Geochronological and spatial distribution of heavy metal contamination in sediment from Lake Naivasha, Kenya

Abstract

Sediment cores hold large information on the history of human interactions with lakes and surrounding environments. Hence, this study investigated the geochronological and heavy metals characteristics of sediment from Lake Naivasha, Kenya. Geochronological characteristics were established from sediment cores, using 210 Pb and 137 Cs. On the other hand, heavy metals; Al, As, Cr, Cu, Fe, Mn, Ni, Pb, and Zn were analyzed using Inductively Coupled Plasma -Optical Emission Spectrometer (ICP -OES). Their probable sources were predicted using Pearson's correlation and Principal Component Analysis (PCA) while heavy metal contamination levels were assessed using geoaccumulation Index (Igeo), Contamination Factor (CF) and Enrichment Factor (EF) pollution indices. Results showed that the cores were about 140 years old with an estimated average mass sedimentation rate of 0.32 g/cm 2 /yr. Vertical fluctuations of heavy metal contamination were observed along the sediment cores with high values recorded near the surface. Further, PCA and pollution indices showed that Al, Cr, Cu, Ni, and Pb were from natural sources while, Zn, Mn, Fe, and As, (in order of contamination levels), were both from natural and anthropogenic sources. Therefore, this study showed the geochronological trends of sedimentation and impacts of human activities on Lake Naivasha.

Sediment distribution and accumulation in Lake Naivasha, Kenya over the past 50 years

“…On the other hand, the sedimentation rate derived from Lake Naivasha dated sediment cores reported by Maina et al (), corresponding to the periods investigated in the present study, were 1.33, 0.93 and 1.24 cm/year, respectively. The difference in the estimated sediment accumulation rate from the two methods could be attributable to the fact that the first method considered sediment volume and lake area, but did not consider the sediment bulk density, which can vary over time because of compaction.…”

“…The sediment cores were longitudinally split into two in the laboratory and sliced into layers according to visually identified stratigraphic changes. Sediment cores collected from Lake Naivasha were dated using 137 Cs and 210 Pb radionuclides, following the procedure described in Maina et al (). The sediment cores were used to countercheck the APS sediment depth results, by overlaying the core with the acoustics images, as described by Dunbar et al (), Dunbar et al ().…”

“…The length of sediment cores collected in various sections of the lake was determined, and the findings were compared with sediment thicknesses of the acoustic images. The findings from Maina et al () were integrated into post‐processing of the acoustic data to establish the sediment layers that correspond to the past 20 and 50 years.…”

“…A combination of vibe-coring, APS profiling images and geochronological interpretation using 137 Cs radionuclides was previously utilized by Dunbar et al (1999), Dunbar et al (2003), Dunbar, Allen, Higley, and Bennett (2013) to assess sediment impoundment volume. Maina, Sang, Raude, and Mutua (2019) dated sediment cores from Lake Naivasha, Kenya using the 210 Pb and 137 Cs radionuclides. The assigned dates facilitated investigation of the accumulation history of heavy metal contaminants on sediments in Lake Naivasha over the past 50 years.…”

Assessment of the metal pollution in surface sediments of coastal Tasaul Lake (Romania)

“…To consider the contribution of elements to a given group, the components with factor loadings of > 0.6, 0.4–0.6, and 0.3–0.4 were classified as highly, moderately, or weakly associated with elements in that class, respectively. Similar classification procedures have been used in similar studies focusing on the identification of heavy metal sources in sediments (Wu et al 2014 ; Javed et al 2018 ; Maina et al 2019 ).…”