High spatial resolution hyperspectral mapping of in-stream habitats, depths, and woody debris in mountain streams

This article evaluates the potential of 1-m resolution, 128-band hyperspectral imagery for mapping in-stream habitats, depths, and woody debris in third- to fifth-order streams in the northern Yellowstone region. Maximum likelihood supervised classification using principal component images provided overall classification accuracies for in-stream habitats (glides, riffles, pools, and eddy drop zones) ranging from 69% for third-order streams to 86% for fifth-order streams. This scale dependency of classification accuracy was probably driven by the greater proportion of transitional boundary areas in the smaller streams. Multiple regressions of measured depths (y) versus principal component scores (x₁, x₂,…, x_n) generated R² values ranging from 67% for high-gradient riffles to 99% for glides in a fifth-order reach. R² values were lower in third-order reaches, ranging from 28% for runs and glides to 94% for pools. The less accurate depth estimates obtained for smaller streams probably resulted from the relative increase in the number of mixed pixels, where a wide range of depths and surface turbulence occurred within a single pixel. Matched filter (MF) mapping of woody debris generated overall accuracies of 83% in the fifth-order Lamar River. Accuracy figures for the in-stream habitat and wood mapping may have been misleadingly low because the fine-resolution imagery captured fine-scale variations not mapped by field teams, which in turn generated false “misclassifications” when the image and field maps were compared.The use of high spatial resolution hyperspectral (HSRH) imagery for stream mapping is limited by the need for clear water to measure depth, by any tree cover obscuring the stream, and by the limited availability of airborne hyperspectral sensors. Nonetheless, the high accuracies achieved in northern Yellowstone streams indicate that HSRH imagery can be a powerful tool for watershed-wide mapping, monitoring, and modeling of streams.     

Development of a diatom-based specific conductivity model for the glacio-isostatic lakes of Truelove Lowland: implications for paleoconductivity and paleoenvironmental reconstructions in Devon Island lakes, N.W.T., Canada

Diatoms are identified and enumerated from the surface sediments of 100 lakes of Truelove Lowland, Devon Island, N.W.T., Canada. These lakes range from large oligotrophic lakes, to small tundra ponds, to coastal marine lagoons which are diverse in terms of ionic concentration and composition. The relationship between diatoms and 15 limnological variables is examined using Canonical Correspondence Analysis (CCA). Specific conductivity is identified as the most important variable influencing the distribution of diatoms in the Truelove lakes. A Weighted Averaging (WA) calibration model is developed to predict diatom-inferred specific conductivity. The reliability of the model is tested by evaluating the correlation between observed and diatom-inferred values and determining the error of prediction by bootstrapping. The applicability of the predictive conductivity equation is demonstrated by reconstructing the paleoconductivity history of Fish Lake.     

Sediment budget-based estimates of trace metal inputs to a Chesapeake estuary

This article evaluates whether a sediment budget for the South River, Maryland, can be coupled with metals data from sediment cores to identify and quantify sources of historic metal inputs to marsh and subtidal sediments along the estuary. Metal inputs to estuarine marsh sediments come from fluvial runoff and atmospheric deposition. Metal inputs to subtidal sediments come from atmospheric deposition, fluvial runoff, coastal erosion, and estuarine waters. The metals budget for the estuary indicates that metal inputs from coastal erosion have remained relatively constant since 1840. Historical variations in metal contents of marsh sediments have probably resulted primarily from increasing atmospheric deposition in this century, but prior to 1900 may reflect changing fluvial sources, atmospheric inputs, or factors not quantified by the budget. Residual Pb, Cu, and Zn in the marsh sediments not accounted for by fluvial inputs was low to moderate in 1840, decreased to near zero circa 1910, and by 1987 had increased to levels that were one to ten times greater than those of 1840. Sources of variability in subtidal cores could not be clearly discerned because of geochemical fluxes, turbulent mixing, and bioturbation within the cores. The sediment-metal budgeting approach appears to be a viable method for delineating metal sources in small, relatively simple estuarine systems like the South River and in systems where recent deposition (for example, prograding marshes) prevents use of deep core analysis to identify background levels of metal. In larger systems or systems with more variable sources of sediment and metal input, however, assumptions and measurement errors in the metal budgeting approach suggest that deep core analysis and normalization techniques are probably preferable for identifying anthropogenic impacts.Field and laboratory research conducted at the Department of Geography, University of Maryland, College Park, Maryland, 20742, USAField and laboratory research conducted at the Marine and Estuarine Environmental Science Program, University of Maryland, College Park, Maryland, 20742, USA     

A new solid state diffusion model applied to inverse zoning and diffusion rims in minerals

Any oxide and silicate mineral which is nominally anhydrous but crystallized in the presence of H₂O incorporates traces of H₂O in solid solution. In the case of MgO it can be shown that OH^? pairs convert into H₂+O ₂ ^2? . If the H₂ molecules are lost, the O ₂ ^2? remain in the lattice as excess oxygen stabilized by excess cation vacancies. When the O ₂ ^2? anions decay either thermally or by decompression unbound O^? states (positive holes) are generated which lead to surface charges and subsurface space charge layers. Calculated space charge profiles are presented. O^? concentrations as small as 10–20 ppm suffice to create electric surface fields of the order of 4·10⁷ V·m^?1. The diffusion mechanism which derives from these premises incorporates novel features: the cation diffusion is coupled to the counterdiffusion of unbound and vacancy-bound O^? states. The cation diffusion is predicted to be very fast because first, it is field-enhanced (electrochemically driven) and second, it is not rate-limited by the intrinsic cation vacancy concentration nor by the counter-diffusion of other cations. The model may apply to cases of inverse zoning and diffusion rim formation in minerals under certain P-T conditions.     

Assessment of the Comparative Toxicity of Sewage Effluent from 10 Sewage Treatment Plants in the Area of Sydney, Australia using an Amphipod and Two Sea Urchin Bioassays

In 1995, Sydney Water Corporation undertook an ecological and human health risk assessment for 10 sewage treatment plants (STPs) that discharge primary (6 STPs) and secondary (4 STPs) treated effluents into coastal waters in the Sydney and Illawarra regions, NSW, Australia. A program of toxicity testing of effluent from the 10 STPs was undertaken to determine the toxic effects of the effluents and as a weight-of-evidence study for the risk assessment.

Three types of bioassays were used to test multiple samples of effluent from each STP. Tests used were the sea urchin (Heliocidaris tuberculata) fertilization and larval development bioassays and the amphipod (Allorchestes compressa) survival bioassay.

Comparing between STPs, primary treated effluent was slightly more toxic than secondary treated effluent for all three tests. The highest toxicity was recorded for those STPs that use primary treatment and discharge to the shoreline. Comparing between tests, the sea urchin fertilization bioassay was slightly more sensitive than the sea urchin larval development bioassay, with the amphipod survival bioassay being the least sensitive.

This paper will describe the results of this toxicity testing program and discuss the application of the study results as weight-of-evidence for the risk assessment study.     

A RELATIVE ORIENTATION FOR MOTOR VEHICLE ACCIDENT PHOTOGRAMMETRY

Relative orientations of eight stereomodels of a motor vehicle accident scene taken with stereometric cameras were made on an Adam Technology MPS-2 microphotogrammetric system. The most consistent results for the relative orientations were achieved with 12 pass points—six around the extremities and six in the centre of the format. Systematic errors in the direction normal to the photography were detected. Two methods to correct these errors were investigated—scaling of the camera base and computing a camera convergence correction. The best results were achieved with the convergence correction.     

Chronology and development of the 1980 earthquake at El Asnam (Algeria): a postscript

Radiocarbon dating has now confirmed the alluvial chronology that was used in assessing the extent of deformation during the 1980 El Asnam earthquake. It also supports the suggestion that earlier movements were related to a hypocentre further to the east.     

Microearthquake seismicity and active tectonics of northwestern Greece

We carried out a microearthquake survey lasting for six weeks in northwest Greece using 18 portable seismograph stations to examine a region in which normal and thrust faulting have been reported in close proximity to one another. With this array we located 148 events and determined fault plane solutions for eight events using only rays radiated upwards. The seismicity of the region is diffuse with events extending to depths of nearly 30 km, and there is a minimum in activity near a depth of 15 km. The fault plane solutions exhibit a wide spectrum of fault types and orientations and are not consistent with simple zones of shortening or extension. Neither tractions applied to the edges or bottom of the region nor deviatoric stresses that compensate for lateral variations in crustal thickness can account for the variety of fault plane solutions. We think that the complicated behavior is a manifestation of inhomogeneous deformation due, at least in part, to a pre-existing complicated juxtaposition of structures and formations.