Water Quality and Trace Metal Distribution in a Pristine Lake in the Lake Basin in Kenya

Abstract

Water and surface sediment samples taken from various locations within Lake Kanyaboli in the Lake Victoria basin were analysed to determine the concentration and distribution of heavy metals. There were wide ranges in concentrations of the metals among the sampling points analysed. Sediment concentrations (microg/g dry weight) ranged from n.d.-2.54 (Ag), 0.25-1.08 (Cd), 0.89-1.64 (Co), 3.7-7.73 (Cr), 1.80-30.27 (Cu), 1073-2627 (Mn), 22.61-55.60 (Ni), 11.42-153.9 (Pb), 40.46-154.7 (Sn) and 65.0-146.5 (Zn). Dissolved metal concentrations (microg/L) ranged from n.d.-9.22 (Ag), n.d.-5.54 (Cd), n.d.-8.30 (Co), 5.26-60.82 (Cr), 10.96-43.11 (Cu), 184.7-375.9 (Mn), 1.84-38.3 (Ni), 5.98-47.77 (Pb), n.d.-540.6 (Sn) and 14.5-55.9 (Zn). Compared with WHO standards and other freshwaters worldwide, this lake was found to be unpolluted, with all metals, except Mn, being detected at concentrations lower than the highest desirable levels and maximum permissible levels. Some of the toxic metals, Cu, Zn, Pb and Cd (in sediment) and Ag, Co and Pb (in water) were detected at lower concentrations than those found in the polluted Kisumu Pier in Winam Gulf in the Lake basin, which confirms the anthropogenic influence on the latter.

Profiles and Risk Assessment of Heavy Metals in Great Rift Lakes, Kenya

“…. But the concentrations of Cu in Lake Bogoria were higher than those in Lake Victoria , Municipal Lake , Lake Curtin and Lake Taihu , and were lower than those in Lake Mangla and Lake Kanyaboli . Comparing with the available criteria of heavy metals in water, the water quality of four lakes of the Great Rift Valley in Kenya, East Africa met the demand for irrigation based on the guidelines of Kenya and FAO .…”

“…In Kenya, heavy metals have been found widely in different water bodies, such as Pristine Lake , coastal zone of Lake Victoria , and Winam Gulf . The investigation of heavy metals in aquatic ecosystems in Kenya is very important for aquatic food safety and human health .…”

Cadmium and Chromium Toxicity to Pseudokirchneriella subcapitata and Microcystis aeruginosa

“…(Ochieng et al 2008). It has been detected that in the contaminated areas, water may contain dissolved metal concentrations as high as 9x10 -7 mol L -1 Cd (Sainz et al 2004) and 2x10 -6 mol L -1 Cr (Bobrowski et al 2004).…”

Chromium Distribution and Spatial Variations in the Finer Sediment Grain Size Fraction and Unfractioned Surficial Sediments on Nyanza Gulf, of Lake Victoria (East Africa)

“…For lake and river bottom sediments, the following values were obtained: Nyanza Gulf (sediments: 0.42 ± 0.05 to 1.12 ± 0.11 mg/kg) [19,20]; Winam Gulf (21.0 ± 0.70 mg/kg [18]; nd to 0.275 ppm) [22]; L. Kanyaboli (lake, 3.7 to 7.73 g/g) [23]; inflowing rivers of Nyanza Gulf (2.92 to 5.36 g/g) [24]; Nyanza Gulf and inflowing rivers (rivers = nd to 125 mg/kg; lake = nd to 85.7 mg/kg) [62,108,109] …”

“…However, sediment cores collected from the deep offshore areas of the main Lake Victoria show peaks of total Hg from the early 1960s [17]. In the Nyanza Gulf, studies on trace metals exist but only very few of them include Cr metal [18][19][20][21][22][23][24]. The Nyanza gulf watershed is known for the presence of gold mines [25][26][27] and also serves as an important agroindustrial zone.…”