Browsing by Author "Tozer, MG"

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    Hydrological and geochemical responses of fire in a shallow cave system
    (2019-04-20) Bian, F; Coleborn, K; Flemons, I; Baker, AA; Treble, PC; Hughes, CE; Baker, AC; Andersen, MS; Tozer, MG; Duan, WH; Fogwill, CJ; Fairchild, IJ
    The influence of wildfire on surface soil and hydrology has been widely investigated, while its impact on the karst vadose zone is still poorly understood. A moderate to severe experimental fire was conducted on a plot (10 m × 10 m) above the shallow Wildman's Cave at Wombeyan Caves, New South Wales, Australia in May 2016. Continuous sampling of water stable isotopes, inorganic geochemistry and drip rates were conducted from Dec 2014 to May 2017. After the fire, drip discharge patterns were significantly altered, which is interpreted as the result of increased preferential flows and decreased diffuse flows in the soil. Post-fire drip water δ18O decreased by 6.3‰ in the first month relative to the average pre-fire isotopic composition. Post-fire monitoring showed an increase in drip water δ18O in the following six months. Bedrock related solutes (calcium, magnesium, strontium) decreased rapidly after the fire due to reduced limestone dissolution time and potentially reduced soil CO2. Soil- and ash-derived solutes (boron, lead, potassium, sodium, silicon, iodine and iron) all decreased after the fire due to volatilisation at high temperatures, except for SO42−. This is the first study to understand the hydrological impact from severe fires conducted on a karst system. It provides new insights on the cave recharge process, with a potential explanation for the decreased d18O in speleothem-based fire study, and also utilise the decreased bedrock solutes to assess the wildfire impacts both in short and long time scales. Open access © 2021 Elsevier B.V
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    The impact of fire on the geochemistry of speleothem-forming drip water in a sub-alpine cave
    (Elsevier, 2018-11) Coleborn, K; Baker, AA; Treble, Pauline C; Andersen, MS; Baker, AC; Tadros, CV; Tozer, MG; Fairchild, IJ; Spate, A; Meehan, S
    Fire dramatically modifies the surface environment by combusting vegetation and changing soil properties. Despite this well-documented impact on the surface environment, there has been limited research into the impact of fire events on karst, caves and speleothems. Here we report the first experiment designed to investigate the short-term impacts of a prescribed fire on speleothem-forming cave drip water geochemistry. Before and after the fire, water was collected on a bi-monthly basis from 18 drip sites in South Glory Cave, New South Wales, Australia. Two months post-fire, there was an increase in B, Si, Na, Fe and Pb concentrations at all drip sites. We conclude that this response is most likely due to the transport of soluble ash-derived elements from the surface to the cave drip water below. A significant deviation in stable water isotopic composition from the local meteoric water line was also observed at six of the sites. We hypothesise that this was due to partial evaporation of soil water resulting in isotopic enrichment of drip waters. Our results demonstrate that even low-severity prescribed fires can have an impact on speleothem-forming cave drip water geochemistry. These findings are significant because firstly, fires need to be considered when interpreting past climate from speleothem δ18O isotope and trace element records, particularly in fire prone regions such as Australia, North America, south west Europe, Russia and China. Secondly, it supports research that demonstrates speleothems could be potential proxy records for past fires. © 2018 Elsevier B.V.
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    The impact of wildfire on the geochemistry and hydrology the vadose zone
    (National Centre for Groundwater Research And Training, 2017-07-12) Coleborn, K; Baker, AA; Treble, PC; Baker, AC; Andersen, MS; Tozer, MG; Fairchild, IJ; Spate, A; Meehan, S
    Wildfire can dramatically modify the surface environment by removing surface vegetation, killing microbial communities and changing the soil geochemical and physical structure. Wildfires are a widespread phenomenon in Australia with 87,810 ha burnt in 2015-2016 in NSW alone (New South Wales Rural Fire Service, 2016). However, there has been little research on the impact of wildfire on vadose zone hydrology in Australia or elsewhere. Limestone caves can be used as natural laboratories to study the impact of the surface environment on vadose zone hydrology in real time. We conducted a two year monitoring program to examine the short term (less than one year) post-fire impacts on the geochemistry and hydrology of vadose zone water in Glory Hole Cave, Kosciuszko National Park, NSW. We ignited an experimental wildfire on the surface over the cave after 1 year of monitoring and compared the pre- and post-fire data. The findings indicate that there is a short term post-fire response in the organic and inorganic geochemistry vadose zone water. There was a post-fire spike in dissolved organic carbon, dominated by the hydrophilic fraction more than one month post-fire which was most likely due to high influx of ash from the fire. There was a multi-month increase in organic-associated metals such as Cu and Zn. The concentration of trace metals such as Fe and Si increased by an order of magnitude less than three months post-fire and was attributed to a flush of small colloidal organic matter. This study enabled us to establish that there is an organic and inorganic cave vadose zone water response to wildfires. The findings of this study can inform fire management strategies in order to protect sensitive karst environments in addition to water resource managers concerned with fluxes of mobilised metals nutrient fluxes to the vadose zone.