Search results for "Toxicant"
showing 4 items of 24 documents
Ecotoxicological studies with the freshwater rotifer Brachionus calyciflorus II. An assessment of the chronic toxicity of lindane and 3,4-dichloroani…
1993
The effects of chronic exposure of the freshwater rotifer Brachionus calyciflorus to the toxicants lindane and 3,4-dichloroaniline (DCA), were evaluated. The parameters used to determine the toxicity on these compounds were the age-specific and fertility, and the demographic parameters: intrinsic rate of natural increase (r), generation time (T), net reproductive rate (Ro), reproductive value (Vx) and life expectancy (eo). All the demographic parameters studied decreased with increasing toxicant concentrations. The use of life tables techniques with B. calyciflorus as a test method for the determination of chronic toxicity of xenobiotics is discussed.
Model ecosystem for environmental transport of xenobiotics
1982
A compartmentalized aquatic-terrestrial flow-through model ecosystem was constructed for studying the transport of agricultural chemicals from the soil to the aquatic environment in soil drainage. Factors were investigated on the fate of reference toxicant,14C-DDT, in the subsystems of the model. The behavior of DDT corresponds to its behavior in natural soil/water systems. The soil, acting as a reservoir, retained most of the DDT. The transportation of DDT to the aquatic compartment was negligible, with low availability to the aquatic biota. Because of the dynamic nature of the model, variation was evident between and within model units.
Using probability of extinction to evaluate the ecological significance of toxicant effects
2000
A large component of uncertainty in ecological risk assessment (ERA) arises from the disparity between the time scale of toxicity measurements and the time scale of predictions of ERA models. It is difficult to make predictions about the persistence of populations from data from short-term toxicity tests. Reproductive toxicity tests provide data about how population growth rate (r) is reduced with toxicant exposure. Although reduction in r is believed to be one of the most important effects of toxicant exposure, its ecological significance has been difficult to quantify. For rotifers, r is typically reduced by 10 to 15% at no-observed-effect concentrations (NOEC). We investigated r reductio…
Chronic toxicity of diazinon todaphnia magna:Effects on survival, reproduction and growth
1995
The sublethal effect of 0.15, 0.18, 0.22, 0.25 and 0.30 μg/L diazinon on the survival, reproduction and growth of D. magna was monitored for 21 days. Neonates (≤ 24 h) were obtained from the stock cultures and raised individually in 50 mL glass beakers. All daphnids were transfered every other day to a new beaker containing fresh medium, food and the appropriate pesticide concentration. The animals were maintained in an environmental chamber at 22±1°C on a 12L: 12D photoperiod and were fed daily on 5 x 105 cell/mL of the green algae Nannochloris oculata. The parameters used to determine the effect of the pesticide on reproduction were: mean total young per female, mean brood size, mean numb…