Impact of the nature of organic matter and/or its organo-mineral interaction on microbial activity in dam sediment
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SEDIMENTS, SEC 2 • PHYSICAL AND BIOGEOCHEMICAL PROCESSES • RESEARCH ARTICLE
Impact of the nature of organic matter and/or its organo-mineral interaction on microbial activity in dam sediment S. Bascle 1 & I. Bourven 1 & M. Baudu 1 Received: 17 April 2020 / Accepted: 9 August 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Purpose Two models serve to explain organic matter (OM) bioavailability in soil through the nature of the OM and/or its degree of attachment to the organo-mineral matrix. This work directly measures the extracted aerobic biomineralization of OM pools in order to determine the model more heavily affecting bioavailability in dam sediment. Materials and methods The OM from four dam sediments was extracted according to a physicochemical sequential protocol. For each step, an extracted phase and a residual phase were recovered. These extraction steps were then coupled with biochemical oxygen demand (BOD) measurements over a 20-day period. The BOD is measured as follows: (i) on the total sediment; (ii) on the residual phase, thus allowing for a BOD determination of the OM linked to the matrix (OML); and (iii) on the extracted free OM (OMF). Results and discussion The total sediment BOD cannot be correlated with either the total extracted carbon or global C/N ratio. The BOD of each OML has been assessed, revealing that the labile phase achieves the highest rate of aerobic biodegradability (2.3 mgO2/mgC), while contributing a small portion to total sediment biodegradability (6 to 22%). The other phases contributing to sediment biodegradability are particulate phase (labile) > weakly linked phase > strongly linked phases, with a corresponding contribution to BOD of 15–46% > 22–41% > 0–30%. An analysis conducted on the OMF shows that the BOD rates of the strongly linked phases are equivalent to those of the labile phases. Conclusion Organic matter bioavailability and, hence, its biodegradability are mainly affected by the strength of interaction with the organo-mineral matrix. The C/N ratio subsequently alters the biodegradability of bioaccessible OM from dam sediment. Keywords Lacustrine sediment . Organic matter . Bioavailability . Biological oxygen demand (BOD) . Sequential physicochemical extraction Highlights • The aerobic biodegradation of organic matter (OM) from 4 dam sediment matrices is studied. • OM is extracted using an 8-step physicochemical sequential extraction method. • The degree of interaction with the matrix affects the biochemical oxygen demand (BOD). • Free OM from 3 extraction steps show the same BODs. • Bioavailability is due to the bioaccessibility of OM in an organo-mineral matrix. Responsible editor: Haihan Zhang * M. Baudu [email protected] S. Bascle [email protected] I. Bourven [email protected] 1
Laboratoire PEIRENE, EA 7500, Université de Limoges, 123 avenue Albert Thomas, 87060 Limoges, France
1 Introduction Dams disturb river sediment dynamics and induce sedimentary discontinuity and accumulation. The lacustrine sediment, r
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