Mapping short-lived radium isotopes in estuarine residential canals (Gold Coast, Australia)
Distributions of short-lived radium isotopes (224Ra and 223Ra) were investigated on the Gold Coast waterways, one of the largest residential estuarine canal systems on Earth, in an attempt to estimate radium-derived residence times and obtain insights into sources of radium isotopes. Surface and bottom canal waters were sampled in 61 locations over ~300 km of waterways. Radium isotope activities were 12-fold higher in groundwater than estuarine waters. Surprisingly, radium activities were usually higher in surface waters than bottom waters implying a radium source associated with tidal pumping in artificial beach sediments. Estimated radium ages were usually younger within artificial canal surface waters than in the natural estuarine waterways. This study shows that the tidally driven groundwater radium source can be enhanced by the extended canal shoreline.
KeywordsRadium Residence times Residential canal estates Submarine groundwater discharge
Jackie Webb, Jennifer Taylor, Luciana Sanders, Ben Stewart, Mitchell Call, Paul Kelly and Mahmood Sadat-Noori helped with field investigations. A Grant from the WH Gladstones Population and Environment Fund from the Australian Academy of Sciences and the Australian Research Council (DP120101645) provided funding for field work, while the Australian Research Council (LE120100156) funded instrumentation. IRS, DTM and CJS were supported by the Australian Research Council (DE140101733, DE150100581 and DE160100443). We thank the Gold Coast City Council and Nathan Waltham for advice during the design stage.
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