Intra-catchment variability in solute response an east devon example

Modifications to the land use of a small catchment, including clearance, cultivation and an increase in drainage density, are shown to have influenced a number of solute characteristics. Contrasts are drawn between three source areas; an unmodified subcatchment draining an area of mixed deciduous woodland, and a tile drain system and drainage ditch receiving water from cultivated areas. Not only are the modifications identified in terms of mean solute concentrations, but it is also shown that a change in land use alters the interaction between independent hydrological and meteorological variables, and solute response. A tentative explanation is provided for long term solute behaviour in relation to a number of biological geochemical and hydrological controls.     

Development of Quaternary stratigraphy in northeastern United States and adjacent Canada

Quaternary stratigraphy in the northeastern region has developed slowly because researchers have been few and because quartzose bedrock and extensive forest have inhibited field study. The earliest stratigraphic studies antedated 1850, but in most parts of the region the stratigraphic units still recognized today were identified in the present century. Ancient and modern sequences are generalized and are shown in charts.     

Characterization of halophiles in natural MgSO4 salts and laboratory enrichment samples: Astrobiological implications for Mars

The presence of sulfate salts and limited subsurface water (ice) on Mars suggests that any liquid water on Mars today will occur as (magnesium) sulfate-rich brines in regions containing sources of magnesium and sulfur. The Basque Lakes of British Columbia, Canada, represent a hypersaline terrestrial analogue site, which possesses chemical and physical properties similar to those observed on Mars. The Basque Lakes also contain diverse halophilic organisms representing all three Kingdoms of life, growing in surface and near-subsurface environments. Of interest from an astrobiological perspective, crushed magnesium sulfate samples that were analyzed using a modified Lowry protein assay contained biomass in every crystal inspected, with biomass values from 0.078 to 4.21 mg_biomass/g_salt; average=0.74±0.7 mg_biomass/g_salt. Bacteria and Archaea cells were easily observed even in low-biomass samples using light microscopy, and bacteria trapped within magnesium sulfate crystals were observed using confocal microscopy. Regions within the salt also contained bacterial pigments, e.g., carotenoids, which were separate from the cells, indicating that cell lysis might have occurred during entrapment within the salt matrix. These biosignatures, cells, and any ‘soluble’ organic constituents were primarily found trapped within fluid inclusions or fluid-filled void spaces between intergrown crystals. Diffuse reflectance infrared Fourier transform spectroscopy (reflectance IR) analysis of enrichment cultures, containing cyanobacteria, Archaea, or dissimilatory sulfate-reducing bacteria, highlighted molecular biosignature features between 550-1650 and 2400-3000 cm⁻¹. Spectra from natural salts demonstrated that we can detect biomass within salt crystals using the most sensitive biosignatures, which are the 1530-1570 cm⁻¹, C-N, N-H, -COOH absorptions and the 1030-1050 cm⁻¹ C-OH, C-N, PO₄³⁻ bond features. The lowest detection limit for a biosignature absorption feature using reflectance IR was with a natural sample that possessed 0.78 mg_biomass/g_salt. In a model cell, i.e., a 0.5 by 1 μm bacillus, this biomass value corresponds to approximately 7.8×10⁸ cells/g_salt. Based on its ability to detect biomass entrapped within natural sulfate salts, reflectance IR may make an effective remote-sensing tool for finding enrichments of organic carbon within outcrops and surficial sedimentary deposits on Mars.     

Ultraviolet absorption/salinity correlation as an index of pollution in inshore sea waters

Ultraviolet absorption spectra of fresh and marine waters along the southern coast of Viti Levu, Fiji, are recorded. Variations in the magnitude of the absorption from streams deyoid of human influence limit the use of such measurements as a sensitive index of organic pollution. However, where there is a significant difference between the absorption magnitudes of adjacent streams, these can be individually identified in coastal waters by concurrent absorption and salinity measurements. Such measurements characterise water masses in inshore waters, and indicate the origin of their freshwater components. Consequently the method has particular relevance in sea areas influenced by fresh waters with enhanced ultraviolet absorbance due to organic pollution.     

The construction and development of SHRIMP I: An historical outline

In 1973 Bill Compston advocated the building of an ion microprobe at the Research School of Earth Sciences (RSES) at the Australian National University (ANU). The commercial ion probes available at this time were too small to have sufficient sensitivity for trace element analysis and too low in mass resolution to avoid molecular interferences. The project commenced in 1974 with the appointment of a former ANU PhD student Steve Clement who had expertise in beam transport theory. To achieve high sensitivity and high mass resolution, beam transport theory indicated that a much larger magnet than in any commercially available mass spectrometer would be required. Clement chose an ion optical design, by Professor Matsuda of Osaka University in 1974, which had the required combination of high mass resolution and high transmission. Clement's job was to produce the detailed scientific designs and machine drawings for the new instrument as well as testing the completed instrument. Clement coined the term SHRIMP-Sensitive High Resolution Ion MicroProbe. By the end of 1977 nearly all the components had been manufactured and the big electromagnet had been successfully tested. In the following year the secondary mass analyzer was assembled and tested using a thermal ionization source and showed great promise with flat-topped peaks at 5000 resolution and 50% transmission with 50 V energy spread. At this stage the machine had far exceeded the specifications for the available commercial ion probes. Continued development during 1981 to the point where the original design specifications were fully realized was time consuming since learning how to use the entirely novel instrument was no simple task; no one else had an instrument like SHRIMP. The application of the instrument to zircon U–Pb geochronology established the necessary operating conditions for measuring Pb isotopic compositions and the elemental ratios Pb/U and U/Zr from 20 μm diameter spots on single zircon grains. Application of this in the early 1980s started a revolution in Precambrian geology by the ability to produce rapidly accurate and precise age determinations on structurally complex zircon samples.     

Intermittent convection

Abstract

A theoretical analysis of pseudo two-dimensional, finite-amplitude, thermal convection is made for an infinite Prandtl number fluid which is subjected to a constant heat flux out of the top boundary and insulated at the bottom. For large Rayleigh numbers the convective flow becomes intermittent and the system is characterized by the following cyclic process: the formation of a thermal boundary layer by diffusion, the instability of this layer when it becomes sufficiently thick, the destruction of the layer by the convective flow, the dying down of the convection, and the reforming of the thermal boundary layer by diffusion. The periodicity and the horizontal wave number of the intermittent convective flow are found to be independent of the depth of the fluid layer but depend on the rate of cooling and the properties of the fluid.     

Improving the valuation of groundwater

Hydrogeology Journal - An overview of groundwater economics is presented, highlighting the factors contributing to serious resource undervaluation, which is an aspect of resource management that...     

Generalized Born inversion of seismic reflection data

Summary . Born inverse methods give accurate and stable results when the source wavelet is impulsive. However, in many practical applications (reflection seismology) an impulsive source cannot be realized and the inversion needs to be generalized to include an arbitrary source function. In this paper, we present a Born solution to the seismic inverse problem which can accommodate an arbitrary source function and give accurate and stable results. It is shown that the form of the generalized inversion algorithm reduces to a Wiener shaping ***filter, which is solved efficiently using a Levinson recursion algorithm. Numerical examples of synthetic and real field data illustrate the validity of our method.