Phytoremediation capabilities of sunflower (<i>Helianthus annuus</i> L.) in heavy metal (As and Cd) contaminated soil

Abstract

The study investigated the phytoremediation capabilities of oil seed plant (Helianthus annus). The plant was grown on potted soils polluted with heavy metals (As and Cd) contaminant in a randomized complete block design (RCBD) and analyzed to evaluate its efficacy for the removal of As and Cd. Results obtained from the preliminary analysis of the soil physicochemical characteristics were within limits for plant optimal growth. There were variations in heavy metal concentration in the different parts (roots, stems, leaves and seeds) of test plants and significant difference (P<0.05) between plant part following a decreasing order of concentration. (300>200>100>0) mg/kg, leaf – Cd content was higher than As content, in the following order: Cd > As and in a decreasing order as per plant parts as follows: leaf > stem > root > seeds. The application of metal concentration in soil increases as metal- ion, uptake in plant increases across the treatments as follows: 300mg/kg > 200mg/kg > 100mg/kg > 0mg/kg. Result indicated that heavy metals concentration in whole and plant parts, exception of the seeds were above the WHO/FAO recommended limits. The general trend of heavy metal accumulation in plants parts of H.annus in terms of Bio concentration factors indicated that H. annuus is an hyper-accumulator of heavy metals having exceeded BCF bench mark of 1 > 10. and is therefore classified as high efficiency plants for metal translocation from root to shoot as the transfer factors were above TF value > 1. However, the plant showed symptoms of phytoxicity, especially when heavy metals were applied at high concentrations (300mg/kg) as evidence in stunted or growth retardation as well as yellowing of leaves and low yield .