Identification of Subaqueous Groundwater Discharge to Large Scale Surface Water Bodies, East Tennessee Technology Park Site, DOE Oak Ridge Reservation, Oak Ridge, Tennessee

In East Tennessee, the Tennessee River and its tributaries cut across many of the sub-parallel strike valleys in the Valley and Ridge several times, including the karstic carbonate strike belts within them. The construction of dams along the Tennessee River and its tributaries, including the Clinch River, has increased the river stage between 5 and 20 m, which caused inundation of considerable areas. This also raised the baselevel for drainage, thus altering the groundwater regime within the valleys intersected by these rivers. The stud area addressed in this research includes an industrial facility situated on karstic carbonate bedrock which is bounded by a Tennessee Valley Authority-controlled run-of-the-river surface impoundment, the Clinch River, and Poplar Cree, a large first order tributary to that impoundment. Surface water flow and state conditions in these water bodies are dictated by reservoir operations at upstream and downstream dams. Surface water stage plays a major role in regulating overall groundwater flow from the facility. Typically, the master surface water drains represent baselevel for groundwater discharge and it was expected that large springs, reflecting the karstic nature of the bedrock underlying the site, would occur along these surface water bodies. However, a comprehensive inventory of springs and seeps within this study area identified only a few small seeps near the impoundment, most of which are transient in nature. Consequently, it was expected that much of the groundwater discharges to surface water via subaqueous springs possibly related to pre-impoundment baselevel conditions. Remote methods such as infrared thermography were attempted in order to locate potential zones of subaqueous groundwater discharge but proved unsuccessful. This study documents an attempt to identify direct subaqueous discharge of groundwater to a flowing surface water body on the basis of inherent differences in temperature and specific conductance between groundwater and the receiving surface water. This approach was applied to a study area which includes the East Tennessee Technology Park (ETTP) located within the Department of Energy Oak Ridge Reservation in east Tennessee. The site is bounded by the Clinch River, a run-of-the-river impoundment and Poplar Creek, a large first order tributary to that impoundment. The geology at this site is highly complex, reflecting structural and stratigraphic controls on groundwater flow, all of which have been overprinted by karst dissolutional processes and the effects of reservoir impoundment and operation. In this effort, a multi-parameter probe was suspended below a small boat and trolled along the bottom of a run-of-the-river impoundment in water depths ranging from ~1 to 16 m. Temperature, specific conductance, dissolved oxygen, head, bathymetry, and boat/probe position were continuously recorded along multiple survey runs oriented roughly parallel to shoreline at 1 - 10 m spacings. Real-time corrected Global Positioning System (GPS) technology was used to provide sub-meter resolution of probe and boat position. Water quality and GPS data were integrated and recorded using onboard portable computers. Field work was completed over and 18-day period in late January to early March 1996. A total of 152 survey runs were performed over nearly 12 km of surface water, yielding more than 157,000 records. From this data, a total of 198 anomalies where identified. Anomalies ranging up to 0.74 C and 38 uS/cm were identified, the majority of which were detected in shallow water \u3c 3 m deep. The magnitude of the anomalies identified are within the range predicted using simple mixing models. These models also indicate that given the high ambient flow rates in the river, many low volume subaqueous springs may be below the resolution for detection. The locations of anomalies identified in this effort were found to coincide with a number of key hydrogeologic features and trends where ground water discharge was expected to occur. The location and character of the anomalies detected appears to represent two distinct modes of groundwater discharge. Where the surface water bodies intersect flowpaths in the saturated overburden above bedrock or, where the creek bottom is mantled with thick alluvium, groundwater appears to discharge as diffuse seepage zones or as continuous seepage face. In contrast, anomalies were more frequently detected where bedrock is exposed along the river/creek bottom. Further, these anomalies were typically of higher magnitude and discrete, representing groundwater discharge along primary bedrock flowpaths. These include solutionally enlarged fractures, faults, and conduits. The dynamic nature of the bounding surface water bodies in this study area results in highly variable and transient patterns of groundwater discharge. It is likely that subaqueous springs inferred from the anomalies are part of a highly complex, interconnected distributary network that functions differently in response to the highly transient surface water boundary conditions. The results of this study support the findings of a previous water balance study, indicating that the majority of groundwater discharge from the ETTP site is occurring through subaqueous discharge to the Clinch River and Poplar Creek. The results further support the contention that there is little potential for significant underflow of these surface water bodies. Direct investigation of subaqueous spring discharge, possibly involving divers and the installation of river bottom seepage meters is recommended to confirm the spring locations identified in this study and to evaluate their role in the overall hydrogeology of the site

Identification and Quantitative Measurements of Chemical Species by Mass Spectrometry

The development of a miniature gas chromatograph/mass spectrometer system for the measurement of chemical species of interest to combustion is described. The completed system is a fully-contained, automated instrument consisting of a sampling inlet, a small-scale gas chromatograph, a miniature, quadrupole mass spectrometer, vacuum pumps, and software. A pair of computer-driven valves controls the gas sampling and introduction to the chromatographic column. The column has a stainless steel exterior and a silica interior, and contains an adsorbent of that is used to separate organic species. The detection system is based on a quadrupole mass spectrometer consisting of a micropole array, electrometer, and a computer interface. The vacuum system has two miniature pumps to maintain the low pressure needed for the mass spectrometer. A laptop computer uses custom software to control the entire system and collect the data. In a laboratory demonstration, the system separated calibration mixtures containing 1000 ppm of alkanes and alkenes

Highlights of OH, H2SO4, and methane sulfonic acid measurements made aboard the NASA P-3B during Transport and Chemical Evolution over the Pacific

Measurements of hydroxyl radical (OH), sulfuric acid (H2SO4), and methane sulfonic acid (MSA) were performed aboard the NASA P-3B using the selected ion chemical ionization mass spectrometry technique during the Transport and Chemical Evolution over the Pacific (TRACE-P) study. Photochemical box model calculations of OH concentrations yielded generally good agreement with an overall tendency to overestimate the measured OH by ∼20%. Further analysis reveals that this overestimation is present only at altitudes greater than ∼1.5 km, with the model underestimating OH measurements at lower altitudes. Boundary layer H2SO4 measurements, performed in a volcanic plume off the southern coast of Japan, revealed some of the largest marine boundary layer H2SO4 concentrations ever observed and were accompanied by new particle formation. Nighttime measurements of OH, H2SO4, and MSA in the remote pacific off Midway Island revealed significant boundary layer concentrations of H2SO4 and MSA, indicating evidence of nighttime boundary layer oxidation processes but in the absence of OH. A cursory exploration of the sources of production of the H2SO4 and MSA observed at night is presented

Contribution of particulate nitrate to airborne measurements of total reactive nitrogen

Simultaneous measurements of speciated, total reactive nitrogen (NOy) and particulate NO3 (particle diameter <1.3 μm) were made on board the NASA P-3B aircraft over the western Pacific in February-April 2001 during the Transport and Chemical Evolution over the Pacific (TRACE-P) experiment. Gas-phase and particulate NOy was measured using a gold tube catalytic converter. For the interpretation of particulate NOy, conversion efficiencies of particulate NH4NO3, KNO3, NaNO3, and Ca(NO3)2 were measured in the laboratory. Only NH4NO3 showed quantitative conversion, and its conversion efficiency was as high as that for HNO3. NOy measured on board the aircraft was found to be systematically higher by 10-30% than the sum of the individual NOy gas components (Σ(NOy)i) at 0-4 km. Particulate NO3- concentrations measured by a particle-into-liquid sampler (PILS) were nearly equal to NOy - Σ(NOy)i under low-dust-loading conditions. The PILS data showed that the majority of the particulate NO3- was in the form of NH4NO3 under these conditions, suggesting that NH4NO3 particles were quantitatively converted to detectable NO by the NOy converter, consistent with the laboratory experiments. The contribution of particulate NO3- to NOy was most important at 0-2 km, where NO3- constituted 10-30% of NOy during TRACE-P. On average, the amounts of particulate NO3- and gas-phase HNO3 were comparable in this region. Copyright 2005 by the American Geophysical Union

Long-path quantum cascade laser–based sensor for methane measurements

Author Posting. © American Meteorological Society, 2016. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Atmospheric and Oceanic Technology 33 (2016): 2373-2384, doi:10.1175/JTECH-D-16-0024.1.A long-path methane (CH4) sensor was developed and field deployed using an 8-μm quantum cascade laser. The high optical power (40 mW) of the laser allowed for path-integrated measurements of ambient CH4 at total pathlengths from 100 to 1200 m with the use of a retroreflector. Wavelength modulation spectroscopy was used to make high-precision measurements of atmospheric pressure–broadened CH4 absorption over these long distances. An in-line reference cell with higher harmonic detection provided metrics of system stability in rapidly changing and harsh environments. The system consumed less than 100 W of power and required no consumables. The measurements intercompared favorably (typically less than 5% difference) with a commercial in situ methane sensor when accounting for the different spatiotemporal scales of the measurements. The sensor was field deployed for 2 weeks at an arctic lake to examine the robustness of the approach in harsh field environments. Short-term precision over a 458-m pathlength was 10 ppbv at 1 Hz, equivalent to a signal from a methane enhancement above background of 5 ppmv in a 1-m length. The sensor performed well in a range of harsh environmental conditions, including snow, rain, wind, and changing temperatures. These field measurements demonstrate the capabilities of the approach for use in detecting large but highly variable emissions in arctic environments.The authors gratefully acknowledge funding for this work by MIRTHE through NSF-ERC Grant EEC-0540832. D. J. Miller acknowledges support by the National Science Foundation Graduate Research Fellowship under Grant DGE-0646086. K. Sun acknowledges support by the NASA Earth and Space Science Fellowship IIP-1263579.2017-05-0

Impacts of biomass burning in Southeast Asia on ozone and reactive nitrogen over the western Pacific in spring

Aircraft measurements of ozone (O3) and its precursors (reactive nitrogen, CO, nonmethane hydrocarbons) were made over the western Pacific during the Transport and Chemical Evolution Over the Pacific (TRACE-P) campaign, which was conducted during February-April 2001. Biomass burning activity was high over Southeast Asia (SEA) during this period (dry season), and convective activity over SEA frequently transported air from the boundary layer to the free troposphere, followed by eastward transport to the sampling region over the western Pacific south of 30°N. This data set allows for systematic investigations of the chemical and physical processes in the outflow from SEA. Methyl chloride (CH3Cl) and CO are chosen as primary and secondary tracers, respectively, to gauge the degree of the impact of emissions of trace species from biomass burning. Biomass burning is found to be a major source of reactive nitrogen (NO x, PAN, HNO3, and nitrate) and O3 in this region from correlations of these species with the tracers. Changes in the abundance of reactive nitrogen during upward transport are quantified from the altitude change of the slopes of the correlations of these species with CO. NOx decreased with altitude due to its oxidation to HNO3. On the other hand, PAN was conserved during transport from the lower to the middle troposphere, consistent with its low water solubility and chemical stability at low temperatures. Large losses of HNO3 and nitrate, which are highly water soluble, occurred in the free troposphere, most likely due to wet removal by precipitation. This has been shown to be the major pathway of NOy loss in the middle troposphere. Increases in the mixing ratios of O3 and its precursors due to biomass burning in SEA are estimated using the tracers. Enhancements of CO and total reactive nitrogen (NOy), which are directly emitted from biomass burning, were largest at 2-4 km. At this altitude the increases in NOy and O3 were 810 parts per trillion by volume (pptv) and 26 parts per billion by volume (ppbv) above their background values of 240 pptv and 31 ppbv, respectively. The slope of the O3-CO correlation in biomass burning plumes was similar to those observed in fire plumes in northern Australia, Africa, and Canada. The O3 production efficiency (OPE) derived from the O3-CO slope and NOx/CO emission ratio (ER) is shown to be positively correlated with the C2H4 /NOx ER, indicating that the C2H4/NO x ER is a critical parameter in determining the OPE. Comparison of the net O3 flux across the western Pacific region and total O3 production due to biomass burning in SEA suggests that about 70% of O3 produced was transported to the western Pacific. Copyright 2004 by the American Geophysical Union

Clarifying the Dominant Sources and Mechanisms of Cirrus Cloud Formation

Formation of cirrus clouds depends on the availability of ice nuclei to begin condensation of atmospheric water vapor. Although it is known that only a small fraction of atmospheric aerosols are efficient ice nuclei, the critical ingredients that make those aerosols so effective have not been established. We have determined in situ the composition of the residual particles within cirrus crystals after the ice was sublimated. Our results demonstrate that mineral dust and metallic particles are the dominant source of residual particles, whereas sulfate and organic particles are underrepresented, and elemental carbon and biological materials are essentially absent. Further, composition analysis combined with relative humidity measurements suggests that heterogeneous freezing was the dominant formation mechanism of these clouds.National Science Foundation (U.S.) (NSF AGS-0840732)National Science Foundation (U.S.) (NSF grant AGS-1036275)United States. National Aeronautics and Space Administration (NASA Earth and Space Science Graduate Fellowship)United States. National Aeronautics and Space Administration (NASA Radiation Sciences Program award number NNX07AL11G)United States. National Aeronautics and Space Administration (NASA Radiation Sciences Program award number NNX08AH57G)United States. National Aeronautics and Space Administration (NASA Earth Science Division Atmospheric Composition program award number NNH11AQ58UI