to the wastewater addition than the sewage sludge amendment. The germination rate as well as other traits indicate that clover may be more sensitive to these fertilizers than cress. The lime addition did not appear to influence growth, nor heavy metal accumulation in cl over. There were major differences in heavy metal accumulation in the root vs. shoot of clover. Hence, the concentrations of Cd, Cu, Fe, Zn, and Pb did not vary in the shoots of the plants under either treatmen ts. The concentrations of the heavy metals in the roots however, great ly varied according to the type of metals. The concentrations of these metals appeared to increase with the increase of the addition treatme nts. The results suggest that for both species, the levels of fertiliz ers used in the present study were below the toxicity levels. Since th e types of soils and the doses of fertilizers influence the rate of he avy metal absorption and their effects on plants, methods for rapid ev aluation/monitoring as well as the types of indicators used should be explored as in the present study. (C) 1998 Elsevier Science B.V. All r ights reserved.