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USGS2017

Methodological considerations of terrestrial laser scanning for vegetation monitoring in the sagebrush steppe

Terrestrial laser scanning (TLS) provides fast collection of high-definition structural information, making it a valuable field instrument to many monitoring applications. A weakness of TLS collections, especially in vegetation, is the occurrence of unsampled regions in point clouds where the sensor’s line-of-sight is blocked by intervening material. This problem, referred to as occlusion, may be mitigated by scanning target areas from several positions, increasing the chance that any given area will fall within the scanner’s line-of-sight from at least one position. Because TLS collections are often employed in remote regions where the scope of sampling is limited by logistical factors such as time and battery power, it is important to design field protocols which maximize efficiency and support increased quantity and quality of the data collected. This study informs researchers and practitioners seeking to optimize TLS sampling methods for vegetation monitoring in dryland ecosystems through three analyses. First, we quantify the 2D extent of occluded regions based on the range from single scan positions. Second, we measure the efficacy of additional scan positions on the reduction of 2D occluded regions (area) using progressive configurations of scan positions in 1 ha plots. Third, we test the reproducibility of 3D sampling yielded by a 5-scan/ha sampling methodology using redundant sets of scans. Analyses were performed using measurements at analysis scales of 5 to 50 cm across the 1-ha plots, and we considered plots in grass and shrub-dominated communities separately. In grass-dominated plots, a center-scan configuration and 5 cm pixel size sampled at least 90% of the area up to 18 m away from the scanner. In shrub-dominated plots, sampling at least 90% of the area was only achieved within a distance of 12 m. We found that 3 and 5 scans/ha are needed to sample at least ~ 70% of the total area (1 ha) in the grass and shrub-dominated plots, respectively, using 5 cm pixels to measure sampling presence-absence. The reproducibility of 3D sampling provided by a 5 position scan layout across 1-ha plots was 50% (shrub) and 70% (grass) using a 5-cm voxel size, whereas at the 50-cm voxel scale, reproducibility of sampling was nearly 100% for all plot types. Future studies applying TLS in similar dryland environments for vegetation monitoring may use our results as a guide to efficiently achieve sampling coverage and reproducibility in datasets.

Idaho↗

USGS2010

The ShakeOut earthquake scenario: Verification of three simulation sets

This paper presents a verification of three simulations of the ShakeOut scenario, an M w 7.8 earthquake on a portion of the San Andreas fault in southern California, conducted by three different groups at the Southern California Earthquake Center using the SCEC Community Velocity Model for this region. We conducted two simulations using the finite difference method, and one by the finite element method, and performed qualitative and quantitative comparisons between the corresponding results. The results are in good agreement with each other; only small differences occur both in amplitude and phase between the various synthetics at ten observation points located near and away from the fault-as far as 150 km away from the fault. Using an available goodness-of-fit criterion all the comparisons scored above 8, with most above 9.2. This score would be regarded as excellent if the measurements were between recorded and synthetic seismograms. We also report results of comparisons based on time-frequency misfit criteria. Results from these two criteria can be used for calibrating the two methods for comparing seismograms. In those cases in which noticeable discrepancies occurred between the seismograms generated by the three groups, we found that they were the product of inherent characteristics of the various numerical methods used and their implementations. In particular, we found that the major source of discrepancy lies in the difference between mesh and grid representations of the same material model. Overall, however, even the largest differences in the synthetic seismograms are small. Thus, given the complexity of the simulations used in this verification, it appears that the three schemes are consistent, reliable and sufficiently accurate and robust for use in future large-scale simulations. ?? 2009 The Authors Journal compilation ?? 2009 RAS.

Geophysical Journal International↗

USGS1995

Distribution and elimination of [ 14 C] sarafloxacin hydrochloride from tissues of juvenile channel catfish (Ictalurus punctatus)

The distribution and loss of radioactivity from tissues were determined in 60 juvenile channel catfish (Ictalurus punctatus) following oral dosing with the candidate fish therapeutant Sarafin® ([ 14 C] sarafloxacin hydrochloride) at 10 mg/kg for 5 consecutive days. Twelve groups of 5 fish each were sampled at selected times ranging from 3 to 240 h after the last dose was administered, The concentration and content of sarafloxacin-equivalent activity was determined in liver, gallbladder, kidney, skin, and skinless fillet by sample oxidation and liquid scintillation counting; content of sarafloxacin-equivalent activity was determined in stomach and anterior and posterior intestines, Skinless fillet tissues were also analyzed for sarafloxacin and for potential metabolites by gradient-elution high-performance liquid chromatography (HPLC) with in-line radiometric and fluorescence detection, Loss of radioactivity from the whole body conformed to a bimodal elimination pattern with a rapid initial phase ( t 1/2 =11 h) and a slower secondary phase ( t 1/2 =222 h). Tissue and contents of the gastrointestinal tract (i.e. stomach and anterior and posterior intestines) were a principal depot of activity during the first four sample times (3, 6, 12, and 24 h); the combined head, skeleton, and fins (i.e. residual carcass) were the principal depot of activity in samples taken after 24 h. Of those tissues sampled 3 h after the last dose, relative sarafloxacin concentration was greatest in the liver (4.06 μg equivalents/g) and least in the residual carcass (1.13 μg equivalents/g), Intermediate concentrations were found in the kidney (2.04 μg equivalents/g), skinless fillet (1.71 μg equivalents/ g), and the skin (1.51 μg equivalents/g). Concentrations of sarafloxacin-equivalent residues in edible skinless fillet were consistently among the lowest of all tissues examined. The highest mean concentration of parent-equivalent material in the fillet tissue was found 12 h after administration of the last dose (2.27 μg equivalents/g) and declined thereafter, Sarafloxacin constituted between 80 and 90% of the extractable radioactive residues from the fillet homogenates. No other peaks were resolved in any of the fillet tissue samples analyzed by HPLC with in-line radiometric detection.

Aquaculture↗

USGS2014

Placing prairie pothole wetlands along spatial and temporal continua to improve integration of wetland function in ecological investigations

We evaluated the efficacy of using chemical characteristics to rank wetland relation to surface and groundwater along a hydrologic continuum ranging from groundwater recharge to groundwater discharge. We used 27 years (1974–2002) of water chemistry data from 15 prairie pothole wetlands and known hydrologic connections of these wetlands to groundwater to evaluate spatial and temporal patterns in chemical characteristics that correspond to the unique ecosystem functions each wetland performed. Due to the mineral content and the low permeability rate of glacial till and soils, salinity of wetland waters increased along a continuum of wetland relation to groundwater recharge, flow-through or discharge. Mean inter-annual specific conductance (a proxy for salinity) increased along this continuum from wetlands that recharge groundwater being fresh to wetlands that receive groundwater discharge being the most saline, and wetlands that both recharge and discharge to groundwater (i.e., groundwater flow-through wetlands) being of intermediate salinity. The primary axis from a principal component analysis revealed that specific conductance (and major ions affecting conductance) explained 71% of the variation in wetland chemistry over the 27 years of this investigation. We found that long-term averages from this axis were useful to identify a wetland’s long-term relation to surface and groundwater. Yearly or seasonal measurements of specific conductance can be less definitive because of highly dynamic inter- and intra-annual climate cycles that affect water volumes and the interaction of groundwater and geologic materials, and thereby influence the chemical composition of wetland waters. The influence of wetland relation to surface and groundwater on water chemistry has application in many scientific disciplines and is especially needed to improve ecological understanding in wetland investigations. We suggest ways that monitoring in situ wetland conditions could be linked with evolving remote sensing technology to improve our ability to better inform decisions affecting wetland sustainability and provide periodic inventories of wetland ecosystem services to document temporal trends in wetland function and how they respond to contemporary land-use change.

North Dakota↗

USGS1985

Uptake, biotransformation, and elimination of rotenone by bluegills (Lepomis macrochirus )

Yearling bluegills ( Lepomis macrochirus ) were exposed to sublethal concentrations of [ 14 C]rotenone (5.2 μg/l) for 30 days in a continuous flow exposure system and then transferred to clean, flowing water for an additional 21-day depuration period. Rates of uptake and elimination and profile of the rotenoid metabolites in head, viscera, and carcass components were evaluated by 14 C counting and by high performance liquid chromatography. Total [ 14 C]rotenone derived activity was relatively uniform in all body components within 3 days after initial exposure and remained constant during the ensuing 27 days of exposure. Initial uptake rate coefficients were highest in viscera (K u = 80· h -1 ) and were nearly identical for head (K u = 14 · h) and carcass (K u = 10 · h -1 ). Analyses of tissue extracts by high performance liquid chromatography confirmed the presence of at least six biotransformation products of rotenone. More than 60% of the activity extracted from viscera was present as a single peak which represented a compound that was extremely soluble in water. Rotenone composed only 0.3% of the extractable activity in viscera taken from fish exposed to rotenone for 30 days; however, rotenone accounted for 15.4% of extractable activity in the head and 20.1% in the carcass components. Rotenolone and 6 ' ,7 ' -dihydro-6 ' -,7 ' --dihydroxyrotenolone were tentatively identified as oxidation products in all tissue extracts. Elimination of 14 C activity from all body components was biphasic; both phases followed first-order kinetics. The rate of elimination was nearly equal for all body components during the initial phase but was most rapid from viscera during the second phase of elimination. Bioconcentration factors for the head, viscera, and carcass were 165, 3,550, and 125, respectively, when calculated on the basis of total 14 C activity but only 25.4, 11, and 26 when calculated as the concentration of parent material.

Aquatic Toxicology↗

USGS2015

Geotechnical soil characterization of intact Quaternary deposits forming the March 22, 2014 SR-530 (Oso) landslide, Snohomish County, Washington

During the late morning of March 22, 2014, a devastating landslide occurred near the town of Oso, Washington. The landslide with an estimated volume of 10.9 million cubic yards (8.3 x 10 6 m 3 ) of both intact glacially deposited and previously disturbed landslide sediments, reached speeds averaging 40 miles per hour (64 kilometers per hour) and crossed the entire 2/3-mile (~1100 m) width of the adjacent North Fork Stillaguamish River floodplain in approximately 60 seconds, resulting in the complete destruction of an entire neighborhood (Iverson and others, 2015). More than 40 homes were destroyed as the debris overran the neighborhood, resulting in the deaths of 43 people. Landslides in glacial deposits are common in the Pacific Northwest (for example, Baum and others, 2008), and in fact, the site of the March 22, 2014 SR-530 landslide had experienced significant reactivation several times in past decades, with the most recent event occurring in 2006 (for example, Miller and Sias, 1998). However, these previous landslides were of considerably less volume and mobility (Iverson and others, 2015), and debris had never reached the Steelhead Haven neighborhood. Further, no landslides with the type of mobility that the March 22, 2014 landslide underwent have been recorded in historic times within the North Fork Stillaguamish River valley. However, mapping performed immediately following the landslide indicates that several other slopes in the North Fork Stillaguamish River valley have experienced large-volume landslides exhibiting high mobility in prehistoric times (Haugerud, 2014). The presence of previous high-mobility landslides in the valley, and the now well-documented occurrence of one involving many fatalities, underscores both the hazard and risk for those that live and travel in this and other river valleys in the Pacific Northwest with similar glacial deposits and precipitation patterns. To understand the hazards posed by highly mobile landslides in the Pacific Northwest, the U.S. Geological Survey (USGS), together with its project partners, the University of California, Berkeley Department of Civil and Environmental Engineering (UCB), and the Washington State Department of Transportation (WSDOT), is undertaking a critically needed study to identify the geologic, hydrogeologic, and geotechnical conditions in which these large landslides initiate, as well as the processes responsible for the exceptional mobility of this, and potentially other, landslides in the region. One of the first study activities involves characterizing the stratigraphy and materials from which the landslide deposits are derived, so that the fundamental geotechnical nature of the soils can be understood. This understanding is required to begin identifying possible conditions leading to slope failure and their relation to the landslide's high mobility. In addition, detailed characterization of each stratigraphic unit encountered in initial geotechnical borings is needed to relate stratigraphy between borings for this study and as a part of ongoing investigations by WSDOT and other project partners. This report provides a description of the methods used to obtain and test the intact soil stratigraphy behind the headscarp of the March 22 landslide. Detailed geotechnical index testing results are presented for 24 soil samples representing the stratigraphy at 19 different depths along a 650 ft (198 m) soil profile. The results include (1) the soil's in situ water content and unit weight (where applicable); (2) specific gravity of soil solids; and (3) each sample's grain-size distribution, critical limits for fine-grain water content states (that is, the Atterberg limits), and official Unified Soil Classification System (USCS) designation. In addition, preliminary stratigraphy and geotechnical relations within and between soil units are presented.

Washington↗

USGS2011

Calibration of Nu-Instruments Noblesse multicollector mass spectrometers for argon isotopic measurements using a newly developed reference gas

The greatest challenge limiting 40 Ar/ 39 Ar multicollection measurements is the availability of appropriate standard gasses to intercalibrate detectors. In particular, use of zoom lens ion-optics to steer and focus ion beams into a fixed detector array (i.e., Nu Instruments Noblesse) makes intercalibration of multiple detectors challenging because different ion-optic tuning conditions are required for optimal peak shape and sensitivity at different mass stations. We have found that detector efficiency and mass discrimination are affected by changes in ion-optic tuning parameters. Reliance upon an atmospheric Ar standard to calibrate the Noblesse is problematic because there is no straightforward way to relate atmospheric 40 Ar and 36 Ar to measurements of 40 Ar and 39 Ar if they are measured on separate detectors. After exploring alternative calibration approaches, we have concluded that calibration of the Noblesse is best performed using exactly the same source, detector, and ion-optic tuning settings as those used in routine 40 Ar/ 39 Ar analysis. To accomplish this, we have developed synthetic reference gasses containing 40 Ar, 39 Ar and 38 Ar produced by mixing gasses derived from neutron-irradiated sanidine with an enriched 38 Ar spike. We present a new method for calibrating the Noblesse based on use of both atmospheric Ar and the synthetic reference gasses. By combining atmospheric Ar and synthetic reference gas in different ways, we can directly measure 40 Ar/ 39 Ar, 38 Ar/ 39 Ar, and 36 Ar/ 39 Ar correction factors over ratios that vary from 0.5 to 460. These correction factors are reproducible to better than ± 0.5‰ (2σ standard error) over intervals spanning ~ 24 h but can vary systematically by ~ 4% over 2 weeks of continuous use when electron multiplier settings are held constant. Monitoring this variation requires daily calibration of the instrument. Application of the calibration method to 40 Ar/ 39 Ar multicollection measurements of widely used sanidine reference materials ACs-2, FCs-2, and TCs-2 demonstrate that calculated 40 Ar*/ 39 Ar K can be accurately corrected to yield model 40 Ar/ 39 Ar ages consistent with those reported by Earthtime 40 Ar/ 39 Ar laboratories. Replicate analyses of 8–12 single-crystal sanidine ages are reproduced to within 1–2‰ (2σ standard error) under optimal analytical conditions. This calibration technique is applicable over a wide range of isotopic ratios and signal sizes. Finally, the reference gas has the added advantage of facilitating straightforward characterization of electron multiplier dead time over a wide dynamic range.

Chemical Geology↗

USGS1969

Pre-nesting and nesting behavior of the Swainson's warbler

The Swainson?s Warbler is one of the least known of southern birds. Although fairly common in some parts of its summer range, observations of its breeding biology have been made by very few persons. The present study was conducted mostly at Macon, Georgia; Pendleton Ferry, Arkansas; and Dismal Swamp, Virginia....In central Georgia and east-central Arkansas, Swainson?s Warblers usually arrive on their territories during the first two weeks in April. Territories in several localities ranged in size from 0.3 to 4.8 acres. A color-marked Arkansas male occupied the same territory for at least four months. Hostile encounters between territorial male Swainson?s Warblers usually take place along the boundary of adjacent territories. Paired males were more aggressive than unpaired males. Toward the end of an encounter one of the two males would usually perform a display in which the wing and tail feathers were spread and the tail vibrated. Following boundary encounters males drifted back onto their territories and usually sang unbroken courses of songs for several minutes.....During pre-nesting at Macon, a mated pair spent the day mostly on the ground within 20 feet of each other, often foragin g 3 to 4 feet apart. What may have been a form of courtship display, in which the male flew from a perch down to the female and either pecked her rump or pounced on her, occurred about three times each hour throughout the day. During this period the male sang less than at other times during the breeding season.....First nests are usually built by the first week in May. Although other investigators reported finding nests of this species outside of the defended territory, all nests that I have found were within the territory. The large, bulky nest of this species usually is placed 2-6 feet above the ground. It is built by the female from materials gathered close to the nest site; and takes two or three days to complete.....Three and occasionally four white eggs are laid. The female incubates for 14-15 days. The Cowbird parasitizes nests in some parts of the breeding range of the Swainson?s Warbler.....During incubation the female spends about 78 per cent of daylight time on the nest. Both sexes feed young and clean nest. Young remain in nest from 10-12 days.

The Wilson Bulletin↗

USGS2007

National volcanic ash operations plan for aviation

The National Aviation Weather Program Strategic Plan (1997) and the National Aviation Weather Initiatives (1999) both identified volcanic ash as a high-priority informational need to aviation services. The risk to aviation from airborne volcanic ash is known and includes degraded engine performance (including flameout), loss of visibility, failure of critical navigational and operational instruments, and, in the worse case, loss of life. The immediate costs for aircraft encountering a dense plume are potentially major—damages up to $80 million have occurred to a single aircraft. Aircraft encountering less dense volcanic ash clouds can incur longer-term costs due to increased maintenance of engines and external surfaces. The overall goal, as stated in the Initiatives, is to eliminate encounters with ash that could degrade the in-flight safety of aircrews and passengers and cause damage to the aircraft. This goal can be accomplished by improving the ability to detect, track, and forecast hazardous ash clouds and to provide adequate warnings to the aviation community on the present and future location of the cloud. To reach this goal, the National Aviation Weather Program established three objectives: (1) prevention of accidental encounters with hazardous clouds; (2) reduction of air traffic delays, diversions, or evasive actions when hazardous clouds are present; and (3) the development of a single, worldwide standard for exchange of information on airborne hazardous materials. To that end, over the last several years, based on numerous documents (including an OFCMsponsored comprehensive study on aviation training and an update of Aviation Weather Programs/Projects), user forums, and two International Conferences on Volcanic Ash and Aviation Safety (1992 and 2004), the Working Group for Volcanic Ash (WG/VA), under the OFCM-sponsored Committee for Aviation Services and Research, developed the National Volcanic Ash Operations Plan for Aviation and Support of the International Civil Aviation Organization’s (ICAO) International Airways Volcano Watch. This plan defines agency responsibilities, provides a comprehensive description of an interagency standard for volcanic ash products and their formats, describes the agency backup procedures for operational products, and outlines the actions to be taken by each agency following an occurrence of a volcanic eruption that subsequently affects and impacts aviation services. Since our most recent International Conference on Volcanic Ash and Aviation Safety, volcanic ash-related product and service activities have grown considerably along with partnerships and alliances throughout the aviation community. In January 2005, the National Oceanic and Atmospheric Administration’s National Centers for Environment Prediction began running the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model in place of the Volcanic Ash Forecast Transport and Dispersion (VAFTAD) model, upgrading support to the volcanic ash advisory community. Today, improvements to the HYSPLIT model are ongoing based on recommendations by the OFCM-sponsored Joint Action Group for the Selection and Evaluation of Atmospheric Transport and Diffusion Models and the Joint Action Group for Atmospheric Transport and Diffusion Modeling (Research and Development Plan). Two international workshops on volcanic ash have already taken place, noticeable improvements and innovations in education, training, and outreach have been made, and federal and public education and training programs on volcanic ash-related products, services, and procedures iv continue to evolve. For example, in partnership with Embry-Riddle Aeronautical University and other academic institutions, volcanic ash hazard and mitigation training has been incorporated into aviation meteorology courses. As an essential next step, our volcanic ash-related efforts in the near term will be centered on the development of an interagency implementation plan to document and address the most critical needs of the volcanic ash advisory community. This interagency plan, developed as the result of the cooperative efforts of six federal agencies, follows the guidelines in support of the ICAO International Airways Volcano Watch. The signatories on the next page are committed to volcanic ash operations for aviation and will work toward full implementation through agency programs, initiatives, and procedures. I extend my sincere thanks to all members of the WG/VA, subject-matter experts, and to my staff for their collaborative and cooperative efforts in developing this first-ever national volcanic ash operations plan.

Report↗

USGS2009

The source of infrasound associated with long-period events at mount St. Helens

During the early stages of the 2004-2008 Mount St. Helens eruption, the source process that produced a sustained sequence of repetitive long-period (LP) seismic events also produced impulsive broadband infrasonic signals in the atmosphere. To assess whether the signals could be generated simply by seismic-acoustic coupling from the shallow LP events, we perform finite difference simulation of the seismo-acoustic wavefield using a single numerical scheme for the elastic ground and atmosphere. The effects of topography, velocity structure, wind, and source configuration are considered. The simulations show that a shallow source buried in a homogeneous elastic solid produces a complex wave train in the atmosphere consisting of P/SV and Rayleigh wave energy converted locally along the propagation path, and acoustic energy originating from , the source epicenter. Although the horizontal acoustic velocity of the latter is consistent with our data, the modeled amplitude ratios of pressure to vertical seismic velocity are too low in comparison with observations, and the characteristic differences in seismic and acoustic waveforms and spectra cannot be reproduced from a common point source. The observations therefore require a more complex source process in which the infrasonic signals are a record of only the broadband pressure excitation mechanism of the seismic LP events. The observations and numerical results can be explained by a model involving the repeated rapid pressure loss from a hydrothermal crack by venting into a shallow layer of loosely consolidated, highly permeable material. Heating by magmatic activity causes pressure to rise, periodically reaching the pressure threshold for rupture of the "valve" sealing the crack. Sudden opening of the valve generates the broadband infrasonic signal and simultaneously triggers the collapse of the crack, initiating resonance of the remaining fluid. Subtle waveform and amplitude variability of the infrasonic signals as recorded at an array 13.4 km to the NW of the volcano are attributed primarily to atmospheric boundary layer propagation effects, superimposed upon amplitude changes at the source.

Washington↗

USGS2020

Combining ash analyses with remote sensing to identify juvenile magma involvement and fragmentation mechanisms during the 2018/19 small eruption of Peteroa volcano (Southern Andes)

The Planchón Peteroa Volcanic Complex (PPVC) is located on the border of Chile and Argentina, and is one of the most active volcanic systems in the Andes. Holocene activity has included magma-water interaction with an evolving series of crater lakes, mainly sourced from Peteroa volcano. This study examines data from the 2018/19 eruption, together with the volcanic history of the PPVC, to elucidate the complex interplay between magmatic activity and summit water and ice. From February 2016 to mid-2019, three seismic swarms occurred in the PPVC, preceding the explosive eruption from September 2018 to April 2019. The activity originated from a small vent nested within the easternmost crater, the most active portion of the complex (Peteroa). The explosions interacted with a crater lake, producing ash plumes up to 2 km above the crater and building a small tephra cone. To investigate the eruption mechanisms, we performed remote sensing analysis of plume dispersal, thermal anomalies and ground deformation, and characterized the volcanic products, including grain size, componentry, morphology, internal textures, composition and mineralogy. Our results suggest that the precursory seismicity beginning in 2016 was related to the intrusion of a new magma batch that reached the surface during the 2018/19 eruption. The eruption was also preceded by thermal anomalies, geomorphic changes and increased hydrothermal activity at the surface, though without any ground deformation recognized through radar interferometry (InSAR). The eruption initially produced predominantly recycled ash (phreatic activity), then evolved to increasing proportions of juvenile magma (phreatomagmatic) by April 2019. The juvenile clasts had a trachyandesite composition (~59 wt% SiO 2 ), with vesicular and dense scoria containing plagioclase and pyroxene. The ash surfaces show external quenching cracks and step fractures consistent with phreatomagmatic fragmentation within the active crater lake. Textural characteristics also point to a slowly ascending batch of magma that was relatively viscous by the time it interacted with water in the crater lake. Notably, these juvenile particles are distinctive from the pre-2018 products. Ash erupted from 2010/11 did not contain recognizable juvenile material, and is inferred to have been a mainly phreatic eruption. Our findings suggest that the interplay between phreatic and phreatomagmatic eruptions fed by small magma batches intruding at shallow levels characterize much of the eruptive behavior of the PPVC during the last three decades. Multi-parametric assessment is a powerful tool to discriminate between phreatic and phreatomagmatic eruptions.

Southern Andes↗

USGS2006

Source parameters of microearthquakes at Mount St Helens (USA)

We estimate the source parameters for a selection of microearthquakes that occurred at Mount St Helens in the period 1995–1998. Excluding the activity of 2004 September, this time period includes the most intense episode of earthquake activity since the last dome-building eruption in 1986 October. 200 seismograms were processed to obtain seismic moments, source radii, stress drops and average fault slip. The source parameters were determined from the spectral analysis of P waves, after correction for attenuation and site effects. In particular, P -wave quality ( Q p ) and site ( S ) factors have been previously calculated in the frequency ranges 2–7 Hz and 18–30 Hz. Because it was impossible to perform corrections for Q p and S over the whole spectrum we applied a new approach, based on the notion of ‘ holed spectrum ’, to estimate spectral parameters. The term ‘ holed spectrum ’ indicates a spectrum lacking corrected spectral amplitude values at certain frequencies. We carried out a statistical study to verify that dealing with the ‘ holed spectrum ’ does not lead to significant differences in the estimates of spectral parameters. We also investigated the dependence of spectral parameters (low-frequency level, corner frequency and high-frequency decay) on the bandwidth of spectral hole, and defined the threshold values for three different spectral models. Displacement ‘ holed spectra ’, corrected by attenuation and site response, are then used to determine spectral parameters in order to calculate seismic source parameters. Seismic moments range from 10 17 to 10 19 dyne-cm, source dimensions from 100 to 350 m, and average fault slip from 0.003 to 0.1 cm. Self-similarity seems to break down in that stress drops are very low (0.1–1 bars). We postulate that seismicity is associated with a brittle shear failure mechanism occurring in a highly heterogeneous material under a relatively low stress regime.

Washington↗

USGS2017

Optimization of on-line hydrogen stable isotope ratio measurements of halogen- and sulfur-bearing organic compounds using elemental analyzer–chromium/high-temperature conversion isotope ratio mass spectrometry (EA-Cr/HTC-IRMS)

Rationale: Accurate hydrogen isotopic analysis of halogen- and sulfur-bearing organics has not been possible with traditional high-temperature conversion (HTC) because the formation of hydrogen-bearing reaction products other than molecular hydrogen (H2) is responsible for non-quantitative H2 yields and possible hydrogen isotopic fractionation. Our previously introduced, new chromium-based EA-Cr/HTC-IRMS (Elemental Analyzer–Chromium/High-Temperature Conversion Isotope Ratio Mass Spectrometry) technique focused primarily on nitrogen-bearing compounds. Several technical and analytical issues concerning halogen- and sulfur-bearing samples, however, remained unresolved and required further refinement of the reactor systems. Methods: The EA-Cr/HTC reactor was substantially modified for the conversion of halogen- and sulfur-bearing samples. The performance of the novel conversion setup for solid and liquid samples was monitored and optimized using a simultaneously operating dual-detection system of IRMS and ion trap MS. The method with several variants in the reactor, including the addition of manganese metal chips, was evaluated in three laboratories using EA-Cr/HTC-IRMS (on-line method) and compared with traditional uranium-reduction-based conversion combined with manual dual-inlet IRMS analysis (off-line method) in one laboratory. Results: The modified EA-Cr/HTC reactor setup showed an overall H2-recovery of more than 96% for all halogen- and sulfur-bearing organic compounds. All results were successfully normalized via two-point calibration with VSMOW-SLAP reference waters. Precise and accurate hydrogen isotopic analysis was achieved for a variety of organics containing F-, Cl-, Br-, I-, and S-bearing heteroelements. The robust nature of the on-line EA-Cr/HTC technique was demonstrated by a series of 196 consecutive measurements with a single reactor filling. Conclusions: The optimized EA-Cr/HTC reactor design can be implemented in existing analytical equipment using commercially available material and is universally applicable for both heteroelement-bearing and heteroelement-free organic-compound classes. The sensitivity and simplicity of the on-line EA-Cr/HTC-IRMS technique provide a much needed tool for routine hydrogen-isotope source tracing of organic contaminants in the environment. Copyright © 2016 John Wiley & Sons, Ltd.

Rapid Communications in Mass Spectrometry↗

USGS2015

Importance of the colmation layer in the transport and removal of cyanobacteria, viruses, and dissolved organic carbon during natural lake-bank filtration

This study focused on the importance of the colmation layer in the removal of cyanobacteria, viruses, and dissolved organic carbon (DOC) during natural bank filtration. Injection-and-recovery studies were performed at two shallow (0.5 m deep), sandy, near-shore sites at the southern end of Ashumet Pond, a waste-impacted, kettle pond on Cape Cod, MA, that is subject to periodic blooms of cyanobacteria and continuously recharges a sole-source drinking-water aquifer. The experiment involved assessing the transport behaviors of bromide (conservative tracer), Synechococcus sp. IU625 (cyanobacterium, 2.6 ± 0.2 µm), AS-1 (tailed cyanophage, 110 nm long), MS2 (coliphage, 26 nm diameter), and carboxylate-modified microspheres (1.7 µm diameter) introduced to the colmation layer using a bag-and-barrel (Lee-type) seepage meter. The injectate constituents were tracked as they were advected across the pond water–groundwater interface and through the underlying aquifer sediments under natural-gradient conditions past push-point samplers placed at &sim;30-cm intervals along a 1.2-m-long, diagonally downward flow path. More than 99% of the microspheres, IU625, MS2, AS-1, and &sim;44% of the pond DOC were removed in the colmation layer (upper 25 cm of poorly sorted bottom sediments) at two test locations characterized by dissimilar seepage rates (1.7 vs. 0.26 m d −1 ). Retention profiles in recovered core material indicated that >82% of the attached IU625 were in the top 3 cm of bottom sediments. The colmation layer was also responsible for rapid changes in the character of the DOC and was more effective (by three orders of magnitude) at removing microspheres than was the underlying 20-cm-thick segment of sediment.

Massachusetts↗

USGS2014

Igneous mineralogy at Bradbury Rise: the first ChemCam campaign at Gale crater

Textural and compositional analyses using ChemCam Remote Micro Imager (RMI) and Laser Induced Breakdown Spectroscopy (LIBS) have been performed on 5 float rocks and coarse gravels along the first 100 meters of the Curiosity traverse at Bradbury rise. ChemCam, the first LIBS instrument sent to another planet, offers the opportunity to assess mineralogic diversity at grain-size scales (∼100μm) and, from this, lithologic diversity. Depth profiling indicates that targets are relatively free of surface coatings. One type of igneous rock is volcanic and includes both aphanitic (Coronation) and porphyritic (Mara) samples. The porphyritic sample shows dark grains that are likely pyroxene megacrysts in a finegrained mesostasis containing andesine needles. Both types have magnesium-poor basaltic compositions and in this respect are similar to the evolved Jake-Matijevic rock [Stolper et al., 2013] analyzed further along the Curiosity traverse both with APXS and ChemCam instruments. The second rock-type encountered is a coarse-grained intrusive rock (Thor Lake) showing equigranular texture with mm size crystals of feldspars and Fe-Ti oxides. Such a rock is not unique at Gale as the surrounding coarse gravels (such as Beaulieu) and the conglomerate Link are dominated by feldspathic (andesine-bytownite) clasts. Finally, alkali feldspar compositions associated with a silica polymorph have been analyzed in fractured filling material of Preble rock and in Stark, a putative pumice or an impact melt. These observations document magmatic diversity at Gale and describe the first fragments of feldspar-rich lithologies (possibly an anorthosite) that may be ancient crust transported from the crater rim and now forming float rocks, coarse gravel or conglomerate clasts.

Journal of Geophysical Research E: Planets↗

USGS2002

Demographic consequences of inbreeding and outbreeding in Arnica montana: A field experiment

1. The genetic constitution of populations may significantly affect demography. Founder populations or isolated remnants may show inbreeding depression, while established populations can be strongly adapted to the local environment. Gene exchange between populations can lead to better performance if heterozygosity levels are restored (heterosis), or to reduced performance if coadapted gene complexes are disrupted (outbreeding depression). 2. Five populations of the self-incompatible perennial Arnica montana (Asteraceae) were analysed for the demographic consequences of inbreeding and of intra- and interpopulation outcrossing, using both small and large populations as donors for the latter. We analysed seed production and seed weight and monitored growth, survival and flowering of offspring introduced as seeds and as 4-week-old seedlings in a 4-year field experiment. 3. Reduced seed set after selfing was probably due to the self-incompatibility system rather than to inbreeding depression. There was a significant increase for seed set after interpopulation crosses, which resulted from the alleviation of low mate availability in one of the small populations. 4. Significant inbreeding depression was observed for growth rates of plants introduced as seedlings. We found significant heterosis for flowering probability of plants introduced as seeds, but for plants introduced as seedlings, heterosis for seedling size and flowering probability was only marginally significant. Outbreeding depression was not observed. 5. The results of this study are important for reinforcement measures in small, remnant populations. Significant differences among populations for all measured fitness components suggest that reinforcement is best achieved using material from several populations. 6. The observed higher survival of seedlings as compared with seeds suggests that it is better to plant individuals than to sow. Sowing, however, is easier and cheaper, and was more likely to eliminate poorly adapted genotypes before they contribute to the next generation.

Journal of Ecology↗

USGS2020

Polymeric nanofiber-carbon nanotube composite mats as fast-equilibrium passive samplers for polar organic pollutants

To improve the performance of polymeric electrospun nanofiber mats (ENMs) for equilibrium passive sampling applications in water, we integrated two types of multiwalled carbon nanotubes (CNTs; with and without surface carboxyl groups) into polyacrylonitrile (PAN) and polystyrene (PS) ENMs. For 11 polar and moderately hydrophobic compounds (−0.07 ≤ log K OW ≤ 3.13), 90% of equilibrium uptake was achieved in under 0.8 days ( t 90% values) in nonmixed ENM-CNT systems. Sorption capacity of ENM-CNTs was between 2- and 50-fold greater than pure polymer ENMs, with equilibrium partition coefficients ( K ENM-W values) ranging from 1.4 to 3.1 log units (L/kg) depending on polymer type (hydrophilic PAN or hydrophobic PS), CNT loading (i.e., values increased with weight percent (wt %) of CNTs), and CNT type (i.e., greater uptake with carboxylated CNTs composites). During field deployment at Muddy Creek in North Liberty, Iowa, optimal ENM-CNTs (PAN with 20 wt % carboxylated CNTs) yielded atrazine concentrations in surface water with a 40% difference relative to analysis of a same-day grab sample. We also observed a mean percent difference of 30 (±20)% when comparing ENM-CNT sampler results to grab sample data collected within 1 week of deployment. With their rapid, high capacity uptake and small material footprint, ENM-CNT equilibrium passive samplers represent a promising alternative to complement traditional integrative passive samplers while offering convenience over large volume grab sampling.

Environmental Science & Technology↗

USGS2023

Toward absolute abundance for conservation applications: Estimating the number of contributors via microhaplotype genotyping of mixed-DNA sample

Molecular methods including metabarcoding and quantitative polymerase chain reaction have shown promise for estimating species abundance by quantifying the concentration of genetic material in field samples. However, the relationship between specimen abundance and detectable concentrations of genetic material is often variable in practice. DNA mixture analysis represents an alternative approach to quantify specimen abundance based on the presence of unique alleles in a sample. The DNA mixture approach provides novel opportunities to inform ecology and conservation by estimating the absolute abundance of target taxa through molecular methods; yet, the challenges associated with genotyping many highly variable markers in mixed-DNA samples have prevented its widespread use. To advance molecular approaches for abundance estimation, we explored the utility of microhaplotypes for DNA mixture analysis by applying a 125-marker panel to 1179 Chinook salmon ( Oncorhynchus tshawytscha ) smolts from the Sacramento-San Joaquin Delta, California, USA. We assessed the accuracy of DNA mixture analysis through a combination of mock mixtures containing DNA from up to 20 smolts and a trophic ecological application enumerating smolts in predator diets. Mock DNA mixtures of up to 10 smolts could reliably be resolved using microhaplotypes, and increasing the panel size would likely facilitate the identification of more individuals. However, while analysis of predator gastrointestinal tract contents indicated DNA mixture analysis could discern the presence of multiple prey items, poor and variable DNA quality prevented accurate genotyping and abundance estimation. Our results indicate that DNA mixture analysis can perform well with high-quality DNA, but methodological improvements in genotyping degraded DNA are necessary before this approach can be used on marginal-quality samples.

California↗