Phytoremediation potential of Tripogandra diuretica for chromium and lead contaminated soils

Abstract

Chromium and lead contamination poses severe threats to human health, water and soil resources. This study investigates the tolerance of Tripogandra diuretica (Commelinaceae), a native South American perennial herb, to lead and chromium contaminated soils. Two greenhouse exposure assays were conducted simultaneously for 35 days with chromium (1001700 mg kg−1) or lead (150–1700 mg kg−1) contaminated soil, comparing them with a metal-free control soil. At the end of the assay, the metal content in leaves, root and soil; total leaves number, chlorophyll levels and dry weight (aerial and root tissue) were measured. Additionally, bioconcentration factor and translocation factor were estimated. T. diuretica demonstrated comparable responses to both chromium and lead exposure, demonstrating good tolerance to high lead doses. Both metals were accumulated in roots with only a minimal lead translocation to aerial parts in the highest lead soil concentration. Therefore, the translocation factor for chromium exposed plants was 0 for both metals and less than 1 for the highest lead concentration. The bioconcentration factor increased as the level of metals in soil increased. In both assays, a root growth stimulation, an increase in root dry weight and a decrease in aerial dry weight were measured. Moreover, the total leaves number and chlorophyll decreased only in chromium treatments. T. diuretica is an excluder plant, suitable as a ground cover in lead or chromium contaminated soils, by stabilizing metals in the roots, preventing their transfer to higher trophic levels.