Abstract:
The study was aimed at investigating the concentrations of trace elements
zinc (Zn), copper (Cu), cadmium (Cd), cobalt (Co), lead (Pb) and molybdenum
(Mo) in water, soil and grass Cynodon nlemfuensis in Olkaria geothermal field
and at the Amboseli reference site. The accumulation of these trace elements
was also investigated at the tissue of zebra Equus burchelli and buffalo
Syncerus caffer from the Olkaria area and in the Amboseli reference site. The
Olkaria geothermal waters recorded the highest
concentrationsof trace elements, especially for Pb (21.0:t11.0ppb and Mo (39.0±28.0ppb) compared to the reference area (S.0:±2.0ppb and 3.0±1.0ppb), respectively. Calculated molar Cu:Mo ratio of geothermal water was below the 2-3 Cu deficiencyindicator ratio.
The soils of the study area contained higher trace elements compared to the
reference area. Notably, Zn and Pb soil maximum concentration values of
87.9ppm and 1S.00ppm were above worldwide "normal" soiI concentration
values 1-S0 ppm and O.S-5.0ppm, respectively. The dry season showed
relatively high Pb concentrations, possibly due to evaporative concentrations.
Concentrations of Pb, Cd, and Co in Cynodon nlemfuensisin Olkaria were
above the "normal" plant concentration levels (0.1-2.0ppm Pb, 0.2-0.Sppm Cd
and 0.1ppm Co).Serum trace element concentrations were within
"normal"serum/blood concentrations in healthy animals, except Co, which was low in serum obtained from zebra of the Olkaria zone. Bio concentration factors indicated variability in animal species abilities to accumulate the trace elements in the organs. Generally the trace element concentrations had not accumulated to zootoxic levels. However, highestellconcentrations (230 ppm) in the liver of
buffalo Syncerus caffer and Cd concentrations (21.33ppm) in the kidney of
zebra Equus burchel/i both from O!karia, were above those regarded as
normal (S5.lppm Cu and 0.32-S.S8ppm Cd) for healthy animals. This study
estabish that qeothemal waters, soils and grass studied, especially in
terms of potentially toxic elements Pb and Cd, and deficiency
relatedelements Cu, Mo and Co are a potential health hazard to the grazing wild
animals. Therefore it is suggested that the trace element levels in the habitat
and in wild animals need to be monitored regularly in terms of animal and
human health especially in the case of game meat consumption. There is also
need for developing exposure model for predicting risk so as to warn in
advance, in case geothermal activities surpassed the carrying capacity of the
natural ecosystem, thereby threatening existence of biodiversity.
