Factors affecting carbon-14 activity of unsaturated zone CO2 and implications for groundwater dating

Simple item page
dc.contributor.authorWood, Cen_AU
dc.contributor.authorCook, PGen_AU
dc.contributor.authorHarrington, GAen_AU
dc.contributor.authorMeredith, KTen_AU
dc.contributor.authorKipfer, Ren_AU
dc.date.accessioned2016-12-12T00:55:10Zen_AU
dc.date.available2016-12-12T00:55:10Zen_AU
dc.date.issued2014-11-27en_AU
dc.date.statistics2016-12-12en_AU
dc.description.abstractUnsaturated zone processes may influence the carbon-14 (14C) activity of infiltrating groundwater and thus introduce error in derived groundwater residence times. However unsaturated zone 14C activities are rarely measured and there is little understanding of how they may vary spatially in a groundwater basin. In this study we measured 14C activity in unsaturated zone gas at five sites with different watertable depths (8.2–31.5 m) in the arid Ti Tree Basin, central Australia. We observed a relatively uniform decrease in 14C activity of unsaturated zone gas with depth at most sites, with variation in unsaturated zone depths leading to variation in 14C activities directly above the watertable at each site (ranging from 54 to 106 percent Modern Carbon (pMC)). Through modelling we show that the profiles are influenced by CO2 production at different depths from sources with different isotopic ratios, including production of ‘modern’ CO2 in the root zone and production of ‘old’ CO2 above the watertable. Scenario modelling showed that these processes are independent of recharge when recharge is low (0–10 mm y−1) but that higher recharge rates (>100 mm y−1) result in more advective transport of atmospheric CO2 to the watertable. The variation in 14C above the watertable was more sensitive to watertable depth and shallow and deep CO2 production rates. These findings offer insight into how unsaturated zone 14C activities may vary spatially and provide guidance as to when 14C depletion in unsaturated zone CO2 may become important for groundwater dating, particularly in arid settings. © 2014, Elsevier B.V.en_AU
dc.identifier.citationWood, C., Cook, P. G., Harrington, G. A., Meredith, K., & Kipfer, R. (2014). Factors affecting carbon-14 activity of unsaturated zone CO2 and implications for groundwater dating. Journal of Hydrology, 519, 465-475. doi:10.1016/j.jhydrol.2014.07.034en_AU
dc.identifier.govdoc7689en_AU
dc.identifier.issn0022-1694en_AU
dc.identifier.journaltitleJournal of Hydrologyen_AU
dc.identifier.pagination465-475en_AU
dc.identifier.urihttp://dx.doi.org/10.1016/j.jhydrol.2014.07.034en_AU
dc.identifier.urihttp://apo.ansto.gov.au/dspace/handle/10238/8146en_AU
dc.identifier.volume519en_AU
dc.language.isoenen_AU
dc.publisherElsevieren_AU
dc.subjectAustraliaen_AU
dc.subjectGround wateren_AU
dc.subjectGroundwater rechargeen_AU
dc.subjectCarbon dioxideen_AU
dc.subjectCarbon 14en_AU
dc.subjectGasesen_AU
dc.subjectWater tablesen_AU
dc.titleFactors affecting carbon-14 activity of unsaturated zone CO2 and implications for groundwater datingen_AU
dc.typeJournal Articleen_AU
Files
License bundle
Now showing 1 - 1 of 1
Thumbnail Image
Name:
license.txt
Size:
1.71 KB
Format:
Item-specific license agreed upon to submission
Description:
Download
Collections
Journal Articles