The distribution of macrozoobenthos in the southern North Sea in relation to meso-scale bedforms

This study investigates the distribution of macrozoobenthos in relation to meso-scale bedforms in the southern North Sea. Three sites on the Dutch Continental Shelf were sampled that are representative of large areas of the North Sea and show diverse morphological settings. These sites are (i) part of a shoreface-connected ridge, (ii) the lower part of a concave shoreface and (iii) a sandwave area. Within these sites, two or three different morphological units were distinguished. Sampling was undertaken in two seasons for two consecutive years. The species composition was analysed for differences in benthic assemblage within sites, based on the meso-scale morphology, and between sites and seasons. In addition, the benthic assemblage was correlated to water depth, median grain size (D50) and sorting (D60/D10). Results show that significant differences in the benthic assemblage can be found related to meso-scale bedforms, but macro-scale morphological setting and seasonal effects are more important.     

Characterization of volume change and strength behavior of micro-silica and lime-stabilized Cyprus clay

Acta Geotechnica - This study aims to assess the suitability of micro-silica (MS) as an industrial waste to modify the hydro-mechanical behavior of expansive soil in comparison with the use of lime...     

Analytical Solution for Modeling Discharge into a Tunnel Drilled in a Heterogeneous Unconfined Aquifer

Predicting transient inflow rates into a tunnel is an important issue faced by hydrogeologists. Most existing analytical solutions overestimate the initial discharge due to the assumption that drilling was instantaneous over the entire tunnel length. In addition, they assume a homogeneous system. An alternative model was recently developed for tunnels intersecting heterogeneous formations, but its application was reduced to the case of confined flow to deep tunnels in weakly diffusive aquifers. In this paper, we adapt existing analytical solutions for drainage systems to the specific case of a tunnel progressively drilled in a highly diffusive heterogeneous unconfined aquifer. The case of a tunnel overlying an impervious layer is analytically solved by applying the superposition principle, while the case of a tunnel constructed some distance above an impervious layer is solved by discretizing the tunnel length into subsectors. Both models can simulate transient discharge into a tunnel drilled at various speeds through a heterogeneous unconfined aquifer, and allow the prediction of discharge rates in shallow tunnels located in highly diffusive aquifers. We successfully applied this approach to a tunnel in heterogeneous volcanic rock.     

Slope‐area thresholds of road‐induced gully erosion and consequent hillslope–channel interactions

Pikes Peak Highway is a partially paved road between Cascade, Colorado and the summit of Pikes Peak. Significant gully erosion is occurring on the hillslopes due to the concentration of surface runoff, the rearrangement of drainage pathways along the road surface and adjacent drainage ditches, and the high erodibility of weathered Pikes Peak granite that underlies the area. As a result, large quantities of sediment are transported to surrounding valley networks causing significant damage to water quality and aquatic, wetland, and riparian ecosystems. This study establishes the slope/drainage area threshold for gullying along Pikes Peak Highway and a cesium‐137 based sediment budget highlighting rates of gully erosion and subsequent valley deposition for a small headwater basin. The threshold for gullying along the road is S_cr = 0 · 21A^–0·45 and the road surface reduces the critical slope requirement for gullying compared to natural drainages in the area. Total gully volume for the 20 gullies along the road is estimated at 5974 m³, with an erosion rate of 64 m³ yr^–1 to 101 m³ yr^–1. Net valley deposition is estimated at 162 m³ yr^–1 with 120 m³ yr^–1 unaccounted for by gullying. The hillslope–channel interface is decoupled with minimal downstream sediment transport which results in significant local gully‐derived sedimentation. Copyright © 2013 John Wiley & Sons, Ltd.     

Sensitivity Analysis of Discharge in the Arctic Usa Basin, East-European Russia

The high sensitivity of the Arctic implies that impact of climate change and related environmental changes on river discharge can be considerable. Sensitivity of discharge to changes in precipitation, temperature, permafrost and vegetation, was studied in the Usa basin, Northeast-European Russia. For this purpose, a distributed hydrological model (RHINEFLOW) was adapted. Furthermore, the effect of climate change simulated by a GCM (HADCM2S750 integration) on runoff was assessed, including indirect effects of permafrost thawing and changes in vegetation distribution. The study shows that discharge in the Usa basin is highly sensitive to changes in precipitation and temperature. The effect of precipitation change is present throughout the year, while temperature changes affect discharge only in seasons when temperature fluctuates around the freezing point (April and October). Discharge is rather sensitive to changes in vegetation. Sensitivity to permafrost occurrence is high in winter, because infiltration and consequently base flow increases if permafrost melts. The effect of climate change simulated by the scenario on discharge was significant. Peak flow can both decrease (by 22%) and increase (by 19%) comparedwith present-day, depending on the amount of winter precipitation. Also, runoff peaks earlier in the season. These results can have implications for the magnitude and timing of the runoff peak, break-up and water-levels.     

The Direct Determination of Rare Earth Elements in Basaltic and Related Rocks using ICP-MS: Testing the Efficiency of Microwave Oven Sample Decomposition Procedures

Tests are described showing the results obtained for the determination of REE and the trace elements Rb, Y, Zr, Nb, Cs, Ba, Hf, Ta, Pb, Th and U with ICP-MS methodology for nine basaltic reference materials, and thirteen basalts and amphibolites from the mafic-ultramafic Niquelândia Complex, central Brazil. Sample decomposition for the reference materials was performed by microwave oven digestion (HF and HNO₃, 100 mg of sample), and that for the Niquelândia samples also by Parr bomb treatment (5 days at 200°C, 40 mg of sample). Results for the reference materials were similar to published values, thus showing that the microwave technique can be used with confidence for basaltic rocks. No fluoride precipitates were observed in the microwave-digested solutions. Total recovery of elements, including Zr and Hf, was obtained for the Niquelândia samples, with the exception of an amphibolite. For this latter sample, the Parr method achieved a total digestion, but not so the microwave decomposition; losses, however, were observed only for Zr and Hf, indicating difficulty in dissolving Zr-bearing minerals by microwave acid attack.     

Sustainability of deep-sea fisheries

As coastal fisheries around the world have collapsed, industrial fishing has spread seaward and deeper in pursuit of the last economically attractive concentrations of fishable biomass. For a seafood-hungry world depending on the oceans' ecosystem services, it is crucial to know whether deep-sea fisheries can be sustainable.The deep sea is by far the largest but least productive part of the oceans, although in very limited places fish biomass can be very high. Most deep-sea fishes have life histories giving them far less population resilience/productivity than shallow-water fishes, and could be fished sustainably only at very low catch rates if population resilience were the sole consideration. But like old-growth trees and great whales, their biomass makes them tempting targets while their low productivity creates strong economic incentive to liquidate their populations rather than exploiting them sustainably (Clark's Law). Many deep-sea fisheries use bottom trawls, which often have high impacts on nontarget fishes (e.g., sharks) and invertebrates (e.g., corals), and can often proceed only because they receive massive government subsidies. The combination of very low target population productivity, nonselective fishing gear, economics that favor population liquidation and a very weak regulatory regime makes deep-sea fisheries unsustainable with very few exceptions. Rather, deep-sea fisheries more closely resemble mining operations that serially eliminate fishable populations and move on.Instead of mining fish from the least-suitable places on Earth, an ecologically and economically preferable strategy would be rebuilding and sustainably fishing resilient populations in the most suitable places, namely shallower and more productive marine ecosystems that are closer to markets.