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Characterising diurnal & synoptic timescale changes in urban air quality using Radon-222
Get PDFUrban air quality is strongly influenced by the atmosphere’s ability to disperse primary emissions and opportunities for secondary pollution formation. In mid- to high-latitude regions that experience enduring winter snow cover or soil freezing, regional subsidence and stagnation associated with persistent anti-cyclonic conditions such as the “Siberian High” can lead to “cold
pool” or “persistent inversion” events. These events can result in life-threatening pollution episodes that last for weeks. While often associated with complex topography [1,2], persistent inversion events can also influence the air quality of urban centres in flat, inland regions [3]. This presentation will describe a recently-developed radon-based technique for identifying and characterising synoptic-timescale persistent inversion events, which is proving to be a simple and economical alternative to contemporary meteorological approaches that require regular sonde
profiles [1]. Furthermore, key assumptions of the radon-based technique to characterise diurnaltimescale changes in the atmospheric mixing state described by Chambers et al. [4] are violated during persistent inversion conditions. Here we demonstrate how atmospheric class-typing, through successive application of radon-based techniques for identifying synoptic- and diurnaltimescale
changes in the atmospheric mixing state, improves understanding of atmospheric
controls on urban air quality in non-summer months across the full diurnal cycle. This knowledge translates directly to statistically-robust techniques for assessing public exposure to pollution, and
for evaluating the efficacy of pollution mitigation measures. Lastly, we show how atmospheric class-typing can be used to enhance the evaluation of chemical transport models. © Author(s) 202
Evaluation of dispersion models DIPCOT and RIMPUFF used in Decision Support Systems for nuclear and radiological emergency response
Get PDFThis paper presents evaluation of the atmospheric dispersion models DIPCOT and RIMPUFF which are incorporated for
operational use in Decision Support Systems for nuclear emergencies. The evaluation is performed through comparisons of model results
with real-scale measurements of gamma radiation dose rates in air obtained during the routine operation of the HIFAR Research Reactor
located in Sydney, Australia. The area surrounding the reactor is characterized by moderately complicated topography and varying land
cover. A total of 16 days have been computationally simulated, covering all atmospheric stability conditions. Qualitative and quantitative
model evaluation is carried out, using comparisons of paired in space and time calculated and measured gamma dose rates, statistical indices,
scatter plots, and contour plots. The models performance is satisfactory for a number of cases, while for others the performance is poor. This
can be attributed to a number of factors, mainly uncertainties in the prediction of meteorological conditions
Late Quaternary palaeoenvironmental change in the Australian drylands
No full textIn this paper we synthesise existing palaeoenvironmental data from the arid and semi-arid interior of the Australian continent for the period 40–0 ka. Moisture is the predominant variable controlling environmental change in the arid zone. Landscapes in this region respond more noticeably to changes in precipitation than to temperature. Depending on their location, arid zone records broadly respond to tropical monsoon-influenced climate regimes, the temperate latitude westerly systems, or a combination of both.
The timing and extent of relatively arid and humid phases vary across the continent, in particular between the westerly wind-controlled temperate latitudes, and the interior and north which are influenced by tropically sourced precipitation. Relatively humid phases in the Murray-Darling Basin on the semi-arid margins, which were characterised by large rivers most likely fed by snow melt, prevailed from 40 ka to the Last Glacial Maximum (LGM), and from the deglacial to the mid Holocene. By contrast, the Lake Eyre basin in central Australia remained relatively dry throughout the last 40 ka, with lake high stands at Lake Frome around 35–30 ka, and parts of the deglacial period and the mid-Holocene. The LGM was characterised by widespread relative aridity and colder conditions, as evidenced by extensive desert dune activity and dust transport, lake level fall, and reduced but episodic fluvial activity. The climate of the deglacial period was spatially divergent. The southern part of the continent experienced a brief humid phase around ∼17–15 ka, followed by increased dune activity around ∼14–10 ka. This contrasts with the post-LGM persistence of arid conditions in the north, associated with a lapsed monsoon and reflected in lake level lows and reduced fluvial activity, followed by intensification of the monsoon and increasingly effective precipitation from ∼14 ka. Palaeoenvironmental change during the Holocene was also spatially variable. The early to mid-Holocene was, however, generally characterised by moderately humid conditions, demonstrated by lake level rise, source-bordering dune activity, and speleothem growth, persisting at different times across the continent. Increasingly arid conditions developed into the late Holocene, particularly in the central arid zone. © 2012 Elsevier Ltd
Dating recent floodplain sediments in the Hawkesbury‐Nepean River system, eastern Australia using single‐grain quartz OSL
No full textTwo fluvial sediment cores taken from a floodplain of the H awkesbury‐N epean R iver system in the S ydney region, eastern A ustralia are dated using Optically Stimulated Luminescence (OSL ) to provide a reliable chronology essential for the management and planning of water resources. Nine charcoal 14C (AMS ) dates constrain these OSL ages. Quartz extracted from seven OSL samples from each of the cores was measured using both single‐grain and multi‐grain OSL techniques. Three of the single‐grain natural dose distributions appear to be well bleached, but the others appear to be incompletely bleached to various degrees. Three minimum‐age models (MAM , MAMUL and IEU ) are applied to the single‐grain dose distributions. We conclude that these models give consistent age estimates. For one of the cores it appears to be necessary to use a minimum‐age model to obtain accurate ages, but in the other core incomplete bleaching is probably less important than postdepositional mixing and mixing during sampling. As a result, the burial age is probably best estimated using the weighted average of the individual single‐grain dose estimates. The application of multi‐grain OSL techniques to these samples results in an average apparent age overestimation of ∼200 years, which is significant for these samples, but negligible for sediments older than a few thousand years. The intention is that the chronology obtained in this study will be used in conjunction with a proxy flood record, derived from floodplain sediments, to gain an understanding of the long‐term variability in periods of high and low rainfall in eastern Australia. © 2013 The Authors. Boreas © 2013 The Boreas Collegiu
A radioisotope tracer study of estuarine goundwater movement of the Eastern Australian coast
No full textGroundwater discharge to coastal waters, and the associated transport of nutrients and contaminants, is believed to have a significant impact on coastal ecosystems. However, complex boundary conditions and rapidly changing short-term fluxes make net flows resulting from local or regional groundwater discharge difficult to quantify. Such boundary conditions include beach face wave runup and storm setup, sub-surface tidal forcing, frequent surface inundation and tidally driven surface/groundwater interactions in estuarine and coastal areas. Tracer techniques can complement hydrological and geochemical studies of such systems and help distinguish longer-term net fluxes from the highly variable short-term fluxes. At Hat Head, NSW, on the eastern Australian coast, a comprehensive study of hydrogeology and hydrogeochemistry has being conducted in an estuarine/coastal sand dune aquifer. A scheme currently under construction will dispose of treated sewage effluent from the small coastal community by injection into the sand dune aquifer. Geochemical and isotopic data from the site indicate a high degree of complexity showing evidence of regional groundwater flow occurring at depth and more localised and highly dynamic conditions in the top 10 m of the aquifer. Tritium data indicate that regional groundwater is modern and stable isotope ratios have been used to distinguish between salt flat and sand dune dominated systems where evaporative and seawater mixing processes are observed. Storm wave setup and beach wave runup have been shown to elevate the water table near the coast leading to flow reversal and potential discharge of effluent to the estuarine zone. A radioisotope tracer study of groundwater flow in response to tidal forcing was conducted adjacent to a tidal creek at Hat Head. Using the short-lived radioisotope conservative tracer, bromine-82, groundwater movement was tracked in-situ over a period of ∼5 days on two occasions encompassing both neap and spring tide conditions. The tracer was injected into a screened borehole and gross gamma counts monitored from an adjacent borehole using a variety of collimated NaI detectors as well as down-hole gamma spectrometry. This technique maps the path of the slow moving tracer without sampling and allows the net groundwater movement to be distinguished from short term tidally driven fluxes. Results from the environmental isotope and radiotracer studies will be presented. © The authors.https://inis.iaea.org/collection/NCLCollectionStore/_Public/34/051/34051744.pd
Characterising diagnostic proxies for identifying palaeotsunamis in a tropical climatic regime, Samoan Islands
No full textThe September 2009 South Pacific Tsunami (2009 SPT) in the Samoa Islands resulted in local public and national calls to improve understanding of the medium- to long-term risks of tsunamis in these islands in order to further mitigate their impacts. This research addresses some of these calls through an interdisciplinary palaeotsunami investigation. Historical data beginning in 1837 indicate that the Samoan Islands have been impacted by tsunamis from all the major tsunamigenic zones within the Pacific Rim of Fire, making it an ideal location for starting to understand tsunami frequency and distribution within this region. Furthermore, the region has an historical record of extreme tropical cyclones. The overarching concept of this study is that tsunamis, like cyclones, leave a distinct geological deposit within coastal landscapes they impact. The origin of a high-energy geological deposit, be it storm or tsunami, can be determined by using a suite of diagnostic criteria. However, the origin of a deposit can still be ambiguous, because some of the diagnostic criteria (e.g. grain size, microfossil assemblages and characteristics) can be extremely similar for both processes. Moreover, local factors can also influence the characteristics of deposits. This project aims to elucidate this enigma by establishing a suite of diagnostic criteria (e.g., stratigraphy, lithology, macro- and micro-palaeontology, geomorphology, grain size characteristics, geochemistry, anthropology, archaeology, numerical modelling) to distinguish between tsunamis and cyclones in this tropical climatic regime. Preliminary studies show that a geological record of historical /palaeotsunamis and storms/palaeostorms is preserved on the south and south east coast of Upolu, west and northeast coast of Savai'i (Independent State of Samoa), and northwest coast of Ta'u in the Manu'a Group (American Samoa). We present preliminary X-ray fluorescence spectroscopy (XRF) and geochronological results (C-14 radiocarbon dates) conducted on samples (sands and paleosols) collected from various sites on Upolu, Savaii, and Ta'u islands. These serve as a starting point for developing a suite of diagnostic proxies for identifying and distinguishing tsunami from storm deposits in the Samoan Islands, and establishing the geochronology of identified events. Numerical modelling of wave resonance around these islands, as well as identified palaotsunamis will form an additional proxy for interpreting the palaeotsunami data. Further, it forms a basis for starting to understand the likely sources of these events, forming a basis for refining the frequency and (likely) magnitude distributions associated with these events. Planned Pb-210, Cs-137 and C-14 dating will enable a detailed interpretation of the chronology of specific events identified in the geologic record. Furthermore, they will enable a correlation of deposits with known historical events, providing a control on distinguishing recent tsunami from storm deposits (subsequent to 1837 AD), and enabling palaeo-events to be identified. This will form a basis for identifying similar events within the geologic record in similar environmental regimes. Ultimately, this work will significantly improve understanding of the nature and risks of coastal hazards in Samoa, thereby improving local capability to mitigate their medium to long-term impacts. It will also contribute to tsunami hazard mitigation efforts within the broader SW Pacific through a strengthened tsunami database in the region. © Copyright 2020 IEE
Lower Hunter particle characterisation study 4th progress report (Summer)
Get PDFThe Lower Hunter Particle Characterisation Study was commissioned by the NSW Environment Protection Authority in 2013 to investigate the composition and major sources of particle pollution in the Lower Hunter. The study was conducted by scientists from the former Office of Environment and Heritage (OEH), CSIRO and the Australian Nuclear Science and Technology Organisation (ANSTO), with oversight from the NSW Ministry of Health, and completed in 2016. Focusing on very small particles, invisible to the human eye, which can be inhaled and can pass through the throat and nose and into the lungs, the study aimed to determine the composition and major sources of fine particles (PM2.5) and coarse particles (PM2.5-10). Fine particles were monitored at four sites, including two sites representative of regional population exposures (Newcastle, Beresfield) and two sites near the Port of Newcastle (Mayfield and Stockton). Coarse particles were monitored at Mayfield and Stockton, the two sites near the Port of Newcastle
Application of stable isotopic techniques to wetlands conservation
Get PDFIdentification of food chain linkages between high trophic order species (particularly those of commercial and recreational importance) and different wetland resources (e.g. saltmarsh, mangrove and seagrass) is fundamental to resource management. The source of energy and trophic connectivity among species in the ecosystem can be quantified using stable isotopic techniques. Stable nitrogen isotopes can be used for tracking of pollutant derived from urban effluent or other anthropogenic sources that contribute to eutrophication and other management issues in aquatic environment. Analysis of non-radioactive, naturally occurring carbon and nitrogen isotopes is one of the most powerful techniques that can be considered in clarifying management questions related to wetland conservation
Eight-years of cave monitoring at Golgotha Cave, SW Australia: implications for speleothem paleoclimate records
No full textSpeleothems are an important archive of paleoenvironmental information but a thorough
understanding of processes are necessary for their interpretation. In order to better understand
speleothem records from the climatically-sensitive southwest region of WA, we have conducted a
detailed eight-year monitoring study at Golgotha Cave, southwest WA.
Oxygen isotopic data demonstrated that the majority of water moved through the porous Quaternary
calcarenite as matrix-flow with an inferred transit time of <1 year. A zone of high-flow dripwater is fed
by high-magnitude rainfall events (Treble et al., 2013). Prior calcite precipitation (PCP) signals of
increased Mg/Ca and Sr/Ca in dripwater are attributed to stalactite deposition. This signal is
enhanced at low-flow sites and minimised at the high-flow site as degassing and subsequent
stalactite deposition are a function of drip interval. Long-term rising trends found in most solutes are
attributed via a mass-balance approach to increasing forest bioproductivity, consistent with an
increase in forest understorey following a low-intensity burn in 2006.
A fundamental message from this study is that individual speleothem records from within Golgotha
Cave will differ, e.g. speleothem δ18O at our high-flow site is biased to recording high-magnitude
rainfall events, whilst PCP will be the main driver of speleothem Mg/Ca and Sr/Ca at low-flow sites.
Forest biomass appears to be modulating transpiration-sensitive ions and these may serve as an
indicator of fire history
Past hydroclimatic variability from southwest Australian speleothems during the last millennium
No full textSpeleothems from Golgotha Cave in SW Western Australia have been investigated to extend our
knowledge of past climate variability for this region during the last millennium. O isotopic datasets,
the primary paleoclimate proxy used for speleothems, were constructed for four stalagmites. A
challenge in their interpretation has been the disagreement between these records, despite
representing coeval growth from within the same cave. Resolving this conundrum has necessitated
the characterisation of the hydrology, hydrochemistry, rainfall isotopes7 and development of
proxy system forward models1,8 for Golgotha Cave. The findings of these studies will be summarised
as a conceptual model in order to present the main karst hydrological features that give rise to each
stalagmite’s isotopic response to hydroclimatic forcing. The paleoclimate interpretation will focus on
the two continuous stalagmite records that were fed predominately by diffuse flow. This will be
supported by evidence from the two stalagmites predominantly fed by fracture flow, which has
resulted in a non-linear response to hydroclimatic forcing