The distribution and relative toxic potential of organic chemicals in a PCB contaminated bay

For reliable monitoring of environmental improvement, the PCB contaminated bay Orserumsviken on Sweden's Baltic coast was investigated prior to remediation. We examined PCB congener patterns and the relative toxic potential of PCBs in extracts of three matrices: bottom sediment, settling particulate matter and the dissolved phase (obtained from semi-permeable membrane devices). Congener patterns were similar in all matrices. Three fractions were isolated from the extracts: (1) aliphatic and monocyclic aromatic compounds (MAC-fraction), (2) dicyclic aromatic compounds (DAC-fraction), including PCBs, and (3) polycyclic aromatic compounds (PAC-fraction), including PAHs. Total extracts and fractions were injected into newly fertilised rainbow trout eggs. At larval stage, hepatic EROD activities were quantified. Though high, the PCB contamination could explain only an estimated 1-5% of the total EROD induction. The order of EROD induction potential was: total extract > PAC-fraction > DAC-fraction > MAC-fraction in all matrices, suggesting that in Orserumsviken PACs made a larger contribution to the EROD induction potential than PCBs and other DACs.     

Biotransformation enzyme activities and PCDD/PCDF levels in pike caught in a Swedish Lake

Recently, analysis of organochlorines in sediment and in pike from Lake Vänern, Sweden, showed a north-south gradient of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs). In the present study, good correlations were found between muscle 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) equivalents and liver ethoxyresorufin-O-deethylase (EROD) activities (and P4501A levels) in pike caught at three sampling sites along the north-south gradient in the lake. This comparison between tissue levels of PCDD/PCDF and EROD activity (and P4501A) may indicate that TCDD or structural analogs could be responsible for the observed induction of the pike P450 system. It must, however, be taken into account that the analysed contaminants often do not appear alone but are, rather, accompanied by a range of other substances which may be inducers or antagonists.     

A numerical study of the influence from pre‐existing cracks on granite rock fragmentation at percussive drilling

The aim of this study is to investigate the effect of pre‐existing, or structural, cracks on dynamic fragmentation of granite. Because of the complex behavior of rock materials, a continuum approach is employed relying upon a plasticity model with yield surface locus as a quadratic function of the mean pressure in the principal stress space coupled with an anisotropic damage model. In particular, Bohus granite rock is investigated, and the material parameters are chosen based on previous experiments. The equation of motion is discretized using a finite element approach, and the explicit time integration method is employed. The pre‐existing cracks are introduced in the model by considering sets of elements with negligible tensile strength that leads to their immediate failure when loaded in tension even though they still carry compressive loads as crack closure occurs because of compressive stresses. Previously performed edge‐on impact tests are reconsidered here to validate the numerical model. Percussive drilling is simulated, and the influence of the presence of pre‐existing cracks is studied. The results from the analysis with different crack lengths and orientations are compared in terms of penetration stiffness and fracture pattern. It is shown that pre‐existing cracks in all investigated cases facilitate the drilling process. Copyright © 2014 John Wiley & Sons, Ltd.     

Basic physiological biomarkers in adult female perch (Perca fluviatilis) in a chronically polluted gradient in the Stockholm recipient (Sweden)

By measuring a battery of basic physiological biomarkers and the concentration of SigmaDDT in adult female perch (Perca fluviatilis), an assumed aquatic pollution gradient was confirmed, with the city of Stockholm (Sweden) as a point source of anthropogenic substances. The investigation included an upstream gradient, westwards through Lake M?laren (46 km), and a downstream gradient, eastwards through the Stockholm archipelago (84 km). The results indicated a severe pollution situation in central Stockholm, with poor health status of the perch: retarded growth, increased frequency of sexually immature females, low gonadosomatic index, and disturbed visceral fat metabolism. SigmaDDT, measured as a pollution indicator, was 10-28 times higher than the background in perch from the Baltic Proper. Besides the main gradient other sources of pollution also influenced the response pattern of the measured biomarkers. In particular, there were strong indications of pollution coming from the Baltic Sea.     

The Spectro Point Spread Function for GAIA

We discuss the point spread function for the Spectro instrument based on realistic effects of the time delayed integration, transverse image motion and pixelization, but assuming rather small wave front errors. Stars brighter than 10 mag, which will saturate the CCD, may be observed photometrically using the image wings, but the central wavelengths will be slightly shifted towards the red. This revised version was published online in July 2006 with corrections to the Cover Date.     

Observational and predictive uncertainties for multiple variables in a spatially distributed hydrological model

In this study, uncertainty in model input data (precipitation) and parameters is propagated through a physically based, spatially distributed hydrological model based on the MIKE SHE code. Precipitation uncertainty is accounted for using an ensemble of daily rainfall fields that incorporate four different sources of uncertainty, whereas parameter uncertainty is considered using Latin hypercube sampling. Model predictive uncertainty is assessed for multiple simulated hydrological variables (discharge, groundwater head, evapotranspiration, and soil moisture). Utilizing an extensive set of observational data, effective observational uncertainties for each hydrological variable are assessed. Considering not only model predictive uncertainty but also effective observational uncertainty leads to a notable increase in the number of instances, for which model simulation and observations are in good agreement (e.g., 47% vs. 91% for discharge and 0% vs. 98% for soil moisture). Effective observational uncertainty is in several cases larger than model predictive uncertainty. We conclude that the use of precipitation uncertainty with a realistic spatio‐temporal correlation structure, analyses of multiple variables with different spatial support, and the consideration of observational uncertainty are crucial for adequately evaluating the performance of physically based, spatially distributed hydrological models.     

Efficiency of mixing by a turbulent jet in a stably stratified fluid

Mixing in a two-layer stably stratified fluid by a turbulent jet was studied by a laboratory experiment. A non-swirling jet was discharged vertically downwards in a confined fluid system consisting initially of a top layer of fresh water and a bottom layer of salt water. In total, 16 experimental cases were considered, where the diameter and exit velocity of the jet were varied together with the density difference between the top and bottom layer. Vertical density profiles were determined from conductivity measurements. A three-layer density structure developed in all cases with an intermediate layer that grew in size with time elapsed as fresh and salt water were mixed. The mixing efficiency, defined as the percentage of the supplied kinetic jet energy that is used for increasing the potential energy of the fluid system, was related to a densimetric Froude number based on the intermediate layer depth. Overall, the calculated jet mixing efficiency displayed higher values than comparable efficiencies for destratification with air-bubble plumes.     

Water column monitoring near oil installations in the North Sea 2001-2004

Fisheries have been vital to coastal communities around the North Sea for centuries, but this semi-enclosed sea also receives large amounts of waste. It is therefore important to monitor and control inputs of contaminants into the North Sea. Inputs of effluents from offshore oil and gas production platforms (produced water) in the Norwegian sector have been monitored through an integrated chemical and biological effects programme since 2001. The programme has used caged Atlantic cod and blue mussels. PAH tissue residues in blue mussels and PAH bile metabolites in cod have confirmed exposure to effluents, but there was variation between years. Results for a range of biological effects methods reflected exposure gradients and indicated that exposure levels were low and caused minor environmental impact at the deployment locations. There is a need to develop methods that are sufficiently sensitive to components in produced water at levels found in marine ecosystems.