Chemical characterisation and source identification of atmospheric aerosols in the Snowy Mountains, south-eastern Australia

Characterisation of atmospheric aerosols is of major importance for: climate, the hydrological cycle, human health and policymaking, biogeochemical and palaeo-climatological studies. In this study, the chemical composition and source apportionment of PM2.5 (particulate matter with aerodynamic diameters less than 2.5 μm) at Yarrangobilly, in the Snowy Mountains, SE Australia are examined and quantified. A new aerosol monitoring network was deployed in June 2013 and aerosol samples collected during the period July 2013 to July 2017 were analysed for 22 trace elements and black carbon by ion beam analysis techniques. Positive matrix factorisation and back trajectory analysis and trajectory clustering methods were employed for source apportionment and to isolate source areas and air mass travel pathways, respectively. This study identified the mean atmospheric PM2.5 mass concentration for the study period was (3.3 ± 2.5) μg m−3. It is shown that automobile (44.9 ± 0.8)%, secondary sulfate (21.4 ± 0.9)%, smoke (12.3 ± 0.6)%, soil (11.3 ± 0.5)% and aged sea salt (10.1 ± 0.4)% were the five PM2.5 source types, each with its own distinctive trends. The automobile and smoke sources were ascribed to a significant local influence from the road network and bushfire and hazard reduction burns, respectively. Long-range transport are the dominant sources for secondary sulfate from coal-fired power stations, windblown soil from the inland saline regions of the Lake Eyre and Murray-Darling Basins, and aged sea salt from the Southern Ocean to the remote alpine study site. The impact of recent climate change was recognised, as elevated smoke and windblown soil events correlated with drought and El Niño periods. Finally, the overall implications including potential aerosol derived proxies for interpreting palaeo-archives are discussed. To our knowledge, this is the first long-term detailed temporal and spatial characterisation of PM2.5 aerosols for the region and provides a crucial dataset for a range of multidisciplinary research. Crown Copyright © 2018 Published by Elsevier B.V

Loss of Maternal CTCF Is Associated with Peri-Implantation Lethality of Ctcf Null Embryos

CTCF is a highly conserved, multifunctional zinc finger protein involved in critical aspects of gene regulation including transcription regulation, chromatin insulation, genomic imprinting, X-chromosome inactivation, and higher order chromatin organization. Such multifunctional properties of CTCF suggest an essential role in development. Indeed, a previous report on maternal depletion of CTCF suggested that CTCF is essential for pre-implantation development. To distinguish between the effects of maternal and zygotic expression of CTCF, we studied pre-implantation development in mice harboring a complete loss of function Ctcf knockout allele. Although we demonstrated that homozygous deletion of Ctcf is early embryonically lethal, in contrast to previous observations, we showed that the Ctcf nullizygous embryos developed up to the blastocyst stage (E3.5) followed by peri-implantation lethality (E4.5–E5.5). Moreover, one-cell stage Ctcf nullizygous embryos cultured ex vivo developed to the 16–32 cell stage with no obvious abnormalities. Using a single embryo assay that allowed both genotype and mRNA expression analyses of the same embryo, we demonstrated that pre-implantation development of the Ctcf nullizygous embryos was associated with the retention of the maternal wild type Ctcf mRNA. Loss of this stable maternal transcript was temporally associated with loss of CTCF protein expression, apoptosis of the developing embryo, and failure to further develop an inner cell mass and trophoectoderm ex vivo. This indicates that CTCF expression is critical to early embryogenesis and loss of its expression rapidly leads to apoptosis at a very early developmental stage. This is the first study documenting the presence of the stable maternal Ctcf transcript in the blastocyst stage embryos. Furthermore, in the presence of maternal CTCF, zygotic CTCF expression does not seem to be required for pre-implantation development

Trace elements: from sources to cave drip water, south-eastern Australia

Speleothem trace element time series are constructed from the infiltrating drip water geochemistry, and hence are examined under contrasting rainfall conditions associated with El Niño and La Niña phases of ENSO. The aim was to identify suitable inorganic element proxies for palaeoclimate interpretation in speleothem records from Harrie Wood Cave, Yarrangobilly. The drip water chemical composition at the stalactite tip reflects a contribution from different endmembers and processes; therefore it is necessary to study the different sources, pathways and processes that occur as water migrates through the atmosphere-soil-karst system. Here we present high resolution aerosol, rainfall and drip water 18O and inorganic drip-water datasets. Analysis of aerosol samples above the caves reveals the atmosphere supplies a suite of elements from automobile emissions, windblown soil, smoke, secondary sulfate and aged sea salt sources. The bedrock and aerosols were identified as contributory sources of solutes to the drip water. The clay-rich soil zone was recognised as a sink for inorganic elements, and a secondary source for Zn. In soil, a number of processes were demonstrated to modify the chemical composition of the resultant drip waters. The drip water chemistry is driven by the long-term gradient in the cumulative water balance. The flow paths feeding the drip sites were shown to be fracture flow, from a ventilated well-mixed pocket within the epikarst storage reservoir. Dilution and reduced prior calcite precipitation (PCP) controlled the drip-water chemistry during the La Niña/wet years whereas enhanced PCP was observed during the El Niño and dry periods. Mg and Sr show particular promise as paleoclimate proxies for drought and flood events, while with further research Na, K and Zn may also be reliably used. These findings will be applied in a modern speleothem record. © Author(s

Rainfall isotope (3H, δ2H and δ18O) input to groundwater in Australia

The stable isotopes of water, δ2H and δ18O, are conservative tracers available for studying mixing of water in the hydrosphere. Radioactive tritium (2H, half-life = 12.3 years), derived from both cosmogenic and anthropogenic sources (nuclear testing), is an important tracer for dating of young groundwater. Measurements of stable water isotopes and tritium in Australian rainfall have been made monthly at six coastal sites and Alice Springs since 1962 as part of the Global Network of Isotopes in Precipitation (GNIP). Since 2006 this network has been expanded to include seven inland sites in New South Wales, Queensland, South Australia and Western Australia (δ2H and δ18O analysed only). In addition, event-based studies of stable water isotopes have been conducted at four locations in the Sydney region since 2005. These data have been analysed to determine local meteoric water lines, weighted averages and to investigate the relationships between rainfall isotopic composition, temperature and precipitation amount. Stable water isotopes are not completely conservative as they undergo fractionation as a result of hydrological processes such as evaporation, precipitation, ice and snow formation and melting, and geothermal activity. The fractionation can be used to understand the provenance and history of groundwater and to define end members for mixing studies. For age dating of groundwater using tritium the rainfall tritium composition is required. In addition to the 50-year tritium record available from GNIP for six sites, data for an additional eleven locations throughout eastern Australia were compiled for varying periods mainly between 1970 and 1991, thereby improving the spatial resolution of the tritium time series in Australia. Unlike δ2H and δ18O, the spatial distribution and seasonal variation of tritium in rainfall is largely controlled by the stratosphere to troposphere exchange of anthropogenic tritium from nuclear testing, with the highest concentrations occurring at Adelaide and Melbourne during the early spring. Modern concentrations appear to be stabilising with average annual concentrations in the range 1–3 TU increasing with latitude. These data have also been used to estimate the tritium composition of rainfall resulting in the January 1974 Queensland floods, which are believed to have resulted in significant recharge to aquifers in Queensland and northern NSW. © Geological Society of Australia In

ENSO–cave drip water hydrochemical relationship: A 7-year dataset from south-eastern Australia

Speleothems (cave deposits), used for palaeoenvironmental reconstructions, are deposited from cave drip water. Differentiating climate and karst processes within a drip-water signal is fundamental for the correct identification of palaeoenvironmental proxies and ultimately their interpretation within speleothem records. We investigate the potential use of trace element and stable oxygen-isotope (δ18O) variations in cave drip water as palaeorainfall proxies in an Australian alpine karst site. This paper presents the first extensive hydrochemical and δ18O dataset from Harrie Wood Cave, in the Snowy Mountains, south-eastern (SE) Australia. Using a 7-year long rainfall δ18O and drip-water Ca, Cl, Mg/Ca, Srg/gCa and δ18O datasets from three drip sites, we determined that the processes of mixing, dilution, flow path change, carbonate mineral dissolution and prior calcite precipitation (PCP) accounted for the observed variations in the drip-water geochemical composition. We identify that the three monitored drip sites are fed by fracture flow from a well-mixed epikarst storage reservoir, supplied by variable concentrations of dissolved ions from soil and bedrock dissolution. We constrained the influence of multiple processes and controls on drip-water composition in a region dominated by El Niño-Southern Oscillation (ENSO). During the El Niño and dry periods, enhanced PCP, a flow path change and dissolution due to increased soil CO2 production occurred in response to warmer than average temperatures in contrast to the La Niña phase, where dilution dominated and reduced PCP were observed. We present a conceptual model, illustrating the key processes impacting the drip-water chemistry. We identified a robust relationship between ENSO and drip-water trace element concentrations and propose that variations in speleothem Mg/Ca and Srg/Ca ratios may be interpreted to reflect palaeorainfall conditions. These findings inform palaeorainfall reconstruction from speleothems regionally and provide a basis for palaeoclimate studies globally, in regions where there is intermittent recharge variability

Primary Study on Response of Water Quality to Land Use Pattern in a Medium-sized Watershed, Southeast of China

Geoinformations technology and multivariate statistical analysis method were coupled to reveal the response of water quality to land use pattern in Jiulong river watershed, the second largest watershed of Fujian province with intensive agricultural activies. The study results obtained show that in entire watershed level, arable land(ALU) is the most important factor influencing DO in stream, moreover, buildup land (ULU) is the important predictor for BOD5, COD(MN), NH3-N. In the buffer-zone level, BOD5 and NH3-N are positive correlated to ULU, and negative correlative to waterbody area, DO is positive correlated to natural land use(NLU), and negative correlated to ALU, which all are similar to the results obtained at entire watershed scale. To great extent, buffer zone of land use pattern can predict river water quality in study watershed. Multiple regression of relationship between land use pattern and water quality in different spatial levels enable us to improve comprehensive understanding of the relationship between land use pattern and land use in a medium-sized watershed in southeast of China

Unsaturated zone hydrology and implications for paleo-climate speleothem reconstructions

Speleothem growth relies on the supply of water which percolates from the surface, through the unsaturated zone and discharges into cavernous voids. The flow path of water feeding individual speleothems varies considerably depending on the karst architecture e.g. micro-fractures, solution pipes, structural voids in the karst, storage reservoirs, etc., all of which may alter the composition of drip waters over the flow route. By monitoring drip waters, we can determine: 1) unsaturated zone flow regimes; 2) connectivity between the surface and cave discharge zone; and 3) thresholds for groundwater recharge. This information can be used to identify suitable speleothems in caves for reconstruction of past climatic and hydrologic variability, at least over the last few thousand years of similar mean climate state. High-frequency, spatially-dense monitoring was conducted in Harrie Wood Cave, Yarrangobilly, Snowy Mountains over a 15 month period to characterise the flow regimes at 14 sites along a depth profile within the cave. Sites were monitored using acoustic drip loggers (stalagmates®). Discharge rates and response to significant rainfall events were highly variable between sites. A moderate relationship was found between decreasing discharge rates and increasing depth (r2 = 0.40). We suggest unsaturated zone storage and mixing, unrelated to depth, also have a significant impact on flow regimes. Using a statistical approach, five different drip types, which often had no spatial commonality, were identified. This information was used to inform the choice of speleothems for paleo-climate reconstruction, using stalagmites with differing hydrological regimes feeding growth, of which the preliminary data 18 will be presented here. The study highlights the need to understand unsaturated zone hydrology at the individual drip discharge level, prior to any speleothem study for paleo-climate, to truly appreciate the drip water signal it is recording. Copyright (C) The Authors

ENSO–cave drip water hydrochemical relationship: A 7-year dataset from south-eastern Australia

Speleothems (cave deposits), used for palaeoenvironmental reconstructions, are deposited from cave drip water. Differentiating climate and karst processes within a drip-water signal is fundamental for the correct identification of palaeoenvironmental proxies and ultimately their interpretation within speleothem records. We investigate the potential use of trace element and stable oxygen-isotope (δ18O) variations in cave drip water as palaeorainfall proxies in an Australian alpine karst site. This paper presents the first extensive hydrochemical and δ18O dataset from Harrie Wood Cave, in the Snowy Mountains, south-eastern (SE) Australia. Using a 7-year long rainfall δ18O and drip-water Ca, Cl, Mg/Ca, Srg/gCa and δ18O datasets from three drip sites, we determined that the processes of mixing, dilution, flow path change, carbonate mineral dissolution and prior calcite precipitation (PCP) accounted for the observed variations in the drip-water geochemical composition. We identify that the three monitored drip sites are fed by fracture flow from a well-mixed epikarst storage reservoir, supplied by variable concentrations of dissolved ions from soil and bedrock dissolution. We constrained the influence of multiple processes and controls on drip-water composition in a region dominated by El Niño-Southern Oscillation (ENSO). During the El Niño and dry periods, enhanced PCP, a flow path change and dissolution due to increased soil CO2 production occurred in response to warmer than average temperatures in contrast to the La Niña phase, where dilution dominated and reduced PCP were observed. We present a conceptual model, illustrating the key processes impacting the drip-water chemistry. We identified a robust relationship between ENSO and drip-water trace element concentrations and propose that variations in speleothem Mg/Ca and Srg/Ca ratios may be interpreted to reflect palaeorainfall conditions. These findings inform palaeorainfall reconstruction from speleothems regionally and provide a basis for palaeoclimate studies globally, in regions where there is intermittent recharge variability