Thomas F. Kraemer

Intragranular Diffusion: An Important Mechanism Influencing Solute Transport in Clastic Aquifers?

Quantification of intragranular porosity in sand-size material from an aquifer on Cape Cod, Massachusetts, by scanning electron microscopy, mercury injection, and epifluorescence techniques shows that there are more reaction sites and that porosity is greater than indicated by standard short-term laboratory tests and measurement techniques. Results from laboratory and field tracer tests show solute nonequilibrium for a reacting ion consistent with a model of diffusion into, and exchange within, grain interiors. These data indicate that a diffusion expression needs to be included in transport codes, particularly for simulation of the transport of radioactive and toxic wastes.

The occurrence and behavior of radium in saline formation water of the U.S. Gulf Coast region

Abstract Radium has been measured in deep saline formation waters produced from a variety of U.S. Gulf Coast subsurface environments, including oil reservoirs, gas reservoirs and water-producing geopressured aquifers. A strong positive correlation has been found between formation-water salinity and Ra activity, resulting from the interaction of formation water with aquifer matrix. Ra isotopes enter the fluid phase after being produced by the decay of parent elements U and Th, which are located at sites on and within the solid matrix. Processes that are belived to be primarily responsible for transferring Ra from matrix to formation water are chemical leaching and alpha-particle recoil. Factors controlling the observed salinity—Ra relationship may be one or a combination of the following factors: (a) ion exchange; (b) increased solubility of matrix silica surrounding Ra atoms, coupled with a salinity-controlled rate of reequilibration of silica between solution and quartz grains; and (c) the equilibration of Ra in solution with detrial barite within the aquifer. No difference was found in the brine-Ra relation in water produced from oil or gas wells and water produced from wells penetrating only water-bearing aquifers, although the relation was more highly correlated for water-bearing aquifers than hydrocarbon-containing reservoirs.

Geochemical and isotopic evolution of water produced from Middle Devonian Marcellus shale gas wells, Appalachian basin, Pennsylvania

The number of Marcellus Shale gas wells drilled in the Appalachian basin has increased rapidly over the past decade, leading to increased interest in the highly saline water produced with the natural gas which must be recycled, treated, or injected into deep disposal wells. New geochemical and isotopic analyses of produced water for 3 time-series and 13 grab samples from Marcellus Shale gas wells in southwest and north central Pennsylvania (PA) are used to address the origin of the water and solutes produced over the long term (>12 months). The question of whether the produced water originated within the Marcellus Shale, or whether it may have been drawn from adjacent reservoirs via fractures is addressed using measurements of and activity. These parameters indicate that the water originated in the Marcellus Shale, and can be more broadly used to trace water of Marcellus Shale origin. During the first 1–2 weeks of production, rapid increases in salinity and positive shifts in values were observed in the produced water, followed by more gradual changes until a compositional plateau was reached within approximately 1 yr. The values and relationships between Na, Cl, and Br provide evidence that the water produced after compositional stabilization is natural formation water, the salinity for which originated primarily from evaporatively concentrated paleoseawater. The rapid transition from injected water to chemically and isotopically distinct water while of the injected water volume had been recovered, supports the hypothesis that significant volumes of injected water were removed from circulation by imbibition.

Use of isotopic data to estimate water residence times of the Finger Lakes, New York

Abstract Water retention times in the Finger Lakes, a group of 11 lakes in central New York with similar hydrologic and climatic characteristics, were estimated by use of a tritium-balance model. During July 1991, samples were collected from the 11 lakes and selected tributary streams and were analyzed for tritium, deuterium, and oxygen-18. Additional samples from some of the sites were collected in 1990, 1992 and 1993. Tritium concentration in lake water ranged from 24.6 Tritium Units (TU) (Otisco Lake) to 43.2 TU (Seneca Lake).The parameters in the model used to obtain water retention time (WRT) included relative humidity, evaporation rate, tritium concentrations of inflowing water and lake water, and WRT of the lake. A historical record of tritium concentrations in precipitation and runoff was obtained from rainfall data at Ottawa, Canada, analyses of local wines produced during 1977–1991, and streamflow samples collected in 1990–1991. The model was simulated in yearly steps for 1953–1991, and the WRT was varied to reproduce tritium concentrations measured in each lake in 1991. Water retention times obtained from model simulations ranged from 1 year for Otisco Lake to 12 years for Seneca Lake, and with the exception of Seneca Lake and Skaneateles Lake, were in agreement with earlier estimates obtained from runoff estimates and chloride balances. The sensitivity of the model to parameter changes was tested to determine possible reasons for the differences calculated for WRTs for Seneca Lake and Skaneateles Lake. The shorter WRT obtained from tritium data for Lake Seneca (12 years as compared to 18 years) can be explained by a yearly addition of less than 3% by lake volume of ground water to the lake, the exact percentage depending on tritium concentration in the ground water.

Uranium geochemistry in geopressured-geothermal aquifers of the U.S. Gulf Coast

Formation water from U.S. Gulf Coast geopressured-geothermal sandstone aquifers has been analyzed to determine the geochemistry of uranium in these systems. Results of chemical analyses and chemical equilibrium modeling indicate the formation waters are in equilibrium with uraninite (UO2) and coffinite (USiO4). The 234U238U activity ratios in the formation waters range from 1.06 to 1.69. These isotopic data suggest that at formation temperatures uranium is continually reequilibrating chemically and isotopically between water, a solid phase of either UO2 or USiO4 and a component of 234U supplied to solution from the aquifer matrix material by alpha recoil processes.

234U and238U concentration in brine from geopressured aquifers of the northern Gulf of Mexico basin

Abstract The 234 U and 238 U concentration in brine from six Gulf Coast geopressured aquifers has been determined. The results reveal very low uranium concentrations (from 0.003 to 0.03 μg/l) and uranium activity ratios slightly greater than unity (from 1.06 to 1.62). Reducing conditions within the aquifers are responsible for the low uranium concentrations. The uranium activity ratios observed are well below those calculated using theoretical considerations of alpha-particle recoil effects. This can be explained by interference with alpha-recoil nuclides entering the liquid phase as a result of quartz overgrowths on sand grains and high-temperature re-equilibration that tends to minimize the effects of the alpha-recoil process. The fact that the uranium activity ratios of the brines are slightly greater than unity instead of the equilibrium value of 1.000 indicates that either the alpha particle recoil blocking and re-equlibration effects are not complete or that another process is operative that enriches the fluid in excess 234 U by selectively removing uranium from radiation induced damage sites in the mineral (sand grain) matrix.

Radium and radon in Charlotte Harbor Estuary, Florida

Abstract Radium-226 and 222 Rn activities are greater in the estuarine waters of northern Charlotte Harbor and the lower tidal Peace and Myakka Rivers, Florida, than in either the freshwater reaches of the rivers or waters of the lower estuary and the Gulf of Mexico. The activity of 226 Ra in the tidal rivers increases with decreasing river inflow, with a maximum value of 548 dpm 1001 −1 measured in the tidal Myakka River. The source of the high activity of 226 Ra and 222 Rn is predominantly ground water inflow. Because of the large ground water input, the contribution of 226 Ra from suspended and bottom sediments is a smaller fraction of the total 226 Ra input than in many other estuaries. Although ground water 226 Ra activity in the area varies widely, we estimate that artesian ground water inflow to the tidal rivers is similar in magnitude to the flow of the rivers above the tidal reach during the dry season.

Uranium isotopes (234U/238U) in rivers of the Yukon Basin (Alaska and Canada) as an aid in identifying water sources, with implications for monitoring hydrologic change in arctic regions

The ability to detect hydrologic variation in large arctic river systems is of major importance in understanding and predicting effects of climate change in high-latitude environments. Monitoring uranium isotopes (234U and 238U) in river water of the Yukon River Basin of Alaska and northwestern Canada (2001–2005) has enhanced the ability to identify water sources to rivers, as well as detect flow changes that have occurred over the 5-year study. Uranium isotopic data for the Yukon River and major tributaries (the Porcupine and Tanana rivers) identify several sources that contribute to river flow, including: deep groundwater, seasonally frozen river-valley alluvium groundwater, and high-elevation glacial melt water. The main-stem Yukon River exhibits patterns of uranium isotopic variation at several locations that reflect input from ice melt and shallow groundwater in the spring, as well as a multi-year pattern of increased variability in timing and relative amount of water supplied from higher elevations within the basin. Results of this study demonstrate both the utility of uranium isotopes in revealing sources of water in large river systems and of incorporating uranium isotope analysis in long-term monitoring of arctic river systems that attempt to assess the effects of climate change.ResumeLa capacité à détecter des variations hydrologiques au sein de grands hydrosystèmes arctiques est essentielle pour la compréhension et la prédiction des effets du changement climatique dans les régions de haute latitude. Le suivi des isotopes de l’uranium (234U et 238U) dans l’eau des cours d’eau du bassin versant du Yukon en Alaska et au Nord-Ouest du Canada pour la période 2001–2005 a permis d’accroître la capacité à identifier l’origine des eaux des cours d’eau ainsi que les modifications de flux qui se sont produites au cours des cinq ans de la période d’étude. Les données isotopiques de l’Uranium pour la rivière du Yukon et de ses principaux affluents (Porcupine et Tanana) permettent d’identifier plusieurs sources qui contribuent aux écoulements, incluant : eaux souterraines profondes, eaux souterraines des alluvions dont les cours d’eau sont gelés de manière saisonnière et l’eau de la fonte des glaciers en haute altitude. Le tronçon principal de la rivière du Yukon montre des modalités de variation isotopique en uranium au niveau de plusieurs sites, reflétant des apports de fonte de glace et d’eaux phréatiques au printemps, ainsi que des variabilités pluriannuelles augmentant avec le temps mais aussi en termes de quantité d’eau provenant des zones les plus élevées du bassin versant. Les résultats de cette étude démontrent l’utilité des isotopes de l’uranium pour révéler l’origine des eaux au sein d’un grand hydrosystème et de leur intégration pour le suivi sur le long terme des systèmes hydrologiques arctiques afin d’essayer d’évaluer les effets du changement climatique.ResumenLa habilidad para detectar variaciones hidrológicas en grandes sistemas de ríos árticos es de fundamental importancia para el entendimiento y la predicción de los efectos del cambio climático en ambientes de altas latitudes. El monitoreo de los isótopos de uranio (234U y 238U) en el agua de ríos de la cuenca del río Yukón de Alaska y noroeste de Canadá (2001–2005) ha mejorado la habilidad para identificar las fuentes de agua que alimentan los ríos, así como para detectar cambios de flujo que hayan ocurrido en los cinco años de estudio. Los datos de isótopos de uranio para el Río Yukón y los principales tributarios (los ríos Porcupine y Tanana) identifican varias fuentes que contribuyen al flujo del río, incluyendo agua subterránea profunda, agua subterránea proveniente de agua estacionalmente congelados en ríos de valles aluviales, y agua de derretimiento de glaciares de altas elevaciones. El curso principal del Río Yukón exhibe esquemas de variaciones de isótopos de uranio en varias localidades que reflejan la entrada de agua partir del derretimiento de hielo y del agua subterránea somera en los manantiales, así como un esquema multianual de variabilidad incrementada en el tiempo y en la cantidad relativa de agua proveniente de las más altas elevaciones dentro de la cuenca. Los resultados de este estudio demuestran tanto la utilidad de los isótopos de uranio para las fuentes de agua relevadas en los grandes sistemas de ríos, como la incorporación del análisis de isótopos del uranio en el monitoreo a largo plazo de sistemas de los ríos árticos que intentan evaluar los efectos del cambio climático.摘要在大规模北极河流系统中监测水文变化的能力对于了解及预测高纬度环境下气候变化的作用很重要。基于对阿拉斯加州及加拿大西北部Yukon流域河水(2001–2005)中铀同位素(234U/238U)五年的监测增强了识别河水来源以及监测流场变化的能力。Yukon河及主要支流(Porcupine和 Tanana 河)的铀同位素数据识别出若干个流向河水的水源,包括:深层地下水、季节性结冰河水-山谷冲积地下水以及高地冰川融水。在Yukon河主干的不同位置显示出多种铀同位素变化模式,表现在来自春天冰融化及浅层地下水的补给,以及时间上多年变化模式和从盆地内较高位置补给水的相对份额。研究结果表明利用铀同位素可揭露大规模河流系统的水源,且结合北极河流系统长期观测中的铀同位素分析可尝试进行气候变化效应评价。ResumoA variação hidrológica em grandes sistemas fluviais do Ártico é de grande importância para compreender e prever os efeitos das alterações climáticas em ambientes de latitude elevada. A monitorização dos isótopos de urânio (234U/238U) na água da Bacia do Rio Yukon, no Alasca e no noroeste do Canadá (2001–2005), aumentou a capacidade de identificar as fontes de água que alimentam os rios, bem como a possibilidade de detetar alterações de fluxo que têm ocorrido neste período de cinco anos. Os dados de isótopos de urânio do Rio Yukon e dos seus principais afluentes (os Rios Porcupine e Tanana) permitem identificar as diversas fontes que contribuem para o fluxo do rio, incluindo: águas subterrâneas profundas, as que provêm da água subterrânea sazonalmente congelada dos aluviões do rio e águas que provêm do degelo dos glaciares a elevada altitude. O rio principal, oYukon, apresenta padrões de variação isotópica de urânio em diversos locais que refletem a entrada de águas subterrâneas de aquíferos subsuperficiais e do degelo na Primavera, assim como um padrão multianual de variabilidade crescente no tempo e da quantidade relativa de água que provém das partes mais altas da bacia. Os resultados deste estudo demonstram tanto a utilidade de isótopos de urânio em revelar as fontes de água em grandes sistemas fluviais, como a importância da análise de isótopos de urânio incorporando monitorização, a longo prazo, de sistemas fluviais do Ártico, para avaliação dos efeitos das alterações climáticas.

Environmental fate of Ra in cation-exchange regeneration brine waste disposed to septic tanks, New Jersey Coastal Plain, USA: migration to the water table.

Fate of radium (Ra) in liquid regeneration brine wastes from water softeners disposed to septic tanks in the New Jersey Coastal Plain was studied. Before treatment, combined Ra ((226)Ra plus (228)Ra) concentrations (maximum, 1.54 Bq L(-1)) exceeded the 0.185 Bq L(-1) Maximum Contaminant Level in 4 of 10 studied domestic-well waters (median pH, 4.90). At the water table downgradient from leachfields, combined Ra concentrations were low (commonly < or =0.019 Bq L(-1)) when pH was >5.3, indicating sequestration; when pH was < or =5.3 (acidic), concentrations were elevated (maximum, 0.985 Bq L(-1) - greater than concentrations in corresponding discharged septic-tank effluents (maximum, 0.243 Bq L(-1))), indicating Ra mobilization from leachfield sediments. Confidence in quantification of Ra mass balance was reduced by study design limitations, including synoptic sampling of effluents and ground waters, and large uncertainties associated with analytical methods. The trend of Ra mobilization in acidic environments does match observations from regional water-quality assessments.

Quantitative Eolian Transport of Evaporite Salts from the Makgadikgadi Depression (Ntwetwe and Sua Pans) in Northeastern Botswana: Implications for Regional Ground-Water Quality

Eolian salts from the evaporite-covered Makgadikgadi Depression in Botswana were observed in the soil as far as 150 km downwind from the depression. Over three million metric tons of chloride, sodium, and bicarbonate are transported each year from the basin to the adjacent land. Infiltering soil water mobilizes and transports these soluble salts to the ground water, where they degrade the water quality. A relation between the size of the evaporative floor area and the length of the downwind salt “footprint” on the soil was established. This permits use of readily available topographic maps to estimate the area and length of potential degradation of ground water without extensive field sampling. Significant mass of naturally-occurring radioactive 226-radium is present in the eolian-transported salts that may have deleterious health consequences for individuals residing in the downwind area.