Toxic chemicals in Canadian fish-eating birds

Cross-country comparison of DDE and PCB residue levels in cormorant, gull and tern eggs in Canada reveal that bird populations at the Great Lakes are most contaminated with those pollutants. DDE levels have been correlated with reproductive failure in Double-crested Cormorants in the Great Lakes with eggshell thinning as a major factor. Low reproductive success in Herring Gull colonies at Lake Ontario is associated with high chlorinated hydrocarbon levels in eggs. Fish-eating birds in the Wabigoon River system, northwestern Ontario, are among the most known mercury contaminated birds. It is suggested that the effects of mercury on the reproduction of fish-eating birds should be further examined there.Fish-eating birds occupy the highest levels of the food web and magnification of toxic chemicals through prey organisms in this web makes those birds vulnerable to the effects of environmental contaminants. Since fish-eating birds are present everywhere in Canada's freshwater and marine habitats and occupy various niches there, they may serve as pollution indicators in various food chains of our aquatic environment. Colonial birds are especially valuable indicators as pollution effects on total bird populations can be studied. Baseline information on fish-eating bird populations should now be collected everywhere in Canada for measuring present and future effects of environmental pollutants, as well as other man-made disturbances on their populations.     

The analysis of finite strain using lines with an initial random orientation

The effect of homogeneous strain on random samples from an initially uniform distribution of lines in two dimensions is investigated. After doubling the data and treating each as a unit vector, the orientation and length of the resultant vector allows the orientation of the X-axis and the strain ratio to be estimated. The appropriate confidence limits of these estimates are evaluated. The method is illustrated using samples of weakly deformed desiccation cracks and a comparison with other methods of strain analysis made.     

Suspended material in Narragansett Bay: fatty acid and hydrocarbon composition

Suspended material collected at various stations in Narragansett Bay was analyzed for fatty acids and hydrocarbons. The qualitative and quantitative distributions of these compounds indicated that the influence of sewage and other pollutants was greatest in the river areas. Based on concentrations of polyunsaturated fatty acids, the highest densities of phytoplankton were interpreted to occur at the mid and lower Bay stations, and the percentage of phytoplankton in suspended material was estimated from the concentration of heneicosahexaene. The concentrations of fatty acids and hydrocarbons in the suspended material decreased from the river stations to the mid and lower Bay stations, closely following a similar trend observed in the sediment. Possible sources of the suspended material and the influence of these sources on this material in various areas of the Bay are discussed, and attempts are made to interrelate the suspended material, resuspended sediment, phytoplankton, and sewage effluent with chemical and biochemical diagenetic changes.     

Late-Pleistocene and Holocene remains of Hysterocarpus traski (Tule Perch) from Clear Lake,California, and inferred Holocene temperature fluctuations

The remains of scales of Hysterocarpus traski Gibbons (Tule perch) were found throughout a 27.44-m core from Clear Lake. Most scales occurred between the mud surface and deposits approximately 11,000 years old. Changes in growth rates of the animals were examined by measuring scale annuli and applying an empirically established regression of fish length on scale radius. The data indicate a pattern of accelerating growth rates, reaching a peak between ?4000 and 2800 BP. After ?2800 BP, growth rates decline markedly. Because the growth rates of these animals are essentially dependent on temperature, the changes observed in the patterns of growth probably reflect changes in climate in the northern Coast Range. The general pattern of inferred temperature increase during the early and middle Holocene, ending between ?4000 and 2800 BP, is consistent with evidence from tree-line studies and palynology indicating higher temperatures in parts of the western United States during this period.     

An appreciation of galena concentration using a steady-state flotation model

A general-purpose computer program has been developed for the steady-state modelling of flotation plants. It permits simulation of flotation banks, made up of any number of cells, interconnected if necessary through a regrind unit. Specification of the fresh feed material in terms of the relative amounts and flotation-rate behaviour of its flotable components is necessary so that the program can then calculate the concentration of these components in all the plant streams.The use of the program for plant investigation is demonstrated using data for a lead concentration plant. The model was fitted to steady-state plant data and then tested by comparing the predictions of the model with actual plant measurements at a second feed condition. Full circuit simulation results are also presented to show how steady-state modelling can be used to give information on the likely response of the plant to other changes in feed material and the benefits which might result from rearrangements of the circuit.     

Geological maps from the British Antarctic Survey

In a bold move the British Antarctic Survey has published the naturally fragmentary results of their ongoing geological mapping and research programme in the Antarctic Peninsula and offshore islands, plus South Georgia. The later is classified as a United Kingdom overseas territory, along with the volcanically active South Sandwich Islands just north of 60 degrees south. Beyond this latitude to the South Pole all territorial claims have been frozen by the Antarctic treaty, which built upon the International Geophysical Year of 1957 and came into force in 1961. Since then this monumental achievement, developed during the height of the cold war, has succeeded in keeping Antarctica demilitarized, including banning the disposal of nuclear waste, and untainted by mineral exploration. In 1998 this treaty was renewed for a further fifty years and extended to cover the impact of tourism. Although geological research had been conducted since the pioneering days of Shackleton, Scott and Amundsen, the original 1908 territorial claim was backed up by a continuing presence since 1943, and the Falklands Islands Dependencies Survey was renamed the British Antarctic Survey in 1962 to chime with the spirit of purely scientific research entailed by this treaty which has now expanded to a membership of nearly fifty nations.     

A thermo‐mechanical model for variably saturated soils based on hypoplasticity

The paper presents a mechanical model for non‐isothermal behaviour of unsaturated soils. The model is based on an incrementally non‐linear hypoplastic model for saturated clays and can therefore tackle the non‐linear behaviour of overconsolidated soils. A hypoplastic model for non‐isothermal behaviour of saturated soils was developed and combined with the existing hypoplastic model for unsaturated soils based on the effective stress principle. Features of the soil behaviour that are included into the model, and those that are not, are clearly distinguished. The number of model parameters is kept to a minimum, and they all have a clear physical interpretation, to facilitate the model usefulness for practical applications. The step‐by‐step procedure used for the parameter calibration is described. The model is finally evaluated using a comprehensive set of experimental data for the thermo‐mechanical behaviour of an unsaturated compacted silt. Copyright © 2011 John Wiley & Sons, Ltd.