12A pilot study has produced 31 groundwater samples from a coal seam gas (CSG) 13 exploration well located in Maramarua, New Zealand. This paper describes sources of CSG water 14 chemistry variations, and makes sampling and analytical recommendations to minimize these 15 variations. The hydrochemical character of these samples is studied using factor analysis, 16 geochemical modelling, and a sparging experiment. Factor analysis unveils carbon dioxide (CO 2 ) 17 degassing as the principal cause of sample variation (about 33%). Geochemical modelling 18 corroborates these results and identifies minor precipitation of carbonate minerals with degassing. 19The sparging experiment confirms the effect of CO 2 degassing by showing a steady rise in pH while 20 maintaining constant alkalinity. Factor analysis correlates variations in the major ion composition 21 (about 17%) to changes in the pumping regime and to aquifer chemistry variations due to cation 22 exchange reactions with argillaceous minerals. An effective CSG water sampling program can be put 23 into practice by measuring pH at the well head and alkalinity at the laboratory; these data can later 24 be used to calculate the carbonate speciation at the time the sample was collected. In addition, TDS 25 variations can be reduced considerably if a correct drying temperature of 180°C is consistently 26 implemented. 27 2

The extraction of coal seam gas (CSG) produces large volumes of potentially contaminated water. It has raised concerns about the environmental health impacts of the co-produced CSG water. In this paper, we review CSG water contaminants and their potential health effects in the context of exposure pathways in Queensland's CSG basins. The hazardous substances associated with CSG water in Queensland include fluoride, boron, lead and benzene. The exposure pathways for CSG water are (1) water used for municipal purposes; (2) recreational water activities in rivers; (3) occupational exposures; (4) water extracted from contaminated aquifers; and (5) indirect exposure through the food chain. We recommend mapping of exposure pathways into communities in CSG regions to determine the potentially exposed populations in Queensland. Future efforts to monitor chemicals of concern and consolidate them into a central database will build the necessary capability to undertake a much needed environmental health impact assessment.

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Environmental context Water associated with coal seam gas is generally of poor quality and thus its management and potential further usage is a subject of concern. In a comprehensive study involving chemical and bioanalytical assessments of coal seam gas associated water, we found that less than 5% of the biological effects could be explained by chemical analysis. The use of bioanalytical tools to complement chemical analysis is recommended for monitoring the quality of water associated with coal seam gas. Abstract A comprehensive study was undertaken involving chemical (inorganic and organic) and bioanalytical assessments of coal seam gas associated water (CSGW) in Queensland, Australia. CSGW is a by-product of the gas extraction process and is generally considered as water of poor quality. CSGW is disposed of by release to surface water, reinjected to groundwater or beneficially reused. In this study, groundwater samples were collected from private wells tapping into the Walloon Coal Measures, the same coal aquifer exploited for coal seam gas production in the Surat Basin. The inorganic characteristics of these water samples were almost identical to the CSGW from the nearby gas field, with high sodium, bicarbonate and chloride concentrations but low calcium, magnesium and negligible sulfate concentrations. As for organic compounds, low levels of polyaromatic hydrocarbons (PAHs) were detected in the water samples, and neither phenols nor volatile organic compounds were found. Five of the fourteen bioassays tested gave positive responses (arylhydrocarbon-receptor gene activation, estrogenic endocrine activity, oxidative stress response, interference with cytokine production and non-specific toxicity), whereas the other nine assays showed no genotoxicity, protein damage or activation of hormone receptors other than the estrogen receptor. The observed effects were benchmarked against known water sources and were similar to secondary treated wastewater effluent, stormwater and surface water. As mixture toxicity modelling demonstrated, the detected PAHs explained less than 5% of the observed biological effects. These results showed that bioanalytical assessment can open new avenues for research into the potential environmental and health risk from CSGW.