The movement of oil under non-breaking waves

The combined effects of wave kinematics, turbulent diffusion, and buoyancy on the transport of oil droplets at sea were investigated in this work using random walk techniques in a Monte Carlo framework. Six hundred oil particles were placed at the water surface and tracked for 500 wave periods. A dimensionless formulation was presented that allowed reporting distances in terms of the wave length and times in terms of the wave period. Stokes' drift was, expectedly, the major mechanism for horizontal transport. It was also found that plumes that have large terminal rise velocities move faster forward but spread less than those that have small terminal rise velocities. The increase in wave slope (or wave steepness) caused an increase in transport and spreading of the plume. Our results supported treating the oil as completely mixed vertically in a layer near the surface. In the horizontal direction, buoyant plumes had spreading coefficients that are essentially constant after about 200 wave periods. But neutrally buoyant plumes had horizontal spreading coefficients that increased with time (for the simulation time of 500 wave periods). Techniques for generalizing the results for a wide range of wave parameters were presented.     

A Dye Tracer Approach for Quantifying Fluid and Solute Flux Across the Sediment–Water Interface

We propose a dye tracer method to characterize fluid and solute fluxes across the sediment-water interface. Zones of groundwater discharge within the streambed are first identified, and small volume slugs of 0.5 to 1 mL fluorescein dye are released at known subsurface depths. Fluorescein dye allows for visual identification of interface breakthrough locations and times, and dye concentrations at the point of discharge are recorded over time by a fluorometer to generate high resolution breakthrough curves. Groundwater velocities and dispersivities at the demonstration site are estimated by numerically fitting dye breakthroughs to the classical advection-dispersion equation, although the methodology is not limited to a specific transport model. Breakthroughs across the stream-sediment interface at the demonstration site are nonlinear with tracer release depth, and velocity estimates from breakthrough analysis are significantly more reliable than visual dye (time to first dye expression) and Darcy methods which tend to overestimate and underestimate groundwater velocity, respectively. The use of permanent injection points within the streambed and demonstrated reproducibility of dye breakthroughs allow for study of fluid and solute fluxes under seasonally varying hydrologic conditions. The proposed approach also provides a framework for field study of nonconservative, reactive solutes and allows for the determination of characteristic residence times at various depths in the streambed to better understand chemical and nutrient transformations.     

Flybys in the planar, circular, restricted, three-body problem

An analysis is presented of gravity assisted flybys in the planar, circular, restricted three-body problem (pcr3bp) that is inspired by the Keplerian map and by the Tisserand- Poincaré graph. The new Flyby map is defined and used to give insight on the flyby dynamics and on the accuracy of the linked-conics model. The first main result of this work is using the Flyby map to extend the functionality of the Tisserand graph to low energies beyond the validity of linked conics. Two families of flybys are identified: Type I (direct) flybys and Type II (retrograde) flybys. The second main result of this work shows that Type I flybys exist at all energies and are more efficient than Type II flybys, when both exist. The third main result of this work is the introduction of a new model, called ??Conics, When I Can??, which mixes numerical integration and patched conics formulas, and has applications beyond the scope of this work. The last main result is an example trajectory with multiple flybys at Ganymede, all outside the linked-conics domain of applicability. The trajectory is computed with the pcr3bp, and connects an initial orbit around Jupiter intersecting the Callisto orbit, to an approach transfer to Europa. Although the trajectory presented has similar time of flight and radiation dose of other solutions found in literature, the orbit insertion ??v is 150 m/s lower. For this reason, the transfer is included in the lander option of the Europa Habitability Mission Study.     

Key findings from the Indian Ocean Climate Initiative and their impact on policy development in Australia

Since the mid-1970s the climatic changes that have taken place in southwest Western Australia have generated a variety of impacts, the most prominent of which is a reduction in dam inflows of at least 50 percent. These impacts were the catalyst for the formation of the Indian Ocean Climate Initiative in 1998, a research partnership between two national research organizations and several state government departments and agencies. This paper describes the key scientific findings of the Initiative with respect to the nature of the climatic changes that have taken place within the region, explores the factors that might have caused these changes, and describes the most recent climate projections for the region. We reflect on the factors leading to the rapid acceptance of the research outcomes from the Initiative, the impact of the Initiative on policy development across Australia and its likely evolution post-2006.     

How to speak for aquifers and people at the same time: Environmental justice and counter-network formation at a hazardous waste site

A common source of conflict at hazardous waste sites in the US Environmental Protection Agency’s Superfund program is the accuracy of scientific investigations and representations produced to inform cleanup decisions. Liable firms often produce these technical representations themselves, and communities surrounding sites frequently argue that such “voluntary” investigations are compromised by conflicts of interest. In order to challenge the representations of powerful firms, locally situated actors often develop trans-local connections with expertise and equipment concentrated at distant centers of calculation. Although some interpret the spatial politics of such connecting in terms of “jumping scales,” another important spatial dimension of this network construction is differential positioning. In a conflict over groundwater models at the St. Regis Superfund Site in Minnesota, the counter-network that emerged to challenge the owner’s representations of the site positioned some actors as “outsiders” and others as “insiders.” This differential positioning enabled the counter-network to balance the need to demonstrate the reliability and impartiality of its claims with the requirement to maintain its accountability to local public interests. I argue that these requirements result from the prevalent view of the science-policy interface, which assumes a rigid separation between science and politics. Nonetheless, the conflict over groundwater at St. Regis reveals how at the science-policy interface, speaking for things and speaking for people are thoroughly entangled.     

Ceramic production during the Middle Horizon: Wari and Tiwanaku clay procurement in the Moquegua Valley,Peru

As the only place simultaneously occupied by the Middle Horizon (A.D. 600–1000) Andean states, the Tiwanaku and the Wari, the Moquegua Valley in southern Peru is of critical importance to understanding relations between the two states. Visual studies of Tiwanaku and Wari ceramics in the valley have elucidated differences in form and decoration. The procurement of raw clays was central to the production of these ceramics, and understanding where people procured their clay may provide insight into the social and economic interactions between these two states. Survey of the Moquegua Valley indicates the extensive availability of raw clays. Results of laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) analyses of clays indicate that there is heterogeneity in the chemical signature of the valley's clays and that at least five different clay groups can be distinguished. Comparison of these clays with LA‐ICP‐MS analysis of ceramics from a Tiwanaku site and a Wari site demonstrates that although Tiwanaku and Wari colonists in Moquegua used locally available clays during the Middle Horizon, the clay sources exploited by potters from each state were different and derived from areas located within their respective middle and upper valley territories. This information provides a basis for future chemical analysis of ceramics from the Moquegua Valley and improved understanding of past social and economic interactions. © 2009 Wiley Periodicals, Inc.     

Linking the Abundance of Estuarine Fish and Crustaceans in Nearshore Waters to Shoreline Hardening and Land Cover

Human alteration of land cover (e.g., urban and agricultural land use) and shoreline hardening (e.g., bulkheading and rip rap revetment) are intensifying due to increasing human populations and sea level rise. Fishes and crustaceans that are ecologically and economically valuable to coastal systems may be affected by these changes, but direct links between these stressors and faunal populations have been elusive at large spatial scales. We examined nearshore abundance patterns of 15 common taxa across gradients of urban and agricultural land cover as well as wetland and hardened shoreline in tributary subestuaries of the Chesapeake Bay and Delaware Coastal Bays. We used a comprehensive landscape-scale study design that included 587 sites in 39 subestuaries. Our analyses indicate shoreline hardening has predominantly negative effects on estuarine fauna in water directly adjacent to the hardened shoreline and at the larger system-scale as cumulative hardened shoreline increased in the subestuary. In contrast, abundances of 12 of 15 species increased with the proportion of shoreline comprised of wetlands. Abundances of several species were also significantly related to watershed cropland cover, submerged aquatic vegetation, and total nitrogen, suggesting land-use-mediated effects on prey and refuge habitat. Specifically, abundances of four bottom-oriented species were negatively related to cropland cover, which is correlated with elevated nitrogen and reduced submerged and wetland vegetation in the receiving subestuary. These empirical relationships raise important considerations for conservation and management strategies in coastal environments.     

Scenarios of land use and land cover change in the conterminous United States: Utilizing the special report on emission scenarios at ecoregional scales

Global environmental change scenarios have typically provided projections of land use and land cover for a relatively small number of regions or using a relatively coarse resolution spatial grid, and for only a few major sectors. The coarseness of global projections, in both spatial and thematic dimensions, often limits their direct utility at scales useful for environmental management. This paper describes methods to downscale projections of land-use and land-cover change from the Intergovernmental Panel on Climate Change's Special Report on Emission Scenarios to ecological regions of the conterminous United States, using an integrated assessment model, land-use histories, and expert knowledge. Downscaled projections span a wide range of future potential conditions across sixteen land use/land cover sectors and 84 ecological regions, and are logically consistent with both historical measurements and SRES characteristics. Results appear to provide a credible solution for connecting regionalized projections of land use and land cover with existing downscaled climate scenarios, under a common set of scenario-based socioeconomic assumptions.