title: Trench 'bathtubbing' and surface plutonium contamination at a legacy radioactive waste site.
abstract: Radioactive waste containing a few grams of plutonium (Pu) was disposed between 1960 and 1968 in trenches at the Little Forest Burial Ground (LFBG), near Sydney, Australia. A water sampling point installed in a former trench has enabled the radionuclide content of trench water and the response of the water level to rainfall to be studied. The trench water contains readily measurable Pu activity (~12 Bq/L of (239+240)Pu in 0.45 μm-filtered water), and there is an associated contamination of Pu in surface soils. The highest (239+240)Pu soil activity was 829 Bq/kg in a shallow sample (0-1 cm depth) near the trench sampling point. Away from the trenches, the elevated concentrations of Pu in surface soils extend for tens of meters down-slope. The broader contamination may be partly attributable to dispersion events in the first decade after disposal, after which a layer of soil was added above the trenched area. Since this time, further Pu contamination has occurred near the trench-sampler within this added layer. The water level in the trench-sampler responds quickly to rainfall and intermittently reaches the surface, hence the Pu dispersion is attributed to saturation and overflow of the trenches during extreme rainfall events, referred to as the 'bathtub' effect.
authors.affiliation: Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, Sydney, New South Wales 2232, Australia.
authors.forename: Timothy E
authors.initials: TE
authors.lastname: Payne
authors.forename: Jennifer J
authors.initials: JJ
authors.lastname: Harrison
authors.forename: Catherine E
authors.initials: CE
authors.lastname: Hughes
authors.forename: Mathew P
authors.initials: MP
authors.lastname: Johansen
authors.forename: Sangeeth
authors.initials: S
authors.lastname: Thiruvoth
authors.forename: Kerry L
authors.initials: KL
authors.lastname: Wilsher
authors.forename: Dioni I
authors.initials: DI
authors.lastname: Cendón
authors.forename: Stuart I
authors.initials: SI
authors.lastname: Hankin
authors.forename: Brett
authors.initials: B
authors.lastname: Rowling
authors.forename: Atun
authors.initials: A
authors.lastname: Zawadzki
mesh_terms: D004784:Environmental Monitoring / Q000379:methods / Q000706:statistics & numerical data*; D064371:Hazardous Waste Sites / Q000706:statistics & numerical data*; D009517:New South Wales; D011005:Plutonium / Q000032:analysis*; D011850:Radioactive Waste / Q000032:analysis*; D012588:Scintillation Counting; D012990:Soil Pollutants, Radioactive / Q000032:analysis*; D014875:Water Pollutants, Radioactive / Q000032:analysis*
chemical_list: D011850:Radioactive Waste; D012990:Soil Pollutants, Radioactive; D014875:Water Pollutants, Radioactive; D011005:Plutonium