Tracing carbon dynamics of groundwater in an evaporative environment
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Date
2015-07-08
Journal Title
Journal ISSN
Volume Title
Publisher
University of New South Wales and Australian Nuclear Science and Technology Organisation
Abstract
Radiocarbon (14C) is one of the most widely used isotopes to date groundwater. Estimating groundwater 'age' is important for any groundwater resource assessment to provide information on groundwater recharge rates. However, the calculation of a 14C groundwater 'age' still has many challenges associated with it because of the many complex hydrogeochemical reactions and/or physical processes that can dilute the initial 14C activity of the dissolved inorganic carbon (DIC) after recharge and flow through the aquifer. There are a multitude of reasons why traditional correction methods cannot be transferred to arid zone groundwater systems, but in particular most studies typically do not measure all of the variables contained within the equations and hence fundamental assumptions are made.
Groundwater samples were collected from nested monitoring wells over an 8 year period along a 7 km transect from the Darling River in northwestern New South Wales, Australia. In this study, we measure groundwater, river water, soil, calcrete, soilßas and vegetation samples to capture the complex carbon isotopic systematics displayed in all the various soil-water-plant components that influence the geochemical evolution of groundwater in an arid zone environment.
At first inspection of the data, it appeared that carbonate dissolution was the primary hydrochemical process relating to the high concentrations of DIC and low 14CDl of shallow groundwaters (<20 m below ground surface). Indeed, this was the original hypothesis for this study, but when all the environmental components were measured, the complexity of the carbon cycle was revealed. This study provides insight into the errors that can result from using traditional correction models that were originally designed for northern hemisphere groundwater systems with no supporting data.
Description
Keywords
Tracer techniques, Carbon, Ground water, Evaporation
Citation
Meredith K., Hollins S., Cendón D., Jacobsen G., Chisari R., & Levchenko V. (2015). Tracing carbon dynamics of groundwater in an evaporative environment. Paper presented to the 13th Australasian Environment Isotope Conference (AEIC), Sydney, 8-10th July 2015, (pp. 40.)