CFCs are frquently used for dating young groundwater, see the project section for examples. Text is taken from: Cook, P. Chlorofluorocarbons CFCs are man-made organic compounds which are produced for a range of industrial and domestic purposes Rowland, Concentrations of these CFCs in ocean basins have been used to study mixing processes, and the movement of deep ocean currents Trumbore et al. CFC concentrations in groundwater have been used to estimate groundwater age Thompson and Hayes, ; Busenberg and Plummer, ; Dunkle et al. Measurements of atmospheric concentrations have been made since July at stations throughout the world as part of the Atmospheric Lifetime Experiment Prinn et al. This is in strong contrast to the spatially variable nature of 3 H concentrations in rainfall. For CFCs, the atmospheric input to the ground-water can be known with a high degree of precision, even at remote sites. Atmospheric concentrations for the period before their regular measurement have been reconstructed from estimates of world-wide production of chlorofluorocarbons and their rate of release to the atmosphere McCarthy et al.
Environmental tracers and groundwater dating
Solomon The mean transit time of groundwater is a fundamental and robust characteristic of a subsurface flow system. In unconfined aquifers, the mean groundwater transit time is related to 1 the volume of water stored in the aquifer and 2 the flux of water into or out of the aquifer. Environmental tracers such as tritium have been used to estimate the mean transit time, but generally require a time series of measurements from the early s to approximately and such data sets are very rare.
Moreover, young groundwater dating tracers, 85Kr, chlorofluorocarbons (CFCs), sulphur hexafluoride (SF6), and tritium (3H), were analyzed for 9, 36, 27, and 3.
Methods for using argon to age-date groundwater using ultra-low-background proportional counting. Argon can be used as a tracer for age-dating glaciers, oceans, and more recently, groundwater. With a half-life of years, 39Ar fills an intermediate age range gap , years not currently covered by other common groundwater tracers. Therefore, adding this tracer to the data suite for groundwater studies provides an important tool for improving our understanding of groundwater systems.
We present the methods employed for arriving at an age-date for a given sample of argon degassed from groundwater. Degradation of sucralose in groundwater and implications for age dating contaminated groundwater. The artificial sweetener sucralose has been in use in Canada and the US since about and in the EU since , and is now ubiquitous in sanitary wastewater in many parts of the world. It persists during sewage treatment and in surface water environments and as such, has been suggested as a powerful tracer of wastewater.
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It showed that CFC and CFC were suitable tracers for groundwater dating because of their stability in the wetland environment. Furthermore, the mixture of groundwater with different age was discussed by CFC and CFC based on the binary mixing model and piston-flow model. As one of the most active factors, groundwater age is a key to understand the hydrological cycle as well as the associated hydro-ecological processes in a watershed.
The knowledge of the residence time would also help to illuminate processes that control subsurface flow routing since it is directly related to the diversity of flow pathways in a catchment Pearce et al. There are many ways to identify the residence time.
Georgia CFCs were used to trace and date leakage of river water through sinkholes into the Upper Floridan aquifer near Valdosta, Georgia (Plummer and others.
Environmental tracers are natural or man made anthropogenic compounds or isotopes that are widely distributed in the near-surface environment. Variations in their quantities can be used to determine pathways and timescales of environmental processes. They include naturally occurring isotopes such as carbon and anthropogenic tracers such as Chlorofluorcarbons CFCs.
Releases of anthropogenic environmental tracers include catastrophic events such as nuclear bomb testing releasing, as well as gradual leakage of tracers from industrial production processes. One of the principal uses of environmental tracers is for determining the ages of soil waters and groundwaters. Information on soil water and groundwater age allows determination of timescales for a range of processes in the sub-surface.
The use of environmental tracers to determine water ages allows groundwater recharge rates and flow velocities to be determined independently, and commonly more accurately, than with more traditional hydraulic methods where hydraulic properties of aquifers are poorly known or spatially variable. Groundwaters residence times in the investigated reference aquifers range from a few years up to many thousands of years. For these time scales, dating using tracers relies on substances which were already present in the geosphere at the time of recharge.
Department Water Resources and Drinking Water
In the early s, USGS scientists Busenberg and Plummer, developed a method to date resource use on the basis of chlorofluorocarbon CFC content of the water.
Shallow ground-resource systems are commonly used for drinking resource sources and they make up a large part of the baseflow in rivers and lakes. However, shallow use-water supplies are generally young recently recharged and, because there has used a local variety of man-made pollutants produced in the meteoric century, are more susceptible to contamination than deeper ground water. Information about ground-water age can be used to determine recharge rates and refine meteoric models of ground-water systems Reilly and others, ; Szabo and techniques, and thus to identify the contamination potential and estimate the time used to flush contaminants through a use-water system.
The 0- to year time scale is particularly relevant to environmentally sensitive shallow ground-water systems. Prior to the late s, however, there were no reliable means of dating ground water recharged during this time scale and, until recently, none of those methods were considered practical for use in establishing regional patterns. In the early s, USGS scientists Busenberg and Plummer, developed a method to date resource use on the basis of chlorofluorocarbon CFC content of the water that is practical, use-effective, and applicable to most shallow ground-water systems.
The feasibility of using CFCs as tracers of recent recharge and indicators of ground-water age was first recognized in the s see Plummer and Busenberg, and references therein. Use have been increasingly used in oceanic studies since the late s as tracers of oceanic circulation, ventilation, and mixing processes. USGS isotopes Busenberg and Plummer, adapted global procedures developed by the oceanographic scientific community for ground-water studies and designed sampling equipment and procedures for collection and use of water techniques in the field.
Water samples for CFC analysis are now routinely collected from domestic, irrigation, monitoring, and municipal wells, and from springs. A closed path is established between the well or pump to a valve dating that is used to fill glass ampoules with water, creating a headspace with CFC-free, ultra-pure nitrogen gas. The samples are then transported to the U. Ground-water dating with CFC, CFC and CFC is possible because 1 their amounts in the atmosphere over the past 50 years have been reconstructed, 2 their solubilities in water are known, and 3 concentrations in air and young water are high enough that they can be measured.
As with any environmental tracer, age applies to the use of introduction of the chemical substance into the water, and not to the water itself.
The Reston Groundwater Dating Laboratory
Kluwer Acadmic Press. Chlorofluorocarbons CFCs are stable, synthetic, halogenated alkanes, developed in the early s as safe alternatives to ammonia and sulphur dioxide in refrigeration. CFCs are nonflammable, noncorrosive, nonexplosive, very low in toxicity, and have physical properties conducive to a wide range of industrial and refrigerant applications.
The hydrogeological functioning of four different areas in a complex evaporite-karst unit of predominantly aquitard behavior in S Spain was investigated. Environmental dating tracers 3 H, 3 He, 4 He, CFC, SF 6 and hydrochemical data were determined from spring samples to identify and characterize groundwater flow components of different residence times in the media. Ne values show degassing of most of the samples, favored by the high salinity of groundwater and the development of karstification so that the concentration of all the considered gases were corrected according to the difference between the theoretical and the measured Ne.
The presence of modern groundwater in every sample was proved by the detection of 3 H and CFC At the opposite, the higher amount of radiogenic 4 He in most samples also indicates that they have an old component. The large SF 6 concentrations suggest terrigenic production related to halite and dolomite. Particularly, GA 50 is derived from the median groundwater age and is presented as a new way of interpreting mixed groundwater age data.
A greater fraction of old groundwater 3 H and CFC free was identified in discharge areas, while the proportion and estimated infiltration date of the younger fractions in recharge areas were higher and more recent, respectively. The application of different approaches has been useful to corroborate previous theoretical conceptual model proposed for the study area and to test the applicability of the used environmental tracer in dating brine groundwater and karst springs.
Andreo, M. Mudarra The hydrogeological functioning of four different areas in a complex evaporite-karst unit of predominantly aquitard behavior in S Spain was investigated.
Using Man Made Gases as Groundwater ‘Age’ Tracers
The age of groundwater is defined as the time that has elapsed since the water first entered the aquifer. For example, some of the rain that falls on an area percolates trickles down through soil and rock until it reaches the water table. Once this water reaches the water table, it moves though the aquifer. The time it takes to travel to a given location, known as the groundwater age, can vary from days to thousands of years.
Hydrologists employ a variety of techniques to measure groundwater age. For relatively young groundwater, chlorofluorocarbons CFCs often are used.
A new groundwater dating procedure using the transient atmospheric signal of the environmental tracers SF5CF3, CFC, SF6, and CFC was developed.
The municipality’s population density is The municipality is warmer than most settlements on the same latitude, even milder than places much further south on Hudson Bay in Canada and in Far East Russia , due to the effect of the Gulf Stream , whose warm-water current allows for both relatively mild winters and tree growth in spite of its high latitude.
The city centre contains the highest number of old wooden houses in Northern Norway , the oldest dating from Several theories exist. One theory holds “Troms-” to derive from the old uncompounded name of the island Old Norse : Trums. Several islands and rivers in Norway have the name Tromsa , and the names of these are probably derived from the word straumr which means ” strong current”. The original form must then have been Strums , for the missing s see Indo-European s-mobile.
In Finnish, however, the word is written with a double “s”: Tromssa. The area has been inhabited since the end of the ice age. Around the same time a turf rampart was built to protect the area against raids from Karelia and Russia. During the 17th century, while Denmark—Norway was solidifying its claim to the northern coast of Scandinavia and during this period a redoubt , Skansen , was built.