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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.


Related in: MedlinePlus

Photo of Lake Nakuru from the Baboon Cliff (southwest of the lake) in October 2009, the dotted line showing the shoreline in June 2008.
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fig0015: Photo of Lake Nakuru from the Baboon Cliff (southwest of the lake) in October 2009, the dotted line showing the shoreline in June 2008.

Mentions: Precipitation data for the two lakes are presented in Fig. 2 and compared with the mean monthly rainfall from 1987 to 2006, as measured for Lake Nakuru by the Nakuru meteorological station. For both lakes, rainfall declined significantly compared to the longtime mean, especially during the rainy season from April to July. These deficiencies in precipitation led to a major drop in the depth of Lake Nakuru and a drastic retraction of the waterline (Fig. 3). For Lake Bogoria, no such clear retraction took place, probably due to its much smaller surface/volume ratio and the continuous inflow of thermal wells. Nonetheless, a reduction of volume was observed here as well, indicated by rising concentrations of salts (see below). Although distinct fluctuations in the water level and shoreline of Lake Nakuru have been described before, amongst others by Burgis and Morris (1987), the drastic reduction of lake water during the present survey is exceptionally high; this led to a near dry-out of the lake, a situation last described in 1962 (Burgis and Morris, 1987).


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)

Photo of Lake Nakuru from the Baboon Cliff (southwest of the lake) in October 2009, the dotted line showing the shoreline in June 2008.
© Copyright Policy
Related In: Results  -  Collection

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

fig0015: Photo of Lake Nakuru from the Baboon Cliff (southwest of the lake) in October 2009, the dotted line showing the shoreline in June 2008.
Mentions: Precipitation data for the two lakes are presented in Fig. 2 and compared with the mean monthly rainfall from 1987 to 2006, as measured for Lake Nakuru by the Nakuru meteorological station. For both lakes, rainfall declined significantly compared to the longtime mean, especially during the rainy season from April to July. These deficiencies in precipitation led to a major drop in the depth of Lake Nakuru and a drastic retraction of the waterline (Fig. 3). For Lake Bogoria, no such clear retraction took place, probably due to its much smaller surface/volume ratio and the continuous inflow of thermal wells. Nonetheless, a reduction of volume was observed here as well, indicated by rising concentrations of salts (see below). Although distinct fluctuations in the water level and shoreline of Lake Nakuru have been described before, amongst others by Burgis and Morris (1987), the drastic reduction of lake water during the present survey is exceptionally high; this led to a near dry-out of the lake, a situation last described in 1962 (Burgis and Morris, 1987).

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.


Related in: MedlinePlus