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For the past two years students of the Summer of Applied Geophysical Experience (SAGE) program used various geophysical techniques to map portions of the San Marcos Pueblo, New Mexico. SAGE, a field-based educational program in applied geophysical methods completed its 23rd year of operation in July 2005. SAGE teaches major geophysical exploration methods and applies them to the solution of specific local problems. The San Marcos Pueblo was a large and significant Tano pueblo in the Galisteo Basin south of Santa Fe. It is a sixty-acre preserve, currently owned by the Archaeological Conservancy, containing the remains of thirty-eight room blocks, up to 5,000 rooms, two springs, and the foundations of a seventeenth-century Franciscan Mission complex. Complementary geophysical methods were used to delineate room block walls and kivas, chambers used for ceremonies and meetings. Sufficient evidence was gathered to predict the location of two kivas in 2004. In 2005 we extended the survey areas and confirmed the previous results using ground penetrating radar, loop-loop electromagnetic, magnetic, and shallow refraction and reflection seismic data. The two kivas located in the 2004 fieldwork were resurveyed in addition to structures to the south.

We present results of 32-month project using absolute gravity measurements to monitor groundwater in an arid to semi-arid region in northern New Mexico. Over 100 permanent gravity stations have been established in the groundwater basin. A-10 absolute gravity meters, manufactured by Micro-g LaCoste, Inc., have been used to monitor long-term gravity changes in the groundwater basin. Over fifty A-10 sites have been established; other gravity sites have been established by reference to the primary A-10 sites using Scintrex CG-3M and CG-5 relative gravimeters. Geodetic-quality GPS surveys were used to directly measure any possible elevation changes at the gravity sites. At good sites, away from regions where we expect changes due to groundwater removal, reproducibility of the A-10 measurements is ±4 μGal. Gravity stations were observed approximately every six months over the course of the project. Systematic changes in both gravity and station elevation have been observed at a number of sites. On the basis of our observations, we can delineate three areas which appear to have systematic changes in storage. We conclude that the use of high-precision absolute gravity measurements, in conjunction with precise observations of station elevation, can provide useful information for evaluating groundwater storage changes over time.

Since 2001, the Summer of Applied Geophysical Experience (SAGE) geophysical field course has been applying geophysical techniques to the exploration of archaeological sites in northern New Mexico. Magnetic, electromagnetic (EM), ground penetrating radar (GPR) and seismic methods have been employed. Important results have been obtained at four different sites. Two examples of interpretive results are presented in this abstract. The application of geophysics to archaeology has both scientific and regulatory consequences. Widespread use of geophysics could potentially improve the site evaluation process. From an educational perspective, the data and problems associated with these archaeological sites have been challenging, stimulating and compatible with the goals of the SAGE course.

As part of the Summer of Applied Geophysical Experience (SAGE), a field-based educational program in applied geophysical methods, several geophysical surveys were performed at the San Marcos Pueblo for archaeological purposes. The San Marcos Pueblo was a large and significant Tano pueblo in the Galisteo Basin south of Santa Fe, NM. It is a sixty-acre preserve, currently owned by the Archaeological Conservancy, containing the remains of thirty-eight room blocks, up to 5,000 rooms, two springs, and the foundations of a seventeenth-century Franciscan Mission complex. Over two days in June 2004 SAGE students acquired ground penetrating radar (GPR), loop-loop electromagnetic (EM), magnetic, and shallow refraction seismic data to investigate the buried secrets. The seismic GPR, EM and magnetic data proved to be complementary in delineating room block walls and a possible kiva, a chamber used by men for ceremonies and council meetings. The seismic data were definitive in terms of the dimensions of the kiva.

A-26 ABSOLUTE AND RELATIVE GRAVITY DATA INTEGRATION FOR HIGH PRECISION 4D RESERVOIR MONITORING 1 Based on an estimate 3µGals per 1cm. EAGE 65th Conference & Exhibition — Stavanger Norway 2 - 5 June 2003 1 Abstract In October 2002 BP Exploration Alaska (BPXA) the primary operator of the Prudhoe Bay Oil Field began a large-scale water injection program to counter decreasing pressure on the Prudhoe Bay gas cap. To monitor the progress of the injection program surface gravity measurements will be taken once per year. Reservoir models require total measurement uncertainty to be better than ±10µGals a challenging specification to

The world's first 4-D surface gravity surveillance of a waterflood is being implemented at Prudhoe Bay, Alaska. This monitoring technique is an essential component of the surveillance program for the approved Gas Cap Waterflood Project (GCWI) at Prudhoe Bay. A major factor in the approval of the waterflood was to show that water movement could be economically monitored with a very limited number of wells. Conventional monitoring techniques would have been cost prohibitive due to the requirement for drilling numerous new surveillance wells. Modeling studies indicate that density changes associated with water replacing gas can be detected using high-resolution surface gravity measurements. Field tests at Prudhoe Bay have demonstrated that sufficiently accurate gravity data can be obtained. This paper will discuss both inverse modeling of time differenced gravity maps and four test surveys that have been completed to perfect the gravity measurement technique. Forward and inverse gravity modeling was carried out on a suite of reservoir simulations of the GCWI. Differences in the gravity field with time reflect changes in the reservoir densities, which in turn reflect pore fluid content. A constrained least squares method was used to invert synthetic gravity data for the subsurface density distribution. The modeling procedure has been formulated to allow testing for sensitivity to gravity sampling patterns, noise and various constraints on model parameters such as density, total mass, and moment of inertia. These simulation results have shown that greater than 95% of the injected water can be accounted for in the inverse model. These estimates include reasonable assumptions concerning the noise level in the measurements of both the gravity data and the location data using the Global Positioning System (GPS). The average flood front can be reliably detected within 2000 - 3000 ft. for the Prudhoe Bay reservoir that is buried at 8200 ft to 8800 ft tvd. Time differenced surface gravity and GPS data were gathered over the Arctic Ocean in typical winter conditions (-40 F) accurately enough to monitor the waterflood (gravity = ± 10 ìGals and GPS = ± 1 cm elevation, a íGal is about one billionth of the Earth's normal gravity).

The world’s first 4-D surface gravity surveillance of a waterflood is being implemented at Prudhoe Bay, Alaska. This monitoring technique is an essential component of the surveillance program for the Gas Cap Waterflood Project. A major factor in the approval process for the waterflood was to show that water movement could be economically monitored, with a very limited number of wells penetrating the waterflood area. Conventional monitoring techniques would have been cost prohibitive since they would have required the drilling of numerous surveillance wells. Modeling studies indicate that density changes associated with water replacing gas can be readily detected using high-resolution surface gravity measurements. Modeling of the gravity data determines the mass distribution, mass balance and flood front location. This paper will focus on how to perform an extremely accurate, high-resolution surface gravity survey in the Arctic. Details on survey methodology, meter testing and calibration will be covered. The use of gravity meters in combination with the NAVSTAR Global Positioning System (GPS) for location and elevation will be described. Field tests at Prudhoe Bay indicate that gravity survey accuracy of 5-10 µGal can be achieved using relative gravity meters in combination with GPS. Model results, using reservoir simulations, have indicated that gravity surveys with this accuracy should be able to account for greater than 95% of the injected water.

A recent gravity survey conducted in Prudhoe Bay, Alaska using a newly developed A-10 portable absolute field gravity meter is described. The survey was performed for BP Exploration Alaska (BPXA) to obtain a regional baseline gravity map prior to the initiation of a water injection program scheduled for Fall 2002. Absolute gravity measurements will be used to monitor subsurface density changes over time, and in this current survey, absolute gravity was measured at over 200 sites located on land and ice. The measurements showed repeatability of 3.5 Gal, and production rates were as high as 10 new points per day.

The past decade has seen some very exciting developments in time-lapse or 4D gravity surveys. We are very pleased to present a diverse sampling of applications and new technologies in this special section of GEOPHYSICS, which captures the state of the art in 4D gravity at a time when new reservoir-monitoring applications are maturing into operational status. We think these methodologies have an important future in the development of energy and groundwater resources as well as in carbon sequestration and reduction of natural hazards. It is our hope that the papers in this special section will stimulate further application and development of 4D gravity methods.

A fluidized-bed reactor (FBR) was used to enrich an aerobic chlorophenol-degrading microbial culture. Long-term continuous-flow operation with low effluent concentrations selected oligotrophic microorganisms producing good-quality effluent for pentachlorophenol(PCP)-contaminated water. PCP biodegradation kinetics was studied using this FBR enrichment culture. The results from FBR batch experiments were modeled using a modified Haldane equation, which resulted in the following kinetic constants: qmax = 0.41 mg PCP mg protein-1 day-1, Ks = 16 micrograms l-1, Ki = 5.3 mg l-1, and n = 3.5. These results show that the culture has a high affinity for PCP but is also inhibited by relatively low PCP concentrations (above 1.1 mg PCP l-1). This enrichment culture was maintained over 1 year of continuous-flow operation with PCP as the sole source of carbon and energy. During continuous-flow operation, effluent concentrations below 2 micrograms l-1 were achieved at 268 min hydraulic retention time (tHR) and 2.5 mg PCP l-1 feed concentration. An increase in loading rate by decreasing tHR did not significantly deteriorate the effluent quality until a tHR decrease from 30 min to 21 min resulted in process failure. Recovery from process failure was slow. Decreasing the feed PCP concentration and increasing tHR resulted in an improved process recovery.

When designing models for 2-D seismic refraction inversion, it is desirable to frame the models as polygonal units with well‐defined geophysical characteristics. Such inversion is strongly nonlinear. Random search methods for nonlinear inversion, such as the genetic algorithm and simulated annealing, have received much attention in recent years. Such methods are well suited when the model space is large and contains multiple global minima to the misfit function. Constraints are necessary in the automatic construction of polygonal models. Controlled random search (CRS) is a member of this class of methods that has not been widely exploited. CRS is an iterative process based on the polytope algorithm, which offers a means by which linear constraints may be used. The CRS samples large model spaces, resists local minima, and can find multiple global minima. A new program has been developed for inversion of 2-D seismic refraction data which incorporates geologic compatibility constraints for polygon‐based models. A theoretical example and practical applications of this technique to environmental investigations illustrate its characteristics.

J.L. Brady, SPE, ARCO Alaska Inc., D.S. Wolcott, SPE, Stephen Dean Consulting, P. H. Daggett, ARCO Alaska, Inc., J. F. Ferguson, J. L. Hare, C.L.V. Aiken, and M. Balde, University of Texas at Dallas, J.E. Seibert, EDCON Inc., G. Mader, National Geodetic Survey Abstract A unique method to monitor gas cap water movement in an Arctic environment has been developed and tested. The novel surveillance technique for monitoring the water movement had to be developed given the very limited number of wells that penetrate the gas cap. Conventional fluid monitoring techniques require drilling numerous observation wells to adequately monitor water movement. Modeling studies indicate that density changes associated with water replacing gas can be detected using high-resolution surface gravity measurements. Modeling gravity effects of water movement mass distribution, mass balance and water front detection are discussed. A test of the gravity meter and essential high precision station positioning under typical Arctic winter conditions is evaluated using the Global Positioning System (GPS). Modeling results have shown the general shape of the water front can be detected using surface gravity with Gal precision. With high precision gravity measurements, greater than 90% of the increased water can be accounted for in the resulting gravity anomaly. These estimates include reasonable assumptions concerning the noise level in the measurements of both the gravity data and the location data using the Global Positioning System (GPS). The average water front can be reliably detected within a producing well spacing (approximately 2000 ft (610 m)). Surface gravity and GPS data were gathered over the Arctic Ocean in typical winter conditions (-44 F) accurately enough to monitor the water movement (surface gravity = 5 Gals: GPS = 1 cm elevation). In fact, this was the first high precision gravity survey using a GPS antenna as an integral part of the surface gravity meter housing. Introduction This study evaluates a novel surveillance technique to monitor water movement in the gas cap of a North Slope oil field. The novel surveillance technique uses surface gravity measurements to define water and gas movements. The primary problem with monitoring gas cap water movement using traditional techniques is the sparcity of monitor wells and the lack of producing wells in the gas cap. Since a gas pipeline has not been constructed to market the gas from the North Slope reservoirs, it is re-injected to aid in reservoir pressure maintenance. This results in very few wells in the gas cap area that can be used for water monitoring. Distance between some monitoring wells is greater than 10,000 ft (3048 m). The major concern for monitoring the water movement is to ensure that water added in the gas cap does not prematurely flow down dip into the oil producing portions of the field. Surface gravity instruments measure the Earth's gravitational field at a specific point. With a grid of these measurements local structural traps, stratigraphic traps or fluid movement can be identified from surrounding regional geology providing there is a sufficient density contrast. The surface gravity technique can be applied to any field depending upon the reservoir thickness and size, depth of burial, and the density contrast between the fluids. The surface gravity technique requires that several time lapse gravity surveys be made over the life of the field. The first survey should be performed prior to any change in the fluid volumes to obtain baseline data. Future gravity surveys can be subtracted from the baseline survey to obtain the gravity anomaly associated with the change in fluid volumes. The technique assumes that any other subsurface or near surface gravity anomalies changing with time fall within a tolerable noise level from which the fluid gravity signal can be extracted, or that they be accounted for through direct measurement or modeling. The large reservoir evaluated in this study is buried at approximately 8200 ft (2500 m) and has gas-water density contrast of 0.13 g/cc as the formation gas is replaced by water. P. 381

Abstract The placement of cement in an annulus is a crucial operation in the life of an oil well. To ensure zonal isolation, the drilling mud must be completely displaced from the annulus. Poor displacements require remedial squeeze cementing which is both costly and time consuming. The process is complex, involving the time-dependent motion of multiple non-Newtonian fluids, with different densities and rheologies, flowing in a three dimensional well-bore. Hence, it is not surprising that there are conflicting views on the best possible way to control displacement. This paper discusses the displacement process from both a theoretical and experimental points of view. A lab scale facility has been designed by applying dynamic similarity. This allows a careful investigation of displacement. A brief outline is given of a model for predicting the process. It is shown that the experiments and theory are in excellent qualitative agreement. We discuss some of the controlling mechanisms and show that under some circumstances azimuthal instabilities arise. Finally, we simulate a typical complicated situation and show the importance of good spacer design. Introduction The key to a successful cement job is efficient removal of mud from the annulus between the casing and wellbore. In an eccentric annulus, restricted flow in the narrow side of the annulus may give rise to channeling of the displacing fluid in the wide side, leaving slow moving or immobile mud behind. A widely accepted guideline for cement placement is to pump under turbulent flow conditions. To maximize displacement, the flow must be turbulent all around the annulus. However, this requires higher pump rates in eccentric annuli, which may not always be attainable. Hence, there is a need to design cement jobs under laminar flow conditions. The displacement achieved under laminar flow conditions can vary greatly depending on the material properties of the fluids involved, the pump rate and the well geometry. In some cases, stable high efficiency displacements are obtained, while in others unstable fingering of the displacing fluid occurs resulting in very inefficient displacements. Much of the earlier work followed an empirical approach and provided guidelines that increased the success rate of primary cementing, e.g. pipe movement, use of spacers, etc. McLean et al. defined a critical gel strength in terms of the mud yield stress and the wellbore geometry; minimizing this critical value increases displacement efficiency. Buoyancy forces and pipe movement also contribute to the displacement process. Clark and Carter used a scaled model of a wellbore to study the relative importance of the driving forces that influence mud removal. They conclude that mud/cement density difference, standoff and mud conditioning are the factors affecting the displacement efficiency. Smith reports the results of a series of field tests designed to optimize the displacement efficiency. He regards the fluid velocity as the main factor affecting the displacement process, and suggests that cementing programmes should be designed to achieve high annular velocities. Lockyear et al observe that the criterion for efficient mud removal is a minimum pressure gradient necessary to overcome the combined forces due to the mud yield stress and the mud/displacing fluid density difference. Below this minimum value some mud would remain immobile in the narrow part of the annulus. P. 191^

Determination of fracture orientation can be an important aspect of structural analysis in reservoir characterization. The availability of ground-based laser scanner systems opens up new possibilities for the determination of fracture surface orientation in rock outcrops. Scanners are available in low-sample-density, low-accuracy, and fast, high-sample-density, high-accuracy models. These automatic laser scanner systems produce enormous volumes or “clouds” of point data at an instrument-dependent accuracy and resolution, which can be at the millimeter level. This huge volume of data calls for an automated and objective method of analysis. We have developed a surface classification algorithm based on a multipass partitioning of the point cloud. The method makes use of both spatial proximity and the orientation of an initial coarse-grained model of the point cloud. Unsupervised classification of surface sets is demonstrated herein using the new algorithm. Both previously mentioned types of scanners have been used to map the Jackfork sandstone outcrop at Big Rock Quarry in Little Rock, Arkansas. We apply the surface classification algorithm to these data to extract fracture surface orientations from the point cloud. The effectiveness of these new technologies when applied to fracture analysis is clearly demonstrated in this example. It is also shown that the low-density, low-resolution type of scanner is adequate to define general geomorphology but is inadequate for fracture definition. The surface classification algorithm can be used to reliably extract fracture and bedding strike and dip angles from the three-dimensional point locations acquired using centimeter-accurate, high-density laser scanner systems.

Natural organic matter (NOM) is a ubiquitous and important component of natural waters. Polymeric species related to humus found in soils constitute the major part of NOM. NOM is of major importance for the speciation of metals in waters but its effects on metal corrosion are little known. The influence of NOM on the morphology of corroding copper surfaces is discussed in this communication. The studies were performed for copper coupons exposed for 7 weeks to waters supporting an intense localized corrosion attack called pitting. Two types of waters were used: highly mineralized water at pH close to 7.3 (water A) and soft water at pH close to 9.3 (water B). The morphology of the surface was examined using conventional photography and SEM (JEOL 5200). The range of accelerating voltages was from 10 to 25 kV.Profound effects of NOM on the state of the corroding copper surface were found.

Velocities determined for 50 global positioning system sites within the central Walker Lane indicate differential motion among tectonic blocks forming a boundary zone between the Great Basin extensional province and the Sierra Nevada. The velocity field is related to displacement transfer from the Owens Valley and Furnace Creek fault systems of east- ern California to transtensional structures of the Walker Lane and extensional faults of the central Nevada seismic belt. Block boundaries are sharp and appear to be inherited from pre-Tertiary crustal structure. The block geometries exert strong influence on dif- ferential displacements concentrated along boundaries as belts of divergent, transcurrent, and convergent motion. The aggregate velocity accounts for about 25% of the relative motion between the Pacific and North American plates. About 5 mm/yr of the motion is localized along the eastern margin of the Sierra Nevada, whereas about 10 mm/yr is stepped 100 km east along a belt of east-northeast-trending transtensional faults that merge with northwest-trending transcurrent structures of the Walker Lane. About 6 mm/ yr of the velocity field is transferred to north-northeast-trending extensional faults of the central Nevada seismic belt. The heterogeneous distribution of motions is consistent with partitioning of a regional velocity field formed by westward extension and N408W-directed shear.

“The second AGU Excellence in Geophysical Education Award was presented to the faculty of the Summer of Applied Geophysical Experience (SAGE): Scott Baldridge, Shawn Biehler, Larry Braile, John Ferguson, Bernard Gilpin, and George Jiracek. The persistence and commitment of this group has provided the geophysical community with a superb educational program for over 16 years, reaching nearly 400 students, including undergraduates, graduates, and professionals. The award was presented at the AGU Fall Meeting Honors Ceremony, which was held on December 8, 1998, in San Francisco, California.

Investigations conducted during the 1997 Summer of Applied Geophysical Experience (SAGE) field course at one site at Los Alamos National Laboratory (LANL) successfully delineated a waste disposal trench dug in the 1940s. The survey, which was popular with the students, provided them with important experience in “real world” geophysical problems and demonstrated that students can obtain useful and important results during a short field exercise. The utility of the magnetic, seismic refraction, and ground-penetrating radar methods will be demonstrated on a profile through one of the major waste trenches at the site. The magnetic and radar methods are sensitive to the presence of metallic objects buried within the trenches. A low-velocity trench structure is defined by the seismic refraction data. Models of the trench structure are both accurate (linear dimensions are probably good to within a few meters) and somewhat different from prior expectations.

An Airy‐type geophysical experiment was conducted in a 2‐km‐deep hole in the Greenland ice cap at depths between 213 m and 1673 m to test for possible violations of Newton's inverse square law. The experiment was done at Dye 3, the location of a Distant Early Warning Line radar dome and the site of the deepest of the Greenland Ice‐Sheet Program (GISP) drill holes. Gravity measurements were made at eight depths in 183‐m intervals with a LaCoste&Romberg borehole gravity meter. Prior to the experiment the borehole gravity meter was calibrated with an absolute gravity meter, and the wireline depth‐rinding system used in the borehole logging was calibrated in a vertical mine‐shaft against a laser geodimeter. The density of the ice in the region was calculated from measurements taken from ice cores obtained from earlier drilling observations. Ice penetrating radar was employed in order to correct the gravity data for the topography of the ice‐rock interface. Surface gravity observations were made to assess the extent to which density variations in the sub‐ice rock could affect the vertical gravity gradient. The locations of the gravity observation points were determined with a combination of GPS recording, first‐order leveling, and EDM surveying. An anomalous variation in gravity totaling 3.87 mGal (3.87×10−5 m/s2) in a depth interval of 1460 m was observed. This may be attributed either to a breakdown of Newtonian gravity or to unexpected density variations in the rock below the ice.

La polarisation lineaire permet de mesurer les taux de corrosion et de tirer les conclusions suivantes. Les parametres consideres etant la temperature, le pH, l'oxygene dissous, le chlorure residuaire, le flux et la conductivite, le cuivre est sensible a tous sauf le flux. Le zinc n'est affecte que par la temperature, l'oxygene dissous, le chlore et la conductivite

A geophysical experiment was conducted in a 2-km-deep hole in the Greenland ice cap at depths between 213 m and 1673 m to test for possible violations of Newton's inverse-square law. A detailed ice-sounding radar survey was carried out to 5 km from the hole and merged with regional airborne radar data to define the basement interface. Highly accurate gravity measurements were carried out to 15 km from the hole to detect lateral density changes in the bedrock. The measurements were controlled with very accurate satellite and conventional positioning techniques. The basement interface model was input into a Newtonian computation to correct the observed gravity for known earth structure resulting in an anomalous gravity gradient of +3.87 mGal. A 3 dimensional ideal body analysis of the surface and borehole gravity data provided a means of bounding all possible Newtonian solutions for lateral density variation below the ice. Solutions with regional gravity offsets greater than or equal to10 mGal and density contrasts less than or equal to0.30 g/cm/sup 3/ are possible. We cannot unambiguously attribute the anomalous gradient to a breakdown of Newtonian gravity because there remains the possibility it is due to unexpected geological features in the rock below themore » ice. 11 refs., 6 figs., 1 tab.« less

While the importance of several metal basic carbonates has been recognized in natural and wastewater systems, the existence of the Zn basic carbonate, hydrozincite, has not been fully appreciated even though solubility data have been available. In the presence of 2 mM total inorganic carbonate, Zn 2+ solutions below pH 8.2 were found to precipitate hydrozincite within 24 h and to contain total dissolved Zn concentrations that were comparable to those predicted from equilibrium with hydrozincite. The identity of the hydrozincite was confirmed by X-ray diffraction and elemental analyses. In the pH range 8.2–10.5, the total dissolved Zn concentrations were less than that expected from equilibrium with hydrozincite by factors of up to 3, while the precipitated solids had C:Zn ratios intermediate between those of hydrozincite and give oxide and exhibited weak hydrozincite X-ray diffraction patterns. At pHs above 10.5, zinc oxides with strong X-ray diffraction patterns were present and total dissolved Zn concentrations approached those expected for equilibrium with zinc oxide. In solutions prepared to exclude carbonate, the total dissolved zinc concentrations in all solutions were similar to those expected for equilibrium with zinc oxide. However, two solids in these “carbonate-free” solutions contained small amounts of inorganic carbonate and exhibited weak hydrozincite X-ray diffraction patterns. The presence of well-defined or poorly-crystalline hydrozincite in all 2 mM inorganic carbon solutions between pH 8–10 and its presence in two solutions prepared to exclude carbonate contamination suggest that hydrozincite is probably a common Zn solid formed in conventional precipitation processes.

We present an analysis of the anomalous gravitational attraction found in the Greenland icesheet experiment. If the anomalous gradient is due to the existence of a single new, attractive, force, then the force has a range between 225 m and 5.40 km and a coupling constant between 2.4% and 3.5% that of newtonian gravity, with a best fit of about 805 m and 3.1%, respectively. From our procedure, the chi-squared analysis describing the quality of any fit to parameter values can be immediately scaled if a fraction of the gravitational anomaly is actually due to density anomalies in the bedrock.

An Airy-type geophysical experiment was conducted in a 2-km-deep hole in the Greenland ice cap at depths between 213 and 1673 m to test for possible violations of Newton's inverse-square law. An anomalous gravity gradient was observed. We cannot unambiguously attribute it to a breakdown of Newtonian gravity because we have shown that it might be due to unexpected geological features in the rock below the ice.

A study of sequential anaerobic and aerobic treatment was conducted with combinations of kraft evaporator condensate (KEC) and caustic extraction (CE) stage bleaching effluent. In addition to conventional measures of treatment efficiency, the transformations and removal of sulfur compounds from the KEC and changes in molecular size fraction of organic carbon and organic chlorine were measured. A large fraction of the BOD in the combined waste could be removed in the anaerobic stage at loadings of up to at least 15 kg COD/m3-d. The overall process produced an effluent with

This paper presents a theoretical analysis of antimony corrosion, tin corrosion, and galvanic coupling relationships. Results of coupon and field tests conducted to verify the theory are included. The theoretical and experimental results obtained in this study indicate that 95-5 tin-antimony solder has a potential for replacing lead-based solders in plumbing systems.

When phytoplankton assimilate CO, at the low concentrations existing at high pI1 their uptake rates may be limited by diffusion transport. Dehydroxylation of IICO, to CO, will, however, reduce the effect of transport limitation. In this paper the equation for diffusion with chemical reaction that produces the diffusing substance is solved for a spherical ccl1 with a surface absorption rate given by an equation of the Monod form to yield uptake rate as a function of CO, concentration when transport limited. The influence of cell motility is included. A criterion is derived by which the importance of transport limitation can be ascertained for a cell whose half-saturation constant and maximmn uptake rate are known. In an attempt to explain phytoplankton succession in lakes during summer, King ( 1970) assumed that some species of planktonic algae are limited in growth rate by the very low concentrations of aqueous COZ present in lake water as the pI1 rises during the course of summer. He suggested that organisms that can assimilate CO2 most rapidly at very low concentrations replace those less able to assimilate COz rapidly, Hc also assumed that HC03-, present at equilibrium with and in large concentration relative to C’OQ, acts as a reservoir for COa. King recognized that organisms may assimilate CO2 at such a rapid rate that diffusion transport cannot maintain its concentration near the cell surface at the same magnitude as the equilibrium concentration in the medium in which the cell is immerscd. Hc noted that mixing processes in the water would diminish this effect of the limitation of the supply of COZ by diffusional transport. However, hc assumed that CO2 is formed so rapidly from HC03- that an equilibrium concentration of CO2 is maintained, but did not reconcile this with the lower CO8 concentration near the cell. Goldman et al. ( 1974)) in a study of the kinetics of inorganic carbon uptake by algae, maintained that the uptake rate of or

Arsenate adsorption on amorphous aluminum hydroxide was studied as a model system for aqueous anion adsorption on oxide surfaces. Adsorption and electrophoretic mobility of the suspended adsorbent particles were measured as functions of equilibrium pH. A transformation of variables allowed the adsorption to be explained in terms of the chemical and physical forces controlling the adsorption reaction. When used in conjunction with the Langmuir adsorption equation, the results allow calculation of levels of arsenate removal for any given amount of adsorbent and any pH.

Summary Bioassay studies were conducted on the anaerobic degradation of a simulated pulping wastewater (evaporator condensate) containing sulfur compouds (sulfate, sulfite, or dithionite). Sulfite and dithionite (1000 mg S/l) totally inhibited methane production while sulfate (1000 mg S/l) had a minor effect. High concentrations of sulfite (1000 mg S/l) appeared to inhibit sulfite reduction. Biochemical reduction of dithionite (100–1000 mg S/l) could not be demonstrated. Methane bacteria outcompeted sulfate-reducing bacteria when methanol was the only substrate available. Methanol was utilized by sulfate reducers in the presence of a specific methanogen inhibitor, BES. Increase of the methanol concentration in an acetate -methanol medium stimulated sulfate reduction.

Batch bioassays have been conducted to characterize the response of methanogenic bacteria to several constituents of sulfite evaporator condensate. The results can be grouped into three ranges with increasingly severe consequences to anaerobic reactors: a low concentration, no effect range; a medium concentration range where methanogenesis is temporarily interrupted or slowed down, but may return to normal; and a high concentration range where methanogenesis is permanently inhibited. In some cases the toxicant was metabolized when present in the lower concentration ranges. There was also evidence that mechanisms other than fermentation to methane were significant in accounting for removal of the toxicants from solution. Organisms acclimated to low concentrations of a toxicant are better able to withstand a shock load of that toxicant than are unacclimated organisms.

The Bouguer gravity anomaly at Yucca Flat, Nevada, has been modeled by two different techniques: the Cordell‐Henderson and Parker‐Oldenburg methods. The three‐dimensional model has incorporated known density and structural information where possible. These models predict the structural relief on the Cenozoic‐Paleozoic contact to within 150 m or about 15 percent of the actual depth. The three‐dimensional Parker‐Oldenburg method has been found to be efficient in an application involving a large (9000 sample) data base. Numerical stability was ensured by the application of a consistent regularization (a low‐pass filter tuned to suppress the noise‐dominated portion of the data spectrum) of the downward continuation operator. The use of a single regularizing filter for the entire model is not completely satisfactory due to the oversmoothing of shallow regions of the basin. The model is useful in the delineation of the geologic history of the area. Structural features in the model support the hypothesis that regional stress fields rotated significantly during the Tertiary. Major structural elements of the basin are well defined on the Cenozoic‐Paleozoic interface. The principal basin‐bounding fault is the large‐throw Carpetbag fault on the west. This fault was most active during the earliest phases of subsidence. The Yucca fault is seen to be a much smaller feature in the model presented here. The basin is rotated down to the west, with normal hinge faults on the eastern margin.

The feasibility of recycling ferrihydrite in a metal adsorption process was investigated. In this process, metal ions are removed from dilute solution by sorption onto ferrihydrite and are then desorbed into a more concentrated solution at lower pH. The ferrihydrite thus becomes available for reuse in subsequent sorption operations. Copper, lead, nickel, zinc, cadmium, and chromium(III) can be quantitatively sorbed onto ferrihydrite at pH 9.5. Lowering the pH to 4.5 substantially desorbs the metals. However, for all metals except cadmium, a measurable fraction of the bound metal is not easily desorbed. This fraction increases with increasing pH and duration of the high-pH stage and increases more or less continuously in sequential cycles. The retention of metals in the solid does not interfere with sorption in subsequent cycles, within the range of concentrations investigated. This included retention of up to 0.7 mol of Cr(III)/mol of Fe in the adsorbent. This process has the potential to provide the advantages of sorption processes, including low residual soluble metal concentrations, moderate pH requirements, and simultaneous removal of several metals, without excessive sludge production.

Microearthquake surveys were carried out in three sections of Central and Northern Philippines during 1975-1976 for a period of 5 months. A 4-month survey of Bataan Peninsula identified a major tectonic feature near Manila Bay which could not have been postulated from examination of seismicity maps. This feature appears to be situated near the southern end of ultramafic rocks of West Central Luzon and West Luzon Trough and trends W-SW from east of Corregidor Island toward Manila Trench for a distance of about 100 km. This survey also showed no microearthquake activity beneath two presently inactive volcanoes on Bataan Peninsula. The rate of activity in Bataan Peninsula region was found to be very low (8.4 events/1000 km2/yr). A short-duration survey (16 days) of the Philippine Fault in North Central Luzon revealed no microearthquake activity on the fault. During a third short-duration survey (16 days), the Verde Island Passage area between Luzon and Mindoro was found to be as highly active at the microearthquake level as it is for large earthquakes.

A preliminary analysis of high-frequency (1 to 20 Hz) ambient seismic noise at a very quiet site in southwest Texas is presented. At frequencies greater than 1 Hz, the displacement noise power decreases at a rate between f−4 and f−5. The ambient seismic noise is also characterized by persistent narrow-band peaks (Δf < 0.2 Hz) of unknown origin. The noise appears to be propagating at phase velocities 2.5 to 4 km/sec or greater which suggests higher mode surface or body waves. Estimates of coherence and degree of polarization of three-component array data indicate that the high-frequency ambient noise is relatively well organized over distances of at least 600 to 700 m for a single component but is relatively unorganized in a three-component sense. A principal result of this preliminary analysis is that the use of three-component, high-frequency (1 to 20 Hz) arrays at very quiet sites, coupled with three-component processors, may result in substantial improvement of the thresholds for detection and discrimination of weak seismic events.

Pure cultures of facultative anaerobic bacteria and yeasts were isolated from anaerobic reactors fed synthetic wastewater which contained eight different chlorophenolic compounds. The concentration of facultative anaerobic micro-organisms was followed in the reactor throughout the experimental period, during which the chlorophenol concentrations were increased and many of the chloronated phenols were removed nearly completely. The most common species were Klebsiella spp. and K. Pneumoniae. Some of the common colonies were tentatively identified as Pseudomonas-like organisms and Aeromonas hydrofila. Methanogenic bacteria in the reactor were mainly acetate users. When the total chlorophenol concentration in the feed was increased from zero to 2.4 or 5.3 mg/1, the concentration of Pseudomonas-like organisms increased, as did the concentration of yeasts. Pure and mixed cultures were tested for use of 2,4,6-trichlorophenol (246-TCP) as a sole carbon and energy source under anaerobic conditions. None of the isolates were able to degrade 246-TCP under anaerobic conditions in pure culture. However, mixed cultures containing only P. aeruginosa and K. oxytoca were able to degrade 246-TCP.

During the first year of full-time operation of ten highway runoff monitoring sites in the State of Washington, a total of 241 storms were sampled with a composite sampling system developed by Clark. Vehicle traffic during the storm was found to be the principal factor influencing the mass of suspended solids in the runoff. During winter ice conditions a major fraction of solids loadings in runoff can be traced to sand used. A predictive model for total suspended solids loadings was derived as a function of cumulative traffic during storms. Traffic during the dry periods appeared to remove pollutants from the highways and is not significant in predicting pollutant loadings in the State of Washington.

Presentation de nouvelles procedures pour la conduite des essais de vitesses de corrosion bases sur la mesure des pertes de masse

A device has been developed to measure and to make a composite sample of stormwater runoff from highways. The device was laboratory calibrated and field tested on a portion of Interstate-5 in Seattle, Washington. Performance of the composite sampling device has been compared with conventional discrete sampling instruments. The major discrepancies between the two systems are due to laboratory and flow measurement errors. When these errors are resolved, the performance of the composite and discrete systems are almost identical.

Anaerobic treatment requires maintenance of a stable pH near the neutral range. In evaluating treatment of an acidic waste from chemical pulping, neutralization costs were identified as an important factor. Conceptual and mathematical models of the anaerobic process were formulated incorporating bacterial transformations and chemical equilibria. Simulations were used to compare the effects of several sodium bases, to assess the role of SO 2 and H 2 S in controlling the neutralization requirements, and to evaluate effluent recycle as a tool for increasing influent pH. Gas stripping to reduce CO 2 in the recycle was also evaluated. This modeling approach can be applied to other industrial wastes that may be treated anaerobically and can be an important tool in assessing feasibility of treatment of acidic wastes.

A list of 59 earthquake events felt in North Carolina between 1732 and 1900 has been compiled. It is the most complete such list yet catalogued. Thirty-eight of these events probably had their epicenters within the state or within a few miles of the state line. Much of the activity cannot easily be related to known geologic structures although some of the epicenters fall near the Blue Ridge front and the Brevard zone, near the border faults of the Dan River and Deep River Triassic Basins, and in the Cape Fear Arch region. Magnitudes of the N.C. events were all probably less than 4.5 on the Richter Scale. The maximum intensities experienced were due to the New Madrid, Missouri, earthquakes of 1811–12 and the Charleston, South Carolina, earthquake of 1886. There is a correlation between the growing population of N. C. from 1732 and the number of reported events but the state probably became saturated with respect to seismic detection around 1855 and, hence, the increase in seismic activity after 1870 is probably of genuine geologic origin. Among the most interesting events is the 1874 swarm near Rumbling Bald Mountain in McDowell County when more than 75 earthquakes occurred in two months. Field inspection of the site shows huge relatively recent-looking splits in the mountains there that could have been due to this swarm. The historical record of N. C. is probably not long enough to be a very valid basis for making earthquake risk projections into the future. It may be that the greatest threat to N.C. is large earthquakes outside her borders such as those in the Mississippi Valley and South Carolina. On the otherhand, there is nothing now known that can rule out the possibility that the greatest threat to N.C. is within her own boundaries. This latter possibility becomes a very real and serious concern when one studies the land elevation changes currently in progress in eastern N. C.