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31.
Trace Element Behavior in Methane‐Rich and Methane‐Free Groundwater in North and East Texas
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Roxana Darvari Jean‐Philippe Nicot Bridget R. Scanlon Patrick Mickler Kristine Uhlman 《Ground water》2018,56(5):705-718
There is concern about adverse impacts of natural gas (primarily methane) production on groundwater quality; however, data on trace element concentrations are limited. The objective of this study was to compare the distribution of trace elements in groundwater samples with and without dissolved methane in aquifers overlying the Barnett Shale (Hood and Parker counties, 207 samples) and the Haynesville Shale (Panola County, 42 samples). Both shales have been subjected to intensive hydraulic fracturing for gas production. Well clusters with high dissolved methane were previously found in these counties and are thought to be of natural origin. Overall, groundwater in these counties is of excellent quality with typically low elemental concentrations. Several statistical analyses strongly suggest that most trace element concentrations, generally at low background levels, are no higher and even reduced when dissolved methane is present. In addition, trace element concentrations are not correlated with distance to gas wells. The reduction in trace element concentrations is attributed to anaerobic microbial degradation of methane, is associated with a higher pH (>8.5), and, likely, with precipitation of carbonates and pyrite and formation of clays. Trace and other elements are likely incorporated within the precipitating mineral crystalline network or sorbed. High pH values are found throughout these high‐methane clusters (e.g., Parker‐Hood cluster), even in subregions where methane is not present, which is consistent with a pervasive natural origin of dissolved methane rather than a limited gas well source. 相似文献
32.
Kathryn M. Scanlon 《Geo-Marine Letters》1984,4(1):1-4
The first continuous overview of a large segment of the continental slope and rise off the northeastern United States has been obtained using the GLORIA II long-range sidescan-sonar system. Extensive dissection by canyon and gully systems and evidence of possible large-scale sediment sliding are seen on the slope. The style and degree of incision, as well as the numbers and locations of canyons, have been found to differ significantly from previously published maps. It is suggested that the slope is a significant source of the sediment that has been deposited on the rise, and that some abrupt changes in the courses of canyons may be the result of local structural control. 相似文献
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Lead distribution on a public shotgun range 总被引:1,自引:0,他引:1
James R. Craig David Edwards Donald J. Rimstidt Patrick F. Scanlon Thomas K. Collins Oliver Schabenberger Jeffrey B. Birch 《Environmental Geology》2002,41(8):873-882
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Yun Huang Bridget R. Scanlon Jean-Philippe Nicot Robert C. Reedy Alan R. Dutton Van A. Kelley Neil E. Deeds 《Hydrogeology Journal》2012,20(4):783-796
Understanding groundwater-pumpage sources is essential for assessing impacts on water resources and sustainability. The objective of this study was to quantify pumping impacts and sources in dipping, unconfined/confined aquifers in the Gulf Coast (USA) using the Texas Carrizo-Wilcox aquifer. Potentiometric-surface and streamflow data and groundwater modeling were used to evaluate sources and impacts of pumpage. Estimated groundwater storage is much greater in the confined aquifer (2,200?km3) than in the unconfined aquifer (170?km3); however, feasibility of abstraction depends on pumpage impacts on the flow system. Simulated pre-development recharge (0.96?km3/yr) discharged through evapotranspiration (ET, ~37%), baseflow to streams (~57%), and to the confined aquifer (~6%). Transient simulations (1980–1999) show that pumpage changed three out of ten streams from gaining to losing in the semiarid south and reversed regional vertical flow gradients in ~40% of the entire aquifer area. Simulations of predictive pumpage to 2050 indicate continued storage depletion (41% from storage, 32% from local discharge, and 25% from regional discharge capture). It takes ~100?yrs to recover 40% of storage after pumpage ceases in the south. This study underscores the importance of considering capture mechanism and long-term system response in developing water-management strategies. 相似文献