Accelerator mass spectrometry measurements of U in groundwater, soil and vegetation at a legacy radioactive waste site.

Low-level radioactive wastes were disposed at the Little Forest Legacy Site (LFLS) near Sydney, Australia between 1960 and 1968. According to the disposal records, U contributes a significant portion of the inventory of actinide activity buried in the LFLS trenches. Although the presence of U in environmental samples from LFLS has been previously inferred from alpha-spectrometry measurements, it has been difficult to quantify because the U and U α-peaks are superimposed.

Rare earth elements and yttrium as tracers of waste/rock-groundwater interactions.

Increasing concentrations of Rare Earth Elements (REE) plus yttrium (REY) are entering the environment due to human activities. The similar chemical behaviour across the whole REY, i.e.

Isotopic evidence for nitrate sources and controls on denitrification in groundwater beneath an irrigated agricultural district.

The application of N fertilisers to enhance crop yield is common throughout the world. Many crops have historically been, or are still, fertilised with N in excess of the crop requirements. A portion of the excess N is transported into underlying aquifers in the form of NO, which is potentially discharged to surface waters.

Constraining source attribution of methane in an alluvial aquifer with multiple recharge pathways.

Identifying the source of methane (CH) in groundwater is often complicated due to various production, degradation and migration pathways, particularly in settings where there are multiple groundwater recharge pathways. This study demonstrates the ability to constrain the origin of CH within an alluvial aquifer that could be sourced from in situ microbiological production or underlying formations at depth. To characterise the hydrochemical and microbiological processes active within the alluvium, previously reported hydrochemical data (major ion chemistry and isotopic tracers (H, C, Cl)) were interpreted in the context of CH and carbon dioxide (CO) isotopic chemistry, and the microbial community composition in the groundwater.

Radionuclide distributions and migration pathways at a legacy trench disposal site.

This paper examines the distributions of several anthropogenic radionuclides (Pu, Am, Cs, Sr, Co and H) at a legacy trench disposal site in eastern Australia. We compare the results to previously published data for Pu and tritium at the site. Plutonium has previously been shown to reach the surface by a bath-tubbing mechanism, following filling of the former trenches with water during intense rainfall events.

Global analysis reveals climatic controls on the oxygen isotope composition of cave drip water.

The oxygen isotope composition of speleothems is a widely used proxy for past climate change. Robust use of this proxy depends on understanding the relationship between precipitation and cave drip water δO. Here, we present the first global analysis, based on data from 163 drip sites, from 39 caves on five continents, showing that drip water δO is most similar to the amount-weighted precipitation δO where mean annual temperature (MAT) is < 10 °C.

Cave drip water solutes in south-eastern Australia: Constraining sources, sinks and processes.

Constraining sources and site-specific processes of trace elements in speleothem geochemical records is key to an informed interpretation. This paper examines a 10-year data set of drip water solutes from Harrie Wood Cave, south-eastern Australia, and identifies the processes that control their response to El Niño-Southern Oscillation events which varies the site water balance. The contributions of aerosol and bedrock end-members are quantified via hydrochemical mass balance modelling.

Author Correction: Seasonal total methane depletion in limestone caves.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

Chemical characterisation and source identification of atmospheric aerosols in the Snowy Mountains, south-eastern Australia.

Characterisation of atmospheric aerosols is of major importance for: climate, the hydrological cycle, human health and policymaking, biogeochemical and palaeo-climatological studies. In this study, the chemical composition and source apportionment of PM (particulate matter with aerodynamic diameters less than 2.5μm) at Yarrangobilly, in the Snowy Mountains, SE Australia are examined and quantified.

Seasonal total methane depletion in limestone caves.

Methane concentration in caves is commonly much lower than the external atmosphere, yet the cave CH depletion causal mechanism is contested and dynamic links to external diurnal and seasonal temperature cycles unknown. Here, we report a continuous 3-year record of cave methane and other trace gases in Jenolan Caves, Australia which shows a seasonal cycle of extreme CH depletion, from ambient ~1,775 ppb to near zero during summer and to ~800 ppb in winter. Methanotrophic bacteria, some newly-discovered, rapidly consume methane on cave surfaces and in external karst soils with lifetimes in the cave of a few hours.

Assessing Connectivity Between an Overlying Aquifer and a Coal Seam Gas Resource Using Methane Isotopes, Dissolved Organic Carbon and Tritium.

Coal seam gas (CSG) production can have an impact on groundwater quality and quantity in adjacent or overlying aquifers. To assess this impact we need to determine the background groundwater chemistry and to map geological pathways of hydraulic connectivity between aquifers. In south-east Queensland (Qld), Australia, a globally important CSG exploration and production province, we mapped hydraulic connectivity between the Walloon Coal Measures (WCM, the target formation for gas production) and the overlying Condamine River Alluvial Aquifer (CRAA), using groundwater methane (CH4) concentration and isotopic composition (δ(13)C-CH4), groundwater tritium ((3)H) and dissolved organic carbon (DOC) concentration.

Trench 'bathtubbing' and surface plutonium contamination at a legacy radioactive waste site.

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.