Multimedia Risk-Based Soil Cleanup at a Gasoline-Contaminated Site Using Vapor Extraction

At a utility service center, gasoline from an underground storage tank had leaked into subsurface vadose zone soils for several years. To remediate the site, a soil vapor extraction (SVE) system was installed and operated. At the completion of the SVE operation, gasoline-containing residues in several confirmation soil borings exceeded agency-mandated cleanup levels. Rather than continue with SVE, a risk-based approach was developed to evaluate what levels of gasoline-containing residues could be left in the soil and still protect human health. The risk-based approach consisted of simulating the fate of chemical residues through the vadose zone and then into both the ground water and atmosphere. Receptor point concentrations were predicted, and health risks were assessed. The risk assessment concluded that ingestion of contaminated ground water and inhalation of air while showering were the largest potential contributors to risk, and that risks associated with inhalation of vapor-containing ambient air are small. However, all predicted risks are below the acceptable risk levels of 10⁻⁶ individual cancer risk probability and 1.0 hazard index. Therefore, the lead agency accepted the recommendation that the site requires no further remediation. The service center continues normal operations today.     

Parameter tests within cosmological simulations of galaxy formation

Numerical simulations of galaxy formation require a number of parameters. Some of these are intrinsic to the numerical integration scheme (e.g., the time-step), while others describe the physical model (e.g., the gas metallicity). In this paper we present results of a systematic exploration of the effects of varying a subset of these parameters on simulations of galaxy formation. We use N -body and 'Smoothed Particle Hydrodynamics' techniques to follow the evolution of cold dark matter and gas in a small volume. We compare a fiducial model with 24 different simulations, in which one parameter at a time is varied, focusing on properties such as the relative fraction of hot and cold gas, and the abundance and masses of galaxies. We find that for reasonable choices of numerical values, many parameters have relatively little effect on the galaxies, with the notable exception of the parameters that control the resolution of the simulation and the efficiency with which gas cools.     

Implications of Quaternary volcanism at Cerro Tuzgle for crustal and mantle evolution of the Puna Plateau,Central Andes,Argentina

The high-K Tuzgle volcanic center, (24° S, 66.5° W) along with several small shoshonitic centers, developed along extensional Quaternary faults of the El Toro lineament on the east-central Puna plateau, 275 km east of the main front of the Andean Central Volcanic Zone (CVZ). These magmas formed by complex mixing processes in the mantle and thickened crust (>50 km) above a 200 km deep scismic zone. Tuzgle magmas are differentiated from shoshonitic series magmas by their more intraplate-like Ti group element characteristics, lower incompatible element concentrations, and lower ⁸⁷Sr/⁸⁶Sr ratios at a given Nd. Underlying Mio-Pliocene volcanic rocks erupted in a compressional stress regime and have back-arc like calc-alkaline chemical characteristics. The Tuzgle rocks can be divided into two sequences with different mantle precursors: a) an older, more voluminous rhyodacitic (ignimbrite) to mafic andestitic (56% to 71% SiO₂) sequence with La/Yb ratios <30, and b) a younger andesitic sequence with La/Yb ratios >35. La/Yb ratios are controlled by the mafic components: low ratios result from larger mantle melt percentages than high ratios. Shoshonitic series lavas (52% to 62% SiO₂) contain small percentage melts of more isotopically enriched arc-like mantle sources. Some young Tuzgle lavas have a shoshonitic-like component. Variable thermal conditions and complex stress system are required to produce the Tuzgle and shoshonitic series magmas in the same vicinity. These conditions are consistent with the underlying mantle being in transition from the thick mantle lithosphere which produced rare shoshonitic flows in the Altiplano to the thinner mantle lithosphere that produced back-are calc-alkaline and intraplate-type flows in the southern Puna. Substantial upper crustal type contamination in Tuzgle lavas is indicated by decreasing Nd (-2.5 to-6.7) with increasing ⁸⁷Sr/⁸⁶Sr (0.7063 to 0.7099) ratios and SiO₂ concentrations, and by negative Eu anomalies (Eu/Eu^* <0.78) in lavas that lack plagioclase phenocrysts. Trace element arguments indicate that the bulk contaminant was more silicic than the Tuzgle ignimbrite and left a residue with a high pressure mineralogy. Crustal shortening processes transported upper crustal contaminants to depths where melting occurred. These contaminants mixed with mafic magmas that were fractionating mafic phases at high pressure. Silicic melts formed at depth by these processes accumulated at a mid to upper crustal discontinuity (decollement). The Tuzgle ignimbrite erupted from this level when melting rates were highest. Subsequent lavas are mixtures of contaminated mafic magmas and ponded silicic melts. Feldspar and quartz phenocrysts in the lavas are phenocrysts from the ponded silicic magmas.     

Spatial Transgression and the BYU Jerusalem Center Controversy*

Dominant groups tend to construct the meaning of places to justify and sustain their ideology and orthodoxy in order to solidify power and to maintain their control over others. New outsider groups whose ideology disrupts the established order and sovereignty of the dominant group can be labeled transgressive ( Sibley 1995; Cresswell 1996 ). Transgressions of hegemonic spaces force dominant groups to reexamine themselves and to reaffirm or to modify their position. This concept of transgression is used to examine the controversy surrounding the building of the Brigham Young University Jerusalem Center in the mid‐1980s in Jerusalem. The public outcry among some Israelis over the building of this educational edifice concerned the potential use of the Jerusalem Center as a focal point for Mormon (Latter‐day Saints) proselytizing efforts. We examine the way the Jerusalem Center was viewed and depicted by its opponents, suggesting how basic geographic concepts such as scale and site further refine the concept of spatial transgression for buildings and urban redevelopment.     

Climate change and river flooding: part 1 classifying the sensitivity of British catchments

Effective national and regional policy guidance on climate change adaptation relies on robust scientific evidence. This two-part series of papers develops and implements a novel scenario-neutral framework enabling an assessment of the vulnerability of flood flows in British catchments to climatic change, to underpin the development of guidance for the flood management community. In this first part, the sensitivity of the 20-year return period flood peak (RP20) to changes in precipitation (P), temperature (T) and potential evapotranspiration (PE) is systematically assessed for 154 catchments. A sensitivity domain of 4,200 scenarios is applied combining 525 and 8 sets of P and T/PE mean monthly changes, respectively, with seasonality incorporated using a single-phase harmonic function. Using the change factor method, the percentage change in RP20 associated with each scenario of the sensitivity domain is calculated, giving flood response surfaces for each catchment. Using a clustering procedure on the response surfaces, the 154 catchments are divided into nine groups: flood sensitivity types. These sensitivity types show that some catchments are (very) sensitive to changes in P but others buffer the response, while the location of catchments of the same type does not show any strong geographical pattern. These results reflect the range of hydrological processes found in Britain, and demonstrate the potential importance of catchment properties (physical and climatic) in the propagation of change in climate to change in floods, and so in characterising the sensitivity types (covered in the companion paper).     

Modern and historical tropical cyclone and tsunami deposits at the coast of Myanmar: Implications for their identification and preservation in the geological record

The catastrophic storm surge of tropical cyclone Nargis in May 2008 demonstrated Myanmar's exposure to coastal flooding. The investigation of sediments left by tropical cyclone Nargis and its predecessors is an important contribution to prepare for the impact of future tropical cyclones and tsunamis in the region, because they may extend the database for long-term hazard assessment beyond the relatively short instrumental and historical record. This study, for the first time, presents deposits of modern and historical tropical cyclones and tsunamis from the coast of Myanmar. The aim is to establish regional sedimentary characteristics that may help to identify and discriminate cyclones and tsunamis in the geological record, and to document post-depositional changes due to tropical weathering in the first years after deposition. These findings if used to interpret older deposits will extend the existing instrumental record of flooding events in Myanmar. Evaluating deposits that can be related to specific events, such as the 2006 tropical cyclone Mala and the 2004 Indian Ocean tsunami, indicates similar sedimentary characteristics for both types of sediments. Landward thinning and fining trends, littoral sediment sources and sharp lower contacts allow for the differentiation from underlying deposits, while discrimination between tropical cyclone and tsunami origin is challenging based on the applied methods. The modern analogues also demonstrate a rather low preservation potential of the sand sheets due to carbonate dissolution, formation of organic top soils, and coastal erosion. However, in coastal depressions sand sheets of sufficient thickness (>10 cm) may be preserved where the shoreline is prograding or stable. In the most seaward swale of a beach-ridge plain at the Rakhine coast, two sand sheets have been identified in addition to the deposits of 2006 tropical cyclone Mala. Based on a combination of optically stimulated luminescence, radiocarbon and ¹³⁷Cs dating, the younger sand layer is related to 1982 tropical cyclone Gwa, while the older sand layer is most probably the result of an event that took place prior to 1950. Comparison with historical records indicates that the archive is only sensitive to tropical cyclones of category 4 (or higher) with landfall directly in or a few tens of kilometres north of the study area. While the presented tropical cyclone records are restricted to the last 100 years, optically stimulated luminescence ages of the beach ridges indicate that the swales landward of the one investigated in this study might provide tropical cyclone information for at least the past 700 years.     

Water mass exchange and diapycnal mixing at Bussol’ Strait revealed by water mass properties

Intensive CTD observations that resolve the mean and tidal components were done with a total of 129 casts in summer of 2001 at Bussol’ Strait. Based on these data and all the available historical data, we have revealed the outflow from Bussol’ Strait to the Pacific and the significant diapycnal mixing in the strait. In the range 27.0−27.3σ _θ , the water property in Bussol’ Strait is almost identical to that of the Kuril Basin Water (KBW). The KBW out of Bussol’ Strait forms a water mass front with the East Kamchatka Current Water (EKCW). This front also corresponds to the front of the Oyashio Current. In the lower part of the intermediate layer (27.3−27.6σ _θ ), part of the water in the strait is characterized by lower temperature, lower salinity, and higher dissolved oxygen than that of KBW and EKCW, which can be explained only by the diapycnal mixing. The strong diapycnal mixing in the strait can also be shown by the density inversion, occurrence frequency of which corresponds well to the amplitude distribution of the diurnal current. In the density range 26.7−26.8σ _θ , the water in Bussol’ Strait has the lowest potential vorticity, suggesting that it is a source region of the low potential vorticity water. Seasonal change of the water can reach up to a density of 26.8σ _θ around Bussol’ Strait. This leads us to propose that the combination of winter convection and local tidal mixing leads to effective ventilation of the intermediate layer.     

Sunyaev–Zel'dovich predictions for the Planck Surveyor satellite using the Hubble Volume simulations

We use the billion-particle Hubble Volume simulations to make statistical predictions for the distribution of galaxy clusters that will be observed by the Planck Surveyor satellite through their effect on the cosmic microwave background – the Sunyaev–Zel'dovich (SZ) effect. We utilize the lightcone data sets for both critical density ( τ CDM) and flat low-density (ΛCDM) cosmologies: a 'full-sky' survey out to z ∼0.5 , two 'octant' data sets out to beyond z =1 , and a 100 square degree data set extending to z ∼4 . Making simple, but robust, assumptions regarding both the thermodynamic state of the gas and the detection of objects against an unresolved background, we present the expected number of SZ sources as a function of redshift and angular size, and also as a function of flux (for both the thermal and kinetic effects) for three of the relevant High Frequency Instrument frequency channels. We confirm the expectation that the Planck Surveyor will detect around 5×10⁴ clusters, though the exact number is sensitive to the choice of several parameters including the baryon fraction, and also to the cluster density profile, so that either cosmology may predict more clusters. We also find that the majority of detected sources should be at z <1.5 , and we estimate that around 1 per cent of clusters will be spatially resolved by the Planck Surveyor , though this has a large uncertainty.     

Pocho volcanic rocks and the melting of depleted continental lithosphere above a shallowly dipping subduction zone in the central Andes

The Late Miocene (7.9 to 4.5 Ma) Pocho volcanic field in Argentina occurs 700 km east of the Chile trench over the modern shallowly dipping Andean Wadati-Benioff zone near 32° S latitude in Argentina. The field is located in the Sierra de Cordoba which is the easternmost Laramide-style, block-faulted range in the Sierras Pampeanas (Pampean ranges). The arrival of the shallowly dipping slab initiated both volcanism and the uplift of the Sierra de Cordoba. Pocho rocks (52% to 68% SiO₂; FeO^*/MgO>2.2) comprise an older (7.5±0.5 Ma) high-K and a younger (5.3±0.7 Ma) shoshonitic series. Mineralogic data and fractionation models show that crystallization occurred under hydrous, oxidizing conditions, which were most extreme in the high-K series. An unusual pattern of successively lower REE at higher SiO₂ concentrations can be modeled by sphene, apatite and amphibole removal. An arc-like trace element signature attributed to an arc component is strongest in the younger shoshonitic series. An important depleted lower crustal/mantle lithospheric source component in both series is indicated by non-radiogenic Sr and Pb isotopic ratios at _Nd= 0 to + 2, low Rb/Sr ratios, and low U and Th concentrations. This depleted signature contrasts with the enriched one in potassic back-arc Central Volcanic Zone (CVZ) lavas over the steeper subduction zone to the north and is attributed to several processes in the shallow subduction zone. First, deep crustal (MASH) processes in the nearly normal thickness crust beneath Pocho incorporated depleted Proterozoic basement components, and not complexly mixed structurally thickened crustal components as in the CVZ. Second, the association of Pocho volcanism with the arrival of the slab allowed little time for modification of the mantle by subduction components. Third, Miocene shallowing of the subduction zone beneath the flat-slab required thinning of both the astenosphere and the subcontinental lithosphere. Thus, an important subcrustal component could be from blocks removed from the base of the lithosphere to the west and recycled into the asthenosphere. Similar magmatic sources would have existed during Laramide shallow subduction in western North America.Deceased