Search

The reactions of different residents to the same level of noise have been assumed to vary depending upon their type of housing and tenure status. However, no empirical evidence has been presented to support this assumption. The analysis described in this paper tests the separate and joint effects of housing type and tenure on various reactions to road traffic noise, with the use of questionnaire data and noise measurements collected at residential sites near to major highways in the Toronto region of southern Ontario. The results show that neither housing type nor tenure has any consistent effect on residents' reactions to road traffic noise. The working assumption in the literature is therefore not supported. Two important conclusions follow from this: first, that no one type of housing is clearly more appropriate in residential areas near to major highways; and second, that a policy of setting different noise standards for different types of residential area cannot be supported.

A method is described for the determination of ionic allcyl lead species in marine fauna. The sample is homogenised in the presence of a mixture of salts which effectively releases the various alkyl lead species which may be present and facilitates their transfer to toluene as a preliminary to back extraction into dilute nitric acid. The differentiation and determination of the alkyl lead species is achieved by differential pulse anodic stripping voltammetry. The efficiency of the extraction procedure has been examined at alkyl lead concentrations up to 2 mgKg-1 as Pb and a detection limit of 0.01 mg Kg-1 established. Typical results obtained from a range of environmental samples are presented.

A maximum likelihood model is developed, using mark-recapture data, to estimate total and fishing mortality rates for the dusky shark Carcharhinus obscurusin South Africa. The model accounts for tag-shedding, non-reporting of recaptured tags, the multiple release and single recapture nature of the study and the usage of two different types of tags (sheep-ear and ORI tags). Tag shedding was quantified as tags washed up on beaches and fouling of tags in protective shark nets, which amounted to 17% of all tags recovered between 1986 and 1993. The ORI tag had a higher tag-shedding rate than the sheep-ear tag. Assuming a 75% reporting rate for recaptured dusky sharks, an instantaneous fishing mortality rate was estimated to be 0.27·year−1, with a 95% confidence level ranging between 0.19 and 0.44·year−1.

An automated continuous monitoring system for the determination of inorganic and total mercury by flow-injection analysis followed by cold-vapour atomic absorption spectrometry is described. The method uses a typical flow-injection manifold where digestion and reduction of the injected sample takes place. Mercury is removed by aeration from the flowing stream in a specially designed air-liquid separator and swept into a silica cell for absorption measurement at a wavelength of 253.7 nm. A calibration curve up to 10 µg Hg ml-1 using three different path length cells is obtained with a detection limit of 0.02 µg Hg ml-1. The sampling rate of an injection every 3 min produces 20 results per hour from a flowing stream.