Salinity

Summary

Salinity (səˈlɪnɪti) is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal to ‰). Salinity is an important factor in determining many aspects of the chemistry of natural waters and of biological processes within it, and is a thermodynamic state variable that, along with temperature and pressure, governs physical characteristics like the density and heat capacity of the water. A contour line of constant salinity is called an isohaline, or sometimes isohale. Definitions Salinity in rivers, lakes, and the ocean is conceptually simple, but technically challenging to define and measure precisely. Conceptually the salinity is the quantity of dissolved salt content of the water. Salts are compounds like sodium chloride, magnesium sulfate, potassium nitrate, and sodium bicarbonate which dissolve into ions

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Effects of deep pools on salinization in coastal reservoirs

David Andrew Barry, Jing Xu

Coastal reservoir contributes to alleviating the freshwater shortage in stressed areas, and the salinization of reservoir water is one of the most important challenges that coastal reservoir faced. Field-investigation indicates that there are many deep pools located at reservoir bed, and a large amount of high-salinity water was found within a deep pool which was hardly be desalted. Laboratory experiments and numerical simulations with different depth and locations of deep pools were conducted to further discuss the influence of deep pool on the salinization of reservoir and adjacent aquifer. Results showed that deep pool has greatly increased the salinity of reservoir water due to high-salinity water stored in the deep pool, which may act as an extra source of saltwater to the coastal reservoir during the dry season. The increasing depth of the deep pool was found to have negative impacts on the salinity of reservoir water, and as the distance from the deep pools to dam increased, the salinization extent in coastal reservoir decreased. Salinity data from the numerical simulations in coastal reservoirs and adjacent aquifer were matched the experimental data well. Flow field indicates that there is a high exchange capacity zone occurred from the deep pool to the seaward boundary, which gave the reasonable reasons for the existence of high-salinity water within deep pools. Those findings highlight the significant influence of deep pool on the salinization of the coastal reservoir, and explain the increased salinization by the deep pool.

2019

Reactive Oxygen Species (ROS) are highly reactive and toxic by-products of the aerobic metabolism, which are overproduced during period of stress. They disturb the cell machinery and induce oxidative damages on important biological macromolecules. Salinity is one of those major abiotic stresses, which affects considerably the growth rate and limits crop productivity. To enhance salinity stress tolerance and find strategies which would cope with global issues related to the rise of salt-affected lands and global food demand, various investigations have been performed. They did mainly focus on the understanding of physiological traits and ion homeostasis responses. However, oxidative stress is also a key part of the plant response to stress, but is still under-investigated. An efficient oxidative stress tolerance mechanism may induce significant improvement in salinity resistance. Nevertheless, recent studies have suggested that ROS play a dual role in cells, both as toxic by-products and as key molecules in complex signalling networks: ROS are essential actors which could influence the expression and regulation of various genes to control many processes, including the stress response. In this project, the production of two ROS, hydrogen peroxide and superoxide, was investigated in roots from various species and genotypes, respectively by DCF-DA and DHE fluorescence. The study gave a basic framework about ROS kinetics accumulation in roots depending on time of exposure to different salt concentrations. Specificities related to growth conditions, plant age and root tissues were also investigated. It was demonstrated that, compared to wheat and even more to pea, barley has a better ability to handle salinity, thanks to a rapid and transient oxidative burst. The aim of this work was also to link the oxidative stress with salinity stress tolerance, which had been investigated in previous studies. Two main conclusions can be drawn from this project: (i) there is a clear correlation between ROS accumulation and K+ leaking studied in previous experiments; (ii) ROS have a significant implication in the signal transduction network. Knowledge about the main mechanisms involved in oxidative stress tolerance and signalling can give a better background in the development of plants with improved salinity tolerance and find adapted solutions to this growing concern.

2013

Freshwater Flux and Spatiotemporal Simulated Runoff Variability into Ilulissat Icefjord, West Greenland, Linked to Salinity and Temperature Observations near Tidewater Glacier Margins Obtained Using Instrumented Ringed Seals

Konrad Steffen

The distribution of terrestrial surface runoff to Ilulissat Icefjord, west Greenland, is simulated for the period 2009-13 to better emphasize the spatiotemporal variability in freshwater flux and the link between runoff spikes and observed hydrographic conditions at theGreenland Ice Sheet tidewater glacier margins. Runoffmodel simulations were forced with automatic weather station data and verified against snow water equivalent depth, equilibrium line altitude, and quasi-continuous salinity and temperature observations obtained by ringed seals. Instrumented seals provide a novel platform to examine the otherwise inaccessible waters beneath the dense ice melange within the first 0-10 km of the calving front. The estimated mean freshwater flux from land was 70.6 +/- 4.2 km(3) yr(-1), with an 85% contribution of ice discharge from Jakobshavn Isbrae (also known as SermeqKujalleq), 14% from runoff, and the remaining 1% from precipitation on the fjord surface area, subglacial geothermal melting, and frictional melting due to basal ice motion. Runoff was simulated to be present from May to November and to vary spatially according to glacier cover and individual catchment size. Salinity and temperature observations correlate (significantly) with simulated runoff for the upper part of both the main fjord and southern fjord arm. Also, at the tidewater glacier margins in the northern and southern arm of Ilulissat Icefjord, salinity changes in the upper water column (upper 50 m) are significant after temporal spikes in runoff during late summer, while small-amplitude runoff variability during the recession of runoff did not create a clear signal in observed salinity variability. Also, in the southern arm near the glacier margin (between 100- and 150-m depth), the heterogeneous distribution in salinity could be because of the mixing of meltwater going upward from passing the grounding line. The effect of runoff spikes on observed salinity is less pronounced near the ice margin of Jakobshavn Isbrae than in the north and south arms.

Amer Meteorological Soc2015