Geochemical dispersion of heavy metals via organic complexing: A laboratory study of copper,lead, zinc,and nickel behaviour at a simulated sediment-water boundary

Data are presented in this study from laboratory model experiments describing the behaviour of Cu, Pb, Zn and Ni at a simulated sediment-water boundary. The interactions involved are sorption by kaolin and by bentonite, organic complexing in solution by fulvic acid and by humic acid, carbonate reactions, hydrolysis, and desorption of the cations from a clay-bound phase and from their metal hydroxides by the organic acids. The organic acids increase the solubility of Cu, Zn and Ni in the presence of clay. The Pb solubility is variable and can even decrease, particularly at acidic pH, with organic complexing likely due to colloidal coagulation. Both Zn and Ni are influenced by hydrolysis at basic pH. When carbonate was added to the metal-organic acid-clay mixtures, a further decrease in solubility was observed for Ni and, to a lesser extent, for Zn. The organic acids prove capable of remobilizing Cu, Pb, Zn and Ni from the solid phases examined. However, there is a general kinetic hindrance to the desorption particularly at basic pH. Copper desorption appears to be the most kinetically hindered. Conclusions pertinent to the geochemical dispersion of these metals are drawn.     

A resistivity section of Holy Island (Anglesey)

An account is given of the use of square array resistivity techniques to derive an apparent resistivity section down the length of Holy Island (Anglesey). Possible interpretations of this section in terms of the distribution of true resistivity with depth are given and discussed briefly in relation to proposed geological structure.     

Equity vs. Efficiency: Public Capital Investment in Ohio, 1988–1992

Recent research on the role of public capital in the economy focuses primarily on assessing its economic, and sometimes spatial economic, impacts. Access to more detailed and disaggregate data than typically used in these analyses allows us to take a fresh perspective on the often conflicting goals of interregional equity and aggregate efficiency. Using the state of Ohio as a case study, and classic definitions of equity and efficiency, we assess the correspondence between distributions of infrastructure investment and the social/economic distress they are intended to alleviate. Traditional map and statistical analysis combined with a graphical device we call the variegated distribution plot reveals that, in both rates and levels, investment is highest in areas of greatest distress. Both patterns are consistent with equity-driven investment distributions.     

Temporal constraints on basin inversion provided by 3D seismic and well data: a case study from the South Viking Graben, offshore Norway

Three-dimensional (3D) seismic, well and biostratigraphic data are integrated to determine the timing of inversion on the hangingwall of the South Viking Graben, offshore Norway. Within the study area two, NW–SE to NE–SW trending normal faults are developed which were active during a Late Jurassic rift event. In the hangingwall of these faults asymmetric, 2–5 km wide anticlines are developed which trend parallel to the adjacent faults and are interpreted as growth folds formed in response to compressional shortening (inversion) of the syn-rift basin-fill. Marked thickness variations are observed in Late Jurassic and Early Cretaceous growth strata with respect to the inversion-related folds, with seismic data indicating onlap and thinning of these units across the folds. In addition, well data suggests that not only are erosional surfaces only locally developed towards the crests of the folds, but these surfaces may also truncate underlying flooding surfaces towards the fold crests. Taken together, these observations indicate that inversion and growth of inversion-related structures initiated in the late Early Volgian and continued until the Late Albian. Furthermore, it is demonstrated that individual folds amplified and propagated laterally through time, and that fold growth was not synchronous across the study area. This study demonstrates that the temporal evolution of structures associated with the inversion of sedimentary basins can be accurately determined through the integration of 3D seismic, well and biostratigraphic data. Furthermore, this study has local implications for constraining the timing of inversion within the South Viking Graben during the Late Mesozoic.     

Invariants in toroidal and tangentially geostrophic frozen-flux velocity fields

We derive two new types of invariant that must be obeyed by the radial magnetic field at the core-mantle boundary if the hypothesis of frozen flux is valid and the fluid motion is either toroidal or tangentially geostrophic there. These general invariants incorporate specific invariants that are already known and can, in principle, be tested using magnetic data that cover an interval of time.     

Flood tide circulation near beaufort inlet, North Carolina: Implications for larval recruitment

Drifter tracks and shipboard CTD observations have revealed a number of distinct features of the flood tide circulation carrying water through Beaufort Inlet, North Carolina. One of the most noteworthy of these features is a nearshore jet in the flow carrying water to the inlet on a flood tide. Characterized by a shoreward increase in longshore flow, the jet produces a narrow coastal zone over which water is carried into the inlet. The jet appears to be principally a tidal phenomenon, as it is closely reproduced by a tidally-driven barotropic numerical model. The model results also indicate the jet may be a near-inlet feature. Model simulations of spring tide conditions show the jet confined to within 4 km of the inlet mouth. Another observed phenomenon, which is reproduced by the tidal model, is a distinct splitting of the flow entering the inlet, in which water passing through a particular inlet segment tends to move up-estuary along a well-defined path. An observed flow feature not reproduced by the tidal model is an eastward skew of the region over which water is drawn into the inlet on a flood tide. This asymmetry is unrelated to the local wind. Modeling results from a previous study suggest it may be due to convergent flow at the edge of the low salinity plume issuing from the inlet. Taken together, the results of this and other recent studies in the Beaufort Inlet region reveal the importance of nearshore currents on the eastern side of the inlet in delivering oceanic-spawned larvae to the estuarine system connected to the inlet.