Detecting Infiltration and Impacts of Introduced Water Using Strontium Isotopes

Abstract

Water introduced to surface drainages, such as agricultural and roadway runoff, mine drainage, or coalbed natural gas (CBNG)-produced water, potentially can be of environmental concern. In order to mitigate potential environmental effects, it may be important to be able to trace water discharged to the surface as it infiltrates and interacts with near-surface aquifers. We have chosen to study water withdrawn during CBNG production for isotope tracing in the hyporheic zone because it poses a variety of economic, environmental, and policy issues in the Rocky Mountain states. Ground water quality must be protected as CBNG water is added to semiarid ecosystems. Strontium (Sr) isotopes are effective fingerprints of the aquifer from which water originates. In this study, CBNG water was found to have a higher (87)Sr/(86)Sr ratio than the local alluvial aquifer water. This measurable difference allows the strontium isotope ratio and concentration to be used as tracers of CBNG water following its discharge to the surface. The dissolution and mobilization of salts from soil are an important contributor to ground water quality degradation. In the Powder River basin of Wyoming, the soils are calcium carbonate-buffered systems. The chemical similarity of strontium to calcium allows it to substitute into calcium minerals and enabled us to use strontium isotopes to identify calcium salts mobilized from the soil. Strontium isotopes are an effective monitor of the source of ions and the volume and direction of introduced water flow in the hyporheic zone.

Rapid expansion of natural gas development poses a threat to surface waters

“…The distinct elemental composition and isotopic signatures of produced water provide unique opportunities for tracer studies that could indicate aquatic system exposure. Stable isotopes of strontium and carbon have been used to trace water from coalbed natural gas production wells to surface waters and hyporheic zones (Brinck and Frost 2007). Osborn et al .…”

Application of a Bayesian model to infer the contribution of coalbed natural gas produced water to the Powder River, Wyoming and Montana

“…The second is used to estimate the CBNG end-member values based on measurements made along Beaver Creek, a tributary of the Powder River that is known to contain large amounts of CBNG produced water (Wyoming Department of Environmental Quality (WDEQ), 2006,2008). Beaver Creek water is known to represent CBNG produced water because the Sr and C isotopic composition of Beaver Creek water is within the range of 87 Sr/ 86 Sr ratios and d 13 C DIC of CBNG-produced water collected directly from wellheads (Frost et al, 2002;Brinck and Frost, 2007;Sharma and Frost, 2008). The third incorporates a four end-member mixing model to determine the contributions of the four different sources (i.e.…”

“…Because of the paucity of gauging stations on the Powder River (five stations; Clark et al ., ), uncertainties in water volumes carried by tributaries, and conveyance loss in holding ponds and infiltration, simple volumetric calculations to determine the proportion of CBNG produced water are not possible. The few studies that have been conducted to evaluate how much infiltration and conveyance loss occurs from the impoundments and ponds that hold CBNG produced water have shown that these quantities are very difficult to estimate, in part because they are temporally (seasonally) dynamic (Brink and Frost, ; Payne and Saffer, ; Wheaton and Brown, ). Two studies, however, examined historical water quality data from the Powder River to determine whether there were changes that may be attributed to development of CBNG activity in the PRB.…”

Use of radiometric (234/238U and 228/226Ra) and mass spectrometry (87/86Sr) methods for studies of the stability of groundwater reservoirs in Central Poland

“…Originally the strontium isotope ratio was used only in geological and archeological sciences [7, 8], but recently it has also been used in hydrology and studies of subsurface water behavior [9, 10]. The study of Voerkelius et al [11] shows the change in the 87 Sr/ 86 Sr isotopic ratio in natural mineral water extracted in Europe.…”