Studies into the formation of dioxins in the sintering process used in the iron and steel industry. 1. Characterisation of isomer profiles in particulate and gaseous emissions

Dioxin analyses using a DB5MS chromatography column are presented for samples of dust from an electrostatic precipitator and emissions from the main stack of a UK sinter plant. The analyses have been repeated using the SP2331 column, for which the elution order has been determined for the whole range of tetra to octachlorodibenzo-p-dioxins and dibenzofurans, and which provides a larger degree of separation than the DB5MS column. Polychlorinated dibenzofurans are present in significantly larger amounts in both the dust and stack emissions, and are the main contributors to the I-TEQ. Analysis using the SP2331 column for dioxins show considerable similarity to those of Bacher et al. for soot from a wood-burning fire, but differ markedly from those of Addink et al. for simulation of waste incineration. The similarities to Bacher's results are less for the dibenzofurans. Comparison of absolute concentrations with reported vapour pressures shows the retention of significant dioxin in the dust to involve mechanisms other than pure condensation.     

The effects of bayluscide and malathion on the survival of Schistosoma mansoni miracidia

Laboratory experiments were conducted to assess the toxic effects of bayluscide and malathion against Schistosoma mansoni miracidia. The results indicate that survival of miracidia varied with times of exposure and concentrations of tested chemicals. Statistical analyses reveal that LC5, LC50 and LC95 for bayluscide were 0.04 ppm, 0.06 ppm and 0.12 ppm after 2 hours of exposure; 0.02 ppm, 0.03 ppm and 0.06 ppm after 4 hours of exposure; and 0.01 ppm, 0.02 ppm and 0.04 ppm after 6 hours of exposure respectively. These data indicate that bayluscide is much more toxic to the first stage larvae of schistosomes than to snail intermediate hosts cited in the literature. Application of lower concentrations of molluscicide in the transmission sites is thus expected to curtail the survival of miracidia; therefore controlling schistosomiasis at relatively low costs. Such applications also reduce the risk of toxicity to non target organisms present in the aquatic environment. Statistical analysis of the results of tests using malathion gave LC5, LC50 and LC95 values of 83.38 ppm, 153.11 ppm and 245.85 ppm after 2 hours of exposure; and 76.86 ppm, 116.48 ppm and 172.04 ppm after 4 hours of exposure respectively. These data indicate that the use of malathion as an insecticide in tropical ecosystems may also affect the survival and viability of schistosome miracidia. Such uses could help reducing the risk of schistosomiasis transmission in these particular locations.     

Biochemical and fine structure evidence for cellular specialization in a large spumellarian radiolarian Thalassicolla nucleata

Thalassicolla nucleata is a skeletonless, large spumellarian radiolarian (ca 3 mm diameter) occurring abundantly in the surface water of the Sargasso Sea. It has a complex cellular organization consisting of (1) a well-defined central capsule surrounded by a non-living capsular wall perforated by numerous cytoplasmic strands and (2) an extracapsulum containing a frothy layer of alveolate cytoplasm penetrated by numerous rhizopodia. Evidence is presented for physiological specialization complementing this structural compartmentalization. Acid acryl phosphatase activity (a digestive vacuole marker enzyme) is approximately 3 times greater in the extracapsulum compared to the intracapsulum; whereas, cytochrome oxidase (a respiratory marker enzyme) is approximately 1.5 times greater in the intracàpsulum compared to the extracapsulum. Furthermore, cytochemical and electron microscopic evidence indicates that the extracapsulum, containing large vacuoles and copious amounts of acid phosphatase reaction product, is a major site of catabolism; while the intracapsulum, containing the nucleus, numerous Golgi bodies, and a rich supply of mitochondria, is a substantial site of anabolism, lysosomal secretory activity, and food product storage. This marked level of cellular specialization in T. nucleata may enhance its biological efficiency and thus partially account for its abundance in oligotrophic environments.     

The role of hatching asynchrony in siblicidal brood reduction of two booby species

Summary Hatching asynchrony (HA) of masked boobies (Sula dactylatra) in the Galápagos Islands differs from that of its sympatric congener, the blue-footed booby (S. nebouxii), in association with differences in brood reduction systems. Masked booby nestlings are obligately siblicidal, have long HA, and the probability and timing of siblicide is strongly influenced by HA. Blue-footed boobies are facultatively siblicidal and have shorter HA. Experimental shortening of masked booby HA demonstrated that this species maintians its HA above an early reduction threshold, below which parents may incur costs of provisioning a brood that they cannot raise to fledging, but that blue-footed booby HA occur above, at, and below the masked booby threshold. Differences in HA alone cannot explain the differences between these two brood reduction systems.     

A new method for determining concentrations of Endod-S (Phytolacca dodecandra) in water during mollusciciding

A hemolytic method was developed for the quantitative determination of oleanane saponin (Endod-S) in Phytolacca dodecandra (Phytolaccaceae), a plant with potent molluscicidal properties. A chemical method based on thin-layer chromatography (TLC) was used as a control for comparison with a hemolysis test. Standard curves for calibration of both tests of Endod-S gave high correlation coefficients. The hemolysis method gave a correlation coefficient of 0.98 for saponin (Endod-S) levels ranging from 1.6 to 4.2 mg/l. The TLC method gave a correlation coefficient of 0.99 for saponin levels above 1.5 micrograms. Due to the action of saponins on erythrocytes, the hemolysis method could not be used at levels below 1.6 and above 4.2 mg/l. Similarly, sample size limited TLC quantitation of these saponins at levels below 1 microgram. Both the TLC and the hemolysis methods on identical Endod-S water samples gave comparable results at saponin levels between 2 and 6 mg/l. A snail bioassay showed that the LC50 and the LC90 concentrations of Endod-S to the snail Biomphalaria glabrata (albino) were 2.57 and 2.92 mg/l respectively. These values fell in the standard curve range for the hemolysis method thus indicating that the hemolysis method is of practical value for testing Endod-S concentrations that would actually be used in field applications for snail control. The hemolysis method is less expensive than TLC and can be easily adapted to field conditions.     

Column leaching and sorption experiments to assess the mobility of potentially toxic elements in industrially contaminated land

Made-up ground collected from layers of a trial pit excavated on a former industrial site was treated with artificial rainwater in a series of column leaching and sorption experiments. Metal mobility and the ability of various layers of material obtained from the pit to act as sources or sinks of potentially toxic elements were assessed. Samples from different layers varied in their abilities to raise the pH of rainwater applied at pH 3.5 and 4.3, and this was reflected in the amounts of metals mobilised by the rainwater as it percolated through the soil column. Material from the top two layers of the pit released cadmium, copper, manganese, lead, nickel and zinc to the aqueous phase, but the lower layers, with higher buffering capacity, were able to resist acidification even when the equivalent of 12 months' rainfall (western UK) was applied. Column sorption experiments confirmed the ability of material from layer 4 (48-50 cm) to take up copper, manganese and zinc. Metals were determined in the leachates by flame and electrothermal atomic absorption spectrometry and principle anions by ion chromatography.     

Taxation of uranium mining in Canada and Australia

The objective of this paper is to compare the nature of the taxation schemes facing uranium mine operators in Australia's Northern Territory and in Canada's Province of Saskatchewan. The findings demonstrate that, although the Canadian system appropriates up to 85% of incremental sales revenue, it is extremely sensitive to industry profitability. Its Australian counterpart is, in contrast, a regressive scheme which, at the current selling price of yellowcake, captures a significantly larger proportion of available economic rent.