A tipping bucket flowmeter for roadside gully runoff

A tipping bucket flowmeter designed for the measurement of inflows to roadside gully pots is described. It is braced within the pot above the liquor and the runoff is fed to it via a glass fibre funnel and a hose. Whilst it can be calibrated to only 0·71 s^?1, it is very effective at low flows and has a number of advantages over the well known Institute of Hydrology Gully Meter. Its use at Redbourn, Hertfordshire for roads on highly permeable soils shows that for both rainfall and artificial irrigation the ‘losses’ are very large and highly variable even within a single housing estate road.     

Evaluating new fault-controlled hydrothermal dolomitization models: Insights from the Cambrian Dolomite,Western Canadian Sedimentary Basin

Fault-controlled hydrothermal dolomitization in tectonically complex basins can occur at any depth and from different fluid compositions, including ‘deep-seated’, ‘crustal’ or ‘basinal’ brines. Nevertheless, many studies have failed to identify the actual source of these fluids, resulting in a gap in our knowledge on the likely source of magnesium of hydrothermal dolomitization. With development of new concepts in hydrothermal dolomitization, the study aims in particular to test the hypothesis that dolomitizing fluids were sourced from either seawater, ultramafic carbonation or a mixture between the two by utilizing the Cambrian Mount Whyte Formation as an example. Here, the large-scale dolostone bodies are fabric-destructive with a range of crystal fabrics, including euhedral replacement (RD1) and anhedral replacement (RD2). Since dolomite is cross-cut by low amplitude stylolites, dolomitization is interpreted to have occurred shortly after deposition, at a very shallow depth (<1 km). At this time, there would have been sufficient porosity in the mudstones for extensive dolomitization to occur, and the necessary high heat flows and faulting associated with Cambrian rifting to transfer hot brines into the near surface. While the δ¹⁸O_water and ⁸⁷Sr/⁸⁶Sr ratios values of RD1 are comparable with Cambrian seawater, RD2 shows higher values in both parameters. Therefore, although aspects of the fluid geochemistry are consistent with dolomitization from seawater, very high fluid temperature and salinity could be suggestive of mixing with another, hydrothermal fluid. The very hot temperature, positive Eu anomaly, enriched metal concentrations, and cogenetic relation with quartz could indicate that hot brines were at least partially sourced from ultramafic rocks, potentially as a result of interaction between the underlying Proterozoic serpentinites and CO₂-rich fluids. This study highlights that large-scale hydrothermal dolostone bodies can form at shallow burial depths via mixing during fluid pulses, providing a potential explanation for the mass balance problem often associated with their genesis.     

Physiological energetics of the fourth instar of Chinese horseshoe crabs (Tachypleus tridentatus) in response to hypoxic stress and re-oxygenation

Hypoxia associated with eutrophication is a potential threat to the Chinese horseshoe crab Tachypleus tridentatus which inhabits intertidal sand flats in Asia. This study investigated the effect of dissolved oxygen level (DO) (6, 4 and 2 mg O₂ l⁻¹) on the physiological energetics in the juvenile T. tridentatus. They were exposed to various oxygen levels for three days and then transferred to normoxia for three days to examine the recovery from low oxygen stress. Feeding rate, respiration rate and scope for growth were reduced at lower DO levels while absorption efficiency and excretion rate were independent of DO levels. Although full recovery of the physiological responses and scope for growth from hypoxis stress was observed when normoxia resumed, their long term survival in suboptimal habitats with frequent occurrence of hypoxia deserves a close monitoring as hypoxia may be even more common in future in a warming world.     

Spatial and temporal distribution of heavy metal concentrations in mussels (Mytilus edulis) from the Baie des Chaleurs, New Brunswick, Canada

Previous studies on heavy metal contamination of the Baie des Chaleurs focus only on industrial centers and overlooked the ecosystem as a whole. To fill this gap, the objective of this study is to establish a baseline of the spatio-temporal distribution of heavy metals in mussels from the Baie des Chaleurs based on the ecosystem approach. Our results show, for the first time, a cadmium contamination in mussels across the south coast of the Baie des Chaleurs and not only in industrial centers. Our results also confirm previous studies showing heavy metal contamination of the Belledune area. This study demonstrates that the use of the ecosystemic approach is essential to obtain a comprehensive picture of environmental contamination in marine ecosystems.     

Dark energy and the evolution of spherical overdensities

We use the non-linear spherical model in cold dark matter (CDM) cosmologies with dark energy to investigate the effects of dark energy on the growth of structure and the formation of virialized structures. We consider dark energy models with a constant equation-of-state parameter w . For  −1 < w < −1/3  , clusters form earlier and are more concentrated in quintessence than in ΛCDM models, but they form later and are less concentrated than in the corresponding open model with the same matter density and no dark energy. We point out some confusion in the literature around the expression of the collapse factor (ratio of the radius of the sphere at virialization to that at turnaround) derived from the virial theorem. We use the Sheth & Tormen extension of the Press–Schechter framework to calculate the evolution of the cluster abundance in different models and show the sensitivity of the cluster abundance to both the amplitude of the mass fluctuations, σ₈, and the σ₈– w normalization, selected to match either the cosmic microwave background observations or the abundance of X-ray clusters.     

Possible long-term decline in impact rates: 1. Martian geological data

Quantin et al. [Quantin, C., Allemand, P., Mangold, N., Delacourt, C., 2004a. Icarus 172, 555-572] tabulated crater count data for 56 landslides along the walls of Valles Marineris. Under the assumption of a constant cratering rate after about 3 Gyr ago, as used in the 1999-2005 iterations of the crater chronology isochron system of Hartmann, and in the Hartmann and Neukum system, these data indicate a regularly increasing rate of landslides, which would be difficult to explain. We suggest that these data may support a decline in inner Solar System cratering rates by about a factor of 3 since 3 Gyr ago, not unlike predictions based on asteroid belt collision models. Such a decline is also supported by our review of data on lunar impact melts and glass spherules in a companion paper [Hartmann, W.K., Quantin, C., Mangold, N., 2007. Icarus 186, 11-23]. Such models produce not only a more uniform rate of landslides over the last 3 Gyr, but also a more uniform rate of resurfacing processes which also had an apparent increase under the assumption of a constant cratering rate.     

Broken Beds,but better science; using multiple hypotheses to interpret geological data

In this study, we propose a multiple hypotheses approach to improve interpretations of limited remotely sensed datasets, such as sparsely exposed outcrops, subsurface datasets, or planetary objects using semi-quantitative scoring and ranking of observable features. This method is demonstrated using an outcrop example from the Broken Beds of the Upper Jurassic–Lower Cretaceous Purbeck Limestone Group exposed along Britain's Jurassic Coast. Four published hypotheses regarding their origin are refined, represented in matrix form, scored and ranked based on carefully selected outcrop features. Semi-quantitative scoring utilises knowledge of likely processes governing the occurrence of a range of features, some of which might be ignored or down-played to favour a single hypothesis. Furthermore, by integrating expertise from different sub-disciplines (e.g. basin analysis, sedimentology, diagenesis), we also consider the combined evidence of multiple features. This new method results in an interpretation that favours a multi-process origin for the Broken Beds due to evaporite dissolution, overpressure release and tectonic folding, with identified uncertainty, all useful to guide further data collection.     

Infant feeding in North East England: contested spaces of reproduction

Decisions about infant feeding are commonly viewed as an issue of personal choice made in the light of information about the benefits of breastfeeding. A pilot study of first-time parents' decisions and experiences in Newcastle upon Tyne, England, suggests that local cultural contexts, in particular how men and women are seen to be parenting in different spaces, have a profound influence on infant feeding.