Assessing connectivity between an overlying aquifer and a coal seam gas resource using methane isotopes, dissolved organic carbon and tritium

Coal seam gas (CSG) production can have an impact on groundwater quality and quantity in adjacent or overlying aquifers. To assess this impact we need to determine the background groundwater chemistry and to map geological pathways of hydraulic connectivity between aquifers. In south-east Queensland (Qld), Australia, a globally important CSG exploration and production province, we mapped hydraulic connectivity between the Walloon Coal Measures (WCM, the target formation for gas production) and the overlying Condamine River Alluvial Aquifer (CRAA), using groundwater methane (CH4) concentration and isotopic composition (δ13C-CH4), groundwater tritium (3H) and dissolved organic carbon (DOC) concentration. A continuous mobile CH4 survey adjacent to CSG developments was used to determine the source signature of CH4 derived from the WCM. Trends in groundwater δ13C-CH4 versus CH4 concentration, in association with DOC concentration and 3H analysis, identify locations where CH4 in the groundwater of the CRAA most likely originates from the WCM. The methodology is widely applicable in unconventional gas development regions worldwide for providing an early indicator of geological pathways of hydraulic connectivity

Soil and aquifer salinization: toward an integrated approach for salinity management of groundwater

Degradation of the quality of groundwater due to salinization processes is one of the key issues limiting the global dependence on groundwater in aquifers. As the salinization of shallow aquifers is closely related to root-zone salinization, the two must be considered together. This chapter initially describes the physical and chemical processes causing salinization of the root-zone and shallow aquifers, highlighting the dynamics of these processes and how they can be influenced by irrigation and drainage practices, thus illustrating the connectivity between soil and groundwater salinization. The processes leading to aquifer salinization in both inland and coastal areas are discussed. The roles of extractive resource industries, such as mining and coal bed methane operations, in causing aquifer salinization are also outlined. Hydrogeochemical changes occurring during salinization of aquifers are examined with the aid of Piper and Mixing Diagrams. The chapter then illustrates the extent of the problem of groundwater salinization as influenced by management and policy using two case studies. The first is representative of a developing country and explores management of salt-affected soils in the Indus Valley, Pakistan, while the second looks at a developed country, and illustrates how through monitoring we can deducecauses of shallow aquifer salinity in the Namoi Catchment of NSW, Australia. Finally, there is a section on integration and conclusions where we illustrate how management to mitigate salinization needs to be integrated with policy to diminish the threat to productivity that occurs with groundwater degradation

Quantitative-spatial assessment of soil contamination in S. Francisco de Assis due to mining activity of the Panasqueira mine (Portugal)

Through the years, mining and beneficiation processes produces large amounts of As-rich mine wastes laid up in huge tailings and open-air impoundments (Barroca Grande and Rio tailings) that are the main source of pollution in the surrounding area once they are exposed to the weathering conditions leading to the formation of AMD and consequently to the contamination of the surrounding environments, in particularly soils. In order to investigate the environmental contamination impact on S. Francisco de Assis (village located between the two major impoundments and tailings) agricultural soils, a geochemical survey was undertaken to assess toxic metals associations, related levels and their spatial distribution, and to identify the possible contamination sources. According to the calculated contamination factor, As and Zn have a very high contamination factor giving rise to 65.4 % of samples with a moderate to high pollution degree; 34.6 % have been classified as nil to very low pollution degree. The contamination factor spatial distribution put in evidence the fact that As, Cd, Cu, Pb, and Zn soils contents, downstream Barroca Grande tailing, are increased when compared with the local Bk soils. The mechanical dispersion, due to erosion, is the main contamination source. The chemical extraction demonstrates that the trace metals distribution and accumulation in S. Francisco de Assis soils is related to sulfides, but also to amorphous or poorly crystalline iron oxide phases. The partitioning study allowed understanding the local chemical elements mobility and precipitation processes, giving rise to the contamination dispersion model of the study area. The wind and hydrological factors are responsible for the chemical elements transport mechanisms, the water being the main transporter medium and soils as one of the possible retention media

Benefits for Dominant Red Deer Hinds under a Competitive Feeding System: Food Access Behavior, Diet and Nutrient Selection

Social dominance is widely known to facilitate access to food resources in many animal species such as deer. However, research has paid little attention to dominance in ad libitum access to food because it was thought not to result in any benefit for dominant individuals. In this study we assessed if, even under ad libitum conditions, social rank may allow dominant hinds to consume the preferred components of food. Forty-four red deer hinds (Cervus elaphus) were allowed to consume ad libitum meal consisting of pellets of sunflower, lucerne and orange, and seeds of cereals, corn, cotton, and carob tree. The meal was placed only in one feeder, which reduced accessibility to a few individuals simultaneously. During seven days, feeding behavior (order of access, time to first feeding bout, total time spent feeding, and time per feeding bout) were assessed during the first hour. The relative abundance of each meal component was assessed at times 0, 1 and 5 h, as well as its nutritional composition. Social rank was positively related to the amount of time spent feeding during the 1st h (P = 0.048). Selection indices were positively correlated with energy (P = 0.018 during the 1st h and P = 0.047 from 1st to 5th) and fat (only during the 1st h; P = 0.036), but also negatively with certain minerals. Thus, dominant hinds could select high energy meal components for longer time under an ad libitum but restricted food access setting. Selection indices showed a higher selectivity when food availability was higher (1st hour respect to 1st to 5th). Finally, high and low ranking hinds had longer time per feeding bout than mid ones (P = 0.011), suggesting complex behavioral feeding tactics of low ranking social ungulates

Characterisation of CH₄ Source Signatures in Melbourne, Australia

Melbourne was founded in 1835 and has grown to become Australia’s second most populous city with a populationof almost 5 million people [ABS, 2019]. As Melbourne’s population has expanded, land use and infrastructure haschanged many times and this has resulted in a variety of potential methane (CH4) sources, such as legacy and newlandfills, leaks from the gas distribution and sewage networks, and houses with a range of heating systems includinggas and wood fires. There are also large wetland areas and coastal ecosystems. Few of these potential sources ofCH4 have been well characterised. Here we present the results of 500 km of mobile methane surveying throughoutthe south-eastern suburbs of Melbourne, during day and night time, that mapped the location of major CH4 sourcesin July 2019. Where major plumes could be attributed to a source based on proximity or smell (for example adomestic distribution gas leak or wood burning fire) the δ13C_CH4 (isotopic signature) of that source wascharacterised.The methane mole fraction ([CH4]) was measured using a Los Gatos Research (LGR) greenhouse gas analyserthat was placed within the car. The air intake was mounted on the roof of the car approximately 2.5 m above theground, and the air was drawn into the analyser via a Teflon tube. The CH4 data were geopositioned using aHemisphere (model A21) GPS unit and all the results were converted to kml files for displaying in Google Earth. Foreach major plume 10 air samples were collected in SKC FlexFoil bags and later analysed for [CH4], δ13C_CH4, [CO2]and δ13C_CO2 using a Picarro G2201-i cavity ring-down spectrometer (CRDS) at the UNSW Sydney greenhouse gaslaboratory. To determine the plume CH4 source signature the ten sample {[CH4], δ13C_CH4} sets were then analysedusing Bayesian regression in Miller-Tans plot [Miller and Tans, 2003].The measured mole fractions of methane ([CH4]) ranged from 1.83 ppm to 147 ppm (associated with gas leak ina residential area). Our preliminary results indicate that there is a need to further investigate the differencebetween bottom-up inventory emissions estimates and top-down measurements from surveys like this one.Our research demonstrates that mobile surveys are a highly efficient way to identify and characterise unknownCH4 sources in cities. Our future work aims to combine the insights from the mobile methane survey results withthe permanent in situ methane mole fraction record and yearlong isotopic methane observations recorded at CSIROOceans and Atmosphere, Aspendale, to quantify the rate and duration of emissions from various sources, and todetermine which sources should be prioritised for mitigation actions

Biogeochemical constraints on the origin of methane in an alluvial aquifer: Evidence for the upward migration of methane from underlying coal measures

Geochemical and microbiological indicators of methane (CH4) production, oxidation and migration processes in groundwater are important to understand when attributing sources of gas. The processes controlling the natural occurrence of CH4in groundwater must be understood, especially when considering the potential impacts of the global expansion of coal seam gas (CSG) production on groundwater quality and quantity. We use geochemical and microbiological data, along with measurements of CH4isotopic composition (δ13C-CH4), to determine the processes acting upon CH4in a freshwater alluvial aquifer that directly overlies coal measures targeted for CSG production in Australia. Measurements of CH4indicate that there is biogenic CH4in the aquifer; however, microbial data indicate that there are no methanogenic archaea in the groundwater. In addition, geochemical data, particularly the isotopes of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC), as well as the concentration of SO42-, indicate limited potential for methanogenesis in situ. Microbial community analysis also shows that aerobic oxidation of CH4occurs in the alluvial aquifer. The combination of microbiological and geochemical indicators suggests that the most likely source of CH4, where it was present in the freshwater aquifer, is the upward migration of CH4from the underlying coal measures

Irrigation bore water in the Condamine Catchment: baselining groundwater quality and assessing pathways of hydraulic connectivity

The expansion of coal seam gas production adjacent to the irrigation farming districts in the Condamine Catchment has raised concerns about the impact of gas production on groundwater in adjoining aquifer systems. To assess the risk, and to be able to detect any future changes in groundwater properties, existing groundwater chemistry data sets need to be updated and expanded. Historically, the testing of groundwater chemistry in the Condamine Catchment has focused on the Queensland Government groundwater-monitoring network, but it is unlikely that these samples come from the same sand and gravel bodies from which the irrigation bores extract groundwater. We report the result of 20 groundwater samples collected from bores that supply irrigation water for cotton and other crops. These samples were collected in January 2014 at the end of the pumping season, when the aquifer system is at peak stress for the year. We compare the major ion chemistry recorded in the irrigation bores to that measured at selected sites from the QLD government groundwater-monitoring network and with historical results reported in the literature. A hydrochemical facies analysis of these data provides one assessment of the likelihood of hydraulic connectivity between the Walloon Coal Measures, other bordering Great Artesian Basin formations and the valley filling sediments of the Condamine Alluvium. The results highlight variation in groundwater chemistry within the Condamine Alluvium, particularly in the Cecil Plains and Dalby regions, where there are signs of water mixing. As a result, further research into the area to explain the baseline data sets would provide a better understanding of hydraulic connectivity and the potential effects of CSG on the groundwater