Eau douce

Résumé

L'eau douce est une eau dont la salinité est très faible ou inexistante, par opposition à l'eau de mer et à l'eau saumâtre. C'est l'eau de pluie, l'eau des rivières, des lacs, des nappes phréatiques, des glaciers, des tourbières Sa très faible salinité permet sa consommation. C'est un critère de potabilité essentiel. Une eau douce contient généralement moins d'un gramme de matières solides dissoutes (comme les sels, métaux et éléments nutritifs) par litre. À titre de comparaison, l'eau de mer en contient plus de trente et le sérum physiologique en contient /litre (0,9 %). Définitions L'eau douce peut être définie comme une eau qui contient moins de de sels dissouts. D'autres sources proposent des limites de salinité plus élevées, par exemple ou . Les eaux contenant plus de sel sont dites saumâtres puis salées. Répartition de l'eau douce sur terre Le rapport de l'eau de mer à l'eau douce sur Terre est d'environ 40 à 1. L'eau douce représente 2,5 % de l'eau

Source officielle

https://fr.wikipedia.org/wiki/Eau_douce

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Effects of groundwater on desalinization in coastal reservoir and adjacent aquifer

David Andrew Barry, Jing Xu

Coastal reservoir provides the additional storage capacity of freshwater in coastal zone which greatly alleviate the water shortage in stressed areas, and the salinization of reservoir water degrade the utility of coastal reservoir. Salinization may result from inadequate desalinization in early operation stage, and groundwater as the important source of freshwater to coastal reservoir and adjacent aquifer was obviously have significant impacts on salinization which was in a dearth research. Laboratory experiments and mathematical model were designed to further discuss the influence of groundwater on the desalinization. The results from experiments shown that with the groundwater discharge rate increased, residual saltwater distribution result from intruded fresh groundwater was further moderated. Coastal reservoirs also greatly changed groundwater discharge pathways to sea. Without coastal reservoir, groundwater discharge to sea directly, while with coastal reservoir, part of groundwater would firstly discharge to coastal reservoir, desalinate the reservoir water, and then to sea. Mathematical model was designed for the prediction of the salinity of reservoir water, and the results from model could indicate the accuracy groundwater discharge pathways in coastal reservoir and adjacent aquifer. These results demonstrate the complexity of the groundwater system in adjacent aquifer of coastal reservoir, and may have great implications for future investigations on the predication of water quality during the full operational period.

2019

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This work focuses on the economic performance and environmental assessment of two biorefinery schemes using 100 t/day of olive tree pruning waste as feedstock. The first scheme is based on a multiproduct biorefinery producing 6363.64 m3/yr of ethanol, 999.31 t/yr of xylitol, and 1221.51 t/yr of antioxidant, obtaining a positive investment balance with a net present value (NPV) of 11.56 Meuro in a 20-year period with an initial investment of 39.5 Meuro (antioxidants account for 60.2% of revenues). In addition, it shows lower environmental impacts: 0.435 kg CO2 eq in global warning, 0.007 kg 1,4-DCB in human carcinogenic toxicity, 0.148 kg oileq in fossil resource scarcity for 1 kg OTP consumed, in comparison to the business-as-usual production of ethanol, xylitol and antioxidants (7.96 kg CO2 eq, 0.444 kg 1,4-DCB and 2.228 kg oileq). The second scheme considered is the standalone production of antioxidants, showing a similar economic performance (NPV = 11.9 Meuro) to the previous multiproduct biorefinery with lower initial investment requirements (24.9 Meuro). This process configuration also reduces some important environmental impacts such as global warming impact (0.55 kg CO2 eq) and freshwater consumption (0.067 m3), with respect to the multiproduct scheme. Thus, it has been demonstrated that antioxidants production from OTP is a promising alternative in terms of both process economics and environmental performance. (c) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.

ELSEVIER2022

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The microbiome of cryospheric ecosystems

Tom Ian Battin, Massimo Bourquin, Susheel Bhanu Busi, Leïla Ezzat, Stylianos Fodelianakis, Tyler Joe Kohler, Grégoire Marie Octave Edouard Michoud, Hannes Markus Peter

The cryosphere includes those parts of Earth where water or soil is frozen, such as snow, ice, glaciers and permafrost soils. Here, the authors present a global inventory of cryospheric microbial communities and their genetic repertoires. The melting of the cryosphere is among the most conspicuous consequences of climate change, with impacts on microbial life and related biogeochemistry. However, we are missing a systematic understanding of microbiome structure and function across cryospheric ecosystems. Here, we present a global inventory of the microbiome from snow, ice, permafrost soils, and both coastal and freshwater ecosystems under glacier influence. Combining phylogenetic and taxonomic approaches, we find that these cryospheric ecosystems, despite their particularities, share a microbiome with representatives across the bacterial tree of life and apparent signatures of early and constrained radiation. In addition, we use metagenomic analyses to define the genetic repertoire of cryospheric bacteria. Our work provides a reference resource for future studies on climate change microbiology.

NATURE PORTFOLIO2022

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