Water quality trends at an upland site in wales,UK, 1983–1993

Ten years of detailed upland stream and bulk deposition water quality data from Plynlimon, mid-Wales, are examined for trend. A robust statistical test (the seasonal Kendall test) is applied and data are presented graphically. Smoothing techniques are used to highlight the patterns of change which underlie high data scatter. The graphs show long-term cycles within the data which violate the assumptions of common statistical tests for trend. These cycles relate to fluctuations in the weather patterns at Plynlimon. Even though the seasonal Kendall test is significant for some determinands, the evidence from the graphs suggests that many of these ‘trends’ are unlikely to continue. For solutes in rainfall, there is no convincing long-term trend. There is a possible increase in ammonium concentrations, which may indicate an increasing atmospheric source generated by farming activities, but this will require a longer data series for confirmation. Several trace metal concentrations increased significantly part way through the study period, but later returned to the original levels. The bulk precipitation sea salt input has been uneven over the 10-year sampling period, with the highest inputs occurring during the wetter winters. For solutes in streamwaters, there are clear trends in dissolved organic carbon (DOC), iodine and bromide, which increase over time and may be attributed to an increase in organic decomposition in the catchment. Previous studies in Wales have shown similar behaviour for colour, which is related to DOC, but the corresponding changes for bromide and iodine are new. For most other streamwater determinands, any changes are masked by the effects of year to year variations in the quality and quantity of rainfall. For example, zinc and chromium variations parallel the corresponding rainfall quantity variations. The effect of rainfall quality variation is marked for marine-derived elements such as chloride. For sulphate, streamwater variations are inverted relative to chloride. This suggests that dry deposition may vary with weather conditions: high when the wind direction is from the land and low when weather systems are predominantly frontal and laden with sea salts. Alternatively, high sea salt rainfall may be affecting absorption/solubility reactions in the soils. There are four main conclusions. Firstly, there is no indication of changing acid deposition inputs or changing acidity within the runoff, despite a decline in UK sulphur dioxide emissions. Secondly, streamwater DOC has shown an increase over time, but there is no clear corresponding decrease in pH as might be expected from acidification theory. Thirdly, there are cyclical variations in bulk precipitation inputs and in streamwater quality, which mean that trends cannot be established even with 10 years of data. Long-term cycles are likely to exist in other environmental data and extreme care is required for the interpretation of trend, especially if data sets are short. This aspect strongly supports the continuation of long-term monitoring programmes over several decades. Finally, the graphical application strongly enhances data analysis and should be considered an essential component of trend investigation.     

The planet formation imager

The Planet Formation Imager (PFI, www.planetformationimager.org) is a next-generation infrared interferometer array with the primary goal of imaging the active phases of planet formation in nearby star forming regions. PFI will be sensitive to warm dust emission using mid-infrared capabilities made possible by precise fringe tracking in the near-infrared. An L/M band combiner will be especially sensitive to thermal emission from young exoplanets (and their disks) with a high spectral resolution mode to probe the kinematics of CO and H₂O gas. In this paper, we give an overview of the main science goals of PFI, define a baseline PFI architecture that can achieve those goals, point at remaining technical challenges, and suggest activities today that will help make the Planet Formation Imager facility a reality.     

Incorporating variable source area hydrology into a curve-number-based watershed model

Many water quality models use some form of the curve number (CN) equation developed by the Soil Conservation Service (SCS; U.S. Depart of Agriculture) to predict storm runoff from watersheds based on an infiltration-excess response to rainfall. However, in humid, well-vegetated areas with shallow soils, such as in the northeastern USA, the predominant runoff generating mechanism is saturation-excess on variable source areas (VSAs). We reconceptualized the SCS–CN equation for VSAs, and incorporated it into the General Watershed Loading Function (GWLF) model. The new version of GWLF, named the Variable Source Loading Function (VSLF) model, simulates the watershed runoff response to rainfall using the standard SCS–CN equation, but spatially distributes the runoff response according to a soil wetness index. We spatially validated VSLF runoff predictions and compared VSLF to GWLF for a subwatershed of the New York City Water Supply System. The spatial distribution of runoff from VSLF is more physically realistic than the estimates from GWLF. This has important consequences for water quality modeling, and for the use of models to evaluate and guide watershed management, because correctly predicting the coincidence of runoff generation and pollutant sources is critical to simulating non-point source (NPS) pollution transported by runoff. Copyright © 2007 John Wiley & Sons, Ltd.     

Central configurations and hyperbolic-elliptic motion in the three-body problem

A refined classification of motion for the planar three-body problem with zero total energy is presented. In addition, the structure and size of the sets of initial conditions are obtained. Limited results for the spatial problem are also given.Proceedings of the Sixth Conference on Mathematical Methods in Celestial Mechanics held at Oberwolfach (West Germany) from 14 to 19 August, 1978.Supported in part by the Natural Science Fund and the University Research Council of Vanderbilt University.     

Timing of Variscan HP-HT metamorphism in the Moldanubian Zone of the Bohemian Massif: U-Pb SHRIMP dating on multiply zoned zircons from a granulite from the Dunkelsteiner Wald Massif, Lower Austria

In an attempt to better constrain the timing of Variscan HP-HT metamorphism in the SE Bohemian Massif we have dated zoned zircons from a garnet-kyanite granulite of granitic composition from the Dunkelsteiner Wald Massif, Lower Austria, by means of sensitive high-resolution ion microprobe (SHRIMP) technique. In order to combine isotopic information with crystal growth textures, CL and BSE images were systematically taken from the dated zircons. A characteristic threefold concentric zoning was found in many zircons. This involves pre-Variscan protolithic cores followed by two distinct metamorphic/anatectic overgrowth shells of Variscan age. The inner overgrowth shell is characterized by a weak CL but bright BSE signal, and yields high contents of uranium (0.1 to 0.2 wt.%). A pooled U-Pb Concordia age for this zone is 342.0?±?3.0?Ma (n?=?11, MSWD?=?0.12). The second, outer, overgrowth shell is always bright in the CL image, dark in the BSE image, and has generally low uranium contents (mostly <500?ppm). A pooled U-Pb Concordia age for this zone is 337.1?±?2.7?Ma (n?=?11, MSWD?=?0.22). These results imply that the Variscan HT crystallisation history of the Moldanubian granulites took place over a period of a few million years and was not an extremely rapid subduction-exhumation process. SHRIMP measurements in the protolithic cores yield a cluster of (sub)concordant ages between ??390 and 460?Ma and a few outliers at higher ages mostly represented by cores in cores. Core domains, which are large, homogeneous and with undisturbed igneous oscillatory zoning, yielded preferentially ages between 430 and 460?Ma. We therefore consider that granitic protolith formation took place at that time. The still older inner cores are interpreted as inherited into the granitic melt.     

Near-infrared spectroscopy of powerful compact steep-spectrum radio sources

We have obtained near-infrared spectroscopy of a small sample of powerful compact steep-spectrum (CSS) radio sources mainly, but not exclusively, from the 3CR sample. We find no differences between the distributions in the equivalent width and luminosity of the [O  iii ]λ5007 line for our sample and other larger, presumably older, high-redshift 3C objects, suggesting that the underlying quasar luminosity remains roughly constant as quasars age. We also find a possible broad line in 3C 241, adding to recent evidence for broad lines in some radio galaxies.     

The hydrocarbons in the Isla Vista marine seep environment

Hydrocarbon analyses on samples of sediment, interstitial water, and dissolved and particulate fractions of the water column from the vicinity of the Isla Vista seep near Santa Barbara, California, are presented. The results demonstrate that a very heterogeneous distribution of hydrocarbon composition and concentration exists in the seep environment and that the life-style and feeding habits of the organisms in this environment will have a dramatic effect on their hydrocarbon exposure.     

On the origin of cold dark matter halo density profiles

N -body simulations predict that cold dark matter (CDM) halo-assembly occurs in two phases: (i) a fast-accretion phase with a rapidly deepening potential well; and (ii) a slow-accretion phase characterized by a gentle addition of mass to the outer halo with little change in the inner potential well. We demonstrate, using one-dimensional simulations, that this two-phase accretion leads to CDM haloes of the Navarro, Frenk & White (NFW) form and provides physical insight into the properties of the mass-accretion history that influence the final profile. Assuming that the velocities of CDM particles are effectively isotropized by fluctuations in the gravitational potential during the fast-accretion phase, we show that gravitational collapse in this phase leads to an inner profile  ρ( r ) ∝ r ⁻¹  . Slow accretion on to an established potential well leads to an outer profile with  ρ( r ) ∝ r ⁻³  . The concentration of a halo is determined by the fraction of mass that is accreted during the fast-accretion phase. Using an ensemble of realistic mass-accretion histories, we show that the model predictions of the dependence of halo concentration on halo formation time and, hence, the dependence of halo concentration on halo mass, and the distribution of halo concentrations all match those found in cosmological N -body simulations. Using a simple analytic model that captures much of the important physics, we show that the inner   r ⁻¹  profile of CDM haloes is a natural result of hierarchical mass assembly with an initial phase of rapid accretion.