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Major and trace element geochemistry of Lake Bogoria and Lake Nakuru, Kenya, during extreme draught.

Jirsa F, Gruber M, Stojanovic A, Omondi SO, Mader D, Körner W, Schagerl M - Chem. Erde (2013)

Bottom Line: Due to an extreme draught from March to October 2009, the water level of Lake Nakuru dropped significantly.In Lake Bogoria the evapoconcentration effects were less pronounced (total salinity changed from about 40‰ to 48‰).The results show a high abundance of the REE and a very distinct Eu depletion of Eu/Eu* = 0.33-0.45.

View Article: PubMed Central - PubMed

Affiliation: University of Vienna, Institute of Inorganic Chemistry, Währingerstrasse 42, A-1090 Vienna, Austria.

ABSTRACT

The physico-chemical properties of water samples from the two athalassic endorheic lakes Bogoria and Nakuru in Kenya were analysed. Surface water samples were taken between July 2008 and October 2009 in weekly intervals from each lake. The following parameters were determined: pH, salinity, electric conductivity, dissolved organic carbon (DOC), the major cations (FAAS and ICP-OES) and the major anions (IC), as well as certain trace elements (ICP-OES). Samples of superficial sediments were taken in October 2009 and examined using Instrumental Neutron Activation Analysis (INAA) for their major and trace element content including rare earth elements (REE). Both lakes are highly alkaline with a dominance of Na > K > Si > Ca in cations and HCO3 > CO3 > Cl > F > SO4 in anions. Both lakes also exhibited high concentrations of Mo, As and fluoride. Due to an extreme draught from March to October 2009, the water level of Lake Nakuru dropped significantly. This created drastic evapoconcentration, with the total salinity rising from about 20‰ up to 63‰. Most parameters (DOC, Na, K, Ca, F, Mo and As) increased with falling water levels. A clear change in the quality of DOC was observed, followed by an almost complete depletion of dissolved Fe from the water phase. In Lake Bogoria the evapoconcentration effects were less pronounced (total salinity changed from about 40‰ to 48‰). The distributions of REE in the superficial sediments of Lake Nakuru and Lake Bogoria are presented here for the first time. The results show a high abundance of the REE and a very distinct Eu depletion of Eu/Eu* = 0.33-0.45.

No MeSH data available.


Geographical position of Lake Nakuru and Lake Bogoria, Kenya. Open circles: sampling points. “S” south, “C” central, “N” north.
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fig0005: Geographical position of Lake Nakuru and Lake Bogoria, Kenya. Open circles: sampling points. “S” south, “C” central, “N” north.

Mentions: The basins of the athallasic endorheic lakes Bogoria and Nakuru were formed through tectonic and volcanic activities and lie on the Eastern Kenyan branch of the Great Rift Valley (Schlueter, 1997). The runoff from the alkaline volcanic rocks characteristic for the Eastern Rift Valley (King, 1970) is rich in sodium and hydrogen carbonate, constituting the major source of these ions in the lake water (Yuretich, 1982). Both lakes are located in semi-arid regions (Fig. 1) with annual rainfall in their catchment areas of app. 700–900 mm (McCall, 1967) showing high variability. The climate is characterised by two rainy seasons, one from April to August (the so-called long rains) and one during October and November (“short rains”). Neither lake has a surface outflow; the water budget is therefore dependent on direct precipitation, evaporation, inflows and anthropogenic use. Both catchment areas are completely occupied by alkaline volcanic rocks (trachyphonolite, phonolite and basalts) (McCall, 1967).


Major and trace element geochemistry of Lake Bogoria and Lake Nakuru, Kenya, during extreme draught.

Jirsa F, Gruber M, Stojanovic A, Omondi SO, Mader D, Körner W, Schagerl M - Chem. Erde (2013)

Geographical position of Lake Nakuru and Lake Bogoria, Kenya. Open circles: sampling points. “S” south, “C” central, “N” north.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4375630&req=5

fig0005: Geographical position of Lake Nakuru and Lake Bogoria, Kenya. Open circles: sampling points. “S” south, “C” central, “N” north.
Mentions: The basins of the athallasic endorheic lakes Bogoria and Nakuru were formed through tectonic and volcanic activities and lie on the Eastern Kenyan branch of the Great Rift Valley (Schlueter, 1997). The runoff from the alkaline volcanic rocks characteristic for the Eastern Rift Valley (King, 1970) is rich in sodium and hydrogen carbonate, constituting the major source of these ions in the lake water (Yuretich, 1982). Both lakes are located in semi-arid regions (Fig. 1) with annual rainfall in their catchment areas of app. 700–900 mm (McCall, 1967) showing high variability. The climate is characterised by two rainy seasons, one from April to August (the so-called long rains) and one during October and November (“short rains”). Neither lake has a surface outflow; the water budget is therefore dependent on direct precipitation, evaporation, inflows and anthropogenic use. Both catchment areas are completely occupied by alkaline volcanic rocks (trachyphonolite, phonolite and basalts) (McCall, 1967).

Bottom Line: Due to an extreme draught from March to October 2009, the water level of Lake Nakuru dropped significantly.In Lake Bogoria the evapoconcentration effects were less pronounced (total salinity changed from about 40‰ to 48‰).The results show a high abundance of the REE and a very distinct Eu depletion of Eu/Eu* = 0.33-0.45.

View Article: PubMed Central - PubMed

Affiliation: University of Vienna, Institute of Inorganic Chemistry, Währingerstrasse 42, A-1090 Vienna, Austria.

ABSTRACT

The physico-chemical properties of water samples from the two athalassic endorheic lakes Bogoria and Nakuru in Kenya were analysed. Surface water samples were taken between July 2008 and October 2009 in weekly intervals from each lake. The following parameters were determined: pH, salinity, electric conductivity, dissolved organic carbon (DOC), the major cations (FAAS and ICP-OES) and the major anions (IC), as well as certain trace elements (ICP-OES). Samples of superficial sediments were taken in October 2009 and examined using Instrumental Neutron Activation Analysis (INAA) for their major and trace element content including rare earth elements (REE). Both lakes are highly alkaline with a dominance of Na > K > Si > Ca in cations and HCO3 > CO3 > Cl > F > SO4 in anions. Both lakes also exhibited high concentrations of Mo, As and fluoride. Due to an extreme draught from March to October 2009, the water level of Lake Nakuru dropped significantly. This created drastic evapoconcentration, with the total salinity rising from about 20‰ up to 63‰. Most parameters (DOC, Na, K, Ca, F, Mo and As) increased with falling water levels. A clear change in the quality of DOC was observed, followed by an almost complete depletion of dissolved Fe from the water phase. In Lake Bogoria the evapoconcentration effects were less pronounced (total salinity changed from about 40‰ to 48‰). The distributions of REE in the superficial sediments of Lake Nakuru and Lake Bogoria are presented here for the first time. The results show a high abundance of the REE and a very distinct Eu depletion of Eu/Eu* = 0.33-0.45.

No MeSH data available.