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Zinc isotope composition of settling particles as a proxy for biogeochemical processes in lakes: Insights from the eutrophic Lake Greifen, Switzerland
Author(s) -
Peel Kate,
Weiss Dominik,
Siggc Laura
Publication year - 2009
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.2009.54.5.1699
Subject(s) - settling , biogeochemical cycle , hypolimnion , epilimnion , environmental chemistry , eutrophication , stable isotope ratio , chemistry , environmental science , nutrient , environmental engineering , physics , organic chemistry , quantum mechanics
The isotope composition of zinc (Zn) was determined in settling particles collected monthly over a year in the hypolimnion of the eutrophic Lake Greifen (Switzerland) in order to explore the potential of this novel isotope system as a proxy for biogeochemical processes in aqueous environments. Significant variation in Δ 66 Zn JMC3‐0749L of 0.9‰(where Δ 66 Zn JMC3‐0749L 5 [{ 66 Zn : 64 Zn}sample/{ 66 Zn : 64 Zn} JMC3‐0749L ‐ 1] x 1000) was found throughout the seasonal cycle of productivity. The most negative Δ 66 Zn JMC3‐0749L values (down to ‐0.66‰ ± 0.08‰) were observed during the productive summer period from June to September, when the Zn in the settling particles was predominantly associated with organic material, and when Zn concentrations in the epilimnion were lowest. This observation is likely explained with preferential uptake of the light Zn isotopes during algal growth. During the other months, the Zn in the sediment traps showed higher Δ 66 Zn values, reflecting increasing contributions of anthropogenic or lithogenic components. The average isotopic signature of the settling particles during the autumn‐winter‐spring period (≪‐0.2‰ for Δ 66 Zn JMC3‐0749L ) was somewhat lower than typical for anthropogenic and natural sources, and this possibly reflects the effect of the preferential adsorption of lighter dissolved Zn isotopes onto the settling particles. We suggest that Rayleigh fractionation plays a minor role in controlling the isotopic composition of the settling particles in the lake. Our work demonstrates the presence of an obvious seasonal cycle in Δ 66 Zn, and this suggests that Zn isotopes can be employed to study nutrient utilization and other biogeochemical processes in lakes and other aquatic environments.