Search

Several particular plants are suggested to extract significant parts of heavy metals from soils and accumulate them in their roots and shoots. This research aimed to study the phytoextraction of Cu by several plants from heavy-metal contaminated tropical soils. Soil samples collected from plots treated in 1998 with 0, 15 and 60 Mg industrial waste ha-1 were planted with three different plants, i.e., caisim, water spinach, and lettuce. Plant parts (roots and shoots) and soil samples were harvested after a four-week growth period and analyzed for plant and soil Cu. The results show that the growth of plants was depressed by the increase in the soil Cu (extracted by 1 N HNO3) as affected by waste levels, with water spinach being the most progressive and produced the most significant biomass. The absorption of Cu by caisim and water spinach increased with the soil extracted Cu (linear R2 = 0.71* for caisim and 0.32* for water spinach) and accumulated greater in plant roots than that in shoots. The translocation factor (TF << 1.00) indicates that all plants were good Cu phytostabilizators rather than phytoextractors, with water spinach being the best Cu extractor.

The utilization of red mud, which is a residue from the extraction of aluminum from mined bauxite ore, as a plant growing medium, needs to be studied further. There are some chemical aspects that may hinder the growth of, or even cause mortality in, plants such as very high pH, electrical conductivity (EC) and exchangeable Na (Na exch ), and very low nutrient elements content. The objective of this study was to investigate the effects of adding Ultisol soil material, mixed with compost, both soil ameliorating agents, to red mud for use as a growing medium for Sengon ( Paraserianthes falcataria ) seedlings. This study was conducted in two stages, namely: washing of the red mud, and trial planting in the greenhouse using different combinations of the soil ameliorants. Washing of the red mud with tap water was intended to reduce the levels of Na, EC, and pH. Trial planting in the greenhouse was carried out in 2-factorial Completely Randomized Design (CRD). Factor 1 was the proportion of the mixture of Ultisol soil material (sm-Ultisol) and red mud, viz : (1) 1500 g red mud + 0 g sm-Ultisol, (2) 1000 g red mud + 500 g sm-Ultisol, and (3) 750 g red mud + 750 g sm-Ultisol. Factor 2 was the dosage of compost that was mixed with the red mud and sm-Ultisol, namely: 0, 58.6, and 117.2 g/polybag which corresponded to 0, 2.5 and 5 kg/planting hole, respectively. The results of the trial indicated that washing the red mud could reduce the level of EC from 28.70 dS m -1 to 2.68 dS m -1 ; but it reduced pH and Na exch only from 11.91 and 149.38 cmol (+) kg -1 to become 10.55, and 66.74 cmol (+) kg -1 , respectively. A better outcome was obtained after the red mud was washed and then, mixed with sm-Ultisol up to 1:1 proportion in which resulted in lower rates of pH, EC, and Na exch from 10.28, 2.53 dS m -1 and 62.79 cmol (+) kg -1 to 8.65, 2.07 dS m -1 and 45.01 cmol (+) kg -1 , respectively. The treatment of using a mixture of 750 g red mud + 750 g sm-Ultisol, and adding compost at 117.18 g/polybag gave the best result in improving the chemical property of the red mud growing medium, and producing the best plant growth among all treatment combinations.