Case Studies of PSDDF for Phased Placement of Dredged Soils

Use of Terzaghi's one-dimensional consolidation theory is not suitable for consolidation of highly deformable soft clays such as dredged soils. To model this condition, it is necessary to consider non-linear finite strain consolidation behavior, i.e., changes in compressibility and permeability with increasing stress. A one-dimensional non-linear finite strain numerical model, Primary Consolidation, Secondary Compression, and Desiccation of Dredged Fill (PSDDF), has been used to predict the stress-dependent settlement of fine-grained dredged materials. In this paper, two case studies of using PSDDF are discussed to illustrate the applicability and accuracy of PSDDF. The first case study involves PSDDF simulations of laboratory-phased placement of a marine clay dredged from Busan, Korea. PSDDF results are in good agreement with the corresponding results of the laboratory large strain consolidation tests. The other involves estimating the service life of the Craney Island Dredged Material Management Area near Norfolk, Virginia, in the United States. The excellent agreement between measured and calculated values shows that PSDDF is a reliable tool for predicting settlement of dredged material.     

Correlations between microbial indicators, pathogens, and environmental factors in a subtropical Estuary

The objective of this study was to evaluate whether indicator microbes and physical–chemical parameters were correlated with pathogens within a tidally influenced Estuary. Measurements included the analysis of physical–chemical parameters (pH, salinity, temperature, and turbidity), measurements of bacterial indicators (enterococci, fecal coliform, Escherichia coli, and total coliform), viral indicators (somatic and MS2 coliphage), viral pathogens (enterovirus by culture), and protozoan pathogens (Cryptosporidium and Giardia). All pathogen results were negative with the exception of one sample which tested positive for culturable reovirus (8.5 MPN/100 L). Notable physical–chemical parameters for this sample included low salinity (<1 ppt) and high water temperature (31 °C). Indicator bacteria and indicator virus levels for this sample were within average values typically measured within the study site and were low in comparison with levels observed in other freshwater environments. Overall results suggest that high levels of bacterial and viral indicators were associated with low salinity sites.     

Monitoring the remediation of a near shore waste disposal site in Antarctica using the amphipod Paramoera walkeri and diffusive gradients in thin films (DGTs)

The water quality of a marine embayment (Brown Bay) was monitored during the remediation of an abandoned waste disposal site at Casey Station, East Antarctica, using a combination of biomonitoring and chemical methods. The Antarctic amphipod Paramoera walkeri, in field mesocosms suspended in the water column, was deployed adjacent to the site and at two reference sites for periods of 14 days, repeated three times during the remediation period (December to February). Diffusive gradients in thin film (DGT) samplers were deployed for the same periods to provide estimates of dissolved metals. No difference in mortality of amphipods was observed between Brown Bay and reference sites. There were significant differences, however, in accumulated metal concentrations between amphipods from Brown Bay and reference sites, with greater concentrations of antimony, copper, cadmium, lead, iron and tin at Brown Bay. The melt water/runoff treatment strategy employed for the remediation was successful in preventing acute toxic effects, but water quality was reduced at Brown Bay, where increased metal bioavailability may have been high enough to induce chronic effects in some biota. DGT samplers were less sensitive than amphipods in detecting differences in metal concentrations between sites, indicating that metals bound to suspended particulates were a potentially significant source of contamination.     

Baseline metal concentrations in Paramoera walkeri from East Antarctica

Remediation of the Thala Valley waste disposal site near Casey Station, East Antarctica was conducted in the austral summer of 2003/2004. Biomonitoring of the adjacent marine environment was undertaken using the gammaridean amphipod Paramoera walkeri as a sentinel species [Stark, J.S., Johnstone, G.J., Palmer, A.S., Snape, I., Larner, B.L., Riddle, M.J., in press, . Monitoring the remediation of a near shore waste disposal site in Antarctica using the amphipod Paramoera walkeri and diffusive gradients in thin films (DGTs). Marine Pollution Bulletin and references therein]. Determination of uptake of metals and hypothesis testing for differences that could be attributed to contamination required the establishment of baseline metal concentrations in P. walkeri. Baseline metal concentrations from two reference locations in the Windmill Islands are presented here. P. walkeri was a found to be a sensitive bioaccumulating organism that recorded spatial and temporal variability at the reference sites. Measurement of metals in P. walkeri required the development of a simple digestion procedure that used concentrated nitric acid. For the first time, rare earth metals were determined with additional clean procedures required to measure ultra low concentrations using magnetic sector ICP-MS. Certified and in-house reference materials were employed to ensure method reliability.     

Rainfall thresholds for the initiation of landslides in central and southern Europe

Summary We review rainfall thresholds for the initiation of landslides world wide and propose new empirical rainfall thresholds for the Central European Adriatic Danubian South-Eastern Space (CADSES) area, located in central and southern Europe. One-hundred-twenty-four empirical thresholds linking measurements of the event and the antecedent rainfall conditions to the occurrence of landslides are considered. We then describe a database of 853 rainfall events that resulted or did not result in landslides in the CADSES area. Rainfall and landslide information in the database was obtained from the literature; climate information was obtained from the global climate dataset compiled by the Climate Research Unit of the East Anglia University. We plot the intensity-duration values in logarithmic coordinates, and we establish that with increased rainfall duration the minimum intensity likely to trigger slope failures decreases linearly, in the range of durations from 20 minutes to ∼12 days. Based on this observation, we determine minimum intensity-duration (ID) and normalized-ID thresholds for the initiation of landslides in the CADSES area. Normalization is performed using two climatic indexes, the mean annual precipitation (MAP) and the rainy-day-normal (RDN). Threshold curves are inferred from the available data using a Bayesian statistical technique. Analysing the obtained thresholds we establish that lower average rainfall intensity is required to initiate landslides in an area with a mountain climate, than in an area characterized by a Mediterranean climate. We further suggest that for rainfall periods exceeding ∼12 days landslides are triggered by factors not considered by the ID model. The obtained thresholds can be used in operation landslide warning systems, where more accurate local or regional thresholds are not available.     

Galaxies under the cosmic microscope: resolved spectroscopy and new constraints on the z= 1 Tully–Fisher relation

We exploit the gravitational potential of massive cluster lenses to probe the emission-line properties of six   z = 1  galaxies which appear as highly magnified luminous arcs. Using the Gemini Multi-Object Spectrograph (GMOS) integral field spectrograph together with detailed cluster lens models, we reconstruct the intrinsic morphologies and two-dimensional velocity fields in these galaxies on scales corresponds to ∼0.5 kpc (unlensed) at   z = 1  . Four of the galaxies have stable disc-like kinematics, whilst the other two resemble interacting or starburst galaxies. These galaxies lie close to the mean rest-frame I -band Tully–Fisher relation for nearby spirals suggesting a clear preference for hierarchical growth of structure. In the rest-frame B band, the observations suggest  0.5 ± 0.3 mag  of brightening, consistent with increased star-formation activity at   z = 1  . However, the galaxies with stable disc kinematics have more slowly rising rotation curves than expected from galaxies with similar surface brightness in the local Universe. We suggest that this may arise because the distant galaxies have lower bulge masses than their local counterparts. Whilst this study is based on only six galaxies, the gain in flux and in spatial resolution achieved via gravitational magnification provides a much more detailed view of the high-redshift Universe than that possible with conventional surveys.     

NN detectability in Pluto’s atmosphere

Based on the vapor pressure behavior of Pluto’s surface ices, Pluto’s atmosphere is expected to be predominantly composed of N₂ gas. Measurement of the N₂ isotopologue ¹⁵N/¹⁴N ratio within Pluto’s atmosphere would provide important clues to the evolution of Pluto’s atmosphere from the time of formation to its present state. The most straightforward way of determining the N₂ isotopologue ¹⁵N/¹⁴N ratio in Pluto’s atmosphere is via spectroscopic observation of the ¹⁴N¹⁵N gas species. Recent calculations of the 80–100 nm absorption behavior of the ¹⁴N₂ and ¹⁴N¹⁵N isotopologues by Heays et al. (Heays, A.N. et al. [2011]. J. Chem. Phys. 135, 244301), Lewis et al. (Lewis, B.R., Heays, A.N., Gibson, S.T., Lefebvre-Brion, H., Lefebvre, R. [2008]. J. Chem. Phys. 129, 164306); Lewis et al. (Lewis, B.R., Gibson, S.T., Zhang, W., Lefebvre-Brion, H., Robbe, J.-M. [2005]. J. Chem. Phys. 122, 144302), and Haverd et al. (Haverd, V.E., Lewis, B.R., Gibson, S.T., Stark, G. [2005]. J. Chem. Phys. 123, 214304) show that the peak magnitudes of the ¹⁴N₂ and ¹⁴N¹⁵N absorption bandhead cross-sections are similar, but the locations of the bandhead peaks are offset in wavelength by ∼0.05–0.1 nm. These offsets make the segregation of the ¹⁴N₂ and ¹⁴N¹⁵N absorption signatures possible. We use the most recent N₂ isotopologue absorption cross-section calculations and the atmospheric density profiles resulting from photochemical models developed by Krasnopolsky and Cruickshank (Krasnopolsky, V.A., Cruickshank, D.P. [1999]. J. Geophys. Res. 104, 21979–21996) to predict the level of solar light that will be transmitted through Pluto’s atmosphere as a function of altitude during a Pluto solar occultation. We characterize the detectability of the isotopic absorption signature per altitude assuming ¹⁴N¹⁵N concentrations ranging from 0.1% to 2% of the ¹⁴N₂ density and instrumental spectral resolutions ranging from 0.01 to 0.3 nm. Our simulations indicate that optical depth of unity is attained in the key ¹⁴N¹⁵N absorption bands located between 85 and 90 nm at altitudes ∼1100–1600 km above Pluto’s surface. Additionally, an ¹⁴N¹⁵N isotope absorption depth ∼4–15% is predicted for observations obtained at these altitudes at a spectral resolution of ∼0.2–0.3 nm, if the N₂ isotopologue ¹⁵N/¹⁴N percent ratio is comparable to the 0.37–0.6% ratio observed at Earth, Titan and Mars. If we presume that the predicted absorption depth must be at least 25% greater than the expected observational uncertainty, then it follows that a statistically significant detection of these signatures and constraint of the N₂ isotopologue ¹⁴N/¹⁵N ratio within Pluto’s atmosphere will be possible if the attainable observational signal-to noise (S/N) ratio is ?9. The New Horizons (NH) Mission will be able to obtain high S/N, 0.27–0.35 nm full-width half-max 80–100 nm spectral observations of Pluto using the Alice spectrograph. Based on the NH/Alice specifications we have simulated 0.3 nm spectral resolution solar occultation spectra for the 1100–1600 km altitude range, assuming 30 s integration times. These simulations indicate that NH/Alice will obtain spectral observations within this altitude range with a S/N ratio ∼25–50, and should be able to reliably detect the ¹⁴N¹⁵N gas absorption signature between 85 and 90 nm if the ¹⁴N¹⁵N concentration is ∼0.3% or greater. This, additionally, implies that the non-detection of the ¹⁴N¹⁵N species in the 1100–1600 km range by NH/Alice may be used to reliably establish an upper limit to the N₂ isotopologue ¹⁵N/¹⁴N ratio within Pluto’s atmosphere. Similar results may be derived from 0.2 to 0.3 nm spectral resolution observations of any other N₂-rich Solar System or exoplanet atmosphere, provided the observations are attained with similar S/N levels.     

Shear strength of municipal solid waste for stability analyses

This paper investigates the shear strength of municipal solid waste (MSW) using the back analysis of failed waste slopes as well as field and laboratory test results. Shear strength of MSW is a function of many factors such as waste type, composition, compaction, daily cover, moisture conditions, age, decomposition, overburden pressure, etc. These factors together with non-standardized sampling methods, insufficient sample size to be representative of in situ conditions, and limited shear displacement or axial strain imposed during the laboratory shear testing have created considerable scatter in reported results. Based on the data presented herein, large shear displacements are required to mobilize the peak shear strength of MSW which can lead to displacement incompatibility between MSW and the underlying material(s) such as geosynthetic interfaces and foundation soils. The data presented herein are used to develop displacement compatible shear strength parameters for MSW. Recommendations are presented for modeling the displacement and stress dependent strength envelope in stability analyses.     

Smooth profiles from τ (p) and X(p) data

Summary. We reduce the problem of constructing a smooth, 1-D, monotoni-cally increasing velocity profile consistent with discrete, inexact τ ( p ) and X( p ) data to a quadratic programming problem with linear inequality constraints. For a finite-dimensional realization of the problem it is possible to find a smooth velocity profile consistent with the data whenever such a profile exists. We introduce an unusual functional measure of roughness equivalent to the second central moment or 'Variance' of the derivative of depth with respect to velocity for smooth profiles, and we prove that its minimal value is unique. In our experience, solutions minimizing this functional are very smooth in the sense of the two-norm of the second derivative and can be constructed inexpensively by solving one quadratic programming problem. Still smoother models (in more traditional measures) may be generated iteratively with additional quadratic programs. All the resulting models satisfy the τ ( p ) and X( p ) data and reproduce travel-time data remarkably well, although sometimes τ ( p ) data alone are insufficient to ensure arrivals at large X; then an X( p ) datum must be included.