Evolution of organic matter in lignite-containing sediments revealed by analytical pyrolysis (Py–GC–MS) |
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| Institution: | 1. Centre for Microbial Ecology and Genomics, Department of Biochemistry, Genetics and Microbiology, University of Pretoria, Pretoria, South Africa;2. Gobabeb Research and Training Centre, Walvis Bay, Namibia;1. Department of Earth and Environmental Studies, Montclair State University, Montclair, NJ, USA;2. Department of Biology, Montclair State University, Montclair, NJ, USA;3. Indiana Geological and Water Survey, Indiana University, Bloomington, IN, USA;4. University of Oviedo, Mieres, Asturias, Spain;5. Department of Chemistry and Biochemistry, Montclair State University, Montclair, NJ, USA;6. PSEG Institute for Sustainability Studies, Montclair State University, Montclair, NJ, USA |
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| Abstract: | Newly vegetated sites provide opportunities to enlighten organic matter (OM) transformation mechanisms in soils and sediments at very early stages of development which, in turn, is relevant to better understand general ecosystem functioning. Mine acid soils and sediments in the Lusatian open cast lignite mining district (Germany) contains a high concentration of fossil carbon (lignite) in ad mixture with recent OM from the local vegetation, both contributing to the humified OM pool. In this study, analytical pyrolysis (Py–GC–MS) was used to monitor the different C sources (lignite or plant derived) in developing mine tailing soils and sediments and their degree of degradation in contrasting environments. Representative vegetation and the organic carbon (OC) rich soil/sediment fraction (humus fraction) were sampled at two depths (0–5 and 5–10 cm) in three plots along a transect covering an upland forest soil, a partially submerged sediment at the land–water interface and a constantly submerged sediment. The analysis of plant (lipds, isoprenoids, methoxyphenols and carbohydrates) and possible lignite (alkyl napththalenes, alkyl benzenes and PAHs) biomarkers released after pyrolysis supports previous findings in the area using other proxies. It was possible to discern OM sources in soil/sediment humus fractions, both from the substrate (lignite) as well as from the prevailing vegetation of the area. Environmental conditions in the submerged sediment seem to favour OM protection and the accumulation of decomposing plant material, whereas more intense OM degradation seems to prevail in the land–water interface areas characterized by fluctuating water level. In addition, a well resolved series of organic sulfur compounds (OSCS) found in the submerged sediments of rehabilitated acid lakes, indicates the possible occurrence of particular mechanisms of C preservation in this extreme anoxic S rich environment, i.e. via sulphur “quenching” with plant derived lipids during early diagenesis. |
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