Search

In northern Australia (NAUS), mean rainfall during the Australian summer monsoon (AUSM) season exhibits distinct interannual variability despite weak influence from tropical sea surface temperature (SST) variability. The present study investigates mechanisms for the strong and persistent rainfall anomalies throughout the AUSM season. When the AUSM is stronger than normal, the low-level monsoonal circulation intensifies in response to the stronger convective activity over NAUS. The intensified surface westerlies over the tropical southeastern Indian Ocean (SEIO) enhance oceanic evaporation locally and downstream moisture transport into NAUS. This wind–evaporation feedback is verified through a moist static energy budget analysis. For this feedback to work effectively, SST cooling due to the stronger AUSM should be weak enough not to suppress the oceanic evaporation in the tropical SEIO. Our mixed layer heat budget analysis based on an ocean model hindcast experiment reveals that anomalous downwelling in the subsurface SEIO, which is induced dynamically by the intensified monsoon westerlies, partially offsets the SST cooling. The land surface evaporation over the continental inland area is also enhanced significantly in the middle and later portions of the monsoon season associated with increased soil moisture, suggesting its memory effect for the persistence of rainfall anomalies. The AUSM variability can therefore be regarded as a self-sustaining internal variability in the atmosphere–ocean–land surface coupled system, rather than just an atmospheric internal variability. Significance Statement: We aim to understand why summer monsoon rainfall in northern Australia varies markedly from one year to another even under the weak influence of large-scale sea surface temperature fluctuations, such as El Niño/La Niña. Our analyses based mainly on observational datasets reveal that wind-induced changes in oceanic evaporation south of Java significantly modulates the water vapor transport into northern Australia. We also find that ocean dynamics helps this wind–evaporation feedback process and continental soil moisture may act to prolong anomalous rainfall by its memory effect. This study shows the self-sustaining nature of the Australian summer monsoon variability under the atmosphere–ocean–land surface interactions, which deepens our understandings of the monsoon system. [ABSTRACT FROM AUTHOR]

Coastal wetlands are essential for regulating the global carbon budget through soil carbon sequestration and greenhouse gas (GHG – CO2 , CH4 , and N2O) fluxes. The conversion of coastal wetlands to agricultural land alters these fluxes' magnitude and direction (uptake/release). However, the extent and drivers of change of GHG fluxes are still unknown for many tropical regions. We measured soil GHG fluxes from three natural coastal wetlands – mangroves, salt marsh, and freshwater tidal forests – and two alternative agricultural land uses – sugarcane farming and pastures for cattle grazing (ponded and dry conditions). We assessed variations throughout different climatic conditions (dry–cool, dry–hot, and wet–hot) within 2 years of measurements (2018–2020) in tropical Australia. The wet pasture had by far the highest CH4 emissions with 1231±386 mgm-2d-1 , which were 200-fold higher than any other site. Dry pastures and sugarcane were the highest emitters of N2O with 55±9 mgm-2d-1 (wet–hot period) and 11±3 m gm-2d-1 (hot-dry period, coinciding with fertilisation), respectively. Dry pastures were also the highest emitters of CO2 with 20±1 gm-2d-1 (wet–hot period). The three coastal wetlands measured had lower emissions, with salt marsh uptake of -0.55±0.23 and -1.19±0.08 gm-2d-1 of N2O and CO2 , respectively, during the dry–hot period. During the sampled period, sugarcane and pastures had higher total cumulative soil GHG emissions (CH4+N2O) of 7142 and 56 124 CO2-eqkgha-1yr-1 compared to coastal wetlands with 144 to 884 CO2-eqkgha-1yr-1 (where CO2-eq is CO2 equivalent). Restoring unproductive sugarcane land or pastures (especially ponded ones) to coastal wetlands could provide significant GHG mitigation. [ABSTRACT FROM AUTHOR]

With the presence of highly permeable pathways, such as faults and fractures zones, coal seam gases, particularly CO2, could potentially migrate upwardly from the coal deposits into the shallow subsurface and then to the atmosphere. This letter reports soil gas mapping and gamma ray survey in coal basin of Hunter River Valley, Australia. The survey facilitated the delineation of fault structures across the sampling regions, where the identified faults were confirmed by an independent drilling investigation later. Furthermore, to evaluate the gas emission fluxes from coalbeds through fault zones, the measured CO2 concentrations, coupled with an inverse modeling, enable the estimation of the width of the fault zone and associated CO2 emission flux in the range of 2 × 10−5–6 × 10−5 mol/m2/s at the study site. Our new approach provides a way to determine emissions of gases from deep formations, which may contribute considerably to the greenhouse gases cycles. Plain Language Summary: Australia is one of the world's biggest coal exporters. Total fugitive emissions in Australia have increased in line with the expanding coal and gas production sector. CO2 emissions may occur during the operation and following the closure of coal mines and coal seam gas fields. Leakage of gases to the atmosphere may be induced through fractured gas‐bearing strata and open vents. Hence, the emissions of CO2 from coal basins should be counted toward the overall emissions budget. The new approach proposed by the current study can be applied to estimate emissions of CO2 from fracture and fault zones, which have not been well quantified and yet can be potentially an important source of greenhouse gases contributing to the overall budget at a global scale. So this work could provide a better track progress on international emission commitments. Key Points: Field assessments on gas emission fluxes from coal basin at fault zones in the Hunter River Valley, AustraliaSoil gas mapping and gamma ray survey delineated several fault structures across the sampling transects, which were later confirmed by an independent borehole drilling investigationAn inverse modeling is applied to determine the width of the fault zone and its CO2 emission flux at the study site [ABSTRACT FROM AUTHOR]

Exposure to radon in show caves is an existing exposure situation. A survey of radon levels in underground show caves around Australia, carried out in 1994, found that most of the show caves located in South-Eastern Australia had yearly average radon levels exceeding the Australian radon reference level of 1000 Bq m−3. At the time of the original survey, the radiation doses from exposure to radon progeny of the tour guides in these caves were estimated using the epidemiologically based dose conversion factors and all dose were assessed to be less than 10 mSv per year. In February 2018, the International Commission for Radiological Protection (ICRP) published updated radon and radon progeny dose conversion factors (DCF) applicable to worker exposure to radon in show caves. These updated DCF values are based on dosimetric modelling and are sensitive to the radon progeny activity size distribution. The recommended DCF values are up to a factor four times higher than the previous ICRP recommendations. The ICRP has published data that allows for the estimation of site-specific radon progeny dose coefficients if required. A reassessment of the radiation doses to workers in Australian show caves has been made using these updated ICRP DCF values and the historical measurements of radon progeny activity size distributions in Australian show caves. Using the site-specific DCF values, it is estimated that 15% of the workers exceeded 10 mSv y−1 and 6% exceeded 20 mSv y−1. Although the total number of show cave workers in Australia is very small, the updated radon progeny dose estimates are a significant radiation protection issue for the affected individuals and their employers. [ABSTRACT FROM AUTHOR]

In this study, we evaluated three soil moisture (SM) products (Advanced Microwave Scanning Radiometer-2 [AMSR2], Advanced SCATterometer [ASCAT], and European Reanalysis Interim [ERA-interim]) across Australia in four climate zones by comparing against the Australian Water Resources Assessment-Landscape (AWRA-L) SM products from July 2012 to June 2017. The ASCAT SM indicated better performance than other SM products over Australia. To evaluate the applicability and reliability for monitoring agricultural drought, an agricultural drought index, the Soil Water Deficit Index, was estimated from three SM products and compared with three commonly-used drought indices (atmospheric water deficit [AWD], Evaporative Stress Index, and Reconnaissance Drought Index). Volumetric contingency tables were compiled to quantitatively assess the performance of agricultural drought detection using various SM products compared with the AWD. All products had reliable drought detection capability over Australia based on the results of temporal evolution and contingency tables with a mean volumetric hit index of 0.700, 0.728, and 0.787 for AMSR2, ASCAT, and ERA-interim, respectively. The slight incapability of drought detection capability of SWDI in tropical region was low due to the variation in persistence times of moisture in the atmosphere and soil. Except arid zone, in all climate zones, the reliability of SM products for drought detection followed the following order ASCAT > ERA-interim > AMSR2. • Evaluation of AWRA-L SM and three satellite and reanalysis SM products across Australia. • Comparison of SWDI from three different SM product and AWD from AWRA-L at different climate zones. • The result of ASCAT showed reasonable performance among different SM products. [ABSTRACT FROM AUTHOR]

A dimethyl sulfide (DMS) vertical concentration profile and DMS surface emission flux were quantified in undisturbed acid sulfate soils (ASS) at Cudgen Lake on the north coast of New South Wales, Australia. A deuterated internal standard was used to account for soil adsorption characteristics. The DMS vertical concentration profile increased exponentially from 0.6 m depth to the surface layer. This profile reflected the adsorption properties of the ASS horizons present and the experimentally determined octanol/water partition coefficient for DMS of 1.36, suggesting that DMS would be mobilised in the soil water medium for upward translocation in time due to surface evaporation. The organic material in the oxidised ASS crustal layer had a chemically strong adsorption affinity for DMS, which appeared to restrain its emission from surface soil particles to the atmosphere. The seasonally averaged DMS surface flux estimate from the Cudgen Lake ASS was 9 ng S m−2 min−1, which is relatively low by comparison to DMS fluxes reported from other wetland soils such as salt-marshes and acidic peat bogs. The worldwide annual average DMS emission from ASS was estimated to be 1.14 × 10−3 Tg S, which is globally insignificant by comparison to DMS emission from the world's oceans. Image 1 • Dimethyl sulfide is most abundant in the oxidised organic crustal soil layer. • Soil-air surface flux of dimethyl sulfide is restrained by crustal adsorption. • Acid sulfate soils appear to be a globally insignificant source of dimethyl sulfide. [ABSTRACT FROM AUTHOR]

Prescribed burning is a forest management practice that is widely used in Australia to reduce the risk of damaging wildfires. It can affect both carbon (C) and nitrogen (N) cycling in the forest and thereby influence the soil-atmosphere exchange of major greenhouse gases, i.e. carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). To quantify the impact of a prescribed burning (conducted on 27 May 2014) on greenhouse gas exchange and the potential controlling mechanisms, we carried out a series of field measurements before (August 2013) and after (August 2014 and November 2014) the fire. Gas exchange rates were determined at 4 replicate sites which were burned during the combustion and another 4 adjacent unburned sites located in green islands, using a set of static chambers. Surface soil properties including temperature, pH, moisture, soil C and N pools were also determined either by in situ measurement or by analysing surface 10 cm soil samples. All of the chamber measurements indicated a net sink of atmospheric CH4, with mean CH4 uptake ranging from 1.15 to 1.99 mg m-2 day-1. The burning significantly enhanced CH4 uptake as indicated by the significant higher CH4 uptake rates at the burned sites measured in August 2014. While within the next 3 months the CH4 uptake rate was recovered to pre-burning levels. Mean CO2 emission from forest soils ranged from 2721.76 to 7113.49 mg m-2 day-1. The effect of prescribed burning on CO2 emission was limited within the first 3 months, as no significant difference was observed between the burned and the adjacent unburned sites in both August and November 2014. The temporal dynamics of the CO2 emission presented more seasonal variations, rather than burning effects. The N2O emission at the studied sites was quite low, and no significant impact of burning was observed. The changes in understory plants and litter layers, surface soil temperature, C and N substrate availability and microbial activities, resulting from the burning, were the factors that controlled the greenhouse gas exchanges. Our results suggested that the low intensity prescribed burning would decrease soil CO2 emission and increase CH4 uptake, however, this effect would be present within a relative short period. Only slight changes in the surface soil during the combustion and very limited damages in the mineral soils supported the quick recovery of the greenhouse gas exchange rates. [ABSTRACT FROM AUTHOR]

Savanna ecosystems are subject to accelerating land use change as human demand for food and forest products increases. Land use change has been shown to both increase and decrease greenhouse gas fluxes from savannas and considerable uncertainty exists about the non-CO2 fluxes from the soil. We measured methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2) over a complete wet-dry seasonal cycle at three replicated sites of each of three land uses: savanna, young pasture and old pasture (converted from savanna 5-7 and 25-30 yr ago, respectively) in the Douglas Daly region of northern Australia. The effect of break of season rains at the end of the dry season was investigated with two irrigation experiments. Land use change from savanna to pasture increased net greenhouse gas fluxes from the soil. Pasture sites were a weaker sink for CH4 than savanna sites and, under wet conditions, old pastures turned from being sinks to a significant source of CH4. Nitrous oxide emissions were generally very low, in the range of 0 to 5 µg N2O-N m-2 h-1, and under dry conditions soil uptake of N2O was apparent. Break of season rains produced a small, short lived pulse of N2O up to 20 µg N2O-N m-2 h-1, most evident in pasture soil. Annual cumulative soil CO2 fluxes increased after clearing, with savanna (14.6 t CO2-C ha-1 yr-1) having the lowest fluxes compared to old pasture (18.5 t CO2-C ha-1 yr-1) and young pasture (20.0 t CO2-C ha-1 yr-1). Clearing savanna increased soil-based greenhouse gas emissions from 53 to ~70 t CO2-equivalents, a 30% increase dominated by an increase in soil CO2 emissions and shift from soil CH4 sink to source. Seasonal variation was clearly driven by soil water content, supporting the emerging view that soil water content is a more important driver of soil gas fluxes than soil temperature in tropical ecosystems where temperature varies little among seasons. [ABSTRACT FROM AUTHOR]

Abstract: Climatic conditions and cultural practices in the sub-tropical and tropical high-rainfall regions in which sugarcane is grown in Australia are conducive to rapid carbon and nitrogen cycling. Previous research has identified substantial exchanges of methane (CH4) and nitrous oxide (N2O) between sugarcane soils and the atmosphere. However, that research has been mostly short-term. This paper describes recent work aimed at quantifying exchanges of CH4 and N2O from fertilised sugarcane soils over whole growing seasons. Micrometeorological and chamber techniques provided continuous measurements of gas emissions in whole-of-season studies in a burnt-cane crop on an acid sulfate soil (ASS) that was fertilised with 160kg nitrogen (N)ha−1 as urea in the south of the sugarcane belt (Site 1), and in a crop on a more representative trash-blanketed soil fertilised with 150kg urea-Nha−1 in the north (Site 2). Site 1 was a strong source of CH4 with a seasonal emission (over 342 days) of 19.9kg CH4 ha−1. That rate corresponds to 0.5–5% of those expected from rice and wetlands. The many drains in the region appear to be the main source. The net annual emission of CH4 at Site 2 over 292 days was essentially zero, which contradicts predictions that trash-blankets on the soil are net CH4 sinks. Emissions of N2O from the ASS at Site 1 were extraordinarily large and prolonged, totalling 72.1kgN2Oha−1 (45.9kgNha−1) and persisting at substantial rates for 5 months. The high porosity and frequent wetting with consequent high water filled pore space and the high carbon content of the soil appear to be important drivers of N2O production. At Site 2, emissions were much smaller, totalling 7.4kgN2Oha−1 (4.7kgNha−1), most of which was emitted in less than 3 months. The emission factors for N2O (the proportion of fertiliser nitrogen emitted as N2O–N) were 21% at Site 1 and 2.8% at Site 2. Both factors exceed the default national inventory value of 1.25%. Calculations suggest that annual N2O production from Australian sugarcane soils is around 3.8ktN2O, which is about one-half a previous estimate based on short-term measurements, and although ASS constitute only about 4% of Australia''s sugarcane soils, they could contribute about 25% of soil emissions of N2O from sugarcane. The uptake of 50–94tCO2 ha−1 from the atmosphere by the crops at both sites was offset by emissions of CH4 and N2O to the atmosphere amounting to 22tCO2-eha−1 at Site 1 and 2tCO2-eha−1 at Site 2. [Copyright &y& Elsevier]

Abstract: Forests are the largest C sink (vegetation and soil) in the terrestrial biosphere and may additionally provide an important soil methane (CH4) sink, whilst producing little nitrous oxide (N2O) when nutrients are tightly cycled. In this study, we determine the magnitude and spatial variation of soil–atmosphere N2O, CH4 and CO2 exchange in a Eucalyptus delegatensis forest in New South Wales, Australia, and investigate how the magnitude of the fluxes depends on the presence of N2-fixing tree species (Acacia dealbata), the proximity of creeks, and changing environmental conditions. Soil trace gas exchange was measured along replicated transects and in forest plots with and without presence of A. dealbata using static manual chambers and an automated trace gas measurement system for 2 weeks next to an eddy covariance tower measuring net ecosystem CO2 exchange. CH4 was taken up by the forest soil (−51.8μg CH4-Cm−2 h−1) and was significantly correlated with relative saturation (S r) of the soil. The soil within creek lines was a net CH4 source (up to 33.5μg CH4-Cm−2 h−1), whereas the wider forest soil was a CH4 sink regardless of distance from the creek line. Soil N2O emissions were small (<3.3μg N2O-Nm−2 h−1) throughout the 2-week period, despite major rain and snowfall. Soil N2O emissions only correlated with soil and air temperature. The presence of A. dealbata in the understorey had no influence on the magnitude of CH4 uptake, N2O emission or soil N parameters. N2O production increased with increasing soil moisture (up to 50% S r) in laboratory incubations and gross nitrification was negative or negligible as measured through 15N isotope pool dilution. The small N2O emissions are probably due to the limited capacity for nitrification in this late successional forest soil with C:N ratios >20. Soil–atmosphere exchange of CO2 was several orders of magnitude greater (88.8mg CO2-Cm−2 h−1) than CH4 and N2O, and represented 43% of total ecosystem respiration. The forest was a net greenhouse gas sink (126.22kg CO2-equivalents ha−1 d−1) during the 2-week measurement period, of which soil CH4 uptake contributed only 0.3% and N2O emissions offset only 0.3%. [Copyright &y& Elsevier]

Abstract: The aim of the CO2CRC Otway Project (Otway) is to demonstrate that carbon capture and storage (CCS) is a viable option for CO2 mitigation under Australian conditions. The Otway Project is Australia’s first demonstration project and is well underway with injection having started in April 2008 and over 23,000 tonnes of CO2 injected by the end of September. Project activities commenced in late 2004 and being the first, faced significant regulatory and execution challenges. In 2005, the emphasis was on feasibility and project development. Following a rigorous technical and consultative approach, the project regulatory permitting process was defined, the site characterisation and risk assessment started and the field implementation organization defined. In 2006 the project focused on reducing the uncertainties and following Front End Engineering Development (FEED) process as part of seeking approval for major expenses. Several technical challenges were faced and dealt with in finalising the new injection well location and the plant design. The monitoring and verification plan was defined and data acquisition for the pre-injection atmospheric, soil gas and water chemistry characteristics started. In 2007, the project entered the execution phase with the successful drilling of a new injection well. A rich data set of cores and logs was collected enhancing the reservoir model and dynamic simulations. Monitoring activities continued and a 3D surfaceseismic and vertical seismic profile (VSP) acquired concurrently to define the pre injection baseline. Through a complex workover operation, the observation well was equipped with an integrated geophysical and geochemical sensor assembly to facilitate collecting monitoring data during injection. Surface installations, such as the process plant and the pipeline were constructed and the system commissioned in readiness to commence injection. At each stage the project faced several non-technical and technical challenges. In overcoming these, valuable insights have been gained and lessons learnt. These have been incorporated in the proposed Australian legislation on CCS and planning for future projects. To date the project has been positively received by the community. Injection has commenced and supported by a rigorous monitoring and modeling program, is well on its way towards gaining public acceptance for CCS under Australian conditions, through a comprehensive community consultation program and safe and successful operations. [Copyright &y& Elsevier]

Soil moisture and precipitation are important parameters that influence Hg air-surface exchange at background sites, thereby influencing Hg distribution in the environment. Australia is a unique and understudied climatic region. Rainfall across the temperate regions of Australia is highly variable on both annual and inter-annual scales and is overall a relatively dry continent. As such, it is plausible that Australian terrestrial fluxes do not respond to precipitation and soil moisture changes in the same way as observed in the Northern Hemisphere. This study focused on investigating Hg flux in response to precipitation and soil moisture changes at a background site in south-eastern Australia over a 14-month measurement period. The Austral summer experienced the highest rainfall, with a cumulative average of 3.21 mm d−1 and rainfall occurring during 5.95% of the half-hourly measurements during this period. Autumn 2018 had the lowest daily rainfall (1.20 mm d−1). Hg fluxes during rainfall averaged 1.03 ng m−2 h−1 (standard deviation (SD), 20.78), compared to the overall study average of 0.002 ng m−2 h−1 (SD 14.23), signifying influence from the occurrence of rain. Mercury fluxes at this site show substantial spikes that often coincided with the occurrence of rainfall. Mercury released from the substrate during rainfall is primarily due to the interstitial release of Hg as the water infiltrates the soil pore space. Deposition during rainfall also indicated rapid recycling of Hg between the soil and air. There was little evidence of enhanced Hg fluxes occurring caused by increased soil volumetric water content. Lack of enhancement suggests that Hg stores within the substrate are depleted during the initial release. • Investigated Hg flux in response to precipitation at a background site in Australia. • Hg fluxes during rainfall were higher than the overall study average. • Hg fluxes showed spikes during rainfall due to interstitial release from the substrate. • Little evidence of enhanced Hg fluxes occurring because of increased soil moisture. • Lack of enhancement suggests Hg within the substrate is depleted during initial spike. [ABSTRACT FROM AUTHOR]

Australian ecosystems, particularly wetlands, are facing new and extreme threats due to climate change, land use, and other human interventions. However, more fundamental knowledge is required to understand how nutrient turnover in wetlands is affected. In this study, we deployed a mechanistic biogeochemical model of carbon (C), nitrogen (N), and sulfur (S) cycles at 0.25 ∘ × 0.25 ∘ spatial resolution across wetlands in Australia. Our modeling was used to assess nutrient inputs to soil, elemental nutrient fluxes across the soil organic and mineral pools, and greenhouse gas (GHG) emissions in different climatic areas. In the decade 2008–2017, we estimated an average annual emission of 5.12 Tg-CH 4 , 90.89 Tg-CO 2 , and 2.34 × 10 − 2 Tg-N 2 O. Temperate wetlands in Australia have three times more N 2 O emissions than tropical wetlands as a result of fertilization, despite similar total area extension. Tasmania wetlands have the highest areal GHG emission rates. C fluxes in soil depend strongly on hydroclimatic factors; they are mainly controlled by anaerobic respiration in temperate and tropical regions and by aerobic respiration in arid regions. In contrast, N and S fluxes are mostly governed by plant uptake regardless of the region and season. The new knowledge from this study may help design conservation and adaptation plans to climate change and better protect the Australian wetland ecosystem. [ABSTRACT FROM AUTHOR]

• Commercial gas sensors were tested over two years at a geological CO 2 storage site. • A technical and economic assessment of sensor technology for CCS sites is presented. • Sensors were tested for achieving process-based soil-gas CO2 leakage attribution. • Sensors were inadequate for real-time environmental monitoring of surface anomalies. • We recommend development of Enhanced Raman Gas Sensing (ERGS) for CO2, N2, and O2. A process-based approach to soil gas monitoring at geologic CO 2 storage sites is an accurate, simple, and cost-effective alternative to other "concentration-based" soil gas methods which require complicated long-term baseline data collection and analysis. The current limitation to implementing a process-based method on an industrial scale (e.g. gigatons of storage) is a lack of technology for economical field-deployable smart data collection of all required gas concentrations (CO 2 , CH 4 , O 2, N 2). To address this gap, the Carbon Transport and Storage Corporation Pty Ltd (CTSCo) deployed commercially-available automated sensors at their proposed future Glenhaven CO 2 storage site, located 21 km SW of the town of Wandoan, Queensland, Australia. The goal was to assess the suitability of currently-available sensors for implementing a process-based monitoring approach with the aim of providing real-time answers on source attribution of surface anomalies that could represent CO 2 migration to surface. Here we report the results of a first-ever long-term (2 years) test of commercially available sensors for the purpose of process-based soil gas environmental monitoring. The accuracy and precision of data collected with an array of sensors for measuring CO 2 , CH 4 , and O 2 , with additional sensors for measuring temperature, relative humidity, and pressure were compared against the current method using gas chromatography. The results indicate that currently-available sensors are not adequate for attaining the long-term monitoring goals set forth by a process-based monitoring approach and additional technology development is recommended. [ABSTRACT FROM AUTHOR]

Source-pathway-receptor analyses involving solute migration pathways through soil and shallow groundwater are typically undertaken to assess how people and the environment could come into contact with chemicals associated with coal seam gas operations. For the potential short-term and long-term release of coal seam gas fluids from storage ponds, solute concentration and dilution factors have been calculated using a water flow and solute transport modelling framework for an unsaturated zone-shallow groundwater system. Uncertainty about dilution factors was quantified for a range of system parameters: (i) leakage rates from storage ponds combined with recharge rates, (ii) a broad combination of soil and groundwater properties, and (iii) a series of increasing travel distances through soil and groundwater. Calculated dilution factors in the soil increased from sand to loam soil and increased with an increasing recharge rate, while dilution decreased for a decreasing leak rate and leak duration. In groundwater, dilution factors increase with increasing aquifer hydraulic conductivity and riverbed conductance. For a hypothetical leak duration of three years, the combined soil and groundwater dilution factors are larger than 6980 for more than 99.97% of bores that are likely to be farther than 100 m from the source. Dilution factors were more sensitive to uncertainty in leak rates than recharge rates. Based on this dilution factor, a comparison of groundwater predicted environmental concentrations and predicted no-effect concentrations for a subset of hydraulic fracturing chemicals used in Australia revealed that for all but two of the evaluated chemicals the estimated groundwater concentration (for a hypothetical water bore at 100 m from the solute source) is smaller than the no-effect concentration for the protection of aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Heatwaves are common in many viticultural regions of Australia. We evaluated the potential of satellite-based remote sensing to detect the effects of high temperatures on grapevines in a South Australian vineyard over the 2016–2017 and 2017–2018 seasons. The study involved: (i) comparing the normalized difference vegetation index (NDVI) from medium- and high-resolution satellite images; (ii) determining correlations between environmental conditions and vegetation indices (Vis); and (iii) identifying VIs that best indicate heatwave effects. Pearson's correlation and Bland–Altman testing showed a significant agreement between the NDVI of high- and medium-resolution imagery (R = 0.74, estimated difference −0.093). The band and the VI most sensitive to changes in environmental conditions were 705 nm and enhanced vegetation index (EVI), both of which correlated with relative humidity (R = 0.65 and R = 0.62, respectively). Conversely, SWIR (short wave infrared, 1610 nm) exhibited a negative correlation with growing degree days (R = −0.64). The analysis of heat stress showed that green and red edge bands—the chlorophyll absorption ratio index (CARI) and transformed chlorophyll absorption ratio index (TCARI)—were negatively correlated with thermal environmental parameters such as air and soil temperature and growing degree days (GDDs). The red and red edge bands—the soil-adjusted vegetation index (SAVI) and CARI2—were correlated with relative humidity. To the best of our knowledge, this is the first study demonstrating the effectiveness of using medium-resolution imagery for the detection of heat stress on grapevines in irrigated vineyards. [ABSTRACT FROM AUTHOR]