TY - JOUR
T1 - Recent paleorecords document rising mercury contamination in Lake Tanganyika
AU - Conaway, Christopher H.
AU - Swarzenski, Peter W.
AU - Cohen, Andrew S.
N1 - Funding Information:
Mercury analyses were conducted at Russ Flegal’s laboratory at the University of California Santa Cruz. PWS graciously acknowledges continued support from the USGS Coastal and Marine Geology Program. Geochronologies and mass sedimentation rates on core LT-98-58 were determined by Brent A. McKee and others. We thank James Russell, Chris Johnson and Jessica Tierney for providing data and assistance on lake sediment core MC1. We thank Kiram Lezzar, James McGill and the students of the Nyanza Project for assistance with core collection. The Tanzania Fisheries Research Institute and the Tanzanian Council of Science and Technology authorized and facilitated core collection. The Lake Tanganyika Biodiversity Project (UNDP-GEF) and the Nyanza Project (NSF-ATM 0223920 and BIO 0383765) provided funding for field research. Manuscript comments were provided by USGS reviewers Geoffrey Ellis, Peter Van Metre and John E. Gray.
PY - 2012/1
Y1 - 2012/1
N2 - Recent Lake Tanganyika Hg deposition records were derived using 14C and excess 210Pb geochronometers in sediment cores collected from two contrasting depositional environments: the Kalya Platform, located mid-lake and more removed from watershed impacts, and the Nyasanga/Kahama River delta region, located close to the lake's shoreline north of Kigoma. At the Kalya Platform area, pre-industrial Hg concentrations are 23±0.2ng/g, increasing to 74ng/g in modern surface sediment, and the Hg accumulation rate has increased from 1.0 to 7.2μg/m 2/a from pre-industrial to present, which overall represents a 6-fold increase in Hg concentration and accumulation. At the Nyasanga/Kahama delta region, pre-industrial Hg concentrations are 20±3ng/g, increasing to 46ng/g in surface sediment. Mercury accumulation rate has increased from 30 to 70μg/m 2/a at this site, representing a 2-3-fold increase in Hg concentration and accumulation. There is a lack of correlation between charcoal abundance and Hg accumulation rate in the sediment cores, demonstrating that local biomass burning has little relationship with the observed Hg concentration or Hg accumulation rates. Examined using a sediment focusing-corrected mass accumulation rate approach, the cores have similar anthropogenic atmospheric Hg deposition profiles, suggesting that after accounting for background sediment concentrations the source of accumulating Hg is predominantly atmospheric in origin. In summary, the data document an increase of Hg flux to the Lake Tanganyika ecosystem that is consistent with increasing watershed sediment delivery with background-level Hg contamination, and regional as well as global increases in atmospheric Hg deposition.
AB - Recent Lake Tanganyika Hg deposition records were derived using 14C and excess 210Pb geochronometers in sediment cores collected from two contrasting depositional environments: the Kalya Platform, located mid-lake and more removed from watershed impacts, and the Nyasanga/Kahama River delta region, located close to the lake's shoreline north of Kigoma. At the Kalya Platform area, pre-industrial Hg concentrations are 23±0.2ng/g, increasing to 74ng/g in modern surface sediment, and the Hg accumulation rate has increased from 1.0 to 7.2μg/m 2/a from pre-industrial to present, which overall represents a 6-fold increase in Hg concentration and accumulation. At the Nyasanga/Kahama delta region, pre-industrial Hg concentrations are 20±3ng/g, increasing to 46ng/g in surface sediment. Mercury accumulation rate has increased from 30 to 70μg/m 2/a at this site, representing a 2-3-fold increase in Hg concentration and accumulation. There is a lack of correlation between charcoal abundance and Hg accumulation rate in the sediment cores, demonstrating that local biomass burning has little relationship with the observed Hg concentration or Hg accumulation rates. Examined using a sediment focusing-corrected mass accumulation rate approach, the cores have similar anthropogenic atmospheric Hg deposition profiles, suggesting that after accounting for background sediment concentrations the source of accumulating Hg is predominantly atmospheric in origin. In summary, the data document an increase of Hg flux to the Lake Tanganyika ecosystem that is consistent with increasing watershed sediment delivery with background-level Hg contamination, and regional as well as global increases in atmospheric Hg deposition.
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U2 - 10.1016/j.apgeochem.2011.11.005
DO - 10.1016/j.apgeochem.2011.11.005
M3 - Article
AN - SCOPUS:84855444892
SN - 0883-2927
VL - 27
SP - 352
EP - 359
JO - Applied Geochemistry
JF - Applied Geochemistry
IS - 1
ER -