ELSEVIER The Science of the Total Environment 153 (1994) 117-121 the Science of the Total Environment A l ~ m ~ ~ s~mme I~a L . ~ t k ~ ~ b ~ g m Uptake of Zn, Co, Fe and Cr by water hyacinth ( Eichhornia crassipes) in Lake Chivero, Zimbabwe Mark F. Zaranyika*, Felix Mutoko, Howard Murahwa Chemistry Department, Universityof Zimbabwe, P.O. Box MP 167, Mount Pleasant, Harare, Zimbabwe Received 1 June 1993; accepted 24 September 1993 ~stract The levels of Zn, Co, Fe, Ni, Cu, Pb and Cr were determined in water hyacinth growing in Lake Chivero, Zimbabwe, as well as in the water of the lake. Except for Ni, for which levels tended to be similar both in the tops and roots of the plant, levels of the other elements studied were significantly higher in the roots than in the tops. The concentrations of the elements in the plants were much higher than those in the water. Concentration factors of up to 33, 1.7 x 102, 7 x 102 and 8.9 x 10 3 in the tops, and 1.7 x 102, 2.7 x 102, 2 × 103 and 1.5 x 104 in the roots were found for Co, Zn, Cr and Fe, respectively. Keywords: Bioconcentration; Bioaccumulation; Metal uptake; Water hyacinth 1. Introduction Environmental pollution has become a global concern to which developing countries are slowly awakening. One of the major areas of concern in Zimbabwe is pollution of surface and under- ground water systems by discharges from agricul- ture and industry. Thus in recent years much attention has been focussed on the quality of the water in Lake Chivero, the main water source for the city of Harare (Greichus et al., 1978; Mhlanga and Madziya, 1990). The city has a population of one million. Pollution of the lake thus poses a major health risk. Lake Chivero receives its water from three major rivers, Mhanyami, Mukuvisi and Marimba. Fig. 1 shows that the sources of all three rivers * Corresponding author. are in the city, so that the city is the catchment area for its own water supply. Pollution of the Mukuvisi river by toxic heavy metals such as lead, cobalt and cadium has been reported (Mathuthu et al., 1993; Zaranyika et al., 1993). Pollution of the lake waters by toxic heavy metals has also been reported (Greichus et al., 1978). Possible sources of this pollution are industrial effluent and sewage effluent discharged into the three rivers. A further possible source is run-off from agriculture during the rainy season. In view of the location of the lake in relation to Harare (Fig. 1), the problem of pollution of the lake is likely to get worse with time. Among the various ways that are being considered to combat this problem is the possible use of water hyacinth (Eichhornia crassipes) as a scavanger of heavy metal pollutants in the lake and its associated rivers. Both lake and rivers are infested with 0048-9697/94/$07.00 @ 1994 Elsevier Science BV. All rights reserved. SSDI 0048-9697(94)04073-I