Electrolyte Feed Salinity 15 Practical Salinity Units Psu

Surface and Ground Water, Weathering, and Soils

Y.K. Kharaka , J.S. Hanor , in Treatise on Geochemistry, 2003

5.16.2.2 Information from Wire-Line Logs

The salinity of formation waters is often calculated using electrical resistivity and spontaneous-potential (SP) logs, and the values obtained are reasonable, except in geopressured zones with high shale content ( Hearst and Nelson, 1985; Rider, 1996). An alternative technique for calculating salinities of waters in geopressured shaly sediments makes combined use of γ ray, conductivity, and porosity logs (Revil et al., 1998). It is often possible to determine vertical variations in salinity over a distance of several kilometers from a single log.

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Sediments, Diagenesis and Sedimentary Rocks

M. Bąbel , B.C. Schreiber , in Treatise on Geochemistry (Second Edition), 2014

9.17.4.4 Salinity

Salinity is the most important parameter characterizing and defining saline water, brine, or bittern. It is a measure of the total amount of salts dissolved in the water/brine, and brine, by definition, contains a lot of salt. It has been measured using many different units and in a number of ways. The absolute salinity, S, as defined by Forschhammer (1865), is the mass of dissolved salts in seawater, brackish water, brine, or other saline solution per mass of that solution and is given in dimensionless units: g per kg, ‰ (per mill), or ppt (parts per thousand) (Anati, 1999; Gamsjäger et al., 2008):

[1] $S=\mathrm{mass}\left(\mathrm{dissolved}\mathrm{salts}\right)/\mathrm{mass}\left(\mathrm{saline}\mathrm{solution}\right)$

This salinity is very rarely measured directly. Usually, it is evaluated by measuring some other physical parameter (density, i.e., specific gravity, optical refraction index, electrical conductivity, etc.). It may also be measured by the concentration (contents) of some conservative element (ions that do not participate in any of evaporitic precipitation and hence are conserved in the solution) and accumulates in the brine during its evaporation (such as Cl, Mg, K, Li, and Br; e.g., Brantley et al., 1984) for which a calibrated conversion scale is known. Conversion scales are however different for any particular brine with its own chemical composition (e.g., Jellison et al., 1999; Zinabu et al., 2002). Recently, several standard units for the properties of seawater were introduced (Millero, 2010; Wright et al., 2011), of which the standard seawater composition reflecting the chemical composition of seawater is important for geochemical studies ( Table 1 ; Millero et al., 2008).

Table 1. Major and other ions concentrations in seawater after various sources

	Holland et al. (1986) (from Holland, 1978), average concentration in seawater of 35‰ salinity (mmol   kg−   1)	Hay et al. (2006) (after Gill, 1989) a ; concentration ‰ by weight (=   g   kg−   1)	Lowenstein and Risacher (2009) (after Drever, 1988) (mmol   kg−   1 H2O)	Hay et al. (2006) (after Gill, 1989) a ; molal concentration	Millero et al. (2008); mi (mol   kg –1)
Ca2   +	10.2	0.41	11	0.0102	0.0106568
Mg2   +	53.2	1.27	55	0.0524	0.0547421
K+	10.2	0.38	11	0.0097	0.0105797
Na+	468.0	10.59	485	0.4608	0.4860597
SO4 2   −	28.2	2.67	29	0.0278	0.0292643
Cl−	545	19.12	565	0.5394	0.5657647
HCO3 −	2.4	0.12	2.4	0.0020	0.0017803
Sr2   +	nd	0.01	nd	0.0001	0.0000940
Br−	0.84	0.07	nd	0.0008	0.0008728
CO3 2   −	nd	0.02	nd	0.0003	0.0002477
B(OH)4	nd	nd	nd	nd	0.0001045
F−	nd	0.03	nd	0.0015	0.0000708
OH−	nd	nd	nd	nd	0.0000082
B(OH)3	nd	nd	nd	nd	0.0003258
CO2	nd	nd	nd	nd	0.0000100
H2O	nd	965.28	nd	17,389.8474	55.5084720
Other		0.02	nd	nd	nd
Sum of halides		9.22
Sum of components dissolved in water		34.72			1.1605813
Sum of components dissolved in water, and water		1000.00			56.6690534

mi, molality (mol   kg^{−   1} of solvent); nd, no data.

a

With modifications to make chlorinity (Cl) of 19.2 equal to a salinity of 34.72‰ (after Hay et al., 2006)

The recommended measure of salinity for seawater is given as a dimensionless, practical salinity 'unit' that is based on conductivity measurements and is commonly designated as 'psu,' which is not quite appropriate, because the practical salinity scale has no units (Millero, 1993, 2010; Millero et al., 2008). The seawater of average salinity is 35‰, and in the practical salinity scale, it has a salinity of 35.000. The other commonly used dimensional measure of salinity is TDS (g   l^{−   1}). It is the unit of total dissolved grams of solids per liter of brine and has the dimension of density, and, as such, it is both temperature- and pressure-dependent, and therefore, without the known temperature (at least), the information about the absolute salinity is always incomplete (Anati, 1999).

The unit recommended for monitoring the advance of evaporation of seawater, and the associated processes including any salinity rise or fall, is the 'evaporation ratio' defined as the mass (weight) of H₂O (not weight of brine) in the original seawater divided by the mass (weight) of H₂O in resulting evaporated brine (Garrett, 1980; Holser, 1979a). The other similar unit is 'volume ratio' being described as 'X seawater' that is the total volume of original seawater to total volume of brine (including dissolved salts; Holser, 1979a). Logan (1987) used 'volume reduction ratio' (V _er) defined as

[2] $V_{\mathrm{er}}=\left(V_{\mathrm{o}}–V_{\mathrm{e}}\right)/V_{\mathrm{o}}$

where V _o is volume of original seawater and V _e is volume of evaporative outflow. The other recommended method of monitoring the degree of evaporation (DE) of brine, particularly those trapped in halite fluid inclusions, is by the calculation of the degrees of evaporation for various elements (DE_ELEMENTS) of brines related to modern seawater composition (Levy, 1977). Any conservative element not removed during the salt precipitation can be used (McCaffrey et al., 1987; Raab and Spiro, 1991; Vogel et al., 2010; von Borstel et al., 2000). For example, the DE, based on magnesium (DE_Mg), is calculated following the equation (Zimmermann, 2000, 2001):

[3] ${\mathrm{DE}}_{\mathrm{Mg}}={\left(\mathrm{mmol}\mathrm{Mg}/\mathrm{kg}{\mathrm{H}}_2\mathrm{O}\right)}_{\mathrm{brine}}/{\left(\mathrm{mmol}\mathrm{Mg}/\mathrm{kg}{\mathrm{H}}_2\mathrm{O}\right)}_{\mathrm{seawater}}$

During the K–Mg salt precipitation from evaporating seawater, Mg, K, Br, and Rb are removed from the brine, and only Li and B remain as conservative or relatively conservative elements (Vengosh et al., 1992), which more clearly indicate the true DE (Zimmermann, 2001). The ratios of selected ions, for example, (Na/Cl)eq, Mg/Cl, and Br/Cl, also reflect the DE, with some limitations (Holser, 1963; Levy, 1977). The evaporation of seawater brines can be traced on the diagrams comparing the contents of some conservative components (e.g., Na and Cl, Mg and Cl; Lowenstein et al., 2001) or the ratios of such components (e.g., Mg/Cl vs. Br/Cl; Holser, 1963). Concentration ratios for marine sabkha brine aquifers require special calculations (Wood et al., 2002).

The recommended measures of concentration in brines are g/100   g H₂O, g/100   g solution (%), and mol/1000   mol H₂O (Braitsch, 1971, p. 28).

The mutual comparison of various salinity units is complicated, and in particular, such measurement requires the accompanying precise measurements of temperature. For a salinity accuracy of 0.02‰, the temperature during salinity measurement must be monitored with an accuracy of at least 0.04   ᵒC (Anati, 1999). The particular problem is within supersaturated brine in state of salt precipitation. It is difficult to measure its properties accurately not only because of the presence of the invisible suspension of salt microcrystals (<4   μm) but also because the continued salt precipitation changes the chemical composition of brine that influences the other physical parameters characterizing the brine and conversion scales (Anati, 1999; Stiller et al., 1997).

The measured salinity of seawater brine may reach values of 504.8 (TDS, g   l^{−   1}) at the beginning of the final bischofite crystallization stage (Fontes and Matray, 1993) and another type of brine in some continental lakes over 500   g   l^{−   1} (e.g., 557   g   l^{−   1}, TDS), in one of the Wadi El Natrun alkaline lakes, Egypt (Taher, 1999). Boiling hot (110   ᵒC) Na–K–Mg–Cl brine from hydrothermal springs in Dallol salt diapir in Ethiopia attains 420   g   kg^{−   1} (TDS; Hochstein and Browne, 2000). Subsurface brines can reach extremely high salinities such as 643   g   l^{−   1} recorded in Ca–Na–Cl-type brine from the Salina Formation in the Michigan Basin (Case, 1945). This brine showed also one of the highest density, 1.458   g   cm^{−   3}, so far measured in natural brines.

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Geochemistry of Mineral Deposits

R.J. Bodnar , ... M. Steele-MacInnis , in Treatise on Geochemistry (Second Edition), 2014

13.5.10.2.1 Major ions

Salinities of fluid inclusions from orogenic Au deposits are mostly <   10   wt% NaCl eq, with a mode around 5   wt% ( Figure 16(a) ). Note, however, that because FI in these deposits generally contain at least 4–5   mol% CO₂  ±   CH₄  ±   N₂ , ice-melting temperatures may not be representative of the true salinity, which should be determined based on the clathrate melting temperature. Low-eutectic temperatures (e.g., Robert and Kelly (1987), crush/leach, and SIMS analysis (Diamond et al., 1990, 1991) indicate the presence of salts other than NaCl in some cases. These data suggest concentration of Na⁺ (100–10   000s ppm)   >>   Ca^{2   +} and K⁺ (10s–1000s ppm)   >   Mg^{2   +} (10–100s ppm) in orogenic gold fluids and that Cl⁻ is the dominant anion, with minor amounts of F⁻ and Br⁻ sometimes detectable. Sulfate has been detected in FI from these deposits, but it should be emphasized that SO₄ ^{2   −} concentrations are significantly less than those of H₂S (e.g., Yardley et al., 1993).

Owing to the wide miscibility gap in the H₂O–CO₂–NaCl system, phase separation of the low-salinity, CO₂-bearing mineralizing fluid produces a CO₂-rich H₂O–CO₂ fluid with salinity less than a few wt% coexisting with intermediate salinity aqueous phase with up to about 15–20   wt% NaCl eq and little to no CO₂ ( Figure 15 ). Thus, where phase separation has occurred, saline–aqueous inclusions can have salinities significantly greater than the precursor single-phase fluid. It should be noted that FI evidence of fluid-phase immiscibility appears to be more common among the orogenic Au deposits of Precambrian ages and less common in Phanerozoic deposits, which may reflect more CO₂ production during devolatilization of greenstones compared to metasediments (R. Goldfarb, pers. comm.; See Chapter 13.15).

High-salinity, CaCl₂-rich FI in some deposits are recognized as late-stage overprinting by saline groundwater and are unrelated to ore formation (e.g., Robert et al., 1995). These inclusions commonly have low T _h (ranging from <   100   °C up to about 200   °C) (Robert and Kelly, 1987), and their chemistry is consistent with that of brines occurring in crystalline rocks of the Canadian Shield (e.g., Fritz and Frape, 1982). Notice on Figure 16(a) that high-salinity, low-temperature fluids are common in orogenic Au deposits. This reflects the fact that FI unrelated to mineralization are common.

Saline aqueous FI from orogenic gold deposits rarely contain halite daughter crystals (e.g., Boullier et al., 1998; Goldfarb et al., 2004). During heating, the vapor bubble often disappears before halite dissolves, and/or the inclusions decrepitate before halite completely dissolves (Boullier et al., 1998). Dawsonite, NaAlCO₃(OH)₂, was first recognized in fluid inclusions in gold-bearing quartz veins from the Alleghany district by Coveney and Kelley (1971). Nahcolite, NaHCO₃, is a fairly common daughter mineral in the inclusions from orogenic gold deposits (e.g., Hrstka et al., 2011; Robert and Kelly, 1987), consistent with the presence of HCO₃ ⁻-rich fluids. Hrstka et al. (2011) estimated that the nahcolite-bearing inclusions entrapped fluids with up to 20   wt% HCO₃ ⁻.

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Nanotechnology: A potential approach for abiotic stress management

Rakhi Mahto , ... Amitava Rakshit , in Advances in Nano-Fertilizers and Nano-pesticides in Agriculture, 2021

10.2.1 Salinity stress

Salinity is the most threatening abiotic stresses which affects the metabolism of plant cells and also provokes a number of secondary stresses leading to severe crop damage (Morari et al., 2015; Haider et al.,2019). Under salinity stress, electrons that have a high-energy state are transferred to molecular oxygen (O₂) to form ROS and this cause oxidative damage like lipid peroxidation in plant cells, protein denaturation, DNA damage, pigment breakdown, carbohydrate oxidation and interference with enzymatic activity (Gill et al., 2015). They reported that exogenous spray of 0.5 and 1   mM of nanosilicon oxide (nano-SiO₂) lowering down the Na⁺ concentration, lipid peroxidation, and reactive oxygen species by improving production of K⁺, antioxidant enzymes, non-enzymatic compounds and lipid peroxidation in soybean seedlings. Salinity inhibits the water absorption, germination of seeds and seedling root elongation. Nanoparticles are considered to modify physiological and biochemical processes in plants by affecting endogenous phytohormone levels thereby enhance the germination percentages and growth (Hossain et al., 2015) Crop cultivation under salt stress condition restricts the plant growth and production, mostly in dry lands. About 23% of the world's cultivated lands are saline and 37% are sodic (Jouyban, 2012). Salt stressed plant showed a significant reduction in yield loss due to reduction of photosynthesis, degradation of cell membranes, reduction of water available to plants and Na⁺ accumulation in the leaves were the main causes of weight loss under the salt stress (Hajiaghayi-Kamrani et al., 2013). Haghighi et al. (2012) found that nanosilicon (1   mM) reduced the oxidative stress of salinity on tomatoes during germination and improved the germination rate, root length, and dry weight of tomato plants in 25   mM NaCl condition.

Seed treatment of soybean with 0.5 and 1   mM of nanosilicon oxide (nano-SiO₂) reduced the destructive effects of salt toxicity (5 and 10   dS/m of NaCl salinity) by improving ROS scavenging mechanism in plants which enhanced the shoot and root growth of seedlings (Farhangi-Abriz and Torabian, 2018). It may be due to Si NPs easily absorbed by plant roots and form a fine layer in the cell wall which helps plant to resist various stresses and maintain yield (Derosa et al., 2010). However Abdel-Haliem et al. (2017) reported that nano Si derived from rice straw did not give any response to silicon uptake genes LSi1 and LSi2 in rice under increasing NaCl salt concentration.

Under saline and alkaline soils main limiting factor for crop production is iron deficiency due to high pH of the soil. Haghighi and Pessarakli (2013) reported that SNPs did increase photosynthesis parameters and slightly increased the total chlorophyll content under salt stress. Khan (2016) reported that foliar spray of nano-TiO₂ (20   mg/L) on Tomato (Lycopersicon esculentum Mill.) mitigated the deleterious effects of salt stress (200   mM   NaCl). Application of nano-TiO₂ was improved the activities of carbonic anhydrase, nitrate reductase, superoxide dismutase (SOD) and peroxidase (POX) and also increase accumulation of proline and glycine betaine. Likewise Fathi et al. (2017) found that foliar spray of nano Fe₂O₃ and ZnO at 2   g/L in wheat protected the plant from salinity stress and promoted plant height, shoot DW, leaf area and Fe and Zn concentration, and declined Na concentration.

Silver NP ameliorate the inhibitory effect of salinity by stimulating IBA, NAA, 6-benzylaminopurine (BAP) contents and by reducing abscicic acid (ABA) content. Abou-Zeid and Ismail (2018) reported the seed priming of wheat (Triticum aestivum L.) with silver nanoparticles (1   mg/L) synthesize from Capparis spinosa stimulate the seed germination, seedling growth, chlorophyll content and photosynthetic efficiency of plants under salinity stress condition (25 and 100   mM   NaCl). Similarly, Almutairi (2015) reported that the AgNPs (2.5   mg/L) appeared to mitigate the deleterious effect salinity (150   mM   NaCl) in Solanum lycopersicum L. Torabian et al. (2016) compared the nano-sized particles of ZnO to normal ZnO in sunflower cultivars under salt stress condition and observed that foliar application of nano ZnO increased shoot dry weight, leaf area, photosynthesis parameters and Zn concentration and decreased Na concentration in leaves compared to ordinary form.

Under different salinity condition application of Fe₂O₃ NP (30   μM) with irrigation water increased the leaf fresh weight and dry weight, phosphorus, potassium, iron, zinc, and calcium contents of the peppermint (Mentha piperita) by improving defense mechanism against total antioxidant enzymes (Askary et al., 2017). Moreover Kalteh et al. (2014) examined the effect of Basil (Ocimum basilicum) under salinity stress and found that silica nanoparticles reduce Na toxicity by reducing Na absorption and more proline degradation resulting higher fresh and dry biomass with higher chlorophyll. Since Si NP affects the xylem humidity and water translocation which enhance the water use efficiency of plant (Wang and Naser, 1994). Siddiqui et al. (2014) reported that seed treatment in Squash (Cucurbita pepo L. cv. white bush marrow) with nano-SiO₂ enhanced seed germination and other growth characteristics by reducing malondialdehyde and hydrogen peroxide levels as well as electrolyte leakage under NaCl stress. Likewise Alharby et al. (2016) proved the anti stress property of ZnO NP against the salinity in tomato and found that lower dose of ZnO NP (15   mg/L) unregulated the antioxidant enzymes SOD and GPX. Likewise seed priming of lupine (Lupinus termis) with ZnO NP (60   mg/L) positively affected the growth traits of salt stressed plant (150   mM   NaCl) by improving the IAA activity and protecting the sulfydryl group which helps in improving chlorophyll synthesis thus helped in minimizing uptake of the Na⁺ (Latef et al., 2017)

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Evaluating Water Quality to Prevent Future Disasters

Sanjay Bajpai , ... Piyalee Biswas , in Separation Science and Technology, 2019

4.9.1 Inland salinity

Groundwater salinity is common in the regions of Rajasthan, Haryana, Punjab, Gujarat, Uttar Pradesh, and to a lesser extent, in Madhya Pradesh, Maharashtra, Karnataka, Bihar, and Tamil Nadu. In some parts of Gujarat and Rajasthan, the salinity in groundwater is so high that salt is manufactured directly from these wells by solar evaporation ( http://cgwb.gov.in/wqoverview.html).

The saline aquifer areas are enlarging because of the intensive development of fresh groundwater resources in Punjab, Haryana, and Uttar Pradesh, thereby enlarging the area covered with saline groundwater. Thus, there is a need to check the ingress of saline groundwater in fresh groundwater areas by intensive development of the saline groundwater and treating the same with updated technologies. Besides geogenic reasons, salinity of aquifer is also caused because of the practice of irrigation by surface water without taking into consideration the status of groundwater. The rise in groundwater levels with time has resulted in water logging and intense water evaporation in semiarid regions leading to salinity in the affected areas.

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The Oceans and Marine Geochemistry

T.K. Lowenstein , ... A.D. Anbar , in Treatise on Geochemistry (Second Edition), 2014

8.21.5.3 The Analysis of Unevaporated Seawater in Fluid Inclusions

The salinity of ancient seawater may be obtained from the freezing point depression of aqueous fluid inclusions in marine calcites ( Goldstein and Reynolds, 1994). Specifically, the final melting temperature of ice in seawater with a salinity of 35‰ is −   1.9   ºC; the final melting temperature of ice decreases with an increase in salinity (Goldstein and Reynolds, 1994; Lyman and Fleming, 1940). Johnson and Goldstein (1993) analyzed single-phase aqueous inclusions in low-magnesium calcite cement of the Wilberns Formation in Texas, which almost certainly contain Cambro–Ordovician seawater. The salinity of the inclusion fluids ranges from 31‰ to 47‰, similar to the range found in present-day surface seawater in shallow marine environments, from open to slightly restricted (Johnson and Goldstein, 1993). Primary fluid inclusions in low-magnesium calcite cements from the Upper Devonian Canning Basin, Western Australia (Kwong, 1995; Ward, 1996; Ward et al., 1993), revealed a similar range of paleosalinities. From these limited data, it appears that seawater salinity has not varied dramatically, at least in the Paleozoic.

One further step would be to determine the major ion composition of unevaporated samples of ancient seawater preserved as primary fluid inclusions in low-magnesium calcite. The lower concentration and smaller size of these fluid inclusions compared to those found in halite have so far defied quantitative analysis by conventional techniques. Such analyses will be important for further defining the evolution of the major ion chemistry of Phanerozoic seawater.

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The Role of Water in Unconventional in Situ Energy Resource Extraction Technologies

Tanya J. Gallegos , ... Mark Engle , in Food, Energy, and Water, 2015

Water Chemistry Challenges to Agricultural Reuse

Salinity, the dissolved inorganic constituents in water, can be the greatest obstacle to beneficial agricultural use of produced waters, due to negative effects on both crop growth and soil properties. Salinity is the sum of dissolved ions and is most directly measured by evaporating to dryness; it is reported as TDS in units of milligrams per liter. The TDS in produced waters varies widely from around >500,000  mg/L measured in some oil field brines, down to <1000   mg/L found in certain coalbed methane produced waters. ^82,83 By comparison, drinking water typically contains <1000   mg/L TDS and seawater around 35,000   mg/L, making some produced waters >10 times saltier than seawater. Because ions in solution contribute fairly straightforwardly to the electrical conductivity (EC) of water at lower concentrations, this more rapid determination is often used in agricultural applications and the results reported in milliSiemens per centimeter (mS/cm). The EC of relatively pure water is approximately 0.002   mS/cm, that of drinking water is typically <0.5   mS/cm, and seawater has an EC of around 58   mS/cm.

Crops can suffer direct negative impacts from salinity in two ways: through osmotic effects and direct ion toxicity. Osmotic effects occur when solute concentrations in soil water exceed those in root cells of a plant, decreasing the favorability of soil-to-root water transfer. To compensate, plants take up salts or synthesize organic compounds to restore the osmotic gradient. Such processes need energy that is diverted from plant growth. For each crop there is a threshold soil salinity below which normal yields can be achieved. Above that threshold, yields generally decrease in linear fashion with slopes that vary from crop to crop. Crops vary widely in their tolerance of soil salinity, with threshold tolerance values ranging more than an order of magnitude. Certain crops, termed halophytes, actually grow better at relatively high salinity.

Direct ion toxicity effects on plants have been reported for sodium and chloride. Such effects can be difficult to distinguish from osmotic effects of salinity, however, even in test settings, if other ions are not also tested. ⁸⁴ Nevertheless, sodium is not essential for plant growth, and leaf injuries are observed when it accumulates to higher levels. High sodium levels in soil may impair plant uptake of calcium, resulting in nutrient imbalances and impaired growth. Chloride is an essential micronutrient, but like sodium, higher concentrations can damage leaves and impair growth. Crop tolerances to chloride vary by over an order of magnitude. Boron is another essential micronutrient, but for many plants there is a relatively narrow difference between levels optimum for growth and those that cause toxicity. Natural boron levels can be high in soils of arid climates, compounding issues with its presence in produced waters.

Depending upon the proportions and concentrations of major ions in a produced water, its use for irrigation has the potential to negatively impact soil physical properties. The ability of water and air to permeate soil, and for mechanized equipment to manipulate the soil, is influenced positively when mineral particles form stable aggregates. Aggregation in turn is influenced by the degree to which clay particles are drawn together to agglomerate or pushed apart to disperse. Clay particles generally have a net negative charge, attracting positively charged ions (cations) to their surfaces. Such ions are loosely held by electrostatic forces, allowing them to exchange as the composition of the surrounding solution changes. Sodium ions have a larger hydrated radius than calcium or magnesium ions and are less attracted to clay surfaces. As the proportion of sodium ions in the soil solution increases, the thickness of the layers of ions on clay surfaces increases, and as the positively charged layers repel each other, the clays are forced apart and disperse.

The percentage of exchangeable sodium on clays, relative to calcium and magnesium, correlates most directly with clay dispersion, but has a strong relationship with the sodium adsorption ratio (SAR) of water in contact with the soil. The SAR is defined as

$\text{SAR}=\frac{\left[\text{Na}\right]}{\sqrt{\frac{\left[\text{Ca}\right]+\left[\text{Mg}\right]}{2}}}$

where [Na], [Ca], and [Mg] are concentrations of sodium, calcium, and magnesium, respectively, expressed in units of milliequivalents per liter (meq/L). Units of SAR are meq^1/2/L^1/2, but common convention in reporting data is to omit the units. In addition to SAR, the overall concentration of solutes in water also influences clay dispersion. At lower concentrations, more water moves in between clay particles, drawn by the higher concentrations of ions on the clay surfaces. Thus, both the salinity (measured via EC) and SAR of irrigation water can influence clay dispersion and the ability of water to infiltrate the soil. Guidelines have been published to suggest how combinations of those parameters will or will not influence infiltration. ⁸⁵ While guidelines are useful, the particle size distribution, clay mineralogy, and other properties particular to a given soil will also influence how it responds to irrigation waters of a given EC and SAR. In particular, soils with a higher proportion of swelling clays like smectites are more likely to suffer from problems with dispersion and permeability.

Soil salinity and the proportion of sodium on exchange sites of clays must be managed for irrigation with produced waters to be successful. A time-tested means of addressing problems with sodium is by boosting the calcium supply via addition of gypsum (CaSO₄∙2H₂O), a comparatively soluble mineral and relatively inexpensive agricultural amendment. Removal of salts from soil can only be accomplished by flushing them down deeper through application of water in excess of evapotranspiration demand. ⁸⁶

Hydrocarbons, hydraulic fracturing additives, toxic trace metals, and radionuclides are other components of produced waters that can limit their use for irrigation. Some produced waters, like those associated with coalbed methane, tend to have lower hydrocarbon content compared to those from conventional oil and gas production. The sheer diversity of hydrocarbon compounds and the variety of their occurrence in produced waters limits the generalizations that can be made. Higher concentrations of some compounds are likely to generate toxic effects in organisms from plants to soil microbes. At less extreme concentrations, it may be the diversity of the microbial community that is primarily affected, possibly by favoring hydrocarbon-degrading microbes and suppressing others. Such shifts may alter enzyme activity, soil respiration and microbial biomass, all changes that might influence the cycling of nutrients to crops. Organic components such as alkanes may be decomposed rapidly in soil, while others, like asphaltenes, may persist much longer.

Produced waters often need multiple treatment steps to make them suitable for irrigation. Oil can be removed by various devices that coalesce the small drops of suspended oil (<100   μm) into larger volumes and physically separate them. Dissolved organic components can be removed by pH adjustment or adsorption onto activated carbon or organoclays, whereas the more volatile components can be removed by aeration. A variety of technologies are also available for removal of inorganic solutes, including RO, ion exchange, capacitive deionization, and thermal distillation. The energy needed to operate each of these technologies is a primary consideration in their employment, and desalinization costs are perhaps the biggest barrier to beneficial reuse of produced waters. Additional costs come from disposal of the concentrated organics or solutes (brine) that are generated as by-products of purification. Many technologies for removing inorganic solutes produce water that is too poor in ions and nutrients for irrigation use, and blending with untreated water or water from another source is needed. Direct amendment of produced water with gypsum or magnesium sulfate can also be used to adjust both the EC and SAR to values more suitable for irrigation. Additionally, special organic compounds such as polyacrylamide can be added to improve soil aggregation.

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Biopolymer based nanofertilizers applications in abiotic stress (drought and salinity) control

Muhamad Mujtaba , ... Khalid Mahmood Khawar , in Advances in Nano-Fertilizers and Nano-pesticides in Agriculture, 2021

4.6 Conclusion and future directions

Salinity and drought stress are the main limiting factors for many crops in terms of yield and productivity. Taking into account the current world food crises, researchers from divergent fields of sciences are devising the strategies to cope with current situation. In the last decade the spread of nanotechnology in almost every field of research has also helped the plant scientists in a verity of problem by presenting alternative solution to many biotic and abiotic problems. A number of nanofertilizers have been developed for this purpose. In addition, biomaterials like cellulose, chitin, zein and alginate have been applied in form of nanoparticles have been applied solely or as carrier for plant nutrients against abiotic stresses. The application nanocarriers for fertilizers and other nutrients presents a number of advantages over conventional application method such as target delivery, lower dose (eco-friendly), longer time availability in the medium (economical), nontoxic for plants and slow release. Still there is a lot unexplored potential in the field of nanofertilizers which need to be explored in coming future. As future direction it can be said that:

•

New suitable carriers are need to be explored with suitable physicochemical properties,

•

Nanomaterials with enhanced surface area and chemical properties are need to be design for increase reactivity between fertilizers and carrier,

•

Target delivery of organ specific delivery tools are needed to avoid the excess use of fertilizers,

•

Alternative biopolymers can be tested as carrier matrices.

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Environmental Geochemistry

A. Vengosh , in Treatise on Geochemistry, 2003

9.09.5 Salinization of Dryland Environment

Salinity in dryland environment is a natural phenomenon derived from a long-term accumulation of salts on the ground and lack of their adequate flushing in the unsaturated zone. Salt accumulation and efflorescent crusts have been documented in the upper unsaturated zone (e.g., Gee and Hillel, 1988; Nativ et al., 1997; Leaney et al., 2003) and fracture surface (Weisbrod et al., 2000; Weisbrod and Dragila, 2005) in many arid areas. The salt formation has been attributed to surface evaporation (Allison and Barnes, 1985), wetting and drying cycles (Drever and Smith, 1978), soil capillarity, and capillary transport of water and salts from the bulk rock matrix to the fracture surface (Weisbrod et al., 2000).

In the Western United States, recharge typically occurs along surrounding highlands and groundwater flows toward the basin centers. Along the flow path, the salinity of the groundwater increases by several orders of magnitude by both salt dissolution and extensive evaporation (Richter et al., 1993). The chemistry of the residual saline groundwater is primarily controlled by the initial freshwater composition and the subsequent saturation of typical minerals (calcite, gypsum, spiolite, and halite; Hardie and Eugster, 1970; Eugster and Jones, 1979). Evaporation and mineral precipitation control the salinity of groundwater in Deep Spring Lake (Jones, 1965), Death Valley (Hunt et al., 1966), and the Sierra Nevada Basin (Garrels and MacKenzie, 1967).

While the source of the salts is natural, the process of salinization in dryland environment refers to human intervention. The most widespread phenomenon of dryland salinization is the result of land clearing and replacing the natural vegetation with annual crops and pastures. The natural vegetation in the arid and semi-arid zone uses any available water and thus the amount of water that leaks below the root zone is minimal, estimated between 1 and 5   mm   yr⁻¹ in the case of South Australia (Allison et al., 1985). Salts have been accumulated over thousands of years in the unsaturated zone, and discharge to the saturated zone was balanced by the slow recharge flux. Large-scale replacement of the natural vegetation with annual crops and pastures with short roots significantly increased the amount of water leaking beneath the root zone and increased the rate of salts discharged to the underlying groundwater (Williams et al., 2002 and references therein). The salts that were stored in the root zone were consequently flushed into the unsaturated and saturated zone, causing salinization of underlying groundwater. Leaney et al. (2003) predicted that salt flux from the unsaturated zone in the Murray–Darling Basin of South Australia (with soil salinity up to 15,000   mg   l⁻¹) is expected to increase the salinity of the shallow groundwater (∼1,000   mg   l⁻¹) by a factor of 2–6. The combination of increasing of groundwater tables and salt fluxes in the unsaturated zone has caused devastating affects in the dryland environment. This was demonstrated in North America (Miller et al., 1981), Argentina (Lavado and Taboada, 1987), India (Choudhari and Sharma, 1984), Sahel (Culf et al., 1993), and South Africa (Flugel, 1995). However, the most dramatic large-scale salinization process occurs today in the dryland environment of Australia (Allison et al., 1985, 1990; Williams et al., 2002; Peck and Hatton, 2003; Leaney et al., 2003; Fitzpatrick et al., 2000; Herczeg et al., 1993, 2001).

The Australian case is used here to describe the chemical evolution of solutes in the dryland environment. The dryland salinization cycle (Figure 10) is a complex process that begins with salt accumulation on the ground, evaporation, total desiccation, precipitation–dissolution of carbonate minerals, incongruent silicate mineral reactions, and precipitation– dissolution of gypsum and halite minerals (Hardie and Eugster, 1970; Eugster and Jones, 1979). The salts that accumulate in the soil are flushed into the vadose zone. Two factors control the flushing: the mineral solubility and soil physical properties. The difference in solubility between the minerals causes chemical separation along the unsaturated zone; the higher the solubility of the mineral, the longer the travel of the salts that are derived from its dissolution. This process is also known as wetting and drying and involves complete precipitation of dissolved salts during dry conditions and subsequent dissolution of soluble salts during wet conditions (Drever and Smith, 1978). Moreover, this results, in an uneven distribution of ions along the unsaturated zone; Ca²⁺, Mg²⁺, and ${\text{HCO}}_3^{-}$ tend to accumulate at relatively shallow depths, ${\text{SO}}_4^{2-}$ at intermediate depths, and Na⁺ and Cl⁻ are highly mobilized to greater depths of the unsaturated zone. The Na/Ca ratio fractionates along the travel of solute in the vadose zone; Ca²⁺ is removed by precipitation of carbonate minerals whereas Na⁺ remains in the solution, or even increases by dissolution of halite. In addition, the mobilization of Na⁺ triggers base-exchange reactions; Na⁺ is adsorbed on clay and oxides, but the newly generated Ca²⁺ that is released from the adsorbed sites is taken by precipitation of soil carbonate.

Figure 10. The dryland salinization cycle (the Australian model): (1) salt accumulation and precipitation of minerals; (2) selective dissolution and transport of soluble salts in the vadoze zone; (3) storage of salts influenced by soil permeability; (4) leaching and salinization of groundwater; (5) rise of saline groundwater; (6) capillary evaporation of rising groundwater; (7) soil salinization; and (8) lateral solute transport and salinization of streams and rivers (modified from Fitzpatrick et al., 2000).

The overall final chemical composition of the solutes that are generated in the dryland environment depends on the initial fluid composition. In Australia, the solutes are derived from marine aerosols and deposited on the soil (Herczeg et al., 2001 and references therein). ¹⁴C ages of soil chloride reveal that most of the recharge occurred during wet climatic periods more than 20,000 years ago (Leaney et al., 2003). Consequently, with thousands of years of salt accumulation and numerous cycles through the unsaturated zone, the saline groundwater in the dryland environment has become "marine-like" with Na/Cl and Br/Cl ratios identical to that of seawater (Herczeg et al., 1993, 2001; Mazor and George, 1992). Also, the Australian salt lakes, which represent groundwater discharge zones, are characterized by marine chemical and isotopic (sulfur and boron) compositions superimposed by internal lake processes (Chivas et al., 1991; Vengosh et al., 1991a). However, if the initial solute is derived from water–rock interactions induced by the generation of acids from CO₂ accumulation and oxidation of organic matter in the soil, the final product is different. The "nonmarine" signature of the saline groundwater and salt lakes in the Western USA indeed reflects the role of water–rock interaction in shaping the chemical composition of both initial and evolved groundwater in the arid zone of the USA (Hardie and Eugster, 1970; Eugster and Jones, 1979).

The second factor that controls salinization of dryland environments is the physical characteristics (e.g., permeability) of the soil. In the arid zone of Australia, rainfall was not always sufficient to leach the salts, and the clay layers in the deep sodic subsoil prevent downward movement of water and salts, leading to a saline zone (Fitzpatrick et al., 2000). The accumulation of salts in soil can therefore be natural due to the decrease of soil permeability (referred to as "subsoil transient salinity"; Fitzpatrick et al., 2000) or anthropogenic due to the rise of saline groundwater as evidenced in South Australia (Allison et al., 1985, 1990; Herczeg et al., 1993). While the leaching process in the vadose zone controls the salinity of the underlying shallow groundwater, the soil chemistry is also influenced by the chemistry of the rising groundwater (Cox et al., 2002). The selective leaching process affects the composition of the underlying groundwater. In some cases, recharged groundwater is controlled by marine aerosols and/or halite dissolution and has a typical predominance of Na⁺ and Cl⁻ (e.g., Cox et al., 1996). In other cases, the solubility of gypsum produces saline water that is enriched in sulfate.

These two types of groundwater have a direct control on the chemistry of secondary saline soil (Cox et al., 1996; Fitzpatrick et al., 2000). The rising of Na–Cl groundwater creates halite-dominant soils, where chloride is the dominant anion. The rising of sulfate-enriched groundwater creates three types of soils: (1) gypsic soil—under aerobic conditions and saturation of calcium sulfate; (2) sulfidic soil—under anaerobic conditions and sufficient organic carbon, bacteria use the oxygen associated with sulfate and produce pyrite; and (3) sulfunic soil—exposure of pyrite to oxygen in the air causes oxidation of pyrite and formation of sulfuric acid that consequently reduces the soil pH and enhances leaching of basic cations, anions, and trace elements into the soil solution (Fitzpatrick et al., 2000).

The differentiation of soil permeability when soil becomes clogged with clay and mineral precipitation causes lateral flow of saline soil water and shallow groundwater toward low-lying areas. The final stage of the dryland cycle is salinization of adjacent streams and rivers. The chemical composition of the salinized river in the dryland environment reflects the net results of salt recycling between soil, subsoil, groundwater, secondary soil, soil solution, and surface water (Figure 10).

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Evaluating Water Quality to Prevent Future Disasters

B. DeCourten , ... S. Brander , in Separation Science and Technology, 2019

3.2 Adult Effects

Adaption to salinity is well characterized conceptually in later life history stages when the physiological capacity to tolerate stress has fully formed. However, physiological acclimation to alternative salinity regimes alone cannot remediate the potential for toxic interactions between salinity and EDCs. This is because salinity has a unique effect on the solubility properties of chemical stressors that may be present in aquatic systems that can lead to alterations in the chemical uptake and biological disposition for organisms of those environments ( Hooper et al., 2013). In addition to the differential chemical behavior of organic compounds between fresh and saltwater, it is established that aquatic organisms inhabiting saltier waters must intake more water in comparison to freshwater species, in order to maintain equal osmolality (salt content) with their surroundings (Evans, 1980). This may mean that the relative aqueous exposure of marine and estuarine organisms to aqueous pollutants is higher as a result of to the larger volume of water they ingest and reduced urination relative to freshwater organisms.

Not only can salinity alter the toxicity of EDCs but recent work identified that alternative salinities can change the water solubility characteristics of different compounds. Saranjampour et al. (2017) estimated median lethal concentration LC50 values using Estimation Programs Interface (EPI) Suite for a range of aquatic pollutants (pesticides, PAHs) in both fresh and sea water, and found that after 96   h, LC50 values were lower (more toxic) for all compounds in seawater. Factors including the biota, organic matter, suspended sediment, and particulate matter along with water conditions such as pH, temperature, and turbulence can all have deleterious effects on the bioavailability of toxic compounds for marine or estuarine organisms. The impact of salinity is magnified for more hydrophobic compounds, also demonstrated by findings from Yang et al. (2016), which demonstrated that increased salinity pushed a variety of EDCs from the dissolved to solid phase, increasing their propensity to accumulate in sediments and tissue. This work altogether highlights those impacts of co-occurring stress from salinity and EDCs needs to be more reliably predicted by incorporating the physical and chemical characteristics of an ecosystem.

In fact, such a relationship between exposure salinity and endocrine-related responses was recently identified in a meta-analysis performed on a large volume of primary studies investigating-EDCs in fish (Bosker et al., 2017). Their analysis included 12 species of either freshwater or saltwater fish under alternative salinities and co-exposure of two model estrogens, 17α-ethinylestradiol and 17β-estradiol (E2), and three androgens (17β-trenbolone, 5α-dihydrotestosterone, and 17α-methyltestosterone). They found from the 59 studies they included in the analysis that the most sensitive endpoints in fish exposed to both estrogenic and androgenic EDCs are E2 levels and altered fecundity in females under alternative salinities (Bosker et al., 2017; Fig. 3). Not only did their work assess the influence of salinity on reproductive effects in fish exposed to common environmental EDCs, but it also revealed minor differences in the health outcomes between species that would otherwise be difficult to observe with investigations of individual taxa. In another study from Bosker's group with mummichogs (F. heteroclitus), which compared reproductive endpoints in response to dihydrotestosterone (DHT) across two salinities, DHT-exposed adults had lowered egg production compared to controls at 16   ppt, but not at 2   ppt (Glinka et al., 2015). These manuscripts highlight the need for future investigations that develop a clearer understanding of salinity interactions with EDCs in order to work toward more comprehensive environmental risk assessments.

Fig. 3. Endpoint sensitivity for estrogens under fresh (A and C) and saline (B and D) exposure conditions. The number of experiments reported with lowest observed effect concentration (LO) is shown in orange. The number of studies in which observed effects were reported above the LOEC within the same study is shown in yellow. The number of studies in which no observed effects was reported at concentrations higher than the maximum tested concentration is shown in white.

Printed with the permission from Bosker, T., Santoro. G., Melvin, S.D., 2017. Salinity and sensitivity to endocrine disrupting chemicals: a comparison of reproductive endpoints in small-bodied fish exposed under different salinities. Chemosphere 183, 186–196.

Estuarine organisms other than vertebrates have also been identified as susceptible to the effects of EDCs and salinity stress. Bifenthrin, like many pesticides designed with specificity to insects, are similarly toxic to crustaceans because of their conserved arthropod physiology. Work by Hasenbein et al. (2018) examined the toxicity of this potent and widely used insecticide, to the epibenthic amphipod Hyalella azteca. They found that a slight increase in salinity readily decreased survival and reduced the swimming performance of H. azteca in the face of exposure to nanomolar concentrations of bifenthrin (Hasenbein et al., 2018). As well, they found that co-exposure of higher salinities and bifenthrin resulted in a reduced expression of heat shock protein genes associated with cellular stress response, suggesting a lack of protection against cellular damage and oxidative stress (Hasenbein et al., 2018). Therefore, even mild environmental stress such as that predicted for the near future, and that is still well within physiological limits of a species, may synergistically increase toxicological sensitivity.

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