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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

Chondrite normalised REE patterns of sediments; values for elements marked with * were extrapolated.
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fig0030: Chondrite normalised REE patterns of sediments; values for elements marked with * were extrapolated.

Mentions: Table 2 presents the mean REE concentrations of the studied sediments. The obtained REE distribution patterns for both lake sediments were normalised to chondrite composition and show light rare earth element (LREE)/heavy rare earth element (HREE) fractionations and a Eu anomaly (Fig. 6). The sediment samples of both lakes show a high REE abundance range (LaN = 432–438 and YbN = 36–43), characteristic for the pyroclastic rocks and volcanic sediments of the Kenyan Rift Valley. The sediments are characterised by LREE-enriched patterns with relatively flat HREE; they exhibit a progression similar to those of the average upper continental crust (UCC) and the post-Archean fine-grained clastic sediments (Post-Archean Australian Shale (PAAS) and North American Shale Composite (NASC)) reported by Taylor and McLennan (1985) and Condie (1993). The calculated Eu depletion (Eu/Eu* = 0.33–0.45) is also comparable with those of UCC, PAAS, and NASC, as well as with values for hydrothermal cherts from Lake Bogoria described by Kerrich et al. (2002). The high abundance of REE in the investigated sediments corresponds with their volcanic geological background and is in the previously published range, e.g. for the Greater Olkaria Volcanic Complex (see Table 2).


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)

Chondrite normalised REE patterns of sediments; values for elements marked with * were extrapolated.
© Copyright Policy
Related In: Results  -  Collection

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

fig0030: Chondrite normalised REE patterns of sediments; values for elements marked with * were extrapolated.
Mentions: Table 2 presents the mean REE concentrations of the studied sediments. The obtained REE distribution patterns for both lake sediments were normalised to chondrite composition and show light rare earth element (LREE)/heavy rare earth element (HREE) fractionations and a Eu anomaly (Fig. 6). The sediment samples of both lakes show a high REE abundance range (LaN = 432–438 and YbN = 36–43), characteristic for the pyroclastic rocks and volcanic sediments of the Kenyan Rift Valley. The sediments are characterised by LREE-enriched patterns with relatively flat HREE; they exhibit a progression similar to those of the average upper continental crust (UCC) and the post-Archean fine-grained clastic sediments (Post-Archean Australian Shale (PAAS) and North American Shale Composite (NASC)) reported by Taylor and McLennan (1985) and Condie (1993). The calculated Eu depletion (Eu/Eu* = 0.33–0.45) is also comparable with those of UCC, PAAS, and NASC, as well as with values for hydrothermal cherts from Lake Bogoria described by Kerrich et al. (2002). The high abundance of REE in the investigated sediments corresponds with their volcanic geological background and is in the previously published range, e.g. for the Greater Olkaria Volcanic Complex (see Table 2).

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