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Radiotracer methodology
No full textMethods for the use of radiotracers in aquatic environments have been established over the past five decades. The basic principles involve definition of the system or problem to be investigated, selection of a suitable tracer, design of tracer deployment and measurement systems and analysis of the data collected to address the initial problem. These aspects are covered in detail in this paper covering the current state of the art in tracer technology. New developments in the use of nano-particle tracers are also addressed. © The authors.International Atomic Energy Agenc
Characterization of insoluble nanoparticles in ice cores from Law Dome, East Antarctica
No full textInsoluble nanoparticles, in the form of aerosols, have significant affects on climate and biogeochemical cycles. Records of these aerosols are essential for understanding paleoclimate forcing and future climate change. While a large body of research exists with respect to mineral dust particles (micron scale) derived from ice cores and sediment cores, very little is known with regards to the history of insoluble nanoparticles. These particles and their precursors are emitted to the atmosphere from a variety of primary and secondary sources including biomass burning, biogenic, anthropogenic, volcanic, and terrestrial mineral emissions. Ice core records are the only reliable way to study the past history of these particles. Here, we will present new data with regards to the physical and chemical properties of these particles as found in the Law Dome ice core, DSS0506 from East Antarctica.Characterization of insoluble nanoparticles in ice cores from Law Dome, East Antarctic
Identifying historical flood deposits in a sediment core from an oxbow lake
No full textRiver 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
Understanding the production and retention of in situ cosmogenic 14C in polar firn
No full textRadiocarbon in CO
2
, CO and CH4 trapped in polar ice is of interest for dating of ice cores,
studies of past solar activity and cosmic ray flux, as well as studies of the paleoatmospheric
CH4 budget. The major difficulty with interpreting 14C measurements in ice cores stems
from the fact that the measured 14C represents a combination of trapped paleoatmospheric
14C and 14C that is produced within the firn and ice lattice by secondary cosmic ray
particles. This in situ cosmogenic 14C component in ice is at present poorly understood.
Prior ice core 14C studies show conflicting results with regard to the retention of cosmogenic
14C in polar firn and partitioning of this 14C among CO
2
, CO and CH4. Our new study aims
to comprehensively characterize the 14C of CO
2
, CO, and CH4 in both the air and the ice
matrix throughout the firn column at Summit, Greenland. We will present measurements of
14C in Summit firn air (the first phase of this study) and discuss the implications for in situ
cosmogenic 14C production and retention from initial modeling studies. Preliminary results
from firn air indicate a 14CO increase with depth in the lock-in zone resulting from in situ
production by muons, as well as a lock-in zone 14CO
2
bomb peak originating from nuclear
testing in the late 1950s and early 1960s. A decrease in 14CH4 with depth is observed in
the lock-in zone that is in agreement with observations of increasing atmospheric 14CH4
over the past several decades
Paleolimological investigation of the use of stable isotopes of carbon and nitrogen in bulk sediment and cladoceran zooplankton to reveal ecosystem changes in Kings Billaong Northwest Victoria, Australia
No full textNorthwest Victoria hosts a large number of shallow floodplain wetlands along the
Murray River system. One of these, Kings Billabong, is known for its high conservation
values. However, the naturally occurring flood pulses, which maintain ecological
connectivity between river and wetlands, have been altered impacting the ecology of Kings
Billabong. The human-induced river regulation in the Murray River following the arrival of
Europeans, and increased farming activities around Mildura for irrigation, has switched
Kings Billabong to a permanent water regime resulting in accelerated sedimentation rates and
changed sources of carbon and, subsequently, altered ecological character. This study focuses
on a 90 cm long sediment core taken from Kings Billabong in 2011, where the 210Pb dating
detected sediments at c. 60 cm depth to be c. 65 years old. Around this time (c. 1940-1945
AD), a systemic change occurred in the billabong. The enrichment of carbon substantially
declined, while, in the meantime, nitrogen enrichment increased. Coincidently, the subfossil
cladoceran zooplankton assemblages revealed changes in the limnological conditions of the
wetland ecosystem. Among the littoral species, the Chydorus sphaericus group, which prefers
eutrophic water, became dominant. Since the early 2000s, the abundance of Biapertura
affinis, a pioneer plant dwelling species, has declined. Before the assemblage of B. affinis
began to decline, a large number of cladoceran ephippia were recorded in sediment samples
indicating the elevated stress in the wetland. This study suggests that paleolimnological
investigations, together with the use of stable isotopes of carbon and nitrogen in sediment
samples, provides an opportunity to reveal the impacts of anthropogenic disturbances on the
floodplain wetlands of the Murray River system across northwest Victoria, and potentially
more widely across Australia. © The Authors
Orakei maar paleolake (Auckland, NZ):A multi-method approach to the composite stratigraphy of a long sediment core
No full textThe development of records of Quaternary environmental and –climatic changes relies largely on
long, complete sediment sequences. However, coring techniques do not allow extraction of one
continuous record of sedimentation to be recovered from a single drill hole. In order to reconstruct a
complete record, it is common practice to drill two or more overlapping cores with a depth offset to
overcome coring-induced loss and disturbance and then stitch these records together using
stratigraphic markers to produce a master stratigraphy. However, details of the process used and
critical uncertainties are rarely reported despite the fact that spurious correlations may alter
subsequent paleoenvironmental interpretations. Here we detail the procedure employed to build a
composite stratigraphy from three overlapping long lake sediment cores from Orakei maar paleolake
(Auckland). Orakei maar was created by a phreato-magmatic eruption to forming a lake basin of a
low surface-to-depth ratio and virtually no catchment. The accumulated sediment can be considered
a direct recorder of climatic and environmental changes over the Last Glacial Cycle in the Southern
Hemisphere mid-latitudes, a
crucial but under-studied part of
the global climatic system. Finely laminated
sediment in the Orakei
record can be aligned and
correlated along visually distinct
marker horizons, as well as tephra
layers (Fig. 1), with sub-cm to mm
resolution, supplemented by μ-
XRF core scanning elemental and
X-ray density variability.
Complications arise from lateral
inhomogeneities in sedimentation
along the lake bottom and hence,
larger differences between the
three cores. These sections,
usually of coarser grain size, likely
caused by local landslides from
the crater rim, are correlated
based on: visual logging, common
pattern in μ-XRF elemental and Xray
density variation, and typical
depth offset between the
observed debris flows in the
cores.
Figure 1: Composite stratigraphy and
lithology of Orakei maar paleo-lake
record built from three overlapping
sediment cores. © The Author
Developing tree-ring chronologies and climate reconstructions from moisture sensitive Araucariaceae trees in tropical and subtropical Australia
No full textMany parts of tropical and subtropical Australia lack both annually-resolved long-term instrumental
climate data and proxy climate records. This limits our understanding of past climate patterns and
impacts. There are however, remnant forest stands where dendroclimatology could be applied to
extend the climate record. Tree species in these regions are known to be compromised by numerous
ring anomalies and as such are understudied resulting in indistinct tree growth-climate relationships.
Recent research of trees in the Araucariaceae family has attempted to address these issues with the
goal being to develop long-term climate reconstructions across tropical and subtropical Australia.
Araucariaceae trees are commonly found across northern and eastern Australia and are longer lived
than many other local non-temperate species. They are known to produce growth rings that are
mostly annual and their growth appears sensitive to climate, specifically to moisture conditions.
Three Araucariaceae species, hoop pine (Araucaria cunninghamii), bunya pine (Araucaria bidwillii)
and purple kauri pine (Agathis atropurpurea) have been studied at five locations within the
rainforests of eastern Queensland. Ring anomalies including false, faint, locally absent, and pinching
or wedging rings, were identified. This was done by applying bomb-pulse radiocarbon dating and
Itrax radiographic analysis to hoop pine trees from subtropical Lamington and D’Aguilar National
Parks respectively. Additionally, dendrometers were installed on trees of all three species so that the
climate variables influencing seasonal growth could be identified. It was found that moisture
conditions drive annual growth in Araucariaceae trees but that the onset and cessation of the
growth season is dependent on temperature. Forest elevation also needs to be considered as the
growth season length is longer at lower elevation and there is an influence of cloud cover seen in the
north Queensland rainforest, which is close to a cloud forest classification. Annual growth was
confirmed for all species through this analysis and the suitability for their use in climate
reconstruction proven. Following this, a 164-year drought reconstruction for Southeast Queensland
was developed using hoop pine trees from the subtropical rainforest of Lamington National Park.
Additional work is continuing to further develop a network of long-term Queensland tree-ring
climate records. © The Author
Sulphur: a proxy for wildfires in stalagmites
No full textBushfires are a global hazard that can have catastrophic impacts on communities and ecosystems.
However, there is limited baseline data on how fire frequency and intensity have responded to
climate change in the past. A speleothem-based bushfire record will allow us to determine long-term
natural fire regimes and better understand the relationship between bushfires and climate. Recent
research has demonstrated the potential of using sulphur as a speleothem paleofire proxy1 but a full
characterisation of S in the karst environments of SW Western Australia is lacking. Here, we quantify
the relative contributions of different sources of sulphur in a modern cave environment through the
characterisation of rainfall, soil, bedrock, vegetation and cave drip water sulphate concentration and
isotopic values (δ18O- SO4 and δ34S- SO4) to assess the role of sulphur cycling through the biomass
in response to burn events at this site. This information will be used to interpret the SO4 isotope
record, supported by other proxies in a 2-12 ka speleothem from SW Western Australia. This is the
first speleothem SO4 isotope study in the southern hemisphere and the first in the world to use
speleothem S isotopes in a paleofire context. © Author(s
Composition of Clean Marine Air and Biogenic Influences on VOCs during the MUMBA Campaign
Get PDFVolatile organic compounds (VOCs) are important precursors to the formation of ozone and fine particulate matter, the two pollutants of most concern in Sydney, Australia. Despite this importance, there are very few published measurements of ambient VOC concentrations in Australia. In this paper, we present mole fractions of several important VOCs measured during the campaign known as MUMBA (Measurements of Urban, Marine and Biogenic Air) in the Australian city of Wollongong (34°S). We particularly focus on measurements made during periods when clean marine air impacted the measurement site and on VOCs of biogenic origin. Typical unpolluted marine air mole fractions during austral summer 2012-2013 at latitude 34°S were established for CO2 (391.0 ± 0.6 ppm), CH4 (1760.1 ± 0.4 ppb), N2O (325.04 ± 0.08 ppb), CO (52.4 ± 1.7 ppb), O3 (20.5 ± 1.1 ppb), acetaldehyde (190 ± 40 ppt), acetone (260 ± 30 ppt), dimethyl sulphide (50 ± 10 ppt), benzene (20 ± 10 ppt), toluene (30 ± 20 ppt), C8H10 aromatics (23 ± 6 ppt) and C9H12 aromatics (36 ± 7 ppt). The MUMBA site was frequently influenced by VOCs of biogenic origin from a nearby strip of forested parkland to the east due to the dominant north-easterly afternoon sea breeze. VOCs from the more distant densely forested escarpment to the west also impacted the site, especially during two days of extreme heat and strong westerly winds. The relative amounts of different biogenic VOCs observed for these two biomes differed, with much larger increases of isoprene than of monoterpenes or methanol during the hot westerly winds from the escarpment than with cooler winds from the east. However, whether this was due to different vegetation types or was solely the result of the extreme temperatures is not entirely clear. We conclude that the clean marine air and biogenic signatures measured during the MUMBA campaign provide useful information about the typical abundance of several key VOCs and can be used to constrain chemical transport model simulations of the atmosphere in this poorly sampled region of the world. © 2019 The Author
Increasing the understanding and use of natural archives of ecosystem services, resilience and threholds to improve policy, science and practice
No full textDespite the great potential of palaeo-environmental information to strengthen natural resource policy, science and practical outcomes naturally occurring archives of palaeo-environmental and ecosystem service information have not been fully recognised or utilised to inform the development of environmental policy. In this paper, we describe how Australian palaeo-environmental science is improving environmental understanding through local studies and regional syntheses that inform us about past conditions, extreme conditions and altered ecosystem states. Australian innovations in ecosystem services research and palaeo-environmental science contribute in five important contexts: discussions about environmental understanding and management objectives, improving access to information, improved knowledge about the dynamics of ecosystem services, increasing understanding of environmental processes and resource availability, and engaging interdisciplinary approaches to manage ecosystem services. Knowledge of the past is an important starting point for setting present and future resource management objectives, anticipating consequences of trade-offs, sharing risk and evaluating and monitoring the ongoing availability of ecosystem services. Palaeo-environmental information helps reframe discussions about desirable futures and collaborative efforts between scientists, planners, managers and communities. However, further steps are needed to translate the ecosystem services concept into ecosystem services policy and tangible management objectives and actions that are useful, feasible and encompass the range of benefits to people from ecosystems. We argue that increased incorporation of palaeo-environmental information into policy and decision-making is needed for evidence-based adaptive management to enhance sustainability of ecosystem functions and reduce long-term risks. © 2020 by SAGE Publication