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USGS2020

Procedures and best practices for trigonometric leveling in the U.S. Geological Survey

With the advent of highly precise total stations and modern surveying instrumentation, trigonometric leveling has become a compelling alternative to conventional leveling methods for establishing vertical-control networks and for perpetuating a datum to field sites. Previous studies of trigonometric-leveling measurement uncertainty proclaim that first-, second-, and third-order accuracies may be achieved if strict leveling protocols are rigorously observed. Common field techniques to obtain quality results include averaging zenith angles and slope distances observed in direct and reverse instrument orientation (F1 and F2, respectively), multiple sets of reciprocal observations, quality meteorological observations to correct for the effects of atmospheric refraction, and electronic distance measurements that generally do not exceed 500 feet. In general, third-order specifications are required for differences between F1 and F2 zenith angles and slope distances; differences between redundant instrument-height measurements; section misclosure determined from reciprocal observations; and closure error for closed traverse. For F1 observations such as backsight check and check shots, the construction-grade specification is required for elevation differences between known and observed values. Recommended specifications for trigonometric-leveling equipment include a total station instrument with an angular uncertainty specification less than or equal to plus or minus 5 arc-seconds equipped with an integrated electronic distance measurement device with an uncertainty specification of less than or equal to plus or minus 3 millimeters plus 3 parts per million. A paired data collector or integrated microprocessor should have the capability to average multiple sets of measurements in direct and reverse instrument orientation. Redundant and independent measurements by the survey crew and automated or manual reduction of slant heights to the vertical equivalent are recommended to obtain quality instrument heights. Horizontal and vertical collimation tests should be conducted daily during trigonometric-leveling surveys, and electronic distance-measurement instruments should be tested annually on calibrated baselines maintained by the National Geodetic Survey. Specifications that were developed by the National Geodetic Survey for geodetic leveling have been adapted by the U.S. Geological Survey (USGS) for the purpose of developing standards for trigonometric leveling, which are identified as USGS Trigonometric Level I (TL I), USGS Trigonometric Level II (TL II), USGS Trigonometric Level III (TL III), and USGS Trigonometric Level IV (TL IV). TL I, TL II, and TL III surveys have a combination of first, second, and third geodetic leveling specifications that have been modified for plane leveling. The TL III category also has specifications that are adapted from construction-grade standards, which are not recognized by the National Geodetic Survey for geodetic leveling. A TL IV survey represents a leveling approach that does not generally meet criteria of a TL I, TL II, or TL III survey. Site conditions, such as highly variable topography, and the need for cost-effective, rapid, and accurate data collection in response to coastal or inland flooding have emphasized the need for an alternative approach to conventional leveling methods. Trigonometric leveling and the quality-assurance methods described in this manual will accommodate most site and environmental conditions, but measurement uncertainty is potentially variable and dependent on the survey method. Two types of closed traverse surveys have been identified as reliable methods to establish and perpetuate vertical control: the single-run loop traverse and double-run spur traverse. Leveling measurements for a double-run spur traverse are made in the forward direction from the origin to the destination and are then retraced along the same leveling route in the backward direction, from the destination to the origin. Every control point in a double-run spur traverse is occupied twice. Leveling measurements for a single-run loop traverse are made in the forward direction from the origin point to the destination, and then from the destination to the origin point, along a different leveling route. The only point that is redundantly occupied for the single-run loop traverse is the origin. An open traverse method is also considered an acceptable approach to establish and perpetuate vertical control if the foresight prism height is changed between measurement sets to ensure at least two independent observations. A modified version of leap-frog leveling is recommended for all traverse surveys because it reduces measurement uncertainty by forcing the surveying instrumentation into a level and centered condition over the ground point as the instrumentation is advanced to the objective. Sideshots are considered any radial measurement made from the total station that is not part of a traverse survey. F1 and F2 observations are recommended for sideshots measurements for projects that require precise elevations. Quality-assurance measurements made in F1 from the station to network-control points should be considered for surveys that require a high quantity of sideshots. The accuracy of a trigonometric-leveling survey essentially depends on four components (1) the skill and experience of the surveyor, (2) the environmental or site conditions, (3) the surveying method, and (4) the quality of the surveying instrumentation. Although components one and two can sometimes be difficult to evaluate and be highly variable, the objective of this manual is to disseminate information needed to identify, maintain, and operate quality land-surveying instrumentation, and to document procedures and best practices for preparing and executing precision trigonometric-leveling surveys in the USGS.

Techniques and Methods↗

USGS2018

Evaluating the potential for near-shore bathymetry on the Majuro Atoll, Republic of the Marshall Islands, using Landsat 8 and WorldView-3 imagery

Satellite-derived near-shore bathymetry (SDB) is becoming an increasingly important method for assessing vulnerability to climate change and natural hazards in low-lying atolls of the northern tropical Pacific Ocean. Satellite imagery has become a cost-effective means for mapping near-shore bathymetry because ships cannot collect soundings safely while operating close to the shore. Also, green laser light detection and ranging (lidar) acquisitions are expensive in remote locations. Previous research has demonstrated that spectral band ratio-based techniques, commonly called the natural logarithm approach, may lead to more precise measurements and modeling of bathymetry because of the phenomenon that different substrates at the same depth have approximately equal ratio values. The goal of this research was to apply the band ratio technique to Landsat 8 at-sensor radiance imagery and WorldView-3 atmospherically corrected imagery in the coastal waters surrounding the Majuro Atoll, Republic of the Marshall Islands, to derive near-shore bathymetry that could be incorporated into a seamless topobathymetric digital elevation model of Majuro. Attenuation of light within the water column was characterized by measuring at-sensor radiance and reflectance at different depths and calculating an attenuation coefficient. Bathymetric lidar data, collected by the U.S. Naval Oceanographic Office in 2006, were used to calibrate the SDB results. The bathymetric lidar yielded a strong linear relation with water depths. The Landsat 8-derived SDB estimates derived from the blue/green band ratio exhibited a water attenuation extinction depth of 6 meters with a coefficient of determination R 2 =0.9324. Estimates derived from the coastal/red band ratio had an R 2 =0.9597. At the same extinction depth, SDB estimates derived from WorldView-3 imagery exhibited an R 2 =0.9574. Because highly dynamic coastal shorelines can be affected by erosion, wetland loss, hurricanes, sea-level rise, urban development, and population growth, consistent bathymetric data are needed to better understand sensitive coastal land/water interfaces in areas subject to coastal disasters.

Majuro Atoll↗

USGS2020

Constraints on eruption processes and event masses for the 2016–2017 eruption of Bogoslof volcano, Alaska, through evaluation of IASI satellite SO2 masses and complementary datasets

Bogoslof volcano, Alaska, experienced at least 70 explosive eruptions between 12 December 2016 and 31 August 2017. Due to its remote location and limited local monitoring network, this eruption was monitored and characterized primarily using remote geophysical and satellite techniques. SO 2 emissions from Bogoslof were persistently detected by the Infrared Atmospheric Sounding Interferometer (IASI) satellite sensors. Of Bogoslof’s 70 explosive events, 50% produced measurable SO 2 masses ranging from 0.1 to 21.5 kt, with a median and standard deviation of 0.7 ± 4.0 kt SO 2 , respectively. Here, we compare IASI-derived SO 2 masses from Bogoslof events to complementary geophysical datasets to provide insights into eruption source processes, namely the degree of seawater scrubbing of water-soluble SO 2 and variations in magma flux. Correlations with the number of lightning strokes and infrasound energy are expected to indicate magma-flux as a controlling process, while correlations with infrasound frequency index are expected to indicate variations in vent-water content as a controlling factor. These comparisons suggest that the measured SO 2 masses are primarily a function of eruption magnitude (degassed magma mass) and that scrubbing of SO 2 emissions by vent seawater may have exerted a minor effect on the observed SO 2 masses. SO 2 masses were combined with petrologic constraints on melt inclusion and matrix glass S concentrations to calculate degassed magma masses and volumes. The cumulative SO 2 -derived degassed magma mass and estimated volume (dense-rock equivalent) for the full Bogoslof eruption were found to be 2.8 × 10 10 kg and 9.3 × 10 6 m 3 , respectively. When individual event masses are compared against event masses calculated using an empirical plume-height method, a strong correlation is found ( R 2 = 0.83), with better than order-of-magnitude agreement in most cases. These estimates of eruption masses provide useful information on the magnitude, behavior, and associated hazards of the 2016–2017 eruption, and potentially future unrest at Bogoslof volcano.

Alaska↗

USGS2007

Water Budgets: Foundations for Effective Water-Resources and Environmental Management

INTRODUCTION Water budgets provide a means for evaluating availability and sustainability of a water supply. A water budget simply states that the rate of change in water stored in an area, such as a watershed, is balanced by the rate at which water flows into and out of the area. An understanding of water budgets and underlying hydrologic processes provides a foundation for effective water-resource and environmental planning and management. Observed changes in water budgets of an area over time can be used to assess the effects of climate variability and human activities on water resources. Comparison of water budgets from different areas allows the effects of factors such as geology, soils, vegetation, and land use on the hydrologic cycle to be quantified. Human activities affect the natural hydrologic cycle in many ways. Modifications of the land to accommodate agriculture, such as installation of drainage and irrigation systems, alter infiltration, runoff, evaporation, and plant transpiration rates. Buildings, roads, and parking lots in urban areas tend to increase runoff and decrease infiltration. Dams reduce flooding in many areas. Water budgets provide a basis for assessing how a natural or human-induced change in one part of the hydrologic cycle may affect other aspects of the cycle. This report provides an overview and qualitative description of water budgets as foundations for effective water-resources and environmental management of freshwater hydrologic systems. Perhaps of most interest to the hydrologic community, the concepts presented are also relevant to the fields of agriculture, atmospheric studies, meteorology, climatology, ecology, limnology, mining, water supply, flood control, reservoir management, wetland studies, pollution control, and other areas of science, society, and industry. The first part of the report describes water storage and movement in the atmosphere, on land surface, and in the subsurface, as well as water exchange among these compartments. Our ability to measure these phenomena and inherent uncertainties in measurement techniques also are discussed. The latter part of the report presents a number of case studies that illustrate how water-budget studies are conducted, documents how human activities affect water budgets, and describes how water budgets are used to address water and environmental issues.

Circular↗

USGS1996

Numerical evaluation of static-chamber measurements of soil-atmospheric gas exchange--Identification of physical processes

The exchange of gases between soil and atmosphere is an important process that affects atmospheric chemistry and therefore climate. The static-chamber method is the most commonly used technique for estimating the rate of that exchange. We examined the method under hypothetical field conditions where diffusion was the only mechanism for gas transport and the atmosphere outside the chamber was maintained at a fixed concentration. Analytical and numerical solutions to the soil gas diffusion equation in one and three dimensions demonstrated that gas flux density to a static chamber deployed on the soil surface was less in magnitude than the ambient exchange rate in the absence of the chamber. This discrepancy, which increased with chamber deployment time and air-filled porosity of soil, is attributed to two physical factors: distortion of the soil gas concentration gradient (the magnitude was decreased in the vertical component and increased in the radial component) and the slow transport rate of diffusion relative to mixing within the chamber. Instantaneous flux density to a chamber decreased continuously with time; steepest decreases occurred so quickly following deployment and in response to such slight changes in mean chamber headspace concentration that they would likely go undetected by most field procedures. Adverse influences of these factors were reduced by mixing the chamber headspace, minimizing deployment time, maximizing the height and radius of the chamber, and pushing the rim of the chamber into the soil. Nonlinear models were superior to a linear regression model for estimating flux densities from mean headspace concentrations, suggesting that linearity of headspace concentration with time was not necessarily a good indicator of measurement accuracy.

Soil Science Society of America Journal↗

USGS2009

A simple technique for continuous measurement of time-variable gas transfer in surface waters

Mass balance models of dissolved gases in streams, lakes, and rivers serve as the basis for estimating wholeecosystem rates for various biogeochemical processes. Rates of gas exchange between water and the atmosphere are important and error-prone components of these models. Here we present a simple and efficient modification of the SF6 gas tracer approach that can be used concurrently while collecting other dissolved gas samples for dissolved gas mass balance studies in streams. It consists of continuously metering SF6-saturated water directly into the stream at a low rate of flow. This approach has advantages over pulse injection of aqueous solutions or bubbling large amounts of SF6 into the stream. By adding the SF6 as a saturated solution, we minimize the possibility that other dissolved gas measurements are affected by sparging and/or bubble injecta. Because the SF6 is added continuously we have a record of changing gas transfer velocity (GTV) that is contemporaneous with the sampling of other nonconservative ambient dissolved gases. Over a single diel period, a 30% variation in GTV was observed in a second-order stream (Sugar Creek, Indiana, USA). The changing GTV could be attributed in part to changes in temperature and windspeed that occurred on hourly to diel timescales.

Limnology and Oceanography: Methods↗

USGS2017

The difficulty of measuring the absorption of scattered sunlight by H2O and CO2 in volcanic plumes: A comment on Pering et al. “A novel and inexpensive method for measuring volcanic plume water fluxes at high temporal resolution,” Remote Sens. 2017, 9, 146

In their recent study, Pering et al. (2017) presented a novel method for measuring volcanic water vapor fluxes. Their method is based on imaging volcanic gas and aerosol plumes using a camera sensitive to the near-infrared (NIR) absorption of water vapor. The imaging data are empirically calibrated by comparison with in situ water measurements made within the plumes. Though the presented method may give reasonable results over short time scales, the authors fail to recognize the sensitivity of the technique to light scattering on aerosols within the plume. In fact, the signals measured by Pering et al. are not related to the absorption of NIR radiation by water vapor within the plume. Instead, the measured signals are most likely caused by a change in the effective light path of the detected radiation through the atmospheric background water vapor column. Therefore, their method is actually based on establishing an empirical relationship between in-plume scattering efficiency and plume water content. Since this relationship is sensitive to plume aerosol abundance and numerous environmental factors, the method will only yield accurate results if it is calibrated very frequently using other measurement techniques.

Remote Sensing↗

USGS2009

Stratospheric microbiology at 20 km over the Pacific Ocean

An aerobiology sampling flight at 20 km was conducted on 28 April 2008 over the Pacific Ocean (36.5° N, 118–149° W), a period of time that coincided with the movement of Asian dust across the ocean. The aim of this study was to confirm the presence of viable bacteria and fungi within a transoceanic, atmospheric bridge and to improve the resolution of flight hardware processing techniques. Isolates of the microbial strains recovered were analyzed with ribosomal ribonucleic acid (rRNA) sequencing to identify bacterial species Bacillus sp., Bacillus subtilis, Bacillus endophyticus, and the fungal genus Penicillium. Satellite imagery and ground-based radiosonde observations were used to measure dust movement and characterize the high-altitude environment at the time of collection. Considering the atmospheric residency time (7–10 days), the extreme temperature regime of the environment (-75°C), and the absence of a mechanism that could sustain particulates at high altitude, it is unlikely that our samples indicate a permanent, stratospheric ecosystem. However, the presence of viable fungi and bacteria in transoceanic stratosphere remains relevant to understanding the distribution and extent of microbial life on Earth.

Aerobiologia↗

USGS1975

Application of ERTS images and image processing to regional geologic problems and geologic mapping in northern Arizona

The purpose of this study was to apply the techniques of computer image processing to ERTS images as an aid to the solution of some regional geologic problems of significant interest. ERTS-1 images were applied to studies in the Shivwits Plateau, Coconino Plateau, and north-central Arizona regions. Unprocessed ERTS images revealed a wealth of new structural information and enabled a broad regional study to be made of the tectonic history of the southwestern Colorado Plateau. Spectral information from ERTS-1 was shown to be compatible with ground spectral reflectance measurements made with a portable field instrument developed during this investigation, provided that allowance was made for atmospheric effects. Computer image processing yielded lithologic boundary information within the Coconino Plateau region not obtainable from unprocessed images. Various enhancement techniques were compared in the three areas of study, and some simple rules were developed to guide the processing of images in unknown areas. A new hypothesis was developed for the history of the Colorado River. An ancestral and relatively old Upper Colorado Drainage followed approximately its present course as far as the western side of the Kaibab Uplift, where it diverged from the present course by following a strike valley trending north-northwest. This drainage was captured relatively recently by a much younger Lower Colorado Drainage, which developed by headward erosion after the opening of the Gulf of California. A byproduct of the regional studies in each of the three areas was the identification of areas favorable for the localization of shallow and deep ground waters. On the Shivwits Plateau water trapped in the axis of the old strike valley underlying the Shivwits lavas is a potential source. On the Coconino Plateau sandstone lenses, underlain by clays, within the otherwise permeable Kaibab Limestone are potential perched aquifers. These can be identified on computer-enhanced images. Lineaments detected first on ERTS-1 frames and later verified on aerial photographs were used south of Flagstaff, Arizona, to identify maximum fracturing along the Oak Creek fault in the Woody Mountain well field; a site for a new deep well has been selected and is being drilled by the city of Flagstaff.

Arizona↗

USGS1996

Regional evaluation of evapotranspiration in the Everglades

Understanding the water budget of the Everglades system is crucial to the success of restoration and management strategies. Although the water budget is simple in concept, it is difficult to assess quantitatively. Models used to simulate changes in water levels and vegetation resulting from management strategies need to accurately simulate all components of the water budget. One of the most important components of the Everglades water budget is evapotranspiration (ET). ET is water removed from the surface and soils by direct evaporation and plant transpiration. In South Florida, ET rates may exceed 40 in/yr (inches per year) on the average; during dry years, the ET could exceed rainfall (about 50 in/yr). Thus, most of the water that falls on the land surface as rainfall is returned to the atmosphere by ET. Despite the importance of ET in the Everglades water budget, our knowledge of ET is, at present, only semi-quantitative. Recent advances in instrumentation and measurement techniques have made it possible to continuously measure ET, so that an accurate evaluation of ET in the Everglades can be made.

Florida↗

USGS2002

A new method for GPS-based wind speed determinations during airborne volcanic plume measurements

Begun nearly thirty years ago, the measurement of gases in volcanic plumes is today an accepted technique in volcano research. Volcanic plume measurements, whether baseline gas emissions from quiescent volcanoes or more substantial emissions from volcanoes undergoing unrest, provide important information on the amount of gaseous output of a volcano to the atmosphere. Measuring changes in gas emission rates also allows insight into eruptive behavior. Some of the earliest volcanic plume measurements of sulfur dioxide were made using a correlation spectrometer (COSPEC). The COSPEC, developed originally for industrial pollution studies, is an upward-looking optical spectrometer tuned to the ultraviolet absorption wavelength of sulfur dioxide (Millán and Hoff, 1978). In airborne mode, the COSPEC is mounted in a fixed-wing aircraft and flown back and forth just underneath a volcanic plume, perpendicular to the direction of plume travel (Casadevall and others, 1981; Stoiber and others, 1983). Similarly, for plumes close to the ground, the COSPEC can be mounted in an automobile and driven underneath a plume if a suitable road system is available (Elias and others, 1998). The COSPEC can also be mounted on a tripod and used to scan a volcanic plume from a fixed location on the ground, although the effectiveness of this configuration declines with distance from the plume (Kyle and others, 1990). In the 1990’s, newer airborne techniques involving direct sampling of volcanic plumes with infrared spectrometers and electrochemical sensors were developed in order to measure additional gases such as CO2 and H2S (Gerlach and others, 1997; Gerlach and others, 1999; McGee and others, 2001). These methods involve constructing a plume cross-section from several measurement traverses through the plume in a vertical plane. Newer instruments such as open-path Fourier transform infrared (FTIR) spectrometers are now being used to measure the gases in volcanic plumes mostly from fixed locations on the ground. Most FTIR studies to date measure only gas compositions or ratios of gas species (Love and others, 1998; Francis and others, 1998; Horrocks and others, 1999). What all of these methods have in common, however, is the necessity to know plume velocities if accurate gas emission rates are to be calculated. Even open-path FTIR studies done in tandem with a COSPEC require knowledge of plume velocity in order to compute emission rates.

Open-File Report↗

USGS2006

Interferometric synthetic aperture radar: Building tomorrow's tools today

A synthetic aperture radar (SAR) system transmits electromagnetic (EM) waves at a wavelength that can range from a few millimeters to tens of centimeters. The radar wave propagates through the atmosphere and interacts with the Earth’s surface. Part of the energy is reflected back to the SAR system and recorded. Using a sophisticated image processing technique, called SAR processing (Curlander and McDonough, 1991), both the intensity and phase of the reflected (or backscattered) signal of each ground resolution element (a few meters to tens of meters) can be calculated in the form of a complex-valued SAR image representing the reflectivity of the ground surface. The amplitude or intensity of the SAR image is determined primarily by terrain slope, surface roughness, and dielectric constants, whereas the phase of the SAR image is determined primarily by the distance between the satellite antenna and the ground targets, slowing of the signal by the atmosphere, and the interaction of EM waves with ground surface. Interferometric SAR (InSAR) imaging, a recently developed remote sensing technique, utilizes the interaction of EM waves, referred to as interference, to measure precise distances. Very simply, InSAR involves the use of two or more SAR images of the same area to extract landscape topography and its deformation patterns.

Alaska Satellite Facility News and Notes↗

USGS2005

Atmospheric dry deposition in the vicinity of the Salton Sea, California - II: Measurement and effects of an enhanced evaporation system

A study was conducted to determine the effects of salt spray drift from pilot technologies employed by the US Bureau of Reclamation on deposition rates of various air-born ions. An enhanced evaporation system (EES) was tested in the field at the Salton Sea, California. Dry deposition of NO3-, NH4+, SO42-, Cl-, Ca2+, Na+, K+ and Se was assessed by using nylon filters and branches of natural vegetation exposed for one-week long periods. The simultaneous exposure of both lyophilized branches and branches of live plants offered important information highlighting the dynamics of deposited ions on vegetation. The EES significantly increased the deposition rates of Cl-, SO42- and Na+ in an area of about 639-1062 m surrounding the sprayers. Similarly, higher deposition of Ca 2+ and K+ caused by the EES was detected only when deposition was assessed using nylon filters or lyophilized branches. Deposition fluxes of NO3-, NH4+ and Se were not affected by the spraying system. Techniques for measuring dry deposition and calculating landscape-level depositional loads in non-forested systems need further development. ?? 2005 Elsevier Ltd. All rights reserved.

Atmospheric Environment↗

USGS2010

Surface deformation of Augustine Volcano, 1992-2005, from multiple-interferogram processing using a refined Small Baseline Subset (SBAS) Interferometric Synthetic Aperture Radar (InSAR) approach

Augustine Volcano is an active stratovolcano located in southwestern Cook Inlet, about 280 kilometers southwest of Anchorage, Alaska. The volcano produced six significant explosive eruptions between 1812 and 1986. Augustine eruptions typically have an explosive onset followed by dome building. The most recent eruption began on January 11, 2006. We applied the small baseline subset (SBAS) interferometric synthetic aperture radar (InSAR) technique to measure ground surface deformation during 1992-2005 with the use of European Remote Sensing Satellites 1 and 2 (ERS-1 and ERS-2) radar imagery. Through a multiple-interferogram approach, atmospheric delay artifacts, which hinder conventional InSAR measurements, are significantly reduced by spatial and temporal filtering. This allows us to retrieve time-series deformation over coherent points at millimeter-scale accuracy. The deformation results from two independent satellite tracks agree with each other, suggesting 2 to 8 cm wholesale uplift of Augustine Volcano from 1992 to 2005. Global Positioning System (GPS) data acquired in September 2004 and October 2005 confirm the SBAS InSAR results. A preliminary model consisting of a contracting source at 2 to 4 km depth and an inflating source at 7 to 12 km depth fits the observed deformation reasonably well. We interpret the deeper source as a long-term magma storage zone and the shallower source as a subsidiary reservoir that was tapped during the 2006 eruption. The shallow source corresponds approximately to the location of the volcano-tectonic earthquakes that preceded and followed the 1976 and 2006 eruptions, respectively.

Alaska↗

USGS2011

Applying monitoring, verification, and accounting techniques to a real-world, enhanced oil recovery operational CO2 leak

The use of carbon dioxide (CO 2 ) for enhanced oil recovery (EOR) is being tested for oil fields in the Illinois Basin, USA. While this technology has shown promise for improving oil production, it has raised some issues about the safety of CO 2 injection and storage. The Midwest Geological Sequestration Consortium (MGSC) organized a Monitoring, Verification, and Accounting (MVA) team to develop and deploy monitoring programs at three EOR sites in Illinois, Indiana, and Kentucky, USA. MVA goals include establishing baseline conditions to evaluate potential impacts from CO 2 injection, demonstrating that project activities are protective of human health and the environment, and providing an accurate accounting of stored CO 2 . This paper focuses on the use of MVA techniques in monitoring a small CO 2 leak from a supply line at an EOR facility under real-world conditions. The ability of shallow monitoring techniques to detect and quantify a CO 2 leak under real-world conditions has been largely unproven. In July of 2009, a leak in the pipe supplying pressurized CO 2 to an injection well was observed at an MGSC EOR site located in west-central Kentucky. Carbon dioxide was escaping from the supply pipe located approximately 1 m underground. The leak was discovered visually by site personnel and injection was halted immediately. At its largest extent, the hole created by the leak was approximately 1.9 m long by 1.7 m wide and 0.7 m deep in the land surface. This circumstance provided an excellent opportunity to evaluate the performance of several monitoring techniques including soil CO 2 flux measurements, portable infrared gas analysis, thermal infrared imagery, and aerial hyperspectral imagery. Valuable experience was gained during this effort. Lessons learned included determining (1) hyperspectral imagery was not effective in detecting this relatively small, short-term CO 2 leak, (2) even though injection was halted, the leak remained dynamic and presented a safety risk concern during monitoring activities and, (3) the atmospheric and soil monitoring techniques used were relatively cost-effective, easily and rapidly deployable, and required minimal manpower to set up and maintain for short-term assessments. However, characterization of CO 2 distribution near the land surface resulting from a dynamic leak with widely variable concentrations and fluxes was challenging.

Illinois, Indiana, and Kentucky↗

USGS1995

Effects of empirical versus model-based reflectance calibration on automated analysis of imaging spectrometer data: a case study from the Drum Mountains, Utah

Data collected by the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) have been calibrated to surface reflectance using an empirical method and an atmospheric model-based method. Single spectra extracted from both calibrated data sets for locations with known mineralogy compared favorably with laboratory and field spectral measurements of samples from the same locations. Generally, spectral features were somewhat subdued in data calibrated using the model-based method when compared with those calibrated using the empirical method. Automated feature extraction and expert system analysis techniques have been successfully applied to both data sets to produce similar endmember probability images and spectral endmember libraries. Linear spectral unmixing procedures applied to both calibrated data sets produced similar image maps. These comparisons demonstrated the utility of the model-based approach for atmospherically correcting imaging spectrometer data prior to extraction of scientific information. The results indicated that imaging spectrometer data can be calibrated and analyzed without a priori knowledge of the remote target.

Photogrammetric Engineering and Remote Sensing↗

USGS1989

Calorimetry of heterogeneous systems: H+ binding to TiO2 in NaCl

A simultaneous calorimetric and potentiometric technique has been developed for measuring the thermodynamics of proton binding to mineral oxides in the presence of a supporting electrolyte. Modifications made to a commercial titration calorimeter to add a combination pH electrode and maintain an inert atmosphere in the calorimeter reaction vessel are described. A procedure to calibrate potentiometric measurements in heterogeneous systems to correct for the suspension effect on pH is given. The enthalpy change for proton dissociation from TiO 2 in aqueous suspension as a function of pH is reported for 0.01, 0.1, and 0.5 M NaCl. The enthalpy change for proton dissociation is endothermic, ranging from 10.5 ± 3.8 to 45.0 ± 3.8 kJ mol −1 over the pH range from 4 to 10.

Thermochimica Acta↗

USGS2005

Environmental Isotope Characteristics of Landfill Leachates and Gases

The isotopic characteristics of municipal landfill leachate and gases (carbon dioxide and methane) are unique relative to the aqueous and gaseous media in most other natural geologic environments. The δ 13 C of the CO 2 in landfills is significantly enriched in 13 C, with values as high as +20 ‰ reported. The δ 13 C and δD values of the methane fall within a range of values representative of microbial methane produced primarily by the acetate-fermentation process. The δD of landfill leachate is strongly enriched in deuterium, by approximately 30 ‰ to nearly 60 ‰ relative to local average precipitation values. This deuterium enrichment is undoubtedly due to the extensive production of microbial methane within the limited reservoir of a landfill. The concentration of the radiogenic isotopes, 14 C and 3 H, are significantly elevated in both landfill leachate and methane. The 14 C values range between approximately 120 and 170 pMC and can be explained by the input of organic material that was affected by the increased 14 C content of atmospheric CO2 caused by atmospheric testing of nuclear devices. The tritium measured in leachate, however, is often too high to be explained by previous atmospheric levels and must come from material buried within the landfill. The unique isotopic characteristics observed in landfill leachates and gases provide a very useful technique for confirming whether contamination is from a municipal landfill or some other local source.

Groundwater↗