11.9 Salinization and Saline Environments A Vengosh, Duke University, Durham, NC, USA ã 2014 Elsevier Ltd. All rights reserved. 11.9.1 Introduction 327 11.9.2 River Salinization 329 11.9.3 Lake Salinization 336 11.9.4 Groundwater Salinization 338 11.9.4.1 Seawater Intrusion and Saltwater Displacement in Coastal Aquifers 338 11.9.4.2 Mixing with External Saline Waters in Noncoastal Areas 342 11.9.4.3 Salinization of Shallow Groundwater in River Basins 344 11.9.4.4 Salinization of Nonrenewable Groundwater 345 11.9.5 Salinization of Dryland Environment 346 11.9.6 Anthropogenic Salinization 348 11.9.6.1 Urban Environment and Wastewater Salinization 348 11.9.6.2 Deicing and Salinization 350 11.9.6.3 Agricultural Drainage and the Unsaturated Zone 350 11.9.7 Salinity and the Occurrence of Health-Related Contaminants 352 11.9.7.1 Fluoride and Salinity 353 11.9.7.2 Oxyanions and Salinity 353 11.9.7.2.1 Arsenic 353 11.9.7.2.2 Selenium 354 11.9.7.2.3 Boron 354 11.9.7.3 Naturally Occurring Radionuclides and Salinity 356 11.9.7.4 Trihalomethanes and Salinity 356 11.9.7.5 Salinity and Toxic Algae Bloom 357 11.9.8 Elucidating the Sources of Salinity 358 11.9.9 Remediation and the Chemical Composition of Desalination 363 Acknowledgments 367 References 367 þ > Glossary sulfate and bicarbonate; Ca/(SO4 HCO3) 1in Additive agricultural chemicals chemicals added to equivalent units. irrigation water (e.g., nitrogen fertilizers, gypsum, dolomite, Chlorine radioactive isotope ratio the activity of the 36 boron compounds). radioactive Cl isotope is normalized to the total chloride 36 Afforestation an establishment of a forest or plantation in content, Cl/Cl. an area where there were no trees. Conservative mixing mixing of two or more water bodies Arsenate the oxic form (species) of arsenic in water; occurs that involves nonreactive mixing of dissolved salts in the in oxidizing water. water; the concentrations of the dissolved water reflect the Arsenite the reduced form (species) of arsenic in water; relative mixing proportions of the water bodies. occurs in reduced water. Criterion continuous concentration an estimate of the Artificial recharge man-made recharge of aquifers through highest concentration of a material in surface freshwater to artificial basins or reverse pumping wells that replenish the which an aquatic community can be exposed indefinitely aquifer as a compensation for overexploitation. without resulting in an unacceptable effect. Base-exchange reactions chemical reactions that involve Cross-formational flow flow of groundwater from one þ exchange of dissolved and adsorbed cations (e.g., Ca2 , aquifer, typically confined, to an overlying aquifer. À 2þ þ Mg ,Na ) from adsorption sites on clay minerals and/or Denitrification reduction of nitrate molecule (NO3 ) oxides. under reduced conditions to nitrogen gas. Boron species boron in aquatic solutions occurs as Disinfection byproducts formation of hazardous 0 À uncharged boric acid (B(OH)3 ) and borate ion (B(OH)4 ) byproducts during chlorine disinfection of drinking water, forms. typically with high organic matter; generation of Boron isotopes the stable isotope ratio of boron, 11B/10B, is trihalomethanes (THMs), and specifically brominated 11 11 10 defined in delta notation: d B¼{[ B/ B]sample/ trihalomethanes (e.g., bromodichloromethane; BDCM) 11 10 [ B/ B]STD À 1}Â1000, where STD is a standard. during the disinfection process. Ca–chloride water composition the definition of Dissociation of boric acid to borate ion an increase in the water with a high proportion of calcium over the sum of pH will convert boric acid to the borate ion species. The Treatise on Geochemistry 2nd Edition http://dx.doi.org/10.1016/B978-0-08-095975-7.00909-8 325 326 Salinization and Saline Environments dissociation constant is defined at the pH at which the Inner-sphere complex a chemical bond that is typically fraction of boric acid is equal to that of borate ion. covalent between oxyanions and the electron-donating Dissolved inorganic carbon the sum of dissolved inorganic oxygen ion on a mineral surface without the presence of carbon (DIC) species in a solution that is composed of water molecules. carbon dioxide, carbonic acid, bicarbonate anion, and Ionic strength a measure of the salinity of a solution that is carbonate anion. The relative proportions of these species expressed as the square root of the sum of the individual ion À1 vary with pH. concentrations (in molality unit; mol kg {H2O}) Dolomitization a chemical reaction of Mg-rich water multiplied by the charge number of that ion. Generally, with calcium carbonate (e.g., limestone) rocks that involves multivalent ions contribute strongly to the ionic strength of þ þ Mg2 and Ca2 exchange, resulting in Ca-rich residual a solution relative to monovalent ions. solution. Isotopic fractionation preferential and/or selective Efflorescent salt crusts salts that are generated in soil or incorporation of specific isotopes into different phases shallow unsaturated zones that were formed by evaporation (dissolved, solid, vapor) that results in enrichment and/or of saline soil solution that have reached the saturation level depletion of the isotopes and changing of their ratios in the of different soluble minerals (e.g., gypsum, halite). reaction products. Electrical conductivity a field measure of the salinity of Meteoric water line the linear correlation between d2 H and water, known also as specific conductance, that measures a d18O values in precipitation that reflects the local solution’s ability to conduct an electric current. The SI unit is temperature and relative humidity; typically, the linear À siemens per centimeter (S cm 1). A reciprocal quantity is correlation has a slope8 and an intercept value that electrical resistivity. increases with aridity (lower relative humidity), known as Endorheic rivers rivers that flow to inland basins and never deuterium excess. reach the ocean. Mineral saturation the concentration level of ions from Ethylene dibromide (EDB) type of soil fumigant enriched which different minerals will begin to precipitate into a solid in bromide. state. Evapotranspiration the combined evaporation and plant Mobilization leaching of ions and trace elements from a transpiration from soil surface; evaporation involves solid phase (e.g., mineral surface) to the dissolved phase in transport of water to the air from the soil solution, surface water. water, while transpiration accounts for water transport Nitrogen isotopes the ‘delta’ notation, defined as d15 ¼ 15 14 15 14 Â 3 through a plant. The combined effect results in water loss NNO3 [( N/ N)sample/( N/ N)AIR –1] 10 . and accumulation of salt residue. Osteosarcoma bone cancer associated with long-term Exchangeable adsorption sites one of the adsorption exposure to radioactive nuclides that are bioaccumulated in þ reaction processes involves exchange of cations (e.g., Ca2 , bone tissue. þ þ Mg2 ,Na ) from adsorption sites on clay minerals and/or Outer-sphere complex a chemical bond that is typically an oxides and water. The capacity of exchangeable adsorption ion pair in which oxyanions and surface functional groups sites varies among the mineral types and will determine the on a mineral surface are separated by one or more water magnitude of the exchange reaction process. molecules. Fossil water known also as nonrenewable groundwater, Overexploitation of an aquifer water pumping rates of an includes water that was recharged to an aquifer during aquifer beyond the natural replenishment rates. historical/geological time and is not originated from the Oxyanions speciation of trace elements such as arsenic, modern hydrological cycle. Fossil water is typically selenium, and boron into anionic forms. identified by radioactive age-dating isotopes (e.g., 14C, Sodium adsorption ratio (SAR) the relative activity of tritium) and stable oxygen and hydrogen isotopes that are sodium ions in exchange reactions with soil. different from those of modern precipitation. Selenate, Se(VI) the oxidized form of selenium in oxidizing Freshening fresh groundwater flow and displacement of water. saline groundwater. Selenite, Se(IV) the reduced form of selenium in reducing Imported water water that is used from external sources water. outside a region or an aquifer; typically, water is imported Sinkholes a natural depression or hole in land surface from areas of high abundance to areas where natural water caused by subsurface dissolution of rocks. resources are not sufficient to accommodate water demands. Sodic subsoil a dense clay soil zone with high capacity for Incongruent silicate mineral reactions a weathering sodium adsorption, which reduces the hydraulic chemical reaction that involves reaction of silicate minerals conductivity of the soil. (e.g., aluminosilicates) in rocks and soils with carbon Softener backwash saline water saline effluents that are dioxide that generates clay minerals (e.g., kaolinite) and generated during the regeneration process of softener in residual water enriched in bicarbonate. While in congruent which a brine is flushed through the ion-exchange column dissolution the mineral is completely dissolved into to remove calcium to provide available exchangeable sites solution, incongruent dissolution involves formation of a for calcium removal process of softeners. d18 new mineral from the ions that were dissolved from mineral Stable oxygen and hydrogen isotopes in water OH2O ¼ 18 16 18 16 3 d2 weathering. ( [( O/ O)sample/( O/ O)STD –1] x10 ) and HH2O Salinization and Saline Environments 327 2 1 2 1 3 (¼[( H/ H)sample/( H/ H)STD –1] x10 ), where STD is Total organic carbon (TOC) The concentration of carbon standard mean ocean water (SMOW). bound in organic compounds in water; can be used as a Strontium isotopes the ratio of radiogenic 87Sr to stable measure of water quality. 86Sr isotopes, 87Sr/86Sr. Uranium decay chains a group of radioactive nuclides d34 ¼ 34 36 238 235 232 Sulfur isotope in sulfate SSO4 ( [( S/ S)sample/ that are generated from the parent U, U, and Th 34 36 3 ( S/ S)STD –1] x10 ).