Uranium in sediments from the Magela Creek catchment, northern territory, Australia

Noller, B. N.; Hart, Barry T.

doi:10.1080/09593339309385334

Cited by 8 publications

(3 citation statements)

References 11 publications

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“…), the findings presented here point towards the importance of internal mechanisms and feedbacks within the eco‐hydro‐geomorphic system with environmental implications on multiple timescales. Firstly, downstream of mine sites, pollutants such as heavy metals or U are dominantly associated to fine‐grained floodplain sediments (Noller and Hart, ; Taylor, ). Even after decades of stability following site rehabilitation, excavation of these sediments through incision and bank erosion related to knickpoint passage may thus lead to the abrupt liberation and downstream transmission of contaminated sediment and water (East et al , ; Taylor, ; Caitcheon et al , ), demonstrating the need for more integrated bio‐geomorphological perspectives towards a more comprehensive understanding of pollution cycles in general (Mudd and Patterson, ).…”

Section: Discussion: Wangi Creek As a Tropical Cut‐and‐fill River‐flomentioning

confidence: 99%

Late Quaternary biotic and abiotic controls on long‐term sediment flux in a northern Australian tropical river system

Larsen

May

Carah

2019

Earth Surf Processes Landf

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The modern distribution of monsoonal rainforest in the Australian tropics is patchy and is mainly associated with river corridors and groundwater springs, which indicates a strong dependence on hydrologic and geomorphic conditions. While their present distribution is well known, very little data exists on past spatial and temporal dynamics of these ecosystems, or their medium‐ to longer‐term controls. Factors such as (i) fire frequency and type, and/or (ii) hydroclimatic conditions (e.g. droughts) have been proposed to control riverine corridor rainforest extent. Recent observations, however, also suggest an additional (iii) geomorphic control induced by alluvial knickpoint migration. Sediment sequences provide valuable archives for the reconstruction of longer‐term (a) floodplain sedimentary dynamics, (b) local vegetation history, and (c) catchment‐wide fire histories. This study investigates such a sediment sequence at Wangi Creek, and shows that a phase of aggradation, lasting ~4000 years, was recently disrupted by channel incision and floodplain erosion. The aggradational phase is characterized by sand deposition with average vertical floodplain accretion rates of 0.8 cm/yr and includes phases of soil development. The recent incisional phase has changed hydro‐geomorphic conditions and caused widespread degradation of vegetation, erosion and lowering of the macro‐channel surface. While there is no evidence in our data for an erosional event of similar magnitude since the onset of late Holocene floodplain aggradation, Wangi Creek experienced significant erosion and incision immediately before ~4000 years, providing the first evidence for a tropical cut‐and‐fill river system. We hence argue that phases of aggradation mainly controlled by biotic processes alternate and depend on feedbacks with incision phases controlled mainly by abiotic processes. The results show that eco‐hydro‐geomorphic feedbacks may play a crucial role in the medium‐ to longer‐term history of tropical fluvial systems and need to be considered when interpreting fluvial archives with regards to climate, fire or human induced change. © 2019 John Wiley & Sons, Ltd.

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Section: Discussion: Wangi Creek As a Tropical Cut‐and‐fill River‐flomentioning

confidence: 99%

Late Quaternary biotic and abiotic controls on long‐term sediment flux in a northern Australian tropical river system

Larsen

May

Carah

2019

Earth Surf Processes Landf

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“…This assumption was necessitated by the limited organic carbon data available for groundwater, surface water and soil at the site. However, soil sampling (SLR 2018) and sediment sampling (Noller & Hart 1993) have indicated that organic matter would not likely be a limiting factor for the potential formation of ASS in areas where waterlogging of soils and sediments may occur. This is consistent with the understanding that billabongs and wetlands generally have an abundant supply of carbon from decomposing plant material and/or algae (Baldwin 2017a).…”

Section: Premisementioning

confidence: 99%

Development of mine-derived acid sulfate sediments

Windle¹,

Weaver²,

Race³

et al. 2022

Mine Closure 2022: 15th Conference on Mine Closure

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Acid sulfate sediments (ASS) may be present at a mine site due to natural processes but may also develop from mining and water management activities through discharge of impacted groundwater and surface water. This paper outlines conditions under which mine-derived ASS may form and uses that information to develop a conceptual model for ASS in a source-pathway-receptor framework for the Ranger Uranium Mine in the Northern Territory, Australia (the site). The conceptual model was then used to inform the assessment and management of risks associated with potential ASS as the mine site progresses through closure.Key constituents contributing to ASS formation are waterlogged (anoxic) conditions, elevated sulfate concentrations, and organic carbon. For the site, geographic information system (GIS) spatial mapping was used to develop a conceptual site model that identified areas of potential ASS formation based on:1. Groundwater-level data and topographic contours -which were combined to identify areas of shallow (<1 m depth) groundwater since, together with surface water bodies, these represent areas of potential waterlogging.2. The potential waterlogged conditions were overlaid with elevated (>10 mg/L) sulfate concentrations in groundwater and surface water, to identify potential ASS areas.The conceptual model identified potential source areas where ASS may form, including a billabong where acidification events had been observed previously (Coonjimba Billabong) and where subsequent sampling confirmed the presence of ASS. As the identified source areas are associated with shallow groundwater and surface water, these can also act as pathways to transport acidification products to downgradient/ downstream receptors if ASS are disturbed or exposed. Identifying these potential source areas for ASS allows the risks associated with their disturbance or exposure to be managed.Although elevated sulfate concentrations in groundwater or surface water are associated with sulfidic ore or waste rock at many mines, the potential formation of mine-derived ASS is seldom considered and may become particularly relevant as the water balance changes with closure. This assessment approach used existing data to identify and prioritise potential ASS areas for further assessment and management and could be adapted and applied at other mining sites.

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“…As it migrates through the environment it can become 'fixed' in humic rich areas such as peat bogs, 2 and billabongs. 3,4 Typical levels of uranium found in natural waters range from 0.1 to 7 ng ml À1 for streams and 2 to 4 ng ml À1 in seawater. 5 However, these levels can be elevated due to input from anthropogenic sources such as nuclear power plants and radioactive waste repositories.…”

Section: Introductionmentioning

confidence: 99%

Uranium speciation in moorland river water samples: A comparison of experimental results and computer model predictions

et al. 2005

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An on-line method has been developed for separating inorganic and organic bound uranium species present in river water samples. The method utilised a small chelating resin (Hyphan) column incorporated into the sample introduction manifold of an ICP-MS instrument. The method was evaluated for samples from rivers on Dartmoor (Devon, UK), an area of granite overlain with peat bogs. The results indicate that organicuranium species form a major proportion (80%) of the total dissolved uranium present. Further work with synthetic water samples indicated that the level of dissolved organic carbon played a greater role in determining the level of organic-uranium species than did sample pH. Computer models for the water samples were constructed using the WHAM program (incorporating uranium data from the Nuclear Energy Agency Thermochemical Database project) in order to predict the levels of organic-uranium species that would form. By varying the proportion of humic and fulvic acids used in the humic component, predictions within 10% of the experimental results were obtained. The program did exhibit a low bias at higher pH values (7.5) and low organic carbon concentrations (0.5 mg ml À1 ), but under the natural conditions prevalent in the Dartmoor water samples, the model predictions were successful.

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Uranium in sediments from the Magela Creek catchment, northern territory, Australia

Cited by 8 publications

References 11 publications

Late Quaternary biotic and abiotic controls on long‐term sediment flux in a northern Australian tropical river system

Late Quaternary biotic and abiotic controls on long‐term sediment flux in a northern Australian tropical river system

Development of mine-derived acid sulfate sediments

Uranium speciation in moorland river water samples: A comparison of experimental results and computer model predictions

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