Abstract
Phytoremediation strategies utilize plants to decontaminate or immobilize soil pollutants. Among soil pollutants, metalloid As is considered a primary concern as a toxic element to organisms. Arsenic concentrations in the soil result from anthropogenic activities such as: the use of pesticides (herbicides and fungicides); some fertilizers; Au, Pb, Cu and Ni mining; Fe and steel production; coal combustion; and as a bi-product during natural gas extraction. This study evaluated the potential of pigeon pea (Cajanus cajan), wand riverhemp (Sesbania virgata), and lead tree (Leucaena leucocephala) as phytoremediators of soils polluted by As. Soil samples were placed in plastic pots, incubated with different As doses (0; 50; 100 and 200 mg dm-3) and then sown with seeds of the three species. Thirty (pigeon pea) and 90 days after sowing, the plants were evaluated for height, collar diameter and dry matter of young, intermediate and basal leaves, stems and roots. Arsenic concentration was determined in different aged leaves, stems and roots to establish the translocation index (TI) between the plant root system and aerial plant components and the bioconcentration factors (BF). The evaluated species showed distinct characteristics regarding As tolerance, since the lead tree and wand riverhemp were significantly more tolerant than pigeon pea. The high As levels found in wand riverhemp roots suggest the existence of an efficient accumulation and compartmentalization mechanism in order to reduce As translocation to shoot tissues. Pigeon pea is a sensitive species and could serve as a potential bioindicator plant, whereas the other two species have potential for phytoremediation programs in As polluted areas. However, further studies are needed with longer exposure times in actual field conditions to reach definite conclusions on relative phytoremediation potentials.
Highlights
Phytoremediation has been considered as an emerging low-cost technique to reclaim areas polluted by toxic elements
The objective of this work was to determine the potential of pigeon pea, wand riverhemp, and lead tree for potential phytoremediation and/or revegetation of As-polluted areas
The symptoms were characterized by intervein chlorosis followed by wilting and tissue necrosis (Adriano, 1986)
Summary
Phytoremediation has been considered as an emerging low-cost technique to reclaim areas polluted by toxic elements. Few species have been reported as capable of accumulating As. Despite the existence of many sources of soil contamination, there are few studies related to tolerance, absorption and translocation of As in shrub plants. Despite the existence of many sources of soil contamination, there are few studies related to tolerance, absorption and translocation of As in shrub plants These have been widely studied for other metals in polluted environments. For this reason, the knowledge of patterns of absorption, translocation and accumulation of ions such as As, the tolerance limits and phytotoxicity symptoms of species with potential for phytoremediation has gained importance (Huang & Cunningham, 1996, Visoottiviseth et al, 2002). The in-situ application of technologies using plants for immobilization and/or stabilization of toxic metals appears economical rather than other ex-situ non-biological remediation techniques (Glass, 1997; Susarla et al, 2002)
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