TY - JOUR
T1 - Using lead isotopes and trace element records from two contrasting Lake Tanganyika sediment cores to assess watershed - Lake exchange
AU - Odigie, Kingsley O.
AU - Cohen, Andrew S.
AU - Swarzenski, Peter W.
AU - Flegal, A. Russell
N1 - Funding Information:
The authors are grateful to Christopher H. Conaway, Céline Gallon, Christina Richardson, and two anonymous reviewers for their insightful suggestions to earlier drafts of this manuscript; Rob Franks of UCSC for analytical support; and all members of the UCSC WIGS Laboratory, especially Sharon Hibdon, for their support with this project. Cores described in this project were collected with support from the Lake Tanganyika Biodiversity Project and the NSF -supported Nyanza Project ( NSF-ATM0223920 ). This work was partly supported by Department of Energy (DOE) Office of Science Graduate Fellowship Program . All opinions expressed in this work are the authors’ and do not necessarily reflect the policies and views of the DOE Office of Science. PWS thanks the USGS CMG Program for continued support.
Publisher Copyright:
© 2014 Elsevier Ltd.
PY - 2014/12/1
Y1 - 2014/12/1
N2 - Lead isotopic and trace element records of two contrasting sediment cores were examined to reconstruct historic, industrial contaminant inputs to Lake Tanganyika, Africa. Observed fluxes of Co, Cu, Mn, Ni, Pb, and Zn in age-dated sediments collected from the lake varied both spatially and temporally over the past two to four centuries. The fluxes of trace elements were lower (up to 10-fold) at a mid-lake site (MC1) than at a nearshore site (LT-98-58), which is directly downstream from the Kahama and Nyasanga River watersheds and adjacent to the relatively pristine Gombe Stream National Park. Trace element fluxes at that nearshore site did not measurably change over the last two centuries (1815-1998), while the distal, mid-lake site exhibited substantial changes in the fluxes of trace elements - likely caused by changes in land use - over that period. For example, the flux of Pb increased by ~300% from 1871 to 1991. That apparent accelerated weathering and detrital mobilization of lithogenic trace elements was further evidenced by (i) positive correlations (r= 0.77-0.99, p<. 0.05) between the fluxes of Co, Cu, Mn, Ni, Pb, and Zn and those of iron (Fe) at both sites, (ii) positive correlations (r= 0.82-0.98, p<. 0.01, n= 9) between the fluxes of elements (Al, Co, Cu, Fe, Mn, Ni, Pb, and Zn) and the mass accumulation rates at the offshore site, (iii) the low enrichment factors (EF. <. 5) of those trace elements, and (iv) the temporal consistencies of the isotopic composition of Pb in the sediment. These measurements indicate that accelerated weathering, rather than industrialization, accounts for most of the increases in trace element fluxes to Lake Tanganyika in spite of the development of mining and smelting operations within the lake's watershed over the past century. The data also indicate that the mid-lake site is a much more sensitive and useful recorder of environmental changes than the nearshore site. Furthermore, the lead isotopic compositions of sediment at the sites differed spatially, indicating that the Pb (and other trace elements by association) originated from different natural sources at the two locations.
AB - Lead isotopic and trace element records of two contrasting sediment cores were examined to reconstruct historic, industrial contaminant inputs to Lake Tanganyika, Africa. Observed fluxes of Co, Cu, Mn, Ni, Pb, and Zn in age-dated sediments collected from the lake varied both spatially and temporally over the past two to four centuries. The fluxes of trace elements were lower (up to 10-fold) at a mid-lake site (MC1) than at a nearshore site (LT-98-58), which is directly downstream from the Kahama and Nyasanga River watersheds and adjacent to the relatively pristine Gombe Stream National Park. Trace element fluxes at that nearshore site did not measurably change over the last two centuries (1815-1998), while the distal, mid-lake site exhibited substantial changes in the fluxes of trace elements - likely caused by changes in land use - over that period. For example, the flux of Pb increased by ~300% from 1871 to 1991. That apparent accelerated weathering and detrital mobilization of lithogenic trace elements was further evidenced by (i) positive correlations (r= 0.77-0.99, p<. 0.05) between the fluxes of Co, Cu, Mn, Ni, Pb, and Zn and those of iron (Fe) at both sites, (ii) positive correlations (r= 0.82-0.98, p<. 0.01, n= 9) between the fluxes of elements (Al, Co, Cu, Fe, Mn, Ni, Pb, and Zn) and the mass accumulation rates at the offshore site, (iii) the low enrichment factors (EF. <. 5) of those trace elements, and (iv) the temporal consistencies of the isotopic composition of Pb in the sediment. These measurements indicate that accelerated weathering, rather than industrialization, accounts for most of the increases in trace element fluxes to Lake Tanganyika in spite of the development of mining and smelting operations within the lake's watershed over the past century. The data also indicate that the mid-lake site is a much more sensitive and useful recorder of environmental changes than the nearshore site. Furthermore, the lead isotopic compositions of sediment at the sites differed spatially, indicating that the Pb (and other trace elements by association) originated from different natural sources at the two locations.
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U2 - 10.1016/j.apgeochem.2014.10.007
DO - 10.1016/j.apgeochem.2014.10.007
M3 - Article
AN - SCOPUS:84908612047
VL - 51
SP - 184
EP - 190
JO - Applied Geochemistry
JF - Applied Geochemistry
SN - 0883-2927
ER -