Assessment of chemical and physical treatments to selectively kill non-indigenous freshwater zooplankton species

Non-indigenous zooplankton species pose a biosecurity threat to New Zealand’s freshwater native taxa. Nine species are known to have established in New Zealand lakes to date. The spread of some zooplankton taxa is linked to the translocation of farmed fish, principally grass carp (Ctenopharyngodon idella), and recreational vessel movements. The aims of this study were to assess the effectiveness of a range of chemical and physical treatments for transport water and associated equipment to kill freshwater cladoceran, copepod, and rotifer zooplankton species, and their risk to non-target fish. Sodium chloride was the most effective and applicable chemical treatment tested at length in the cladoceran and, combined with physical treatment via mechanical filtration of water or hot water immersion of equipment (to also manage the risk of diapausing eggs), represents an effective option for the control of non-indigenous zooplankton, with limited impact on stenohaline fish.     

An objective procedure to remove observer-bias from phytoplankton time-series

Microscopic analyses of phytoplankton samples from the North Sea were made successively by three different laboratories in 1990 to 1993, 1994 to 1999 and 2000 to 2005. Analysis of the data from monitoring station Nw2 by multivariate ordination revealed that the plankton communities significantly clustered in three groups according to analysing laboratory. Furthermore, in each group a change in community structure was caused by an annual increase in the number of species observed. To remove these observer effects an objective five-step procedure was devised and tested using multivariate statistics. The result is a strongly reduced but still taxonomically diverse dataset with an ordination that is unrelated to the three analysing laboratories. After validating the five-step procedure with two other stations, it is concluded that this procedure is widely applicable, opening the possibility of comparing different time-series from countries along the North Sea.     

Effect of temperature on production of CH4 and CO2 from Peat in a Natural and Flooded Boreal Forest Wetland

Flooding of a small boreal forest wetland (979) in northwestern Ontario, caused the formation of peat islands, which resulted in an approximate 10 °C increase in peat temperatures at a depth of 50 cm. Peat collected from the flooded wetland and a natural unflooded wetland was incubated anaerobically at temperatures of 4 °C, 15 °C, and 20 to 25 °C. Flooding of the wetland greatly increased CH4 production rates by increasing the ratio of CH4:CO2 produced from 979 peat (40% : 60%) compared to 632 peat (20% : 80%), at both preflood and postflood temperatures, likely due to the altered hydrological and geochemical conditions within the peat mats due to flooding. CH4 and CO2 production rates approximately tripled for every 10 °C temperature increase and may have been linked to to the metabolic rate of the methanogens or the fermentors independent of the substrate quality. Methane production rates from deep peat deposits within the islands were also significant and responded well to temperature increases despite peat 14C ages of 1000 years. Due to the large quantity of carbon stored within natural wetlands, artificial reservoirs may act as a significant and long term source of CH4 to the atmosphere.     

The influence of low-density granite bodies on extensional basins

The Carboniferous northern Pennine Basin remains the type locality for the ‘block and basin’ tectonic framework model. It has been widely believed that during periods of tectonic extension, large low-density bodies within the basement permit buoyant blocks to resist isostatic subsidence. However, lithosphere-scale structural and geodynamic modelling experiments dispute this; suggesting instead that the formation of intra-basinal highs occurs prior to lithospheric extension. In northern UK, this tectonic framework is controlled by a combination of tectonic stress, isostasy and the buoyancy forces of low-density granite, lithospheric flexure and, importantly, the inherited structural framework. It is hoped that further study can lead to a greater appreciation of the interplay of structural and geodynamic process that control the ‘block and basin’ framework.     

Numerical modelling of railway ballast at the particle scale

The paper describes the development of a technique to simulate triaxial tests on specimens of railway ballast numerically at the particle scale and its validation with reference to physical test data. The ballast particles were modelled using potential particles and the well‐known discrete element method. The shapes of these elemental particles, the particle size distribution and the number of particles (N = 2800) in each numerical triaxial specimen all matched closely to the real ballast material being modelled. Confining pressures were applied to the specimen via a dynamic triangulation of the outer particle centroids. A parametric study was carried out to investigate the effects on the simulation of timestep, strain rate, damping, contact stiffness and inter‐particle friction. Finally, a set of parameters was selected that provided the best fit to experimental triaxial data, with very close agreement of mobilized friction and volumetric strain behaviour. Copyright © 2015 John Wiley & Sons, Ltd.     

Evaluation of drainage tunnel effectiveness in landslide control

Infiltration of rainfall into hillslopes is often an important factor in triggering landslides. Using underground water drainage works together with anti-slide piles has been an effective method of landslide control, yet their effectiveness is inadequately discussed in the literature. This paper studies the influence of rainfall on the change in the underground water level beneath a slope by real-time and synchronic monitoring of the rainfall, the underground water level in the boreholes, and the flow rate of the underground drainage tunnel. The effectiveness of the underground drainage tunnel in preventing the rise of the underground water level of the slope is discussed. The researchers also study the deformation behavior of the anti-slide piles by monitoring the lateral displacement of the piles and analyzing the thrust that the anti-slide piles bear by numerical inversion techniques. The results indicate that there is an apparent relationship between the lag in the rising of the underground water level caused by a rainfall and that caused by the immediately previous rainfall. When there is a rainfall accumulation before the occurrence of a heavy rain, this particular heavy rainfall will cause a rapid rise of the underground water level beneath the slope. The monitoring data analysis shows that the flow rate of the underground drainage tunnel increases first, and then the underground water level of the slope rises after a rainfall. In other words, the flow rate of the underground drainage tunnel increases at a rate faster than that of the rise of the underground water level. Hence, the underground drainage tunnel can effectively lower the rise of the underground water level induced by a rainfall. Besides, based on the monitoring data of the lateral displacement of the anti-slide piles and subsequent analysis, the working state of the anti-slide piles is justified. It thus indirectly validates the benefits of using underground drainage tunnel in landslide control.     

The stress field at Soultz-sous-Forêts from focal mechanisms of induced seismic events: Cases of the wells GPK2 and GPK3

The stress field at the EGS geothermal site of Soultz-sous-Forêts has been the subject of many studies, because it largely controls the response of the reservoir to fluid injection. The analysis of borehole logging data, especially breakouts and drilling-induced tension fractures, in the four geothermal wells define an average SHmax orientation ranging between 170° and 180° down to 5 km depth. It also reveals strong heterogeneities in several depth intervals. In this paper, the inversion of double-couple source mechanisms of seismic events induced during GPK2 and GPK3 stimulation tests is performed to retrieve the orientation and shape factor of the stress tensor, using the Slickenside Analysis Package of Michael, 1984, Michael, 1987a, Michael, 1987b. The results indicate a well-determined orientation of Shmin in GPK2 and in GPK3; in GPK3 Shmin is clockwise rotated by about 10°. The stress tensor defines an uniaxial extension. The results from both methods, analysis of borehole logging data and inversion of focal mechanisms, are only slightly different; the discrepancy may be due to the larger reservoir volume covered by the focal mechanisms, which can include strong stress heterogeneities.     

Relationships among geochemical indices of coal and carbonaceous materials and implication for hydrocarbon potential evaluation

A worldwide dataset of organic material from 553 samples belonging to coal and carbonaceous materials was used to analyze the evolution of hydrogen index (HI) and bitumen index (BI) with increasing thermal maturity. Basic statistical analyses were applied to detect the boundary lines of HI_max and BI_max in delineating the upper and lower limits of the HI and BI bands for the majority of samples. In addition, cross-plots of HI or BI versus maturity (Ro% and T _max) also provide criteria for defining the HI_max and BI_max boundary lines. The constructed HI and BI bands are broad at low maturities and become narrower with increasing thermal maturities. The petroleum generation potential is completely exhausted at the vitrinite reflectance of 2.0–2.2% or T _max of 510–520°C. An increase in HI implies extra petroleum generation which was related to changes in structure of organic materials. A declining BI means that the oil expulsion window starts to occur at the vitrinite reflectance range of 0.75–1.05%. The petroleum potential can be divided into four different areas based on the cross-plot of HI versus Ro%. The highest petroleum potential area is located in section II with Ro = 0.6–1.0% and HI > 100. The oil generation potential is rapidly exhausted at section III with Ro > 1.0%. This result is also in accordance with the result of curve regression of HI versus Ro% based on 80 samples with Ro = 1.02–3.43% (R ² = 0.72). Overall, the total oil window can be extended up to Ro = ~1.25–1.95%. Finally, in the cross-plots of S1 versus S2, shale or C-shale exhibits a higher and slowly decreased slope, compared with a lower and then sharply increased slope of coal samples, which is attributable to their compositional difference in organic material.     

A quantitative analysis for geomorphic indices of longitudinal river profile: a case study of the Choushui River,Central Taiwan

Due to the plate movement is considerably slow, the human history record is too short to register landscape change for such a long time scale. However, longitudinal river profile can display watershed landscape characteristics. Therefore, this paper applies a quantitative analysis of geomorphic indices coupled with some mathematical models for the Choushui River and its six tributaries, including the gradient index and slope–area relationship. The abnormally high SL and SL/k values indicated that a decreasing trend from lower- to mid-stream areas and south Lishan fault was higher than north Lishan fault on the upstream areas, and the result of slope–area relationship also indicated that the regression line of the upper and lower steam exhibit an obvious right-shift nearby Lishan fault, could be explained by geodynamic models of active deformation in Taiwan area. This study also found that the abnormally high values of SL/k were affected by river and fault intersecting to form a high angle or perpendicular and the abnormally low values of SL/k were affected by river along with a fault or form a low angle, but the channel of Junda River along with Lishan fault is opposite. Based on quantitative results of these geomorphology indices, this study suggests that the important factor influencing landscape of the Choushui River watershed is tectonic uplift.