Abstract

Urbanisation and industrialization lead to heavy metal pollution in the Nakivubo drainage ecosystem. The objectives of this study were to determine heavy metal concentrations and distribution in Commelina benghalensis (L.) and Cynodon dactylon (L.) that grows in different polluted sites along the urban stream sediments of the Nakivubo drainage ecosystem in Kampala, Uganda. To investigate the possibility of using these plant species in phytoextraction and phytostabilisation of heavy metal pollutants, assessment of heavy metals was done using flame atomic absorption spectrophotometer. Bioaccumulation factor and translocation factor values (BAF and TF > 1) for both plant species were greater than one for Cu at some sites suggesting efficient accumulation in the shoot. BAF > 1 and TF < 1 values for Pb, Cd and Zn suggest accumulation in roots and qualify these plants also as good candidates for phytostabilisation. In conclusion, the heavy metal sequestration from urban stream sediments by plant parts that are harvestable are characterized and recommended as good candidates for phytoremediation (phytoextraction and phytostabilisation) and can be used as indicators of heavy metal pollution for the urban stream ecosystem.

Key words: Bioaccumulation, heavy metals, phytostabilisation, translocation, wastewater.