title: Organic matter preservation in the sediment of an acidic mining lake.
abstract: Sustainable management of acidic mining lakes requires knowledge on the origin and reactivity of its sedimentary organic matter. We identified different pools of organic matter (OM) in the Fe-rich sediment (up to 35 wt %) of an acidic (pH 2.8) mining lake using delta13C-signals, C/N ratios, and the markers alkanes, lignin-derived phenols, and benzenepolycarboxylic acids (BPCA). Additionally, a density fractionation was applied to each sediment layer. Three fractions, aquatic (AOM), terrestrial (TOM), and lignite-derived (LOM) organic matter, were discriminated, of which AOM comprises only a small fraction, with a minimum at the sediment bottom. The terrestrial contribution to sedimentary OM is higher than that of AOM but still low throughout the sediment core, whereas lignite-derived OM constitutes the major C-fraction, even in the upper sediment layers. The size of the carbon pools was quantified with a mass-balance approach, in which the BPCA content was utilized as an estimate for the lignite fraction in combination with the delta13C-signals of the three C fractions. The largest amount of OM was found in the heaviest (>2.4 g cm3) of the three density fractions of the two upper sediment layers, which implies strong interaction with iron hydroxides. Comparisons with C-oxidation rates revealed that besides the refractory origin of the OM, sorptive preservation by solid iron phases controls C-reactivity in the sediment and, hence, the internal neutralization capacity of the lake system.
authors.affiliation: laskov@igb-berlin.de
authors.forename: Christine
authors.initials: C
authors.lastname: Laskov
authors.forename: Wulf
authors.initials: W
authors.lastname: Amelung
authors.forename: Stefan
authors.initials: S
authors.lastname: Peiffer
mesh_terms: D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008906:Mining; D009930:Organic Chemicals / Q000032:analysis; D010084:Oxidation-Reduction; D014881:Water Supply
chemical_list: D009930:Organic Chemicals