Browsing by Author "Leahy, PJ"

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    Identifying heavy metal levels in historical flood water deposits using sediment cores
    (Elsevier, 2017-06-27) Lintern, A; Leahy, PJ; Heijnis, H; Gadd, PS; Jacobsen, GE; Deletic, A; McCarthy, DT
    When designing mitigation and restoration strategies for aquatic systems affected by heavy metal contamination, we must first understand the sources of these pollutants. In this study, we introduce a methodology that identifies the heavy metal levels in floodplain lake sediments deposited by one source; fluvial floods. This is done by comparing sediment core heavy metal profiles (i.e., historical pollution trends) to physical and chemical properties of sediments in these cores (i.e., historical flooding trends). This methodology is applied to Willsmere and Bolin Billabongs, two urban floodplain lakes (billabongs) of the Yarra River (South-East Australia). Both billabongs are periodically inundated by flooding of the Yarra River and one billabong (Willsmere Billabong) is connected to an urban stormwater drainage network. 1–2-m long sediment cores (containing sediment deposits up to 500 years old) were taken from the billabongs and analysed for heavy metal concentrations (arsenic, chromium, copper, lead, nickel, zinc). In cores from both billabongs, arsenic concentrations are high in the flood-borne sediments. In Bolin Billabong, absolute metal levels are similar in flood and non-flood deposits. In Willsmere Billabong, absolute copper, lead and zinc levels were generally lower in fluvial flood-borne sediments in the core compared to non-fluvial sediments. This suggests that heavy metal concentrations in Bolin Billabong sediments are relatively similar regardless of whether or not fluvial flooding is occurring. However for Willsmere Billabong, heavy metal concentrations are high when overland runoff, direct urban stormwater discharges or atmospheric deposition is occurring. As such, reducing the heavy metal concentrations in these transport pathways will be of great importance when trying to reduce heavy metal concentrations in Willsmere Billabong sediments. This study presents a proof-of-concept that can be applied to other polluted aquatic systems, to understand the importance of river floods in the contamination of the bed sediments of aquatic systems. As a cost effective and less time consuming alternative to extensive field monitoring, our proposed method can be used to identify the key sources of pollution and therefore support the development of effective management strategies. © 2016, Elsevier Ltd.
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    Identifying historical flood deposits in a sediment core from an oxbow lake
    (Australasian Quaternary Association Inc, 2014-06-29) Lintern, A; Leahy, PJ; Deletic, A; Gadd, PS; Heijnis, H; McCarthy, DT
    River floods are a risk, not only because of the large volume of water that is mobilized, but also because of the potentially high level of nutrients and pollutants contained in these waters. There is limited understanding of flood water quality, which hinders the implementation of appropriate mitigation strategies. Therefore we must better understand the trends in flood water quality to protect society and the natural environment from risks associated with poor quality flood waters. Fluvial flood water quality data could be obtained using sediment cores from floodplains, as sediment cores can preserve historical flood deposits and can also be used to infer long term trends in the water quality of aquatic environments. This presentation aims to identify and separate flood-deposited fluvial sediments from in-situ biogenic sediments in a sediment core from a floodplain lake, and to then identify the pollutant levels contained in these flood-deposited sediments. The Yarra River (South-East Australia) and its floodplain lake (Willsmere Billabong) was used as a case study. Cores taken from Willsmere Billabong were analysed using the ITRAX micro-X-Ray Fluorescence (XRF) core scanner and the optical and radiographic images, magnetic susceptibility and elemental composition profiles were used to infer the sediment type and origins. Using the data obtained from the core scanner, we found that flooding frequency of the Yarra River into Willsmere Billabong decreased in the early to mid-20th century. This is most likely due to increased water extraction with the construction of large reservoirs in the upper river catchment in 1927, 1932 and 1957. Indeed, there is also a decrease in measured flow rates for the Yarra River. Having identified the flood-deposited sediments within the Willsmere Billabong sediment cores, we have determined pollutant levels within the flood-deposited sediment layers, to identify water quality trends in river flood water quality. © 2014, AQUA Biennial Meeting Mildura.
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    Identifying historical flood deposits in a sediment cores
    (Australiasian Quaternary Association Inc., 2014-08-01) Lintern, A; Leahy, PJ; Deletic, A; Gadd, PS; Heijnis, H; McCarthy, DT
    River floods are a risk, not only because of the large volume of water that is mobilized, but also because of the potentially high level of nutrients and pollutants contained in these waters. There is limited understanding of flood water quality, which hinders the implementation of appropriate mitigation strategies. Therefore we must better understand the trends in flood water quality to protect society and the natural environment from risks associated with poor quality flood waters. Fluvial flood water quality data could be obtained using sediment cores from floodplains, as sediment cores can preserve historical flood deposits and can also be used to infer long term trends in the water quality of aquatic environments. This presentation aims to identify and separate flood-deposited fluvial sediments from in-situ biogenic sediments in a sediment core from a floodplain lake, and to then identify the pollutant levels contained in these flood-deposited sediments. The Yarra River (South-East Australia) and its floodplain lake (Willsmere Billabong) was used as a case study. Cores taken from Willsmere Billabong were analysed using the ITRAX micro-X-Ray Fluorescence (XRF) core scanner and the optical and radiographic images, magnetic susceptibility and elemental composition profiles were used to infer the sediment type and origins. Using the data obtained from the core scanner, we found that flooding frequency of the Yarra River into Willsmere Billabong decreased in the early to mid-20th century. This is most likely due to increased water extraction with the construction of large reservoirs in the upper river catchment in 1927, 1932 and 1957. Indeed, there is also a decrease in measured flow rates for the Yarra River. Having identified the flood-deposited sediments within the Willsmere Billabong sediment cores, we have determined pollutant levels within the flood-deposited sediment layers, to identify water quality trends in river flood water quality.
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    Sediment cores as archives of historical changes in floodplain lake hydrology
    (Elsevier, 2016-02-15) Lintern, A; Leahy, PJ; Zawadzki, A; Gadd, PS; Heijnis, H; Jacobsen, GE; Connor, SE; Deletic, A; McCarthy, DT
    Anthropogenic activities are contributing to the changing hydrology of rivers, often resulting in their degradation. Understanding the drivers and nature of these changes is critical for the design and implementation of effective mitigation strategies for these systems. However, this can be hindered by gaps in historical measured flow data. This study therefore aims to use sediment cores to identify historical hydrological changes within a river catchment. Sediment cores from two floodplain lakes (billabongs) in the urbanised Yarra River catchment (Melbourne, South-East Australia) were collected and high resolution images, trends in magnetic susceptibility and trends in elemental composition through the sedimentary records were obtained. These were used to infer historical changes in river hydrology to determine both average trends in hydrology (i.e., coarse temporal resolution) as well as discrete flood layers in the sediment cores (i.e., fine temporal resolution). Through the 20th century, both billabongs became increasingly disconnected from the river, as demonstrated by the decreasing trends in magnetic susceptibility, particle size and inorganic matter in the cores. Additionally the number of discrete flood layers decreased up the cores. These reconstructed trends correlate with measured flow records of the river through the 20th century, which validates the methodology that has been used in this study. Not only does this study provide evidence on how natural catchments can be affected by land-use intensification and urbanisation, but it also introduces a general analytical framework that could be applied to other river systems to assist in the design of hydrological management strategies. © 2015, Elsevier B.V.
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    Uncertainties in historical pollution data from sedimentary records from an Australian urban floodplain lake
    (Elsevier, 2018-05-01) Lintern, A; Leahy, PJ; Deletic, A; Heijnis, H; Zawadzki, A; Gadd, PS; McCarthy, DT
    Sediment cores from aquatic environments can provide valuable information about historical pollution levels and sources. However, there is little understanding of the uncertainties associated with these findings. The aim of this study is to fill this knowledge gap by proposing a framework for quantifying the uncertainties in historical heavy metal pollution records reconstructed from sediment cores. This uncertainty framework consists of six sources of uncertainty: uncertainties in (1) metals analysis methods, (2) spatial variability of sediment core heavy metal profiles, (3) sub-sampling intervals, (4) the sediment chronology, (5) the assumption that metal levels in bed sediments reflect the magnitude of metal inputs into the aquatic system, and (6) post-depositional transformation of metals. We apply this uncertainty framework to an urban floodplain lake in South-East Australia (Willsmere Billabong). We find that for this site, uncertainties in historical dated heavy metal profiles can be up to 176%, largely due to uncertainties in the sediment chronology, and in the assumption that the settled heavy metal mass is equivalent to the heavy metal mass entering the aquatic system. As such, we recommend that future studies reconstructing historical pollution records using sediment cores from aquatic systems undertake an investigation of the uncertainties in the reconstructed pollution record, using the uncertainty framework provided in this study. We envisage that quantifying and understanding the uncertainties associated with the reconstructed pollution records will facilitate the practical application of sediment core heavy metal profiles in environmental management projects. © 2018 Elsevier B.V.