Analysis of selected heavy metals contamination of roadside pond water, their deposition to sediments and potential assimilation into lants: a case of Boko Chama pond

Analyses of selected heavy metals (Cd, Pb, Zn and Cu) were conducted on a roadside pond located at Boko Chama, Dar es Salaam: water; soil sediment; and the surrounding growing plants (Cynodon dactylon and Cyperus species) were studied and analyses carried out using atomic absorption spectrometry (GBC XPLOOR AAS). The heavy metal amounts detected in the pond water samples were 0.0637 ± 0.0023 mg/L for Cd, 0.995 ± 0.073 mg/L for Pb, 0.303 ±0.161 mg/L for Zn and 0.096 ± 0.068 mg/L for Cu. For soil sediments the amount of heavy metals detected ranged from 5.115 ± 0.163 mg/kg to 9.985 ± 2.242 mg/kg for Cu, from 27.433 ± 0.341 to 39.258 ± 3.783 mg/kg for Zn, from 1.043 ± 0.081 to 1.533 ± 0.091 mg/kg for Cd and from 12.665 ± 0.091 mg/kg to 32.250± 0.023 mg/kg for Pb. For Cynodon dactylon species the amount of heavy metals detected ranged from 10.067± 0.462 to 11.401± 0.530 mg/kg for Cd, from 13.133± 0.969 to 18.210± 0.849 mg/kg for Cu, from 65.540± 0.778 to 83.330± 0.071 mg/kg for Pb and from 83.720± 1.881 to 86.47± 0.063 mg/kg for Zn while for Cyperus species the amount of heavy metals detected ranged from 9.53± 0.9452 to 10.410± 0.525 mg/kg for Cd, from 12.220± 0.263 to 13.470± 2.572 mg/kg for Cu, from 27.140± 0.810 to 59.65± 0.495 mg/kg for Zn and from 83.022± 0.071 mg/kg to 90.322± 0.001 mg/kg for Pb. Physical-chemical parameters of the pond water indicated a pH of 7.55 while pH of the soil sediment ranged from 8.38 to 8.68. Electrical conductivity of the pond water was 184 µs while of the soil sediment ranged from 23 to 47 µs. Based on the results of the study, it is concluded that the pond water is not safe for potable uses since it contain Cd and Pb above WHO/TBS safe limits. It is recommended that water regulatory authority body should explore to know the source of the pond water so that if it is from water pipe leakage proper measure be taken to control leakage and prevent the problem; but also more awareness education should be provided on harmful impact of livestock feeding on polluted plants.