Inorganic Ions as Tracers
01 Jan 2000-pp 31-77
TL;DR: In the unsaturated zone, the geochemical evolution, though less intense than in the soil and unsaturated zones, follows progressive changes in water quality towards areas of discharge as mentioned in this paper.
Abstract: As water moves into the ground it begins to record information on the history of its recharge source and properties, mainly from rainfall solutes as well as isotopic ratios of the water molecule. The subsurface accepts water at variable rates of movement through the soil, via the unsaturated zone, to the water table. At this stage the groundwater composition undergoes significant modification due to two major processes: an increase in the concentration of atmospheric solutes due to removal of water via plant uptake and evaporation; and reactions between water and rock, leading to the build-up of dissolved substances with different relative ion concentrations to the atmospheric input. The principal and distinctive characteristics of groundwater are mainly established in the unsaturated zone. In the saturated zone the geochemical evolution, though less intense than in the soil and unsaturated zones, follows progressive changes in water quality towards areas of discharge. These processes are time-dependent and the chemical changes as well as isotopic variations may be used to identify this evolution and provide information on water flow paths.
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TL;DR: For reactive con- taminants like NO 3 -, a combination of chemical, isoto- pic, and environmental-tracer analytical approaches might be required to resolve changing inputs from subse- quent alterations as causes of concentration gradients in groundwater Groundwater records derived from multi- component hydrostratigraphic data can be used to quan- tify recharge rates and residence times of water and dis- solved contaminants, document past variations in recharging contaminant loads, and identify natural contam- inant-remediation processes.
Abstract: Agriculture has had direct and indirect effects on the rates and compositions of groundwater recharge and aquifer biogeochemistry Direct effects include dis- solution and transport of excess quantities of fertilizers and associated materials and hydrologic alterations relat- ed to irrigation and drainage Some indirect effects in- clude changes in water-rock reactions in soils and aqui- fers caused by increased concentrations of dissolved oxi- dants, protons, and major ions Agricultural activities have directly or indirectly affected the concentrations of a large number of inorganic chemicals in groundwater, for example NO 3 - , N 2 , Cl, SO 4 2- , H + , P, C, K, Mg, Ca, Sr, Ba, Ra, and As, as well as a wide variety of pesti- cides and other organic compounds For reactive con- taminants like NO 3 - , a combination of chemical, isoto- pic, and environmental-tracer analytical approaches might be required to resolve changing inputs from subse- quent alterations as causes of concentration gradients in groundwater Groundwater records derived from multi- component hydrostratigraphic data can be used to quan- tify recharge rates and residence times of water and dis- solved contaminants, document past variations in re- charging contaminant loads, and identify natural contam- inant-remediation processes These data indicate that many of the world's surficial aquifers contain transient records of changing agricultural contamination from the last half of the 20th century The transient agricultural groundwater signal has important implications for long- term trends and spatial heterogeneity in discharge
694 citations
TL;DR: In this paper, the authors provide an overview of global salinization phenomena and investigate the different mechanisms and geochemical processes that are associated with salinisation, including the distinction between natural processes and anthropogenic forcing that generates salinity.
Abstract: This chapter provides an overview of global salinization phenomena and investigates the different mechanisms and geochemical processes that are associated with salinization. The overview includes salinization of rivers, lakes, and groundwater from different parts of the world. Special emphasis is given to the distinction between natural processes and anthropogenic forcing that generates salinity, such as wastewater contamination and agricultural runoff. As such, two anthropogenic salinization cycles are introduced – the agricultural and the domestic. The role of the unsaturated zone in shaping the chemical composition of dryland salinization is also discussed. An overview of the effects of salinity on the occurrence of health-related contaminants such as fluoride, oxyanions (arsenic, selenium, boron), radionuclides, trihalomethanes, and fish-kill algae is presented. Some useful geochemical and isotopic fingerprinting tracers are introduced for elucidating the salinity sources. Finally, the chemical and isotopic compositions of man-made ‘new water’ that is produced from desalination are analyzed with implications for predicting the chemical and isotopic compositions of future water resources in the Anthropocene Era.
200 citations
TL;DR: In groundwater from the shallowest Shepparton Formation, homogenisation of Cl/Br and δ 18 O values and a decline in 14 C activities with depth imply that vertical flow dominates as discussed by the authors.
192 citations
TL;DR: In this paper, combined hydrogeological and hydrogeochemical data allow flow systems and the origins of solutes in the Honeysuckle Creek area of the southeastern Murray Basin, which is an area affected by dryland salinity, to be constrained.
165 citations
TL;DR: The hydrogeochemical and isotopic evolution of groundwaters in the Mio-Pliocene sands of the Complexe Terminal (CT) aquifer in central Algeria is described in this paper.
Abstract: The hydrogeochemical and isotopic evolution of groundwaters in the Mio-Pliocene sands of the Complexe Terminal (CT) aquifer in central Algeria are described. The CT aquifer is located in the large sedimentary basin of the Great Oriental Erg. Down- gradient groundwater evolution is considered along the main representative aquifer cross section (south-north), from the southern recharge area (Tinrhert Plateau and Great Oriental Erg) over about 700 km. Groundwater mineralisation increases along the flow line, from 1.5 to 8gl �1 , primarily as a result of dissolution of evaporite minerals, as shown by Br/Cl and strontium isotope ratios. Trends in both major and trace elements demonstrate a progressive evolution along the flow path. Redox reac- tions are important and the persistence of oxidising conditions favours the increase in some trace elements (e.g. Cr) and also NO3 � , which reaches concentrations of 16.8 mg l �1 NO3-N. The range in 14 C, 0-8.4 pmc in the deeper groundwaters, corresponds with late Pleistocene recharge, although there then follows a hiatus in the data with no results in the range 10-20 pmc, interpreted as a gap in recharge coincident with hyper-arid but cool conditions across the Sahara; groundwater in the range 24.7-38.9 pmc signifies a distinct period of Holocene
158 citations
Cites background from "Inorganic Ions as Tracers"
...Chloride, Stable Isotopes (d18O, d2H) and Bromide Chloride concentrations largely reflect the input conditions at the time of recharge and may be modified subsequently by inputs from formation waters or evaporites (Herczeg and Edmunds 1999)....
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...Chloride concentrations largely reflect the input conditions at the time of recharge and may be modified subsequently by inputs from formation waters or evaporites (Herczeg and Edmunds 1999)....
[...]
References
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TL;DR: It is shown that a satisfactory account can be given of open water evaporation at four widely spaced sites in America and Europe, the results for bare soil receive a reasonable check in India, and application of theresults for turf shows good agreement with estimates of evapolation from catchment areas in the British Isles.
Abstract: Two theoretical approaches to evaporation from saturated surfaces are outlined, the first being on an aerodynamic basis in which evaporation is regarded as due to turbulent transport of vapour by a process of eddy diffusion, and the second being on an energy basis in which evaporation is regarded as one of the ways of degrading incoming radiation. Neither approach is new, but a combination is suggested that eliminates the parameter measured with most difficulty—surface temperature—and provides for the first time an opportunity to make theoretical estimates of evaporation rates from standard meteorological data, estimates that can be retrospective. Experimental work to test these theories shows that the aerodynamic approach is not adequate and an empirical expression, previously obtained in America, is a better description of evaporation from open water. The energy balance is found to be quite successful. Evaporation rates from wet bare soil and from turf with an adequate supply of water are obtained as fractions of that from open water, the fraction for turf showing a seasonal change attributed to the annual cycle of length of daylight. Finally, the experimental results are applied to data published elsewhere and it is shown that a satisfactory account can be given of open water evaporation at four widely spaced sites in America and Europe, the results for bare soil receive a reasonable check in India, and application of the results for turf shows good agreement with estimates of evaporation from catchment areas in the British Isles.
6,711 citations
Book•
01 Jun 1989
TL;DR: The chemical composition of natural water is derived from many different sources of solutes, including gases and aerosols from the atmosphere, weathering and erosion of rocks and soil, solution or precipitation reactions occurring below the land surface, and cultural effects resulting from human activities.
Abstract: The chemical composition of natural water is derived from many different sources of solutes, including gases and aerosols from the atmosphere, weathering and erosion of rocks and soil, solution or precipitation reactions occurring below the land surface, and cultural effects resulting from human activities. Broad interrelationships among these processes and their effects can be discerned by application of principles of chemical thermodynamics. Some of the processes of solution or precipitation of minerals can be closely evaluated by means of principles of chemical equilibrium, including the law of mass action and the Nernst equation. Other processes are irreversible and require consideration of reaction mechanisms and rates. The chemical composition of the crustal rocks of the Earth and the composition of the ocean and the atmosphere are significant in evaluating sources of solutes in natural freshwater. The ways in which solutes are taken up or precipitated and the amounts present in solution are influenced by many environmental factors, especially climate, structure and position of rock strata, and biochemical effects associated with life cycles of plants and animals, both microscopic and macroscopic. Taken together and in application with the further influence of the general circulation of all water in the hydrologic cycle, the chemical principles and environmental factors form a basis for the developing science of natural-water chemistry. Fundamental data used in the determination of water quality are obtained by the chemical analysis of water samples in the laboratory or onsite sensing of chemical properties in the field. Sampling is complicated by changes in the composition of moving water and by the effects of particulate suspended material. Some constituents are unstable and require onsite determination or sample preservation. Most of the constituents determined are reported in gravimetric units, usually milligrams per liter or milliequivalents
6,271 citations
Book•
01 Jan 1970
TL;DR: In this paper, the Solid-Water Interface Adsorption Dissolution of Minerals Nucleation and Crystal Growth Particle-Particle Interaction Colloids Coagulation and Filtration Regulation of the Chemical Composition of Natural Waters (Examples) Thermodynamic Data.
Abstract: Chemical Thermodynamics and Kinetics Acid-Base Dissolved Carbon Dioxide Atmosphere-Water Interactions Metal Ions in Aqueous Solution Aspects of Coordination Chemistry Precipitation and Dissolution Oxidation and Reduction Equilibria the Solid-Solution Interface Trace Metals: Cycling, Regulation and Biological Role Kinetics and Redox Processes Photochemical Processes Kinetics at the Solid-Water Interface Adsorption Dissolution of Minerals Nucleation and Crystal Growth Particle-Particle Interaction Colloids Coagulation and Filtration Regulation of the Chemical Composition of Natural Waters (Examples) Thermodynamic Data.
5,963 citations
Book•
01 Jan 1993TL;DR: In this paper, a comprehensive and quantitative approach to the study of groundwater quality is presented in order to predict what the effect of present-day human activities will be on that scale.
Abstract: Groundwater geochemistry is an interdisciplinary science concerned with the chemistry in the subsurface environment. The chemical composition of groundwater is the combined result of the quality of water that enters the groundwater reservoir and reactions with minerals and organic matter of the aquifer matrix may modify the water quality. Apart from natural processes as controlling factors on the groundwater quality, in recent years the effect of pollution, such as nitrate from fertilizers and acid rain, also influences the groundwater chemistry. Due to the long residence time of groundwater in the invisible subsurface environment, the effect of pollution may first become apparent tens to hundreds of years afterwards. A proper understanding of the processes occurring in aquifers is required in order to predict what the effect of present day human activities will be on that scale. This book presents a comprehensive and quantitative approach to the study of groundwater quality. Practical examples of application are presented throughout the text.
4,767 citations
TL;DR: On the basis of analytical chemical data for numerous rain, river, lake, and ocean samples, the three major mechanisms controlling world surface water chemistry can be defined as atmospheric precipitation, rock dominance, and the evaporation-crystallization process.
Abstract: On the basis of analytical chemical data for numerous rain, river, lake, and ocean samples, the three major mechanisms controlling world surface water chemistry can be defined as atmospheric precipitation, rock dominance, and the evaporation-crystallization process.
2,885 citations