Geology topics

T.E. Imbrigiotta

Publications and source records attributed to T.E. Imbrigiotta.

5 recordsLinked to original sources

USGS2009

Flowpath independent monitoring of reductive dechlorination potential in a fractured rock aquifer

The flowpath dependent approaches that are typically employed to assess biodegradation of chloroethene contaminants in unconsolidated aquifers are problematic in fractured rock settings, due to difficulties defining discrete groundwater flowpaths in such systems. In this study, the variation in the potential for chloroethene biodegradation with depth was evaluated in a fractured rock aquifer using two flowpath independent lines of field evidence: (1) the presence of the three biochemical prerequisites [electron donor(s), chloroethene electron acceptor(s), and chlororespiring microorganism(s)] for efficient chloroethene chlororespiration and (2) the in situ accumulation of chloroethene reductive dechlorination daughter products. The validity of this approach was assessed by comparing field results with the results of [1, 2‐ 14 C] cis ‐DCE microcosm experiments. Microcosms were prepared with depth‐specific core material, which was crushed and emplaced in discrete packer intervals for 1 year to allow colonization by the indigenous microbial community. Packer intervals characterized by significant electron donor concentrations, elevated numbers of chlororespiring microorganisms, and high reductive dechlorination product to parent contaminant ratios correlated well with the production of 14 C‐labeled reductive dechlorination products in the microcosm experiments. These results indicate that, in the absence of information on discrete groundwater flowpaths, a modified approach emphasizing flowpath independent lines of evidence can provide insight into the temporal and spatial variability of contaminant biodegradation in fractured rock systems.

Ground Water Monitoring and Remediation↗

USGS2005

Well-purging criteria for sampling purgeable organic compounds

The results indicate that 1) purgeable organic compound concentrations stabilized when three casing volume were purged in only 55% of the cases evaluated in this study, 2) purgeable organic compounds concentrations did not consistently follow the temporal variation of, nor stabilize at the same time as, the measure field characteristics, and 3) purging to achieve hydraulic equilibrium between casing and aquifer water consistently underestimated the time and casing volumes needed to achieve stable values of water-quality measurements in highly transmissive aquifers. The conclusion from these data is that none of the previously recommended criteria for purging a well can be applied reliably to collecting a "representative' sample of purgeable organic compounds. These results indicate that the criteria for purging a well prior to sampling for purgeable organic compounds must take into account other factors, such as the unique hydrogeologic characteristics of a site, the nature and extent of purgeable organic compounds present, and areal extent of the contamination, the well construction, and the sampling objectives of the investigation. -from Authors

Ground Water↗

USGS1994

Displacement of soil pore water by trichloroethylene

Dense nonaqueous phase liquids (DNAPLS) are important pollutants because of their widespread use as chemical and industrial solvents. An example of the pollution caused by the discharge of DNAPLs is found at the Picatinny Arsenal, New Jersey, where trichloroethylene (TCE) has been discharged directly into the unsaturated zone. This discharge has resulted in the formation of a plume of TCE-contaminated water in the aquifer downgradient of the discharge. A zone of dark-colored groundwater containing a high dissolved organic C content has been found near the point of discharge of the TCE. The colored-water plume extends from the point of discharge at least 30 m (100 feet) downgradient. Fulvic acids isolated from the colored-waters plume, from water from a background well that has not been affected by the discharge of chlorinated solvents, and from soil pore water collected in a lysimeter installed at an uncontaminated site upgradient of the study area have been compared. Nuclear magnetic resonance spectra of the fulvic acids from the colored waters and from the lysimeter are very similar, but are markedly different from the nuclear magnetic resonance spectrum of the fulvic acid from the background well. The three-dimensional fluorescence spectrum and the DOC fractionation profile of the colored groundwater and the soil pore water are very similar to each other, but quite different from those of the background water. It is proposed from these observations that this colored water is soil pore water that has been displaced by a separate DNAPL liquid phase downward to the saturated zone.

Journal of Environmental Quality↗

USGS1994

Hydrogeology and hydrochemistry of dunes and wetlands along the southern shore of Lake Michigan, Indiana

The dunes and the wetlands along the southern shore of Lake Michigan are underlain by a complex aquifer system composed of unconsolidated glacial, lacustrine, and eolian deposits. Surficial dune, beach, and glacial lacustrine sands compose an extensive surficial aquifer. The underlying drift contains three major confined sand aquifers. Potentiometric and hydrochemical data are consistent with a conceptual model in which regional and intermediate flow systems, recharged in end moraines south of the dune-beach complexes, discharge into Lake Michigan and the Great Marsh by upward leakage through unconsolidated sediments. Local flow systems in the surficial aquifer, recharged in the major dune-beach complexes, discharge into streams, ditches, and ponded areas in the adjacent interdunal wetlands. Shallow ground water discharges directly into Lake Michigan only north of a water-table divide that underlies the dune-beach complex along the shoreline. The position of ground-water seepage faces is affected by transient water-table mounds observed in the dune-beach complexes at the margins of wetlands. Substantial recharge to the dune complexes probably occurs near these dune-wetland margins. In the dune-beach complexes and intradunal wetlands, the shallow ground and wetland waters are dilute calcium bicarbonate and calcium bicarbonate sulfate types. More mineralized bicarbonate water types having variable proportions of calcium, magnesium, and sodium are found in interior parts of the Great Marsh because this area is probably a discharge zone for the regional and intermediate flow systems.

Open-File Report↗

USGS1982

Ground-water resources of the glacial outwash along the White River, Johnson and Morgan counties, Indiana

An 88-square-mile segment of the White River valley contains an unconfined sand and gravel aquifer ranging-from a featheredge zero, to 120 feet in saturated thickness. Hydraulic conductivity is 340 feet per day, and transmissivity is as much as 35,000 square feet per day. The aquifer, recharged primarily by precipitation, gains same recharge through interbedded till and outwash boundaries and through losing streams. A two-dimensional digital model was used to simulate the steady-state ground-water flow system. Sensitivity analyses tested the reaction of the model to adjustments in hydraulic conductivity, steam bed leakance, and recharge. Simulated pumpage of 20-, 66-, and 122-million gallons per day reduced streamflow by 5, 15, and 30% , respectively. A real drawdown did not exceed 25 feet. Ground water was a calcium bicarbonate type having a median pH of 7.1, a mean alkalinity of 240 milligrams per liter, a mean hardness of 280 milligrams per liter, a mean dissolved oxygen concentration of 2.2 milligrams per liter, a mean redox potential of +347 millivolts, and a mean dissolved-solids concentration of 366 milligrams per liter. Iron and manganese concentrations exceeded National Drinking Water Regulations in 15 and 49% of the analyses, respectively. Temperature and concentration of dissolved organic carbon varied seasonally. Dissolved carbon and manganese varied with seasonally. Dissolved carbon and manganese varied with differing boundary material, till and bedrock. (USGS)

Indiana↗