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Isotopes Trace Biogeochemistry and Sources of Cu and Zn in an intertidal soil
Author(s) -
Bigalke Moritz,
Kersten Michael,
Weyer Stefan,
Wilcke Wolfgang
Publication year - 2013
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2012.0225
Subject(s) - environmental chemistry , sedimentation , soil water , deposition (geology) , anoxic waters , organic matter , biogeochemistry , stable isotope ratio , isotopes of nitrogen , fractionation , chemistry , intertidal zone , nutrient , chernozem , floodplain , calcareous , nitrate , bioturbation , isotope fractionation , sediment , geology , nitrogen , soil science , ecology , oceanography , paleontology , physics , organic chemistry , quantum mechanics , biology
River floodplain soils are sinks and potential sources for toxic trace metals like Cu and Zn. We hypothesize that stable Cu and Zn isotope ratios reflect both the mobilization and the sources of metals. We determined the soil properties, the concentrations and partitioning of Cu and Zn, and variations in δ 65 Cu and δ 66 Zn values in a core obtained from an Aquic Udifluvent developed on a freshwater intertidal mudflat of the River Elbe, Germany. The core was sampled at 2 cm intervals to a depth of 34 cm, which corresponds to approximately 9 yr of sedimentation. Elevated concentrations of Cu (up to 320 μg g −1 ) and Zn (up to 2080 μg g −1 ) indicated anthropogenic pollution. At the time of sampling the redox conditions changed from oxic (Eh 200 to 400 mV, above 22 cm deep) to strongly anoxic conditions (‐100 to ‐200 mV, below 22 cm deep). The δ 65 Cu values varied systematically with depth (from ‐0.02 to 0.16‰) and were correlated with the Fe, C, and N concentrations. Although pre‐depositional variations cannot be ruled out, the systematic variation with depth suggests post‐sedimentation fractionation of δ 65 Cu in response to seasonally variable organic matter deposition and redox conditions. In contrast, the δ 66 Zn IRMM values were uniform (from ‐0.07 to 0.01‰) throughout the core, indicating that the Zn isotopes did not significantly fractionate after deposition and that the Zn sources were homogeneous throughout the sedimentation.