The samples must not be stored or handled in any laboratory or area that uses OR has ever used biomedical or artificially labeled 14C at any time. Water samples that produce activities above pMC will incur extensive costs related to any cleanup necessary, equipment replacement and duplicate analyses required for other samples. We cannot accept seawater samples that have been treated with mercuric chloride HgCl 2 or sodium azide NaN 3 because we do not have the disposal capabilities for these toxic substances. We no longer accept samples that have NaOH or other alkali chemicals added to the sample.
Paper details technique to date groundwater
Sturchio co-authors Nature Geoscience paper on technique to date groundwater
Groundwater age is defined as the time between recharge at the water table to the time when groundwater was sampled. Groundwater age estimates are based on concentrations of environmental tracers i. Because no tracer is perfect, these age estimates are typically referred to as "apparent" ages. Groundwater transit time is the time between recharge and discharge from the aquifer. So groundwater transit time is equal to groundwater age at the point of exit from the aquifer, such as the point of discharge from an irrigation well, or discharge to a stream.
Sulfur hexafluoride SF 6 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. SF 6 holds considerable promise as a dating tool of posts groundwater because, unlike the chlorofluorocarbons with steady or declining atmospheric mixing ratios, atmospheric concentrations of SF 6 are expected to continue increasing Busenberg and Plummer, SF 6 is also stable in reducing ground-water environments, and because there are relatively few uses of the compound, few environments are contaminated by anthropogenic sources. Significant production of SF 6 began in the s for use in high voltage electrical switches. SF 6 is extremely stable, with an estimated atmospheric lifetime of Morris et al.
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