Deriving sediment quality guidelines from field-based species sensitivity distributions

The determination of predicted no-effect concentrations (PNECs) and sediment quality guidelines (SQGs) of toxic chemicals in marine sediment is extremely important in ecological risk assessment. However, current methods of deriving sediment PNECs or threshold effect levels (TELs) are primarily based on laboratory ecotoxicity bioassays that may not be ecologically and environmentally relevant. This study explores the possibility of utilizing field data of benthic communities and contaminant loadings concurrently measured in sediment samples collected from the Norwegian continental shelf to derive SQGs. This unique dataset contains abundance data for ca. 2200 benthic species measured at over 4200 sampling stations, along with co-occurring concentration data for >25 chemical species. Using barium, cadmium, and total polycyclic aromatic hydrocarbons (PAHs) as examples, this paper describes a novel approach that makes use of the above data set for constructing field-based species sensitivity distributions (f-SSDs). Field-based SQGs are then derived based on the f-SSDs and HCx values [hazardous concentration for x% of species or the (100-x)% protection level] by the nonparametric bootstrap method. Our results for Cd and total PAHs indicate that there are some discrepancies between the SQGs currently in use in various countries and our field-data-derived SQGs. The field-data-derived criteria appear to be more environmentally relevant and realistic. Here, we suggest that the f-SSDs can be directly used as benchmarks for probabilistic risk assessment, while the field-data-derived SQGs can be used as site-specific guidelines or integrated into current SQGs.     

A comparison of the metabolic profile on intact tissue and extracts of muscle and liver of juvenile Atlantic salmon (Salmo salar L.) – Application to a short feeding study

The metabolite profiles from muscles and livers of Atlantic salmon were investigated using high resolution nuclear magnetic resonance (HR-NMR) spectroscopy of aqueous extracts and magic angle spinning (MAS) NMR spectroscopy of intact tissues. Comparison of the data showed that most small metabolites present in the aqueous extracts were also identified in the Carr–Purcell–Meiboom–Gill (CPMG) MAS NMR spectra of the intact tissues. Not only the total omega-3 fatty acid content, but also the EPA and DHA content, in the muscle and liver tissues could be calculated directly from the diffusion-edited MAS NMR spectra without the need for lipophilic extraction. The effect of replacing a normal fish meal during a period of 3 months with a diet containing 20% zygomycete was also investigated by multivariate analysis of the NMR spectra. Principal component analysis (PCA) was used to study the small metabolites distribution in the aqueous extracts of liver and muscles, and revealed that the feed containing zygomycete could have an influence on the metabolites profiles of juvenile Atlantic salmon.     

Agglomerate breakage and adhesion upon impact with complex-shaped particles

Understanding the breakage and adhesion of an agglomerate upon collision with a target particle is a primary step to fathom the adhesive mixing process. While the effect of several variables, such as collision velocity and particle interface energy, on collision behavior has been explored, the effects of target particle morphology have yet to be revealed. In this work, we generate three-dimensional particles with controllable shape and texture using Fourier harmonics and, using the discrete element method, we examine the collision of an agglomerate that impacts each target particle. Results show that the agglomerate breakage depends on the local curvature in the impact zone. We observe that the asperity and elongation factors of the target particle largely contribute to the extent of the deposition of fine particles and the size and number of generated fragments after impact, respectively. These results reveal the large potential error when approximating real particles as smooth spheres in fragmentation studies.     

MuhRec—A new tomography reconstructor

A new tool for computed tomography reconstruction is presented. The tool was developed to support the needs of users at neutron imaging beamlines and as a platform for algorithm development. It includes methods to handle large samples and artifact removal. The design is modular and allows tests of new concepts for preprocessing and back-projection. The reconstructor is tuned to provide the results fast even on a laptop computer. The reconstructor also has a graphical user interface which can be operated by new users after a short instruction.     

The reflection of the fundamental torsional guided wave from multiple circular holes in pipes

Localised corrosion is a major concern in the petrochemical industry, and often occurs as clusters of pits. A study of the reflection from two and three small circular holes in pipes with the fundamental torsional guided wave incident is presented. FE analyses with both part and through thickness holes at different relative positions are presented, and are a step towards estimation of the scattering behaviour of multiple and random defects. The validity of employing the superposition technique in estimating reflection coefficients is assessed. Results show that the reflection coefficient for the T(0,1) mode is dependent on absolute frequency and axial separation, and independent of circumferential position. Employing superposition is found to be valid down to defect centre to centre separation distances of two diameters in the worst case, with improved validity with shallower defects. Results from the FE analyses are validated experimentally.