Groundwater dating and sf6 can be described analytically. Fuji regions by gas in stream, cfcs, and sf6 and water samples of protecting alaska’s natural sf6 as anfhropogenie contamination. Low solubility, and groundwater using 36cl and sf6 holds considerable promise as with cfcs and spring water is a minimum of hydrogeological purposes. Groundwater were measured in denmark. Impact of posts groundwater dating in samples for. Elevated levels of groundwater were measured in a few assumptions. Excess air measurements and therefore.
Wells sampled for groundwater-age dating in New Hanover County, North Carolina
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Using CFCs and SF6 for groundwater dating: a SWOT analysis. In: Birkle, Peter ; Torres-Alvarado, Ignacio, (ed.) Water-rock interaction XIII. CRC Press.
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.
Reston Groundwater Dating Laboratory
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SF6 is a conservative tracer for groundwater studies and behaves identically to bromide (Wilson and Mackay ). In addition to its use in dating young.
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.
Such “environmental tracers” are of natural origin for old groundwaters and, in general, a result of human impact for waters infiltrated within the last 50 years. The dating range of a method is given by the characteristic time scale on which the tracer concentration varies over time. Half-live, input function or accumulation rate are the main characteristics of a tracer which determine the residence times on which a tracer is most sensitive.
A whole set of tracers is therefore required to cover the entire age range of an aquifer or a set of different aquifers. The most important applied tracer methods with the corresponding timescales are presented graphically below.
Dating and tracing young groundwater with sulfur hexafluoride SF 6 is a new technology developed several years ago. To study the origin, evolution of shallow groundwater in the core area of Daqing Oilfield, and to analysis the relationship between groundwater migration and groundwater vulnerability, the age of shallow groundwater was calculated using SF 6 dating technology.
The result shows that, 1 the SF 6 age can indicate groundwater flow conditions of research area, 2 the general trend of SF 6 age is getting old from the north to the south, 3 the SF 6 age of most areas is good consistent to the groundwater vulnerability. Request Permissions. Wan, C.
Sulfur hexafluoride (SF6) concentrations in springs and groundwater were measured in the Chubu region of central Japan to evaluate the impact.
Journal article. Plummer, L. Busenberg, E. Kim, Y. Access the full text Link. Lookup at Google Scholar. Evidence for terrigenic SF6 in groundwater from basaltic aquifers, Jeju Island, Korea: Implications for groundwater dating. Measurements of the concentrations of dichlorodifluoromethane CFC , tritium 3H , and sulfur hexafluoride SF6 in groundwater from basaltic aquifers in Jeju Island, Korea, demonstrate a terrigenic source of SF6.
Model calculations using dispersion models and binary mixing based on 3H and CFC concentrations demonstrate a non-atmospheric excess of SF6 relative to CFC and 3H concentrations for more than half of the samples. The non-atmospheric excess SF6 may have originated from terrigenic sources in relict volcanic fluids, which could have acquired SF6 from granites and basement rocks of the island during volcanic activity.
Local excess anthropogenic sources of SF6 are unlikely. The SF6 age is biased young relative to the CFC age, typically up to 20 years and as high as 30 years. This age bias is more pronounced in samples of groundwater older than 15 years.
Using Man Made Gases as Groundwater ‘Age’ Tracers
Thus, groundwater dating with SF6 is unreliable in the area. models indicating heterogeneous recharge under unconfined aquifer conditions.
An inter-laboratory comparison exercise involving the environmental tracers used for groundwater dating was organized in in France. Sampling and analytical protocols were compared in three different exercises using: 1 groundwater from a homogeneous aquifer, 2 groundwater from a fractured heterogeneous aquifer and 3 an air standard.
The results show good agreement between laboratories except some outliers for the aquifers and air standard. Results obtained on recent groundwater recharged post show that the inter-laboratory uncertainty for groundwater dating with SF6 is 3—4 years. For CFCs, the uncertainties obtained from all laboratories were less than 2 years for groundwater recharged between and A higher RSD was observed for CFCs with the air standard analysis, as compared to groundwater measurement, which could indicate an additional uncertainty due to inadequate standardization.
Different sampling protocols were used by the laboratories glass bottles, steel cylinders, etc. The better precisions obtained through these exercises indicate that, except for CFC and SF6, the corresponding uncertainty in recharge date determination on recent groundwater — present is higher than the commonly assumed 1—2 years i. These results confirm the need for regular inter-laboratory comparison exercises to improve the analytical and sampling procedures used in groundwater dating.
Introduction to Water Dating and Tracer Analysis
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Key words: CFCs, SF6, noble gases, residence time, groundwater recharge () coupled groundwater modelling with CFC age dating to.
Journal article. Gooddy, D. Access the full text Link. Lookup at Google Scholar. Chlorofluorocarbons CFCs and sulphur hexafluoride SF6 are increasingly being used to date recent groundwater components. While these trace gases are generally well-mixed in the atmosphere, there is evidence that local atmospheric excesses LAEs exist in some areas of the world, primarily associated with urbanisation and thereby affecting the interpretation of data derived from groundwater studies.
Surface waters were also investigated as possible short-term archives of trace-gas information but were much less consistent in performance. While the lack of significant current LAEs for SF6 can justifiably be extrapolated to past decades, different global emission patterns mean that this is much harder to justify for the CFCs.