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+240Pu in 0.45 μm-filtered water), and there is an
associated contamination of Pu in surface soils. The highest 239+240Pu 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.
Titanium dioxide (TiO(2)) has often served as a model substrate for experimental sorption studies of environmental contaminants. However, various forms of Ti-oxide have been used, and the different sorption properties of these materials have not been thoroughly studied. We investigated uranium sorption on some thoroughly characterized TiO(2) surfaces with particular attention to the influence of surface area, surface charge, and impurities. The sorption of U(VI) differed significantly between samples. Aggressive pretreatment of one material to remove impurities significantly altered the isoelectric point, determined by an electroacoustic method, but did not significantly impact U sorption. Differences in sorption properties between the various TiO(2) materials were related to the crystallographic form, morphology, surface area, and grain size, rather than to surface impurities or surface charge. In-situ attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectroscopic studies showed that the spectra of the surface species of the TiO(2) samples are not significantly different, suggesting the formation of similar surface complexes. The data provide insights into the effect of different source materials and surface properties on radionuclide sorption.
Supplementary Paper S1 Electrical Resistivity Tomography (ERT) profiles. Supplementary Paper S2 Details of well construction. Supplementary Paper S3 Groundwater major physico-chemical parameters, ion concentrations and charge balance error (CBE%). All cations analysed by ICP-AES except for Mg 2+ in the first 3 samplings analysed by ICP-MS. Supplementary Paper S4 Groundwater and surface water information with well location, screened interval and abbreviated water type. Supplementary Paper S5 Selected groundwater minor and trace element concentrations. Al, Mn and Fe analysed by ICP-AES, the rest of elements by ICP_MS. BDL (bellow detection limit); no data represent not analysed elements. Supplementary Paper S6 Groundwater dissolved organic carbon (DOC), stable isotopes (δ 13 C DOC , δ 13 C DIC , water δ 18 O and δ 2 H, sulfate δ 34 S and δ 18 O), calculated deuterium excess (d-excess), 87 Sr/ 86 Sr and tritium ( 3 H). Note 3 H is reported in Bq L −1 (1 Bq L −1 = 8.47 TU). Supplementary Paper S7 Water stable isotopes for leachate samples from Harrington's Quarry. The d is the calculated deuterium excess for the corresponding samples. Supplementary Paper S8 Calculated saturation indexes for common mineral phases in LFLS groundwater.
During the 1960s, radioactive waste containing small amounts of plutonium (Pu) and americium (Am) was disposed in shallow trenches at the Little Forest Burial Ground (LFBG), located near the southern suburbs of Sydney, Australia. Because of periodic saturation and overflowing of the former disposal trenches, Pu and Am have been transferred from the buried wastes into the surrounding surface soils. The presence of readily detected amounts of Pu and Am in the trench waters provides a unique opportunity to study their aqueous speciation under environmentally relevant conditions. This study aims to comprehensively investigate the chemical speciation of Pu and Am in the trench water by combining fluoride coprecipitation, solvent extraction, particle size fractionation, and thermochemical modeling. The predominant oxidation states of dissolved Pu and Am species were found to be Pu(IV) and Am(III), and large proportions of both actinides (Pu, 97.7%; Am, 86.8%) were associated with mobile colloids in the submicron size range. On the basis of this information, possible management options are assessed.
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