Sub-lethal effects of metal exposure: physiological and behavioural responses of the estuarine bivalve Macoma balthica

Variation in glycogen concentration, condition index (CI) and filtration activity were measured in the bivalve Macoma balthica buried in sediment and experimentally exposed to cadmium (Cd). The stress due to elevated but sub-lethal concentrations (300 ppb Cd) affected the overall fitness of the organism as all parameters monitored responded significantly. Lower concentrations tested (10, 30 and 100 ppb) only induced a significant decrease in filtration activity, which may play a protective role, enabling the organism to slow down its metabolic activity and preserving the integrity of its reserves (reflected by stable CI and glycogen levels). Hence, the various endpoints selected show different thresholds. Our results also demonstrate that under high exposure, small individuals loose proportionally more glycogen per unit of weight than larger ones, thus confirming the higher sensitivity of small individuals to metal contamination. Furthermore, exposure to intermediate concentration (30 ppb) seems to be beneficial to the small individuals as indicated by their high CI values compared to the control. These results showed thus that non-sigmoidal concentration-response relationship and sizes of individuals should be considered in monitoring programmes and risk assessment.     

Evolving Turbulence Realizations of Atmospheric Flow

A significant difference exists between estimates of contaminant atmospheric transport and dispersion calculated by an ensemble-averaged model and the turbulent details of any particular atmospheric transport and dispersion realization. In some cases, however, it is important to be able to make inferences of these realizations using ensemble-averaged models. It is possible to make such inferences if there are sensors in the field to report contaminant concentration observations. Any information determined about the atmospheric transport and dispersion realization can then be assimilated into a forecast model. This approach can enhance the accuracy of the atmospheric transport and dispersion forecast of a particular event. This work adopts that approach and reports on a genetic algorithm used to optimize the variational problem. Given contaminant sensor measurements and a transport and dispersion model, one can back-calculate unknown source and meteorological parameters. In this case, we demonstrate the dynamic recovery of unknown meteorological variables, including the transport variables that comprise the “outer variability” (wind speed and wind direction) and the dispersion variables that comprise the “inner variability” (contaminant spread). The optimization problem is set up in an Eulerian grid space, where the comparison of the concentration field variable between the predictions and the observations forms the cost function. The transport and dispersion parameters, which are determined from the optimization, are in Lagrangian space. This calculation is applied to continuous and instantaneous releases in a horizontally homogeneous wind field such as that observed during traditional transport and dispersion field experiments. The method proves to be successful at recovering the unknown transport and dispersion parameters for a numerical experiment.     

A climatological data set of temperature and salinity for the Baltic Sea and the North Sea

Ocean Dynamics - A climatological monthly mean data set for temperature and salinity in the area of the North Sea and Baltic Sea is presented. More than 3.1 million temperature observations (2.9...     

Rayleigh fractionation with continuous removal of liquid

In its simple form the Rayleigh surface equilibrium fractionation equation is only valid for a closed system in which solid separates from liquid, and no liquid is lost. Many natural systems, particularly magma chambers, lose liquid continuously as they fractionate. Here it is shown that evolution in such a system can, if loss of liquid proceeds in a constant ratio to precipitation of solid, be modelled by a modified Rayleigh equation where the solid/liquid distribution coefficientD is replaced byD*=(q·D + 1)/(q + 1), whereq is the ratio of solid precipitated to liquid extracted. This can be visualised as treating the liquid removed as an additional phase extracted during fractionation for whichD = 1. The effect of this is particularly important for incompatible elements, where asD → 0,D* → 1/(q + 1), so that whenq = 1, the most incompatible element givesD* = 0.5.     

A rational interpretation of the role of particle size in flotation

From the examination of data from detailed plant surveys and associated laboratory batch testing, the principal effects of particle size in flotation have been identified. The current state of knowledge concerning the role of this variable is discussed in terms of the evidence presented. It is concluded that the minimum degree of hydrophobicity necessary for the flotation of a particle depends upon its size and as a result, recovery-size curves are a valuable diagnostic aid to the assessment of flotation performance. Entrainment is shown to be an important contributory mechanism to the recovery of fine particles which, when coupled with a low rate of genuine flotation, can account for much of the observed behaviour of such fines. The significance of particle size and its consequences in flotation research, in plant operations and in control schemes has been under-rated. The separate conditioning or flotation or both of separate size fractions seems inevitable as ores become increasingly difficult to concentrate.     

Possible clay structures in frustules of living diatoms

Comparison of X-ray diffraction spectra of marine diatom frustules and suspended clay minerals suggests the presence of a distinctive smectite in diatoms. The frustules contained 1.5% Al₂O₃ and were partly covered with particles of 0.02 μm in diameter. The source of Al and the fate of diatoms in the sediment are briefly discussed.