Uptake of platinum group elements by the marine macroalga, Ulva lactuca

Uptake of environmentally relevant platinum group elements (PGE) by the marine macroalga, Ulva lactuca, has been studied. Removal of nM concentrations of Rh(III), Pd(II) and Pt(IV) added to filtered sea water appeared to proceed via pseudo-first-order kinetics, with respective forward rate constants of either 0.0039 or 0.0042 h^− 1, 0.0058 or 0.0096 h^− 1 and 0.0017 or 0.0032 h^− 1, depending on whether an irreversible or reversible reaction was invoked. The (quasi-) equilibrium distribution coefficients, derived from linear fits to uptake (sorption) isotherms, were about 1400, 900 and 350 mL g^− 1 on a dry mass basis for Rh, Pd and Pt, respectively. With increasing sea water pH, over the range 7.9 to 8.4, uptake of Rh by Ulva increased considerably, whereas a small increase in Pt removal was observed; in contrast, uptake of Pd exhibited no clear dependence on pH. The percentage of metal taken up that was internalised within cells, evaluated by washing selected algal samples in 3 mM EDTA, was about 40% for Rh, 80% for Pd and 95% for Pt. Results of this study were interpreted in terms of what is known about the aqueous speciation of PGE in sea water. Thus, Rh exists as cationic hydrated chloride complexes which are readily adsorbed at the algal surface. Palladium has an exceptional affinity for organic ligands, and uptake (and internalisation) appears to be governed by competition for Pd²⁺ from aqueous and algal binding sites. Platinum (IV) exists predominantly as a series of (mainly) negatively charged chloride and mixed hydroxychloride complexes that have little propensity to interact with the algal surface; however, its high degree of internalisation requires at least some interaction with specific and perhaps physiologically active sites.     

The tidal regime of Shark Bay, Western Australia

A non-linear hydrodynamic model is used to describe the tidal dynamics of Shark Bay, Western Australia. The model is forced by tidal elevations generated by M₂, S₂, K₁ and O₁ constituent data at the open boundaries. The absence of suitable boundary data required a ‘calibration’ of the boundary condition against the known constituent data from within the model domain. The model provides a good match to the available field data, and allows the surface-level and current response to be resolved over the entire domain. Due to a near quarter-wave resonance of the semi-diurnal tide along the eastern Hopeless Reach, which increases the semi-diurnal tide by a factor of 2, the tidal characteristics on each of the Reaches are different: on the eastern Hopeless Reach the tides are mainly semi-diurnal while on the western Freycinet Reach the tides are mainly diurnal. The tidal range is also higher along Hopeless Reach. Tidal harmonics, generated by non-linearity, are important in the shallow regions. The tidal wave is shown to propagate as a progressive wave into the Bay. Substantial phase-lag, attenuation and dissipation occur over the Faure Sill, a major shallow region of the eastern reach of the Bay. Non-linear generation of the M₄ and MS₄ tides is also significant in this region. Depth-averaged residual currents are presented, which show a tidally generated circulation that is enhanced in regions of complex topography. Estimates of tidal dissipation indicate that although the total dissipation is small on a global scale, the areal average is comparable with the Gulf of Carpentaria and approximately one-quarter of the value estimated for the Patagonian Shelf.     

Morphology and sedimentary architecture of a beach‐ridge system (Anholt,the Kattegat sea): a record of punctuated coastal progradation and sea‐level change over the past ∼1000 years

Flakket on the island of Anholt in Denmark is a cuspate foreland facing the microtidal Kattegat sea. It is composed of a number of beach ridges typically covered by dune sand and separated by swales and wetlands. OSL dating indicates that the evolution of Flakket began c. AD 1000. Foreland growth was punctuated by a major episode of coastal reorganization leading to coastal retreat c. AD 1800. Coastal retreat led to the formation of an erosion surface that separates older and higher‐lying beach‐ridge and swale deposits from younger and lower‐lying deposits. The palaeo‐sea level is deduced from the architecture of the deposits, and interpretation of ground‐penetrating radar data and geomophological observations indicates that relative sea level was about 1.90±0.25 m above present sea level c. AD 1000, but about 0.00±0.25 m relative to present sea level c. AD 1830 and c. AD 1870. Anholt is situated at the margin of the uplifted Fennoscandian area; assuming uplift to be about 1.2 mm a^?1 it follows that absolute sea level was about +0.70±0.25 m at AD 1000, but around ?0.22±0.25 m at AD 1830 and around ?0.17±0.25 m at AD 1870. Within the uncertainties of the age control, the sea‐level indicators mapped by ground‐penetrating radar reflections and the variability of estimates of uplift found in the literature, the result obtained for AD 1000 is consistent with findings from the Stockholm area in Sweden and with a recently published global sea‐level curve.     

Luminescence dating of buried cobble surfaces from sandy beach ridges: a case study from Denmark

Here we investigate the use of optically stimulated luminescence (OSL) for dating cobbles from the body of successive beach ridges and compare cobble surface‐derived ages to standard quartz OSL ages from sand. Between four and eight cobbles and sand samples (age control) were dated with the luminescence method, taken from the modern beach and from beach ridges on the south and north extremes of a prograding spit on the westernmost coast of Lolland, Denmark. Luminescence‐depth profiles perpendicular to the surfaces of the cobbles show that the feldspar infrared signals stimulated at 50 °C were fully reset to various depths into the cobbles prior to final deposition; as a result, the equivalent doses determined from close to the surface of such cobbles can be used to calculate burial ages. Beach‐ridge burial ages given by the average of ages of individual cobbles taken from the same site are consistent, within errors, with the ages derived from the sand samples. Cobble‐ and sand‐derived ages show that the southernmost beach ridge at Albuen was formed around 2 ka ago, indicating that this sandy spit is younger than other coastal systems in Denmark. The agreement between ages derived from clasts and from standard quartz OSL in this study confirms that, even in the absence of sandy sediments, we can reliably date sites using OSL by targeting larger clasts. In addition, the record of prior light exposure contained in the shape of the cobbles’ luminescence‐depth profile removes one of the major uncertainties (i.e. the degree of signal reset prior to burial) in the luminescence dating of high latitude sites.     

Predicting the Isotropic Volumetric Compression Response of Hydrating Cemented Paste Backfill (CPB)

Geotechnical and Geological Engineering - Deep and high-stress mining results in stress transfers onto the previously placed backfill, and mines have recorded several MPa induced backfill stresses....     

Coastal management challenges from a community perspective: The problem of ‘stealth privatization’ in a Canadian fishery

Intertidal clam fisheries seem ideal candidates for the devolution of management authority from government to local stakeholders. In St. Mary's Bay, Nova Scotia, a private firm recently applied for a 10-year renewal of a large (1,627 ha) lease for quahog clam aquaculture. This case study examines the challenges of implementing community-based natural resource management (CBNRM) in rural fisheries within a broad integrated coastal management (ICM) institutional environment that favours corporate stakeholders. The challenges facing clam harvesters in rural Digby Neck, Nova Scotia arise from poor communication and coordination within government and between government and communities, as well as higher-level policy conflicts. The most important challenge arises from ‘stealth privatization’ of clam beaches. A single firm was granted rights of first refusal to depurate all clams harvested from closed (polluted) beaches in the region, resulting in the de facto privatization of all (polluted and unpolluted) clam beaches. Experiences in other parts of Canada suggest there may be community-based governance approaches that avoid the pitfalls associated with corporate management of clam beaches. New thinking is required about how to moderate the ‘privatization paradigm’ so prevalent within senior levels of government in order to ensure environmental and social sustainability in rural fishing communities.