lake geneva
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2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Romain Gaillard ◽  
Marjorie Perroud ◽  
Stéphane Goyette ◽  
Jérôme Kasparian

AbstractThe interaction between large inland water bodies and the atmosphere impacts the evolution of regional weather and climate, which in turn affects the lake dynamics, thermodynamics, ice-formation, and, therefore, ecosystems. Over the last decades, various approaches have been used to model lake thermodynamics and dynamics in standalone mode or coupled to numerical atmospheric models. We assess a turbulence-closure $$k-\epsilon$$ k - ϵ multi-column lake model in standalone mode as a computationally-efficient alternative to a full three-dimensional hydrodynamic model in the case of Lake Geneva. While it struggles to reproduce some short-term features, the multi-column model reasonably reproduces the seasonal mean of the thermal horizontal and vertical structures governing heat and mass exchanges between the lake surface and the lower atmosphere (stratified period, thermocline depth, stability of the water column). As it requires typically two orders of magnitude less computational ressources, it may allow a two-way coupling with a RCM on timescales or spatial resolutions where full 3D lake models are too demanding.


Geosciences ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 32
Author(s):  
Agathe Martignier ◽  
Montserrat Filella ◽  
Jean-Michel Jaquet ◽  
Mathieu Coster ◽  
Daniel Ariztegui

In unicellular organisms, intracellular inclusions of amorphous calcium carbonate (ACC) were initially described in cyanobacteria and, later, in unicellular eukaryotes from Lake Geneva (Switzerland/France). Inclusions in unicellular eukaryotes, named micropearls, consist of hydrated ACCs, frequently enriched in Sr or Ba, and displaying internal oscillatory zonations, due to variations in the Ba:Ca or Sr:Ca ratios. An analysis of our database, consisting of 1597 micropearl analyses from Lake Geneva and 34 from Lake Titicaca (Bolivia/Peru), showed that a certain number of Sr- and Ba-enriched micropearls from these lakes contain As in amounts measurable by EDXS. A Q-mode statistical analysis confirmed the existence of five chemically distinct morpho-chemical groups of As-bearing micropearls, among which was a new category identified in Lake Geneva, where As is often associated with Mg. This new type of micropearl is possibly produced in a small (7–12 μm size) bi-flagellated organism. Micropearls from Lake Titicaca, which contain Sr, were found in an organism very similar to Tetraselmis cordiformis, which was observed earlier in Lake Geneva. Lake Titicaca micropearls contain larger As amounts, which can be explained by the high As concentration in the water of this lake. The ubiquity of this observed biomineralization process points to the need for a better understanding of the role of amorphous or crystalline calcium carbonates in As cycling in surface waters.


2021 ◽  
Author(s):  
Hugo Lepage ◽  
Alexandra Gruat ◽  
Fabien Thollet ◽  
Jérôme Le Coz ◽  
Marina Coquery ◽  
...  

Abstract. The Rhône River is amongst the main rivers of Western Europe and the biggest by freshwater discharge and sediment delivery to the Mediterranean Sea. Its catchment is characterized by distinct hydrological regimes that may produce annual sediment deliveries ranging from 1.4 to 18.0 Mt y−1. Furthermore, the course of the Rhône River meets numerous dams, hydro- and nuclear power plants, and agricultural, urban or industrial areas. Thus, suspended particulate matters (SPM) have been involved in the fate of hydrophobic contaminants such as polychlorobiphenyls (PCB), mercury (Hg) and other trace metal elements (TME), and radionuclides for decades. To investigate the concentrations and the fluxes of SPM and associated contaminants, as well as their sources, a monitoring network of 15 stations (three on the Rhône River and 12 on tributaries, from Lake Geneva to the Mediterranean Sea) has been set up in the past decade within the Rhône Sediment Observatory (OSR). A main purpose of this observatory is to assess the long term trend of the main contaminant concentrations and fluxes, and to understand their behavior during extreme events such as floods or dam flushing operations. The dataset presented in this paper contains the concentrations and fluxes of SPM as well as the concentrations and fluxes of several particle bound contaminants of concern (PCB, TME, radionuclides), the particle size distribution and the particulate organic carbon of SPM. Sediment traps or continuous flow centrifuges were used to collect sufficient amount of SPM in order to conduct the measurements. This observatory is on-going since 2011 and the database is regularly updated. All the data are made publicly available in French and English through the BDOH/OSR database at https://doi.org/10.15454/RJCQZ7 (Lepage et al., 2021).


2021 ◽  
Vol 12 (4) ◽  
pp. 1169-1189
Author(s):  
Pascal Perolo ◽  
Bieito Fernández Castro ◽  
Nicolas Escoffier ◽  
Thibault Lambert ◽  
Damien Bouffard ◽  
...  

Abstract. The gas transfer velocity (k) is a major source of uncertainty when assessing the magnitude of lake gas exchange with the atmosphere. For the diversity of existing empirical and process-based k models, the transfer velocity increases with the level of turbulence near the air–water interface. However, predictions for k can vary by a factor of 2 among different models. Near-surface turbulence results from the action of wind shear, surface waves, and buoyancy-driven convection. Wind shear has long been identified as a key driver, but recent lake studies have shifted the focus towards the role of convection, particularly in small lakes. In large lakes, wind fetch can, however, be long enough to generate surface waves and contribute to enhance gas transfer, as widely recognised in oceanographic studies. Here, field values for gas transfer velocity were computed in a large hard-water lake, Lake Geneva, from CO2 fluxes measured with an automated (forced diffusion) flux chamber and CO2 partial pressure measured with high-frequency sensors. k estimates were compared to a set of reference limnological and oceanic k models. Our analysis reveals that accounting for surface waves generated during windy events significantly improves the accuracy of k estimates in this large lake. The improved k model is then used to compute k over a 1-year time period. Results show that episodic extreme events with surface waves (6 % occurrence, significant wave height > 0.4 m) can generate more than 20 % of annual cumulative k and more than 25 % of annual net CO2 fluxes in Lake Geneva. We conclude that for lakes whose fetch can exceed 15 km, k models need to integrate the effect of surface waves.


Author(s):  
Agathe Martignier ◽  
Montserrat Filella ◽  
Jean-Michel Jaquet ◽  
Mathieu Coster ◽  
Daniel Ariztegui

In unicellular organisms, intracellular inclusions of amorphous calcium carbonate (ACC) have been initially described in cyanobacteria and, later, in unicellular eukaryotes of Lake Geneva (Switzerland/France). Inclusions in unicellular eukaryotes ‒named micropearls‒ consist of hydrated ACCs, frequently enriched in Sr or Ba, displaying internal oscillatory zonations due to variations in the Ba:Ca or Sr:Ca ratios. The analysis of our database consisting of 1597 micropearl analyses from Lake Geneva and 34 from Lake Titicaca (Bolivia/Peru) has shown that a certain number of Sr and Ba-enriched micropearls from these lakes contain As in amounts measurable by EDXS. A Q-mode statistical analysis has confirmed the existence of five geochemically distinct morpho-chemical groups of As-bearing micropearls, among which a new category identified in Lake Geneva, where As is often associated with Mg. This new type of micropearl is possibly produced in a small (7-12 m size) bi-flagellated organism. Micropearls from Lake Titicaca, which contain Sr, are found in an organism very similar to Tetraselmis cordiformis, observed in Lake Geneva. Lake Titicaca micropearls contain higher As concentrations which can be explained by the high As concentration in the water of this lake. The ubiquity of the biomineralization process observed points to the need for better understanding of the role of amorphous or crystalline calcium carbonates in As cycling in surface waters.


2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Bieito Fernández Castro ◽  
Damien Bouffard ◽  
Cary Troy ◽  
Hugo N. Ulloa ◽  
Sebastiano Piccolroaz ◽  
...  

AbstractTurbulent mixing controls the vertical transfer of heat, gases and nutrients in stratified water bodies, shaping their response to environmental forcing. Nevertheless, due to technical limitations, the redistribution of wind-derived energy fuelling turbulence within stratified lakes has only been mapped over short (sub-annual) timescales. Here we present a year-round observational record of energy fluxes in the large Lake Geneva. Contrary to the standing view, we show that the benthic layers are the main locus for turbulent mixing only during winter. Instead, most turbulent mixing occurs in the water-column interior during the stratified summer season, when the co-occurrence of thermal stability and lighter winds weakens near-sediment currents. Since stratified conditions are becoming more prevalent –possibly reducing turbulent fluxes in deep benthic environments–, these results contribute to the ongoing efforts to anticipate the effects of climate change on freshwater quality and ecosystem services in large lakes.


2021 ◽  
Author(s):  
J. A. Ezzedine ◽  
A. Janicot ◽  
S. Rasconi ◽  
I. Domaizon ◽  
S. Jacquet
Keyword(s):  

2021 ◽  
Vol 193 (11) ◽  
Author(s):  
Montserrat Filella ◽  
Juan-Carlos Rodríguez-Murillo ◽  
Andrew Turner

AbstractPlastics (n = 3880) have been sampled from 39 beaches of ten Swiss lakes of varying sizes, hydrodynamics, and catchments, with a selection (n = 598) analysed for potentially hazardous (and regulated) chemical elements (As, Ba, Br, Cd, Cr, Hg, Pb, Sb, Se) by X-ray fluorescence spectrometry. Plastic objects and fragments with identifiable or unidentifiable origins were present on all beaches surveyed, and were often most abundant in proximity to major riverine inputs. Chemical elements were detected in between two (Hg) and 340 (Ba) samples with maximum concentrations exceeding 2% by weight for Ba, Cd, Cr, Pb, and Sb. Inter-element relationships and characteristics of the samples suggest that elements are largely present as various additives, including pigments (e.g., Cd2SSe, PbCrO4), stabilizers (in polyvinyl chloride), and flame retardants (Br). Observations are similar to, and complement, those previously reported in Switzerland’s largest lake (Lake Geneva). Comparison of concentrations of targeted chemical elements in beached plastic with currently used plastics illustrate the interest of these types of measurements in providing an insight into the persistence of plastics in standing stocks and in lakes. This information could help to introduce management schemes that consider whether plastic pollution is new or old and act accordingly.


2021 ◽  
Author(s):  
Romain Gaillard ◽  
Marjorie Perroud ◽  
Stéphane Goyette ◽  
Jérôme Kasparian

Abstract The interaction between large inland water bodies and the atmosphere impacts the evolution of regional weather and climate, which in turn affects the lake dynamics, thermodynamics, ice-formation, and, therefore, ecosystems. Over the last decades, various approaches have been used to model lake thermodynamics and dynamics in standalone mode or coupled to numerical atmospheric models. We assess a turbulence-closure k − ε multi-column lake model in standalone mode as a computationally-efficient alternative to a full three-dimensional hydrodynamic model in the case of Lake Geneva. While it struggles to reproduce some short-term features, the multi-column model reasonably reproduces the seasonal mean of the thermal horizontal and vertical structures governing heat and mass exchanges between the lake surface and the lower atmosphere (stratified period, thermocline depth, stability of the water column). It may therefore allow a two-way coupling with a RCM on timescales or spatial resolutions where full 3D lake models are too demanding in terms of computational resources.


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