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Hydro-meteorological influences and multimodal suspended particle size distributions in the Belgian nearshore area (southern North Sea)
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Suspended particulate matter (SPM) concentration and particle size distribution (PSD) were assessed in a coastal turbidity maximum area (southern North Sea) during a composite period of 37 days in January–April 2008. PSDs were measured with a LISST 100X and classified using entropy analysis in terms of subtidal alongshore flow. The PSDs during tide-dominated conditions showed distinct multimodal behaviour due to flocculation, revealing that the building blocks of flocs consist of primary particles (<3 μm) and flocculi (15 μm). Flocculi comprise clusters of clay minerals, whereas primary particles have various compositions (calcite, clays). The PSDs during storms with a NE-directed alongshore subtidal current (NE storms) are typically unimodal and characterised by mainly granular material (silt, sand) resuspended from the seabed. During storms with a SW-directed alongshore subtidal current (SW storms), by contrast, mainly flocculated material can be identified in the PSDs. The findings emphasise the importance of wind-induced advection, alongshore subtidal flow and highly concentrated mud suspensions (HCMSs) as regulating mechanisms of SPM concentration, as well as other SPM characteristics (cohesiveness or composition of mixed sediment particles) and size distribution in a high-turbidity area. The direction of subtidal alongshore flow during SW storm events results in an increase in cohesive SPM concentration, HCMS formation, and the armouring of sand; by contrast, there is a decrease in cohesive SPM concentration, no HCMS formation, and an increase in sand and silt in suspension during NE storms.
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RBINS Staff Publications 2017
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Multimodality of a particle size distribution of cohesive suspended particulate matters in a coastal zone
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Particle size distributions (PSDs) of suspended particulate matters in a coastal zone are lognormal and multimodal in general. The multimodal PSD, which is caused by the mixing of multiple particle and aggregate size groups under flocculation and erosion/resuspension, is a record of the particle and aggregate dynamics in a coastal zone. Curve-fitting software was used to decompose the multimodal PSD into subordinate lognormal PSDs of primary particles, flocculi, microflocs, and macroflocs. The curve-fitting analysis for a time series of multimodal PSDs in the Belgian coastal zone showed the dependency of the multimodality on (1) shear-dependent flocculation in a flood and ebb tide, (2) breakage-resistant flocculation in the spring season, and (3) silt-sized particle erosion and advection in a storm surge. Also, for modeling and simulation purposes, the curve-fitting analysis and the settling flux estimation for the multimodal PSDs showed the possibility of using discrete groups of primary particles, flocculi, microflocs, and macroflocs as an approximation of a continuous multimodal PSD.
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RBINS Staff Publications
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Competition between kaolinite flocculation and stabilization in divalent cation solutions dosed with anionic polyacrylamides
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Divalent cations have been reported to develop bridges between anionic polyelectrolytes and negatively-charged colloidal particles, thereby enhancing particle flocculation. However, results from this study of kaolinite suspensions dosed with various anionic polyacrylamides (PAMs) reveal that Ca2+ and Mg2+ can lead to colloid stabilization under some conditions. To explain the opposite but coexisting processes of flocculation and stabilization with divalent cations, a conceptual flocculation model with (1) particle-binding divalent cationic bridges between PAM molecules and kaolinite particles and (2) polymer-binding divalent cationic bridges between PAM molecules is proposed. The particle-binding bridges enhanced flocculation and aggregated kaolinite particles in large, easily-settleable flocs whereas the polymer-binding bridges increased steric stabilization by developing polymer layers covering the kaolinite surface. Both the particle-binding and polymer-binding divalent cationic bridges coexist in anionic PAM- and kaolinite-containing suspensions and thus induce the counteracting processes of particle flocculation and stabilization. Therefore, anionic polyelectrolytes in divalent cation-enriched aqueous solutions can sometimes lead to the stabilization of colloidal particles due to the polymer-binding divalent cationic bridges.
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RBINS Staff Publications
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The upper Eocene-Oligocene carnivorous mammals from the Quercy Phosphorites (France) housed in Belgian collections
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The Quercy Phosphorites Formation in France is world famous for its Eocene to Miocene faunas, especially those from the upper Eocene to lower Oligocene, the richest of all. The latter particularly helped to understand the ‘Grande Coupure’, a dramatic faunal turnover event that occurred in Europe during the Eocene-Oligocene transition. Fossils from the Quercy Phosphorites were excavated from the middle 19th century until the early 20th century in a series of sites and became subsequently dispersed over several research institutions, while often losing the temporal and geographical information in the process. In this contribution, we provide an overview and reassess the taxonomy of these barely known collections housed in three Belgian institutions: the Université de Liège, KU Leuven, and the Royal Belgian Institute of Natural Sciences. We focus our efforts on the carnivorous mammals (Hyaenodonta and Carnivoramorpha) and assess the stratigraphic intervals covered by each collection. These fossils are derived from upper Eocene (Priabonian), lower Oligocene (Rupelian), and upper Oligocene (Chattian) deposits in the Quercy area. The richness of the three collections (e.g., the presence of numerous postcranial elements in the Liège collection), the presence of types and figured specimens in the Leuven collection, and some identified localities in the RBINS collection make these collections of great interest for further studies on systematics and the evolution of mammals around the ‘Grande Coupure’.
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RBINS Staff Publications 2021
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Integration of landscape genomics, provenance trials and association mapping identifies genetic components underlying cold hardiness adaptation for coastal Douglas-fir (Pseudotsuga menziesii var. menziesii)
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RBINS Staff Publications 2018
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Noble gases in micrometeorites from the Transantarctic Mountains
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The bulk of extraterrestrial matter currently accreted by the Earth is in the form of micrometeorites (MMs) and interplanetary dust particles (IDPs), thus they may have collectively made a substantial contribution to the volatile inventory of the Earth and the other terrestrial planets. We have performed a complete noble gas study, accompanied by a complete petrographic characterization, of MMs from the Transantarctic Mountain (TAM) collection in the size range ∼300 to ∼1000 µm that fell over an extended time period during the last ∼1 Ma. Our noble gas study includes krypton and xenon, which have been largely missing in previous work. Helium and neon are dominated by a solar component, with generally lower abundance in scoriaceous MMs than in unmelted ones, and also generally lower in abundance than in previously studied MMs, which may be explained by the larger particle size (surface/volume ratio) of the MMs we studied. Considering an enhanced MM flux in the early Solar System, such MMs may have supplied a significant fraction of Earth’s neon. A number of MMs have kept what was probably their pre-terrestrial He/Ne ratio, from which we infer that the observed solar component is retained in a tiny surface region not affected by atmospheric entry. The abundances of (volume-correlated) heavier gases are similar to what was found in previous studies of smaller MMs. While Ar contains both solar and “planetary” contributions, the heavy noble gases (Kr, Xe) generally show “planetary” patterns but are often also compromised by terrestrial contamination as evidenced by an enhanced Kr/Xe ratio. Kr and Xe in a subset of scoriaceous MMs are dominated by isotopically fractionated air, possibly acquired during the passage through Earth’s ionosphere. Those not obviously affected by air show isotopic ratios similar to primitive meteorites (the Q component), thus primordial heavy gases supplied to the Earth by MMs are likely as those found in macroscopic meteorites. There is no evidence for the presence of a “cometary” Xe component as identified in the coma of comet 67P/Churyumov-Gerasimenko, hence a cometary source for a significant fraction of MMs in the studied size range is unlikely. Cosmogenic helium, neon and argon were detected in several cases. Cosmic ray exposure ages were calculated based on cosmogenic 21Ne in combination with the Poynting-Robertson effect, but depend on assumptions about atmospheric entry loss. Still, several cases are consistent with an origin from the asteroid belt (even assuming no loss) and one scoriaceous MM (#45b.17) would have to originate from beyond Jupiter. In at least two cases, including #45b.17, the isotopic composition of cosmogenic Ne appears to be inconsistent with predominant production in small particles free-floating in space, however; much of the irradiation of these MMs may have occurred when they were part of larger parent bodies.
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RBINS Staff Publications 2018
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Functional volumes, niche packing and species richness: biogeographic legacies in the Congo Basin
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RBINS Staff Publications 2020
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The phylogeny of the African wood mice (Muridae, Hylomyscus) based on complete mitochondrial genomes and five nuclear genes reveals their evolutionary history and undescribed diversity
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RBINS Staff Publications 2020
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Mainstreaming biodiversity conservation into development cooperation—highlights from an ALTER-NET-EKLIPSE workshop
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RBINS Staff Publications 2020
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The DeepMIP contribution to PMIP4: methodologies for selection, compilation and analysis of latest Paleocene and early Eocene climate proxy data, incorporating version 0.1 of the DeepMIP database.
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RBINS Staff Publications 2019
