Differential Transport of Escherichia coli Isolates Compared to Abiotic Tracers in a Karst Aquifer

Lack of filtration and rapid transport of groundwater and particulate matter make karst aquifers susceptible to bacterial contamination. This study utilized quantitative polymerase chain reaction (qPCR) to examine the transport and attenuation of two nonvirulent isolates of Escherichia coli (E. coli) in relation to traditional groundwater tracers (rhodamine WT dye and 1-µm diameter latex microspheres) in a karst-conduit aquifer in central Kentucky. Bacterial isolates were labeled with stable isotopes (¹⁵N and ¹³C). All tracers were detected more than 6 km downstream from the injection site and demonstrated overlapping breakthrough curves, with differential transport observed between the two bacterial strains. The E. coli isolate containing the kps gene (low attachment) arrived at sampling sites 1.25 to 36 h prior to the bacterial isolate containing the iha gene (high attachment) and was detected in samples collected following storm events in which the iha isolate was not detected. The storage potential of contaminants within karst systems was demonstrated by the remobilization of all tracers during storm events more than 1 month after injection. Bacteria-sized microspheres were more easily remobilized during periods of increased discharge compared to other tracers. The study demonstrated that molecular biology techniques such as qPCR can be utilized as a sensitive analysis of bacterial tracers in karst aquifers and may prove to be a more sensitive analytical technique than stable isotope analysis for field-scale traces.     

The thermal signature of volcanic eruptions on Io and Earth

We investigate a spectrum-based technique to identify the style of active volcanic eruptions on Jupiter's moon Io. Thermal remote sensing of Io has had to rely primarily on low-spatial-resolution data, similar to low-spatial-resolution satellite data applied to detecting and charting the temporal evolution of terrestrial hot spots. These terrestrial analyses use data from sensors designed to monitor the weather and sea surface temperature. On Io, such low-spatial-resolution data are used to classify eruption styles (modes of emplacement) by means of several criteria related to the temporal evolution of the infrared spectrum associated with the eruptive activity at each hot spot, which we term “thermal signature.” We find that the ratio of the emission at 2 and 5 µm, and how this ratio changes with time, is often diagnostic of eruption style, even in low-spatial-resolution data. Tests using thermal data for terrestrial “ground truth” cases show that our classification system is valid on Earth. The results of our analysis can be used to aid in the design of future space-based instruments that can be used for volcano monitoring on Io, as well as Earth.     

Assessment of Offshore New Jersey Sources of Beach Replenishment Sand by Diversified Application of Geologic and Geophysical Methods

Beach replenishment serves the dual purpose of maintaining a source of tourism and recreation while protecting life and property. For New Jersey, sources for beach sand supply are increasingly found offshore. To meet present and future needs, geologic and geophysical techniques can be used to improve the identification, volume estimation, and determination of suitability, thereby making the mining and manag ing of this resource more effective. Current research has improved both data collection and interpretation of seismic surveys and vibracore analysis for projects investigating sand ridges offshore of New Jersey. The New Jersey Geological Survey in cooperation with Rutgers University is evaluating the capabilities of digital seismic data (in addition to analog data) to analyze sand ridges. The printing density of analog systems limits the dynamic range to about 24 dB. Digital acquisition systems with dynamic ranges above 100 dB can permit enhanced seismic profiles by trace static correction, deconvolution, automatic gain scaling, horizontal stacking and digital filtering. Problems common to analog data, such as wave-motion effects of surface sources, water-bottom reverberation, and bubble-pulse-width can be addressed by processing. More than 160 line miles of digital high-resolution continuous profiling seismic data have been collected at sand ridges off Avalon, Beach Haven, and Barnegat Inlet. Digital multichannel data collection has recently been employed to map sand resources within the Port of New York New Jersey expanded dredge-spoil site located 3 mi offshore of Sandy Hook, New Jersey. Multichannel data processing can reduce multiples, improve signal-to-noise calculations, enable source deconvolution, and generate sediment acoustic velocities and acoustic impedance analysis. Synthetic seismograms based on empirical relationships among grain size distribution, density, and velocity from vibracores are used to calculate proxy values for density and velocity. The seismograms are then correlated to the digital seismic profile to confirm reflected events. They are particularly useful where individual reflection events cannot be detected but a waveform generated by several thin lithologic units can be recognized. Progress in application of geologic and geophysical methods provides advan tages in detailed sediment analysis and volumetric estimation of offshore sand ridges. New techniques for current and ongoing beach replenishment projects not only expand our knowledge of the geologic processes involved in sand ridge origin and development, but also improve our assessment of these valuable resources. These reconnaissance studies provide extensive data to the engineer regarding the suitability and quantity of sand and can optimize placement and analysis of vibracore samples.     

The Winchcombe fireball—That lucky survivor

On February 28, 2021, a fireball dropped ∼0.6 kg of recovered CM2 carbonaceous chondrite meteorites in South-West England near the town of Winchcombe. We reconstruct the fireball's atmospheric trajectory, light curve, fragmentation behavior, and pre-atmospheric orbit from optical records contributed by five networks. The progenitor meteoroid was three orders of magnitude less massive (∼13 kg) than any previously observed carbonaceous fall. The Winchcombe meteorite survived entry because it was exposed to a very low peak atmospheric dynamic pressure (∼0.6 MPa) due to a fortuitous combination of entry parameters, notably low velocity (13.9 km s⁻¹). A near-catastrophic fragmentation at ∼0.07 MPa points to the body's fragility. Low entry speeds which cause low peak dynamic pressures are likely necessary conditions for a small carbonaceous meteoroid to survive atmospheric entry, strongly constraining the radiant direction to the general antapex direction. Orbital integrations show that the meteoroid was injected into the near-Earth region ∼0.08 Myr ago and it never had a perihelion distance smaller than ∼0.7 AU, while other CM2 meteorites with known orbits approached the Sun closer (∼0.5 AU) and were heated to at least 100 K higher temperatures.     

Impact cratering as a cause of climate change,surface alteration,and resurfacing during the early history of Mars

Ancient valley networks (VNs) and related open- and closed-basin lakes are testimony to the presence of flowing liquid water on the surface of Mars in the Late Noachian and Early Hesperian. Uncertain, however, has been the mechanism responsible for causing the necessary rainfall and runoff and/or snowfall and subsequent melting. Impact cratering has been proposed (e.g., Segura et al. 2002) as a process for temporarily raising temperatures and inducing conditions that would produce rainfall, snowmelt, runoff, and formation of the VNs and associated lacustrine features. We refer to the collective effects of this process as the ICASE model (impact cratering atmospheric/surface effects). In this contribution, we assess the proposed impact cratering mechanism in order to understand its climatic implications for early Mars: we outline the step-by-step events in the cratering process and explore the predictions for atmospheric and surface geological consequences. For large and basin-scale impacts, rainfall should be globally and homogeneously distributed and characterized by very high temperatures. Rainfall rates are predicted to be high, ~2 m yr⁻¹, similar to rates in tropical rainforests on Earth, and runoff rates are correspondingly very high. These predicted characteristics do not seem to be consistent with the observed VNs, which are mainly equatorial and not homogeneous in their distribution. Prior to the Late Noachian, however, we predict that basin-scale impact effects are very likely to contribute significantly to degradation of crater rims and regional smoothing of terrain, implying vast resurfacing and resetting of crater ages following large crater and basin-scale impacts. Furthermore, the high temperatures of impact-induced rainwater and snowmelt and the pervasive penetration of heat into the regolith substrate are predicted to have a significant influence on the mineralogical alteration of the crust and its resulting physical properties. We conclude by describing a case example (Isidis basin) and describe how the ICASE model provides an alternative scenario for the interpretation of the layered phyllosilicates in the Nili Fossae and NE Sytris regions. We outline specific conclusions and recommendations designed to improve the ICASE model and to promote further understanding of its implications for the geological, mineralogical, and climate history of early Mars.     

Petrology and oxygen isotopic compositions of calcium‐aluminum‐rich inclusions in primitive CO3.0‐3.1 chondrites

The petrologic and oxygen isotopic characteristics of calcium‐aluminum‐rich inclusions (CAIs) in CO chondrites were further constrained by studying CAIs from six primitive CO3.0‐3.1 chondrites, including two Antarctic meteorites (DOM 08006 and MIL 090010), three hot desert meteorites (NWA 10493, NWA 10498, and NWA 7892), and the Colony meteorite. The CAIs can be divided into hibonite‐bearing inclusions (spinel‐hibonite spherules, monomineralic grains, hibonite‐pyroxene microspherules, and irregular/nodular objects), grossite‐bearing inclusions (monomineralic grains, grossite‐melilite microspherules, and irregular/nodular objects), melilite‐rich inclusions (fluffy Type A, compact type A, monomineralic grains, and igneous fragments), spinel‐pyroxene inclusions (fluffy objects resembling fine‐grained spinel‐rich inclusions in CV chondrites and nodular/banded objects resembling those in CM chondrites), and pyroxene‐anorthite inclusions. They are typically small (98.4 ± 54.4 µm, 1SD) and comprise 1.54 ± 0.43 (1SD) area% of the host chondrites. Melilite in the hot desert and Colony meteorites was extensively replaced by a hydrated Ca‐Al‐silicate during terrestrial weathering and converted melilite‐rich inclusions into spinel‐pyroxene inclusions. The CAI populations of the weathered COs are very similar to those in CM chondrites, suggesting that complete replacement of melilite by terrestrial weathering, and possibly parent body aqueous alteration, would make the CO CAIs CM‐like, supporting the hypothesis that CO and CM chondrites derive from similar nebular materials. Within the CO3.0‐3.1 chondrites, asteroidal alteration significantly resets oxygen isotopic compositions of CAIs in CO3.1 chondrites (?¹⁷O: ?25 to ?2‰) but left those in CO3.0‐3.05 chondrites mostly unchanged (?¹⁷O: ?25 to ?20‰), further supporting the model whereby thermal metamorphism became evident in CO chondrites of petrologic type ≥3.1. The resistance of CAI minerals to oxygen isotope exchange during thermal metamorphism follows in the order: melilite + grossite < hibonite + anorthite < spinel + diopside + forsterite. Meanwhile, terrestrial weathering destroys melilite without changing the chemical and isotopic compositions of melilite and other CAI minerals.     

Determination of Scandium, Yttrium and Rare Earth Elements in Rocks by High Resolution Inductively Coupled Plasma-Mass Spectrometry

The high sensitivity, minimal oxide formation and single internal standard capability of high resolution inductively coupled plasma-mass spectrometry (HR-ICP-MS) is demonstrated in the direct determination of Sc, Y and REE in the international reference materials: basalts (BCR-1, BHVO-1, BIR-1, DNC-1), andesite (AGV-1) andultramafics (UB-N, PCC-1 and DTS-1). Time consuming ion exchange separation or preconcentration were found to be unnecessary. Smooth chondrite normalized plots of the REE in PCC-1 and DTS-1 were obtained in the range 0.8-50 ng g-1 (0.01-0.1x chondrite). Method precision was found to be digestion dependent with an average external repeatability of 2-4% for the basalts, AGV-1 and UB-N, and 10% for PCC-1 and DTS-1. The mass peak due to ⁴⁵Sc was completely resolved from ²⁹Si¹⁶O and ²⁸Si¹⁶O¹H spectral interferences using medium resolution, which casts doubt on the accuracy of Sc determinations using quadrupole ICP-MS. Literature values for Y in rock reference materials were found to be approximately 9% high after HR-ICP-MS and XRF analysis.     

Spatiotemporal dynamics of water sources in a mountain river basin inferred through δ2H and δ18O of water

In mountainous river basins of the Pacific Northwest, climate models predict that winter warming will result in increased precipitation falling as rain and decreased snowpack. A detailed understanding of the spatial and temporal dynamics of water sources across river networks will help illuminate climate change impacts on river flow regimes. Because the stable isotopic composition of precipitation varies geographically, variation in surface water isotope ratios indicates the volume-weighted integration of upstream source water. We measured the stable isotope ratios of surface water samples collected in the Snoqualmie River basin in western Washington over June and September 2017 and the 2018 water year. We used ordinary least squares regression and geostatistical Spatial Stream Network models to relate surface water isotope ratios to mean watershed elevation (MWE) across seasons. Geologic and discharge data was integrated with water isotopes to create a conceptual model of streamflow generation for the Snoqualmie River. We found that surface water stable isotope ratios were lowest in the spring and highest in the dry, Mediterranean summer, but related strongly to MWE throughout the year. Low isotope ratios in spring reflect the input of snowmelt into high elevation tributaries. High summer isotope ratios suggest that groundwater is sourced from low elevation areas and recharged by winter precipitation. Overall, our results suggest that baseflow in the Snoqualmie River may be relatively resilient to predicted warming and subsequent changes to snowpack in the Pacific Northwest.