Environmental Pollution (1970)最新文献

Experimental field treatments were employed to examine the thermal mortalities of copepods exposed to the heated effluents of a power generating plant located on a subtropical estuary. Significant lethal effects were observed for all species studied, with mass mortalities occurring during the warmest months of the year. Of the seven species examined, the copepods identified as estuarine species had steeper mortality curves and higher upper lethal thermal limits than the more neritic forms. The estuarine species have apparently evolved the ability to live in subtropical areas under temperature conditions very close to their upper thermal limits. Coastal species, on the other hand, exhibit a greater variation in temperature sensitivity so thermal additions in subtropical estuaries could be very significant in limiting their distribution and abundance.

Paraformaldehyde, capryl alcohol, and 5 surfactants were lethal to rainbow trout at less than 100 mg/litre or μlitre/litre. They were the most toxic of 21 tested materials likely to be present in used well-drilling fluids. Least toxic were bentonite, barite, and several organics. Simulated ‘13-lb’ drilling fluid was lethal at 1·8% concentration, used fluids from the Mackenzie delta at 0·83, 4·2, and 5·3%.

There was no consistent picture for joint action in mixtures. Used fluids were lethal at 0·71, 1·2, and 0·83 times the values predicted from an assumption of additive toxicity of approximated components. Those results were in statistical agreement with additivity. The LC50 of the simulated fluid was 1·5 times the value predicted from its seven components, significantly less-than-additive. When the seven most toxic components were added singly to simulated fluid, about half the results were not different from additive joint action. However, for every component plus fluid, there was antagonism in at least one of three proportions tested. Strongest antagonism was 3·7 times the predicted value for the surfactant B-Free added to fluid. Decreased toxicity may have resulted from sorption of components on bentonite, or different toxic mechanisms for fish. Six of the seven most toxic components lost toxicity upon ageing for 16 days in water, while B-Free increased sharply in toxicity.

The effect of cadmium on the survival and reproductive capacity of Daphnia pulex was determined. Cadmium was present either in the water at chronic (1–30 μg Cd/litre) and acute (40–90 μg Cd/litre) levels or in the algal food source, Chlorella pyrenoidosa. The average longevity of D. pulex was not affected by exposure to 1 μg Cd/litre but it was reduced in a dose-dependent manner between 5 and 30 μg Cd/litre. Exposure to cadmium had no effect on the number of days to onset or frequency of reproduction but it did cause a reduction in the percentage of adults producing young, the number of broods per adult, the number of young per brood, the number of progeny per adult, the intrinsic rate of natural increase (r), and the mean generation time (T). Cadmium-laden Chlorella caused the same effects as did exposure to 1 μg Cd/litre.

Examination of the effects of sulphurous emissions from a coal-burning power plant on the vegetation of a mixed oak forest with white pine Pinus strobus L. and hemlock Tsuga canadensis (L.) Carr revealed that species diversity and importance values of certain species were inversely related to distance from the source of emission. Diversity and importance of white pine Pinus strobus L. and sweet birch Betula lenta L. increased with distance whereas the importance of white oak Quercus alba L. and red maple Acer rubrum L. decreased. Differences with distance were greater downwind than upwind. The data fitted hyperbolic equations using the reciprocal of distance from the emission source. Species richness and diversity were more sensitive indicators of pollution damage than growth assessments of individual overstorey species or groups of species.