Browsing by Author "Stevens, H"

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    Identifying the key sources of metal (loid) deposition to remote Tasmanian lakes: is legacy mining a problem?
    (Springer Nature, 0202-03-07) Stevens, H; Barmuta, LA; Chase, Z; Saunders, KM; Zawadzki, A; Gadd, PS; Proemse, BC
    Reports have shown that even remote lakes have been negatively affected by anthropogenic activities. This study used metal concentrations and enrichment factors to comprehensively determine key metal sources and identify potential impacts of recent anthropogenic activity in remote Central Highland Tasmanian (Australia) lakes. Metal concentrations (Al, As, Cd, Cu, Fe, Pb, and Zn) in these lakes remain below Australian interim sediment quality guidelines but have been slowly increasing since the start of the twentieth century. This increase is likely related to increasing organic matter content, rather than any direct, increased input of metals. The largest anthropogenic impact to these systems was damming, which typically led to an increase in organic matter content either directly, by the trapping of particles and nutrients, or indirectly, by stimulating primary production in the lake. This increased organic matter content, in turn, increased the retention of metals, manifesting as an increase to measured metal concentrations. Minor impacts are the historical use of lead shot, leaded petrol, and industrial processes, which may have contributed to the higher Pb enrichment, compared to the other studied metals, in these lakes. Despite recent concerns of metal contamination in the Tasmanian Wilderness World Heritage Area from distant mining activities, there is no strong evidence in this study indicating that lakes in the Central Highlands (a similar distance away) have been impacted by long-distance atmospheric deposition. This is likely related to the decreased rainfall, and thus decreased rates of wet deposition of aerosols in the east of Tasmania, compared to that of the west and in the Tasmanian Wilderness World Heritage Area. © The Author(s) 2024. - Open Access - This article is licensed under a Creative Commons Attribution 4.0 International License
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    Reconstructing the history of nutrient loads and sources in the Derwent Estuary, Tasmania, Australia, using isotopic fingerprinting techniques
    (Springer Nature, 2021-02-24) Stevens, H; Chase, Z; Zawadzki, A; Wong, HKY; Proemse, BC
    Carbon and nitrogen stable isotope analysis of estuarine sediment cores has proved useful for tracing nutrient sources and for assessing changes to nutrient loading through time. However, this technique has rarely been applied to estuaries in the Southern Hemisphere, despite the vulnerability of urban estuaries to excess nutrient loading and eutrophication because of mounting anthropogenic pressures. This study uses sediment core nutrient concentrations (total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP)) and stable isotope analysis (δ13C, δ15N, and δ34S) in combination with lead-210 (210Pb) dating, to reveal information about past and current nutrient loads and sources to various parts of the Derwent estuary, Tasmania, Australia. The upper estuary was found to experience periods of low dissolved oxygen levels and δ13C and δ15N values indicate that the nutrient sources to the upper estuary are predominantly riverine inputs and pulp and paper mill effluent. The middle estuary was found to have higher nutrient (TN and TP) concentrations than other Australian estuaries (Quibray Bay, Woolooware Bay, and Moreton Bay). Along the whole estuary there was a transition of predominantly terrestrial OM in upper estuary to predominantly marine OM in middle/lower estuary. However, there was a clear influence from a nitrogen source with an enriched δ15N value, likely wastewater treatment plant (WWTP) effluent. 3-endmember mixing analysis between terrestrial OM, marine OM, and WWTP effluent shows that WWTP effluent has contributed to up to 30.9% of sediment composition in the past—highlighting the significance of anthropogenic nutrient inputs, such as waste-water treatment plant effluent, to an urban estuary. © 2021 Coastal and Estuarine Research Federation