A Borehole Test for Chlorinated Solvent Diffusion and Degradation Rates in Sedimentary Rock     

Richelle M. Allen-King  Rebecca L. Kiekhaefer  Daniel J. Goode  Paul A. Hsieh  Michelle M. Lorah  Thomas E. Imbrigiotta 《Ground Water Monitoring & Remediation》2022,42(2):23-34

We present a new field measurement and numerical interpretation method (combined termed “test”) to parameterize the diffusion of trichloroethene (TCE) and its biodegradation products (DPs) from the matrix of sedimentary rock. The method uses a dual-packer system to interrogate a low-permeability section of the rock matrix adjacent to a previously contaminated borehole and uses the borehole monitoring history to establish the pretest condition. TCE and its DPs are removed from the groundwater between the packers at the onset of the testing. The parameters estimated by fitting a radial diffusion model to the concentration history and borehole concentration data, also termed back diffusion, are the tortuosity factor and sorption coefficients of TCE and DPs in the rock matrix and the TCE and DP biodegradation rate coefficients in the borehole. We demonstrate the equipment design and the interpretive method using a borehole accessing the gray mudstone at a TCE contaminated site in the Newark Basin. In this test, both nonreactive (bromide) and reactive (trichlorofluoroethene) tracers are used to constrain the estimated parameters; however, the bromide tracer was not needed to estimate the parameters in this test. The parameters estimated from the field test are consistent with values measured independently in laboratory experiments using field samples of similar lithology. From the interpretation, we compute the TCE and DP concentration distributions in the rock matrix prior to the test to illustrate how the results can be used to enhance understanding of contaminant distribution in the rock matrix.  相似文献   

Integrating observations and models to determine the effect of seasonally frozen ground on hydrologic partitioning in alpine hillslopes in the Colorado Rocky Mountains,USA     

David M. Rey  Eve-Lyn S. Hinckley  Michelle A. Walvoord  Kamini Singha 《水文研究》2021,35(10):e14374

This study integrated spatially distributed field observations and soil thermal models to constrain the impact of frozen ground on snowmelt partitioning and streamflow generation in an alpine catchment within the Niwot Ridge Long-Term Ecological Research site, Colorado, USA. The study area was comprised of two contrasting hillslopes with notable differences in topography, snow depth and plant community composition. Time-lapse electrical resistivity surveys and soil thermal models enabled extension of discrete soil moisture and temperature measurements to incorporate landscape variability at scales and depths not possible with point measurements alone. Specifically, heterogenous snowpack thickness (~0–4 m) and soil volumetric water content between hillslopes (~0.1–0.45) strongly influenced the depths of seasonal frost, and the antecedent soil moisture available to form pore ice prior to freezing. Variable frost depths and antecedent soil moisture conditions were expected to create a patchwork of differing snowmelt infiltration rates and flowpaths. However, spikes in soil temperature and volumetric water content, as well as decreases in subsurface electrical resistivity revealed snowmelt infiltration across both hillslopes that coincided with initial decreases in snow water equivalent and early increases in streamflow. Soil temperature, soil moisture and electrical resistivity data from both wet and dry hillslopes showed that initial increases in streamflow occurred prior to deep soil water flux. Temporal lags between snowmelt infiltration and deeper percolation suggested that the lateral movement of water through the unsaturated zone was an important driver of early streamflow generation. These findings provide the type of process-based information needed to bridge gaps in scale and populate physically based cryohydrologic models to investigate subsurface hydrology and biogeochemical transport in soils that freeze seasonally.  相似文献   

Impact basin relaxation at Iapetus     

Guillaume Robuchon  Francis Nimmo  Michelle Kirchoff 《Icarus》2011,214(1):82-90

We investigate impact basin relaxation on Iapetus by combining a 3D thermal evolution model (Robuchon, G., Choblet, G., Tobie, G., Cadek, O., Sotin, C., Grasset, O. [2010]. Icarus 207, 959-971) with a spherical axisymmetric viscoelastic relaxation code (Zhong, S., Paulson, A., Wahr, J. [2003]. Geophys. J. Int. 155, 679-695). Due to the progressive cooling of Iapetus, younger basins relax less than older basins. For an ice reference viscosity of 10¹⁴ Pa s, an 800 km diameter basin relaxes by 30% if it formed in the first 50 Myr but by 10% if it formed at 1.2 Gyr. Bigger basins relax more rapidly than smaller ones, because the inferred thickness of the ice shell exceeds the diameter of all but the largest basins considered. Stereo topography shows that all basins 600 km in diameter or smaller are relaxed by 25% or less. Our model can match the relaxation of all the basins considered, within error, by assuming a single basin formation age (4.36 Ga for our nominal viscosity). This result is consistent with crater counts, which show no detectable age variation between the basins examined.  相似文献   

Examining the utility of random forest and AISA Eagle hyperspectral image data to predict Pinus patula age in KwaZulu-Natal,South Africa     

Michelle Dye  Onisimo Mutanga  Riyad Ismail 《国际地球制图》2013,28(4):275-289

High-data dimensionality is a common problem in hyperspectral data processing. Consequently, remote sensing techniques that reduce the number of bands are considered essential tools for most hyperspectral applications. The aim of this study was to examine the utility of the random forest ensemble to select the optimal subset of hyperspectral bands to predict the age of Pinus patula stands. Airborne AISA Eagle hyperspectral image data were collected over the study area. The random forest ensemble was used to test whether the forward or backward variable selection methods could identify the optimal subset of bands. Results indicate that both the selection methods produced high-predictive accuracies (root mean square error = 3.097 years). However, the backward variable selection method utilized 206 bands for the final model, while the forward variable selection utilized only a small subset of non-redundant bands (n = 9) while preserving the highest model accuracy (R ² = 0.6).  相似文献   

The Impact of Hurricane Katrina on Reported Crimes in Louisiana: A Spatial and Temporal Analysis     

Michael Leitner  Michelle Barnett  Joshua Kent  Tom Barnett 《The Professional geographer》2013,65(2):244-261

This research assesses the impact that one natural disaster—Hurricane Katrina—and subsequent population movements have had on crime in the state of Louisiana. Using Index Crimes from the Louisiana Commission on Law Enforcement and population estimates from the U.S. Census Bureau, time series of violent and nonviolent crime rates were first analyzed using autoregressive, integrated, and moving average (ARIMA) models. Cumulative percentile maps were created next to analyze spatial trends of crime hot and cold spots in the study area. Overall, results from this research support theories that suggest that crime rates remain stable or actually decline in regions receiving evacuees from areas hardest hit by the hurricane. In the case of Orleans Parish, results are inconclusive due to unreliable crime rates for the period following Hurricane Katrina until the beginning of 2006. It is suggested that crime rates in Orleans Parish fell drastically after the storm. However, some crime types, including robbery, burglary, and larceny, returned to pre-Katrina levels and murder and aggravated assault even exceeded prestorm averages by the end of December 2007.  相似文献   

Abiotic reduction of uranium by Fe(II) in soil     

Drew E. Latta  Maxim I. Boyanov  Kenneth M. Kemner  Edward J. O’Loughlin  Michelle M. Scherer 《Applied Geochemistry》2012

Structural Fe(II) has been shown to reduce several oxidized environmental contaminants, including NO₃, chlorinated solvents, Cr(VI), and U(VI). Studies investigating reduction of U(VI) by soils and sediments, however, suggest that abiotic reduction of U(VI) by Fe(II) is not significant, and that direct enzymatic reduction of U(VI) by metal-reducing bacteria is required for U(VI) immobilization as U(IV). Here evidence is presented for abiotic reduction and immobilization of U(VI) by structural Fe(II) in a redoximorphic soil collected from a hillside spring in Iowa. Oxidation of Fe(II) in the soil after reaction with U(VI) was demonstrated by Mössbauer spectroscopy and reduction of U(VI) by the pasteurized soil using U L_III-edge X-ray absorption spectroscopy (XAS). XAS indicates that both reduced U(IV) and oxidized U(VI) or U(V) are present after U(VI) interaction with the Fe(II) containing soil. The EXAFS data show the presence of a non-uraninite U(IV) phase and evidence of the oxidized U(V) or U(VI) fraction being present as a non-uranyl species. Little U(VI) reduction is observed by soil that has been exposed to air and oxidation of Fe(II) to goethite has occurred. Soil characterization based on chemical extractions, Mössbauer spectroscopy, and Fe K-edge XAS indicate that the majority of Fe(II) in the soil is structural in nature, existing in clay minerals and possibly a green rust-like phase. These data provide compelling evidence for abiotic reduction of U(VI) by structural Fe(II) from soil near Fe-rich oxic–anoxic boundaries in natural environments. The work highlights the potential for abiotic reduction of U(VI) by Fe(II) in reduced, Fe-rich environments.  相似文献   

Building resilience to natural hazards in Indonesia: progress and challenges in implementing the Hyogo Framework for Action   总被引：1，自引：0，他引：1  

Riyanti Djalante  Frank Thomalla  Muhammad Sabaruddin Sinapoy  Michelle Carnegie 《Natural Hazards》2012,62(3):779-803

Over the last 50?years, the cost of natural disasters has increased globally and in Indonesia (EM-DAT 2012). We therefore need more systematic efforts in trying to reduce disaster risks. In 2005, the United Nations International Strategy for Disaster Reduction created the Hyogo Framework for Action (HFA) 2005?C2015: ??Building the Resilience of Nations and Communities??, in order to enable a more systematic planning, implementation and evaluation of disaster risk reduction (DRR) activities. In this paper, we examine Indonesia??s success in improving DRR by reviewing the country??s progress in implementing the HFA Priorities for Actions. This includes an analysis of the drivers, challenges and emerging issues in building resilience to natural hazards. The study is undertaken through literature reviews and interviews with 26 representatives of key organisations in DRR and climate change adaptation (CCA) in Indonesia. Our findings indicate that the building disaster resilience in Indonesia has been, to a large extent, driven by the existence of the necessary regulatory policies and frameworks and the participation of various non-government stakeholders. Impediments to process include a lack of capacity and capability for DRR at the local government level, a lack of systematic learning and a lack of commitment from government to mainstream DRR into broader development agendas. Emerging pressing issues that are likely to challenge future resilience building activities include the integration of DRR and CCA and urban risk governance.  相似文献   

Inter-annual variability of wet season freshwater plume extent into the Great Barrier Reef lagoon based on satellite coastal ocean colour observations     

Schroeder T  Devlin MJ  Brando VE  Dekker AG  Brodie JE  Clementson LA  McKinna L 《Marine pollution bulletin》2012,65(4-9):210-223

Riverine freshwater plumes are the major transport mechanism for nutrients, sediments and pollutants into the Great Barrier Reef (GBR) lagoon and connect the land with the receiving coastal and marine waters. Knowledge of the variability of the freshwater extent into the GBR lagoon is relevant for marine park management to develop strategies for improving ecosystem health and risk assessments. In this study, freshwater extent has been estimated for the entire GBR lagoon area from daily satellite observations of the Moderate Resolution Imaging Spectroradiometer (MODIS) between 2002 and 2010. To enable a reliable mapping of freshwater plumes we applied a physics-based coastal ocean colour algorithm, that simultaneously retrieves chlorophyll-a, non-algal particulate matter and coloured dissolved organic matter (CDOM), from which we used CDOM as a surrogate for salinity (S) for mapping the freshwater extent.  相似文献   

The influence of a season of extreme wet weather events on exposure of the World Heritage Area Great Barrier Reef to pesticides     

Kennedy K  Devlin M  Bentley C  Lee-Chue K  Paxman C  Carter S  Lewis SE  Brodie J  Guy E  Vardy S  Martin KC  Jones A  Packett R  Mueller JF 《Marine pollution bulletin》2012,64(7):1495-1507

The 2010-2011 wet season was one of extreme weather for the State of Queensland, Australia. Major rivers adjacent to the Great Barrier Reef (GBR) were discharging at rates 1.5 to >3 times higher than their long term median. Exposure to photosystem II herbicides has been routinely monitored over a period of up to 5 years at 12 inshore GBR sites. The influence of this wet season on exposure to photosystem II herbicides was examined in the context of this long-term monitoring record and during flood plume events in specific regions. Median exposures expressed as diuron equivalent concentration were an average factor of 2.3 times higher but mostly not significantly different (p<0.05) to the median for the long-term monitoring record. The herbicides metolachlor and tebuthiuron were frequently detected in flood plume waters at concentrations that reached or exceeded relevant water quality guidelines (by up to 4.5 times).  相似文献   

100 Myr record of sequences, sedimentary facies and sea level change from Ocean Drilling Program onshore coreholes, US Mid-Atlantic coastal plain     

James V. Browning  Kenneth G. Miller  Peter J. Sugarman †  Michelle A. Kominz‡  Peter P. McLaughlin§  rew A. Kulpecz  Mark D. Feigenson 《Basin Research》2008,20(2):227-248

We analyzed the latest Early Cretaceous to Miocene sections (～110–7 Ma) in 11 New Jersey and Delaware onshore coreholes (Ocean Drilling Program Legs 150X and 174AX). Fifteen to seventeen Late Cretaceous and 39–40 Cenozoic sequence boundaries were identified on the basis of physical and temporal breaks. Within‐sequence changes follow predictable patterns with thin transgressive and thick regressive highstand systems tracts. The few lowstands encountered provide critical constraints on the range of sea‐level fall. We estimated paleowater depths by integrating lithofacies and biofacies analyses and determined ages using integrated biostratigraphy and strontium isotopic stratigraphy. These datasets were backstripped to provide a sea‐level estimate for the past ～100 Myr. Large river systems affected New Jersey during the Cretaceous and latest Oligocene–Miocene. Facies evolved through eight depositional phases controlled by changes in accommodation, long‐term sea level, and sediment supply: (1) the Barremian–earliest Cenomanian consisted of anastomosing riverine environments associated with warm climates, high sediment supply, and high accommodation; (2) the Cenomanian–early Turonian was dominated by marine sediments with minor deltaic influence associated with long‐term (10⁷ year) sea‐level rise; (3) the late Turonian through Coniacian was dominated by alluvial and delta plain systems associated with long‐term sea‐level fall; (4) the Santonian–Campanian consisted of marine deposition under the influence of a wave‐dominated delta associated with a long‐term sea‐level rise and increased sediment supply; (5) Maastrichtian–Eocene deposition consisted primarily of starved siliciclastic, carbonate ramp shelf environments associated with very high long‐term sea level and low sediment supply; (6) the late Eocene–Oligocene was a starved siliciclastic shelf associated with moderately high sea‐level and low sediment supply; (7) late early–middle Miocene consisted of a prograding shelf under a strong wave‐dominated deltaic influence associated with major increase in sediment supply and accommodation due to local sediment loading; and (8) over the past 10 Myr, low accommodation and eroded coastal systems were associated with low long‐term sea level and low rates of sediment supply due to bypassing.  相似文献