Toggle navigation ScienceBase-Catalog. Your browser does not have support for cookies enabled. Some features of this application will not work. Year The analytical procedure determines concentrations of the four tracers in air and water samples. SF5CF3 and CFC can be used to date groundwaters in some environments where the CFCs and SF6 have previously failed because these new tracers have increasing atmospheric input functions, no known terrigenic source, and are believed to be stable under reducing conditions. SF5CF3 has a dating range from to modern; the mixing ratio mole fraction in North American air has increased from the detection limit of 0. No evidence was found for degradation of SF5CF3 in laboratory anaerobic systems. CFC is a trace atmospheric gas with a dating range in groundwater of about to modern. CFC has been used primarily in very low-temperature refrigeration; thus groundwater environments are less likely to be contaminated with nonatmospheric sources as compared to other widely used CFCs.
The SF 6 mixing ratio in air and the solubility of this gas in water is low. A minimum of a one liter sample of water is required to date groundwater with SF 6. Bottles are available from Qorpak Inc. The caps can be ordered from Brad-Pak Enterprises at The filling and capping procedure for SF 6 is done in the open atmosphere.
Study focus: Simultaneous measurement of groundwater dating tracers (85Kr, chlorofluorocar- bons [CFCs], sulphur hexafluoride [SF6], and 3H) was performed.
Springer Professional. Back to the search result list. Table of Contents. Issue archive. Hint Swipe to navigate through the articles of this issue Close hint. Important notes. Publisher’s Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Abstract The Bamenda Highlands contains numerous dilute and soda springs of unknown hydrological provenance. These dilute springs are a vital source of drinking water to the inhabitants.
A plot of both water types along the local meteoric water line indicated the meteoric origin and rapid recharge following precipitation. SF 6 concentrations in dilute springs revealed exceptionally young ages relative to CFCs modelled ages suggesting a terrigenous enrichment of the former. Thus, groundwater dating with SF 6 is unreliable in the area. Most dilute springs showed exponential mixing models indicating heterogeneous recharge under unconfined aquifer conditions.
The Reston Groundwater Dating Laboratory
Journal article. Plummer, L. Busenberg, E. Kim, Y.
Using CFCs and SF6 for groundwater dating: a SWOT analysis. In: Birkle, Peter ; Torres-Alvarado, Ignacio, (ed.) Water-rock interaction XIII. CRC Press.
Jump to navigation. SF6 is a promising transient tracer for groundwater dating, but elevated levels of atmospheric SF6 may limit application of this dating method in urban areas. To determine the magnitude of this limitation within the United States US , this study derives average atmospheric SF6 mixing ratios from soil air measurements from five major urban areas.
All surveyed sites showed SF6 elevated above Northern Hemisphere clean air levels. In many cases, SF6 mixing ratios were highest within large cities, but significantly elevated Levels persisted hundreds of kilometers beyond the urban centers. These findings imply that caution is needed in choosing an atmospheric input function when using SF6 as a transient tracer within or near urbanized regions. Within the Northeast US, the assumption of remote atmospheric SF6 may lead to significant errors in estimation of groundwater ages, especially in the case of an expected future flattening of the atmospheric mixing ratio curve.
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Introduction to Water Dating and Tracer Analysis
Impact of natural and local anthropogenic SF6 sources on dating springs and groundwater using SF6 in central Japan. Abstract: Sulfur hexafluoride SF6 concentrations in springs and groundwater were measured in the Chubu region of central Japan to evaluate the impact of natural and local anthropogenic SF6 and the validity of SF6 for dating young groundwater in Japan. Sampled water showed detectable concentrations of SF6 at 0.
Most of the mountain springs have SF6 concentration assumed by the dissolution of the clean ambient air in Northern hemisphere. The SF6 ages for mountain springs were consistent with the scale of groundwater flow and with previously determined 3H ages for groundwater in similar settings in Japan, suggesting the loading of natural SF6 in the groundwater is relatively small in the mountainous areas. In the plains, local industrial activities led to high concentrations of SF6 in some of the analyzed groundwater.
chlorofluorocarbon and SF6 groundwater dating groundwater recharge and coupled solute transport in semi-arid settings, and compare travel time ranges.
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.
Reston Groundwater Dating Laboratory
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.
For the dating of such young groundwater, dissolved sulfur hexafluoride (SF6) gas has been effectively used at several sites. The average concentration of SF6.
Wells sampled for groundwater-age dating in New Hanover County, North Carolina
Sulfur hexafluoride SF6 is a trace atmospheric gas that is primarily of anthropogenic origin but also occurs naturally in fluid inclusions in some minerals and igneous rocks, and in some volcanic and igneous fluids. SF6 has been used as a dating tool of groundwater because atmospheric concentrations of SF6 are expected to continue increasing Busenberg and Plummer, The results of these samples were input into a spreadsheet calculator developed by the USGS Groundwater Dating lab in order to estimate groundwater age based on SF6 concentrations.
The wells sampled include monitoring, domestic, and large water user wells within the surficial, Castle Hayne, and Peedee aquifers.
The SF6 mixing ratio in air and the solubility of this gas in water is low. A minimum of a one liter sample of water is required to date groundwater.
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