Mobilisation of sek-lected chemical constituents into the human food chain via Hortiocural produce crown in Dar es Salaam

Chemical constituents in irrigation water samples various localities in Dar es Salaam where horticultural produce is grown were analysed. Treated tap water supply, well and rivers were studied through the following quality parameters pH, conductivity, TDS. turbidity, nitrate, chloride and a selection of heavy metals including lead, admium, iron, manganese, chromium and zinc. The overall irrigation water quality sequence emerging is : treated tap water > well water > river water. The study has revealed that water is an 'excellent• water source for irrigation purposes. Analysis of phyko-chemical parameters of raw water from Upper Ruvu treatment works revealed that the product achieves optimal quality thereafter. Observed quality deterioration of created cap water at consumer points is a result of re-contamination due to factors both internal and external to the system. The mobilisation of heavy metals from the aquatic environment 10 biota was studied by examining comparative levels in the two. The study has revealed lha1.plants have ability to bioaccumulate metal levels in their biomass (bioaccumu lacion factor). Bioaccumulation of heavy metals in plants shows a considerable variation in efficiencies between various plant species. Sugar cane is a potential candidate for phyto remediation as it accumulation toxic heavy metals efficiently from polluted soil and water. Statistical tests validate the sourcing of the metal levels from the aqueous support. Findings reveal heavy metal levels above FAON/HO recommended limits in foods. The dietary load estimate from amaranthus has been attempted for Dar es Salaam consumers for whom it All findings exceed the RDDA levels stipulated in the Codex Alimentarius. Laboratory controlled experiments for bio-concentration of Pb, Cd and Cr in Amarantlws hybridus revealed that Cd was concentrated more in the leaves of the plant while Pb and Cr levels were highest in the roots. The BCR values as well as the metal ion concentration in the components of the vegetable increased with increasing concentration of the metal ions in irrigation water. Bio-concentration order for these three metals was:Cd > Pb > Cr.