Significance of organic matter in the process of aggregation of suspended sediments in retention reservoirs

Author(s):  
Maksymilian Cieśla ◽  
Renata Gruca-Rokosz ◽  
Lilianna Bartoszek
2014 ◽  
Vol 11 (12) ◽  
pp. 3299-3305 ◽  
Author(s):  
C. Rumpel ◽  
V. Chaplot ◽  
P. Ciais ◽  
A. Chabbi ◽  
B. Bouahom ◽  
...  

Abstract. In order to assess whether eroded carbon is a net source or sink of atmospheric CO2, characterisation of the chemical composition and residence time of eroded organic matter (EOM) at the landscape level is needed. This information is crucial to evaluate (1) how fast EOM can be decomposed by soil microbes during its lateral transport and (2) its impact at deposition sites. This study considers a continuum of scales to measure the composition of EOM across a steep hillslope landscape of the Mekong basin with intense erosion. We sampled suspended sediments eroded during rainfall events from runoff plots (1 and 2.5 m2) and the outlets of four nested watersheds (0.6 × 104 to 1 × 107 m2). Here we show that changes in the chemical composition of EOM (measured by nuclear magnetic resonance spectroscopy) and in its 13C and 15N isotope composition from plot scale through to landscape scale provide consistent evidence for enrichment of more decomposed EOM across distances of 10 km. Between individual soil units (1 m2) to a small watershed (107 m2), the observed 28% decrease of the C/N ratio, the enrichment of 13C and 15N isotopes as well as O-alkyl C in EOM is of similar magnitude as changes recorded with depth in soil profiles due to soil organic matter "vertical" decomposition. Radiocarbon measurements indicated ageing of EOM from the plot to the watershed scale. Therefore transport of EOM may lead to enrichment of stabilised soil organic matter compounds, eventually being subject to export from the watershed.


2021 ◽  
Author(s):  
Leonardo Mena-Rivera ◽  
Charlotte E.M. Lloyd ◽  
Michaela K. Reay ◽  
Tim Goodall ◽  
Daniel S Read ◽  
...  

Abstract The dynamic interactions between dissolved organic matter (DOM) and particulate organic matter (POM) are central in nutrient cycling in freshwater ecosystems. However, the molecular-level mechanisms of such interactions are still poorly defined. Here, we study spatial differences in the chemical and molecular composition of suspended sediments in the River Chew, UK. We then applied a compound-specific stable isotope probing (SIP) approach to test the potential assimilation of 13C,15N-glutamate (Glu) and 15N-nitrate into proteinaceous biomass by particle-associated microbial communities over a 72-h period. Our results demonstrate that the composition of suspended sediments is strongly influenced by the effluent of sewage treatment works (STW). Fluxes and percentages of assimilation of both isotopically labelled substrates into individual proteinaceous amino acids (AAs) showed contrasting dynamics in processing at each site linked to primary biosynthetic metabolic pathways. Preferential assimilation of the organic molecule glutamate and evidence of its direct assimilation into newly synthesised biomass was obtained. Our approach provides quantitative molecular information on the mechanisms by which low molecular weight DOM is mineralised in the water column compared to an inorganic substrate. This is paramount for better understanding the processing and fate of organic matter in aquatic ecosystems.


1991 ◽  
Vol 23 (1-3) ◽  
pp. 447-454 ◽  
Author(s):  
H. M. Liljestrand ◽  
Y. D. Lee

The results of controlled batch experimental studies of the adsorption and desorption kinetics of dichlorobenzene to 1) size fractionated, washed sediments, 2) aggregate, washed sediment, 3) dissolved/colloidal sediment materials, and 4) bulk sediments,are used to determine the effect of inhomogeneous mixtures on the overall sorption rates. The size-segregated sediments are modeled as spherical particles with a porous outer shell of organic matter for sorption and an inert, inorganic core. The characteristic times of intraparticle diffusive transport are found to vary with particle size by about two orders of magnitude. The distribution of natural organic matter content with particle size results in sorption rates which differ greatly from that predicted by the monodisperse, homogeneous particle model. Coupled, reversible reactions between the solute and each solid size fraction are presented as a conceptual model for the interpretation of the empirical results of batch experiments.


2020 ◽  
Vol 8 (3) ◽  
pp. 661-678
Author(s):  
Thomas O. Hoffmann ◽  
Yannik Baulig ◽  
Helmut Fischer ◽  
Jan Blöthe

Abstract. Understanding the transport of suspended sediment and associated nutrients is of major relevance for sustainable sediment management aiming to achieve healthy river systems. Sediment rating curves are frequently used to analyze the suspended sediments and their potential sources and sinks. Here we use more than 750 000 measurements of suspended sediment concentrations (SSCs) and discharge (Q) collected at 62 gauging stations along 19 waterways in Germany based on the suspended sediment monitoring network of the German water and shipping authority, which started in the 1960s. Furthermore, we analyze more than 2000 measurements of the loss on ignition (LOI) of suspended matter at two stations along the rivers Moselle and Rhine to provide a proxy for the relative contributions of mineral load and organic matter. SSC and LOI are analyzed in terms of the power-law rating curve to identify discharge-dependent controls of suspended matter. Our results indicate that for most studied gauging stations, rating coefficients are not constant over the full discharge range, but there is a distinct break in the sediment rating curve, with specific SSC–Q domains above and below this break. The transition of the rating exponent likely results from increased supply of mineral suspended sediments from hillslope erosion at high flow and a shift of the organic matter sources from aquatic biomass-derived organic matter (i.e., high % LOI) at low flow, to mineral-associated organic matter with low % LOI eroded from hillslopes at higher flow. Based on these findings we developed a conceptual rating model for large (>10 000 km2) and low-turbidity (SSC < 1000 mg L−1) rivers separating the mineral and organic fraction of the suspended matter in German waterways. This model allows evaluating the sources of the mineral and organic fraction of the suspended matter and facilitates new insights into the first-order control of discharge on the quality and quantity of suspended sediments.


2020 ◽  
Author(s):  
Thomas O. Hoffmann ◽  
Yannik Baulig ◽  
Helmut Fischer ◽  
Jan Blöthe

Abstract. Understanding the dynamics of suspended sediment and associated nutrients is of major relevance for sustainable sediment management aiming to achieve healthy river systems. Sediment rating curves are frequently used to analyze the dynamics of suspended sediments and their potential sources and sinks. Here we are using more than 750 000 measurements of the suspended sediment concentrations (SSC) and discharge at 62 gauging stations along 19 waterways in Germany based on the suspended sediment monitoring network of the German water and shipping authority, which started in the 1960ties. Furthermore, we analyse more than 2000 measurements of the loss on ignition (LOI) of suspended matter at two stations along the rivers Moselle and Rhine to asses the mineral and organic fraction of the suspended matter. SSC and LOI are analysed in terms of the power law rating to identify discharge depended process regimes of suspended matter. Our results indicate that for most studied gauging stations, rating coefficients are not constant over the full discharge range, but there is a distinct break in the sediment rating curve, with specific SSC-Q domains above and below this break. The transition of the rating exponent is likely to be a result of a change of controlling factors of the suspended sediment from intrinsic organic matter formation at low flows to extrinsic sediment supply (including mineral and organic fractions) due to hillslope erosion at high flows. Based on these findings we developed a conceptual rating model separating the mineral and organic fraction of the suspended matter in the Germany waterways. This model allows evaluating the sources of the mineral and organic fraction of the suspended matter and gain new insights into the first order control of discharge dynamics of suspended sediments.


Author(s):  
Eisa Ebrahimi ◽  
Hossein Asadi ◽  
Mehrnosh Joudi ◽  
Mehran Rezaei Rashti ◽  
Mohammad Bagher Farhangi ◽  
...  

Abstract Phosphorus (P), nitrogen (N) and organic component are released from the soil into surface bodies by runoff and erosion, causing the pollution and eutrophication of water resources. This study was aimed to investigate the seasonal changes in loads of N and P components, and organic matter (OM) in the Pasikhan River in flood and normal conditions. Sampling was performed monthly during normal flow conditions and for five flood events. The concentrations of P and N components were measured in the samples. The OM of the suspended sediments was determined by the combustion method. Under the normal flows, the maximum loads of total P and OM were about 0.553 mg l−1 (STD = 0.11) (November) and 3.41% (STD = 1.17) (November) in the autumn, respectively. The total N concentration of 0.533 mg l−1 (STD = 0.12) was observed in the winter. In the flood events, the TP, TN and OM ranged from 0.48 to 3.5 mg l−1, 0.28 to 0.79 mg l−1 and 1.24 to 4.11%, respectively. The results indicated a high risk of eutrophication in the Pasikhan River. Also, the study revealed that in a severe flood event, some 113.9 tons h−1 of OM can be released from the river watershed. Furthermore, there was a high correlation between the amount of P and OM losses with the concentration of suspended sediments in different flood events. Finally, it is concluded that if the floods are not controlled, they not only cause a rapid loss of soil nutrients and OM but also lead to severe eutrophication in the Anzali wetland.


Sign in / Sign up

Export Citation Format

Share Document