Assessment of Geogenic Contaminants in Water Co-Produced with Coal Seam Gas Extraction in Queensland, Australia: Implications for Human Health Risk

Fluorescence Characteristics of Coalbed Methane Produced Water and Its Influence on Freshwater Bacteria in the South Qinshui Basin, China

Production of coalbed methane (CBM) resources commonly requires using hydraulic fracturing and chemical production well additives. Concern exists for the existence of chemical compounds in CBM produced water, due to the risk of environmental receptor contamination. In this study, parallel factor method analysis (PARAFAC), fluorescence index, and the fluorescence area integral methods were used to analyse the properties of CBM produced water sampled from Shizhuang Block (one of the most active CBM-producing regions in the Qinshui Basin). A culture experiment was designed to determine the effect of discharged CBM produced water on microorganisms in freshwater. Water quality analysis shows the hydrochemistry of most water samples as Na-HCO₃ type produced water of CBM appears as a generally weak alkaline (pH 8.69 ± 0.185) with high salinity, high alkalinity, and a high chemical oxygen demand (COD) value. Three individual components were identified by using parallel factor method analysis as humic-like components (C1), fulvic-like components (C2), and amino acid-like substances (C3). The fluorescence characteristic index comprehensively explains that the fluorescent substances in CBM produced water has the characteristics of a low degree of humification and a high recent self-generating source. The region integration results of characteristic peaks show that tyrosine-like and tryptophan-like materials account for more than 67% of fluorescent substances in CBM produced water. The addition of produced water from coalbed methane promotes the growth of freshwater bacteria, and this process is accompanied by the decrease of the proportion of fulvic acid, humic acid, and the increase of the proportion of soluble microbial metabolites. This paper proposes a convenient method for organic matter identification of CBM produced water and provides some theoretical support and reference for the improvement of CBM water treatment and utilization.

Changes Induced by Self-Burning in Technosols from a Coal Mine Waste Pile: A Hydropedological Approach

Coal mining originates environmental impacts on soil and water bodies, including the leaching of Potentially Toxic Elements (PTEs) and Polycyclic Aromatic Hydrocarbons (PAHs) in mine waste piles. This research aims to identify and characterize changes induced by self-burning in Technosols from a coal mine waste pile by means of a comprehensive hydropedological assessment encompassing geochemical, mineralogical, and hydrological data, bearing in mind the potential leaching of PTEs and PAHs. The soil profile from two contiguous areas (an area with normal pedological evolution vs. an area affected by self-burning) was characterized in terms of morphological features. Each soil horizon was sampled and analyzed for geochemical and mineralogical characterization. The unsaturated hydraulic conductivity (Ki) was also measured in all soil horizons. Finally, the leaching potential of PTEs and PAHs in water was evaluated. Several changes induced by self-burning were identified in the studied Technosols: development of specific soil horizons; destruction of humified organic matter; contrasting geochemical composition, especially in the deeper horizons; mineralogical modifications, pointing to clay minerals with higher ion exchange capacity and higher specific surface by sulphates of lower structural order; diverse Ki values in the intermediate and lower part of the soil profile; and specific susceptibility to leaching of PTEs and PAHs. The research demonstrated that self-burning causes severe changes of hydropedological relevance, with influence on the leaching of PTEs and PAHs.

A Generic Method for Predicting Environmental Concentrations of Hydraulic Fracturing Chemicals in Soil and Shallow Groundwater

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.

Is Increasing Coal Seam Gas Well Development Activity Associated with Increasing Hospitalisation Rates in Queensland, Australia? An Exploratory Analysis 1995-2011

The majority of Australia's coal seam gas (CSG) reserves are in Queensland, where the industry has expanded rapidly in recent years. Despite concerns, health data have not been examined alongside CSG development. This study examined hospitalisation rates as a function of CSG development activity in Queensland, during the period 1995-2011. Admissions data were examined with CSG well numbers, which served as a proxy for CSG development activity. Time series models were used to assess changes in hospitalisation rates for periods of "low", "medium", "high", and "intense" activity compared to a period of "very low" activity, adjusting for covariates. "All-cause" hospitalisation rates increased monotonically with increasing gas well development activity in females (324.0 to 390.3 per 1000 persons) and males (294.2 to 335.4 per 1000 persons). Hospitalisation rates for "Blood/immune" conditions generally increased for both sexes. Female and male hospitalisation rates for "Circulatory" conditions decreased with increasing CSG activity. Hospitalisation rates were generally low for reproductive and birth outcomes; no clear associations were observed. This study showed some outcomes were associated with increasing CSG development activity. However, as a condition of data access, the population and outcomes were aggregated to a broad geographic study area rather than using higher geographic resolution data. Higher resolution data, as well as other data sources, should be explored. Further research should be conducted with an expanded time period to determine if these trends continue as the industry grows.

Managing produced water from coal seam gas projects: implications for an emerging industry in Australia

This paper reviews the environmental problems, impacts and risks associated with the generation and disposal of produced water by the emerging coal seam gas (CSG) industry and how it may be relevant to Australia and similar physical settings. With only limited independent research on the potential environmental impacts of produced water, is it necessary for industry and government policy makers and regulators to draw upon the experiences of related endeavours such as mining and groundwater extraction accepting that the conclusions may not always be directly transferrable. CSG is widely touted in Australia as having the potential to provide significant economic and energy security benefits, yet the environmental and health policies and the planning and regulatory setting are yet to mature and are continuing to evolve amidst ongoing social and environmental concerns and political indecision. In this review, produced water has been defined as water that is brought to the land surface during the process of recovering methane gas from coal seams and includes water sourced from CSG wells as well as flowback water associated with drilling, hydraulic fracturing and gas extraction. A brief overview of produced water generation, its characteristics and environmental issues is provided. A review of past lessons and identification of potential risks, including disposal options, is included to assist in planning and management of this industry.