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Eurybiades Busenberg

Publications and source records attributed to Eurybiades Busenberg.

At least 37 records · Page 2Linked to original sources
USGS2007

Evidence for terrigenic SF6 in groundwater from basaltic aquifers, Jeju Island, Korea: Implications for groundwater dating

Measurements of the concentrations of dichlorodifluoromethane (CFC-12), tritium ( 3 H), and sulfur hexafluoride (SF 6 ) in groundwater from basaltic aquifers in Jeju Island, Korea, demonstrate a terrigenic source of SF 6 . Using a lumped-parameter dispersion model, groundwater was identified as young water (<15 years), old water with negligible CFC-12 and 3 H, and binary mixtures of the two. Model calculations using dispersion models and binary mixing based on 3 H and CFC-12 concentrations demonstrate a non-atmospheric excess of SF 6 relative to CFC-12 and 3 H concentrations for more than half of the samples. The non-atmospheric excess SF 6 may have originated from terrigenic sources in relict volcanic fluids, which could have acquired SF 6 from granites and basement rocks of the island during volcanic activity. Local excess anthropogenic sources of SF 6 are unlikely. The SF 6 age is biased young relative to the CFC-12 age, typically up to 20 years and as high as 30 years. This age bias is more pronounced in samples of groundwater older than 15 years. The presence of terrigenic SF 6 can affect the entire dating range for groundwater in mixtures that contain a fraction of old water.

Jeju Island↗
USGS2007

Evidence of CFC degradation in groundwater under pyrite-oxidizing conditions

A detailed local-scale monitoring network was used to assess CFC distribution in an unconfined sand aquifer in southwestern Ontario where the zone of 1–5-year-old groundwater was known with certainty because of prior use of a bromide tracer. Groundwater ⩽5 years old was confined to an aerobic zone at ⩽5 m depth and had CFC concentrations consistent with modern atmospheric mixing ratios at recharge temperatures of 7–11 °C, as was observed in the 3-m thick vadose zone at the site. At depths below 6 m, the groundwater became progressively more reducing, however, with a denitrifying horizon at 6–7 m depth, and a Mn and Fe reducing zone below 7 m depth. In the anaerobic zone, 3 H/ 3 He ratios indicated that groundwater-age continued to increase uniformly with depth, to a maximum value of 27 years at 13 m depth. CFC concentrations, however, decreased abruptly within the denitrifying zone, leading to substantial age overestimation compared to the 3 H/ 3 He ages. Noble gas data indicated that the apparent CFC mass loss was not likely the result of gas stripping from possible bubble formation; thus, CFC degradation was indicated in the anoxic zone. The field data are consistent with first-order degradation rates of 0.3 yr −1 for CFC-12, 0.7 yr −1 for CFC-11, and 1.6 yr −1 for CFC-113. CFC attenuation at this site coincides with a zone where reduced S (pyrite) is actively oxidized by NO 3 and dissolved oxygen (DO). Similar behavior has been observed at other sites [Tesoriero, A.J., Liebscher, H., Cox, S.E., 2000. Mechanism and rate of denitrification in an agricultural watershed: electron and mass balance along groundwater flow path. Water Resour. Res. 36 (6), 1545–1559; Hinsby, K., Hojberg, A.L., Engesgaard, P., Jensen, K.H., Larsen, F., Plummer, L.N., Busenberg, E., Accepted for publication. Transport and degradation of chlorofluorocarbons (CFCs) in a pyritic aquifer, Rabis Creek, Denmark. Water Resour. Res.], further demonstrating that the use of CFCs for age-dating anaerobic groundwater should be approached with caution, particularly if the sediment contains pyrite.

Journal of Hydrology↗
USGS2006

The geochemical evolution of riparian ground water in a forested piedmont catchment

The principal weathering reactions and their rates in riparian ground water were determined at the Panola Mountain Research Watershed (PMRW) near Atlanta, Georgia. Concentrations of major solutes were measured in ground water samples from 19 shallow wells completed in the riparian (saprolite) aquifer and in one borehole completed in granite, and the apparent age of each sample was calculated from chloroflourocarbons and tritium/helium-3 data. Concentrations of SiO 2 , Na + , and Ca 2+ generally increased downvalley and were highest in the borehole near the watershed outlet. Strong positive correlations were found between the concentrations of these solutes and the apparent age of ground water that was modern (zero to one year) in the headwaters, six to seven years midway down the valley, and 26 to 27 years in the borehole, located ∼500 m downstream from the headwaters. Mass-balance modeling of chemical evolution showed that the downstream changes in ground water chemistry could be largely explained by weathering of plagioclase to kaolinite, with possible contributions from weathering of K-feldspar, biotite, hornblende, and calcite. The in situ rates of weathering reactions were estimated by combining the ground water age dates with geochemical mass-balance modeling results. The weathering rate was highest for plagioclase (∼6.4 μmol/L/year), but could not be easily compared with most other published results for feldspar weathering at PMRW and elsewhere because the mineral-surface area to which ground water was exposed during geochemical evolution could not be estimated. However, a preliminary estimate of the mineral-surface area that would have contacted the ground water to provide the observed solute concentrations suggests that the plagioclase weathering rate calculated in this study is similar to the rate calculated in a previous study at PMRW, and three to four orders of magnitude slower than those published in previous laboratory studies of feldspar weathering. An accurate model of the geochemical evolution of riparian ground water is necessary to accurately model the geochemical evolution of stream water at PMRW.

Groundwater↗
USGS2005

Ground water age and nitrate distribution within a glacial aquifer beneath a thick unsaturated zone

The impact on ground water quality from increasing fertilizer application rates over the past 40 years is evaluated within a glacial aquifer system beneath a thick unsaturated zone. Ground water ages within the aquifer could not be accurately determined from the measured distribution of 3 H and as a result, chlorofluorocarbon (CFC) and 3 H/ 3 He dating techniques were applied. Beneath a 25 m thick unsaturated zone, ground water ages based on CFC‐11 concentrations were greater than 3 H/ 3 He ground water ages by 6 to 10 years, due to the time lag associated with the diffusion of CFCs through the unsaturated zone. Using the corrected CFC‐11 and 3 H/ 3 He ground water ages and the estimated travel time of 3H within the unsaturated zone, the approximate position of ground water recharged since the mid‐1960s was determined. Nitrate concentrations within post mid‐1960s recharge were generally elevated and near or above the drinking water limit of 10 mg‐N/L. In comparison, pre mid‐1960s recharge had nitrate concentrations <2.5 mg‐N/L. The elevated NO 3 − concentrations in post mid‐1960s recharge are attributed mainly to increasing fertilizer application rates between 1970 and the mid‐ to late 1980s. Anaerobic conditions suitable for denitrifkation are present within pre mid‐1960s recharge indicating that removal of DO is a slow process taking tens of years. Over the next 10 to 20 years, nitrate concentrations at municipal well fields that are currently capturing aerobic ground water recharged near the mid‐1960s are expected to increase because of the higher fertilizer application rates beginning in the 1970s and 1980s.

Groundwater↗
USGS2005

The stability of chlorofluorocarbons (CFCs) in ground-water samples archived in borosilicate ampoules

The U.S. Geological Survey (USGS) Chlorofluorocarbon (CFC) Laboratory in Reston, Va., has been measuring concentrations of CFCs in ground-water samples since 1989 to estimate the year that a water sample was recharged to a ground-water flow system. The water samples have been collected in flame-sealed borosilicate ampoules. Typically for each site, three samples were analyzed within days to a few months after collection, and additional samples were archived for extended periods of time (up to four years). The stability of CFC concentrations in the archived water samples from the USGS CFC Laboratory was investigated by analyzing the CFC concentrations in archived water samples and comparing them with the CFC concentrations that were obtained soon after the samples were collected. The archived samples selected for analysis were chosen from sites with a wide variety of hydrogeologic and geochemical conditions. For CFC-11 and CFC-12 concentrations, approximately 14% and 10.5%, respectively, of the archived samples were statistically different (both higher and lower) from the concentrations obtained from analyses conducted soon after the sample collection. Most of the extraneous values were attributed to natural variability of CFC concentrations originally in the water discharged from wells, rather than to microbial degradation within the ampoule on storage.

Virginia↗
USGS2004

Transport and time lag of chlorofluorocarbon gases in the unsaturated zone, Rabis Creek, Denmark

Transport of chlorofluorocarbon (CFC) gases through the unsaturated zone to the water table is affected by gas diffusion, air–water exchange (solubility), sorption to the soil matrix, advective–dispersive transport in the water phase, and, in some cases, anaerobic degradation. In deep unsaturated zones, this may lead to a time lag between entry of gases at the land surface and recharge to groundwater. Data from a Danish field site were used to investigate how time lag is affected by variations in water content and to explore the use of simple analytical solutions to calculate time lag. Numerical simulations demonstrate that either degradation or sorption of CFC-11 takes place, whereas CFC-12 and CFC-113 are nonreactive. Water flow did not appreciably affect transport. An analytical solution for the period with a linear increase in atmospheric CFC concentrations (approximately early 1970s to early 1990s) was used to calculate CFC profiles and time lags. We compared the analytical results with numerical simulations. The time lags in the 15-m-deep unsaturated zone increase from 4.2 to between 5.2 and 6.1 yr and from 3.4 to 3.9 yr for CFC-11 and CFC-12, respectively, when simulations change from use of an exponential to a linear increase in atmospheric concentrations. The CFC concentrations at the water table before the early 1990s can be estimated by displacing the atmospheric input function by these fixed time lags. A sensitivity study demonstrates conditions under which a time lag in the unsaturated zone becomes important. The most critical parameter is the tortuosity coefficient. The analytical approach is valid for the low range of tortuosity coefficients (τ = 0.1–0.4) and unsaturated zones greater than approximately 20 m in thickness. In these cases the CFC distribution may still be from either the exponential or linear phase. In other cases, the use of numerical models, as described in our work and elsewhere, is an option.

Rabis Creek↗
USGS2004

Geochemical characterization of ground-water flow in the Santa Fe Group aquifer system, Middle Rio Grande Basin, New Mexico

Chemical and isotopic data were obtained from ground water and surface water throughout the Middle Rio Grande Basin (MRGB), New Mexico, and supplemented with selected data from the U.S. Geological Survey (USGS) National Water Information System (NWIS) and City of Albuquerque water-quality database in an effort to refine the conceptual model of ground-water flow in the basin. The ground-water data collected as part of this study include major- and minor-element chemistry (30 elements), oxygen-18 and deuterium content of water, carbon-13 content and carbon-14 activity of dissolved inorganic carbon, sulfur-34 content of dissolved sulfate, tritium, and dissolved atmospheric gases including nitrogen, argon, helium, chlorofluorocarbons, and sulfur hexafluoride from 288 wells and springs in parts of the Santa Fe Group aquifer system. The surface-water data collected as part of this study include monthly measurements of major- and minor-element chemistry (30 elements), oxygen-18 and deuterium content of water, chlorofluorocarbons, and tritium content at 14 locations throughout the basin. Additional data include stable isotope analyses of precipitation and of ground water from City of Albuquerque production wells collected and archived from the early 1980?s, and other data on the chemical and isotopic composition of air, unsaturated zone air, plants, and carbonate minerals from throughout the basin. The data were used to identify 12 sources of water to the basin, map spatial and vertical extents of ground-water flow, map water chemistry in relation to hydrogeologic, stratigraphic, and structural properties of the basin, determine radiocarbon ages of ground water, and reconstruct paleo-environmental conditions in the basin over the past 30,000 years. The data indicate that concentrations of most elements and isotopes generally parallel the predominant north to south direction of ground-water flow. The radiocarbon ages of dissolved inorganic carbon in ground water range from modern (post-1950) to more than 30,000 years before present, and appear to be particularly well defined in the predominantly siliciclastic aquifer system. Major sources of water to the basin include (1) recharge from mountains along the north, east and southwest margins (median age 5,000-9,000 years); (2) seepage from the Rio Grande and Rio Puerco (median age 4,000-8,000 years), and from Abo and Tijeras Arroyos (median age 3,000-9,000 years); (3) inflow of saline water along the southwestern basin margin (median age 20,000 years); and (4) inflow along the northern basin margin that probably represents recharge from the Jemez Mountains during the last glacial period (median age 20,000 years). Water recharged from the Jemez Mountains during the last glacial period occurs at the water table in the central part of the basin and beneath younger recharge along the Rio Grande and the northern mountain front. In some parts of the basin, boundaries between hydrochemical zones appear to be near major faults that may affect ground-water flow. However, in other parts of the basin, such as along the east side of Albuquerque near the Sandia Fault zone, ground-water flow appears to be unaffected by major faults. Upward leakage of saline water occurs along some faults and can be a source of salinity and elevated arsenic concentrations in some ground water. A trough in the modern and predevelopment water table west of Albuquerque is centered along a zone of predominantly late Pleistocene age water through the center of the basin and is flanked and overlain along the trough boundary by water that infiltrated from the Rio Puerco on the west and the Rio Grande to the east. It is suggested that the groundwater trough is a relatively recent transient feature of the Santa Fe Group aquifer system. At Albuquerque, a distinct north-south boundary in deuterium content of ground water marks the division between recharge from the eastern mountain front and that from the Rio Grande.

New Mexico↗