Acute Toxicity of Sodium Pentachlorophenol on Carassius Auratus under Unsteady Exposure I: Without Suspended Particles

Water quality standards of toxicants for protection of aquatic organisms are mainly based on standard laboratory tests where constant exposure concentrations and fixed exposure time are applied. However, aquatic organisms are usually exposed to time-varying concentrations of contaminants in a natural water environment. Also, the toxic effects of pollutants on organisms depend on the residual level and metabolic rule of pollutants. In order to study the effects in a more realistic setting, we experimentally investigated the acute toxicity of sodium pentachlorophenol (NaPCP) to Carassius auratus, and the uptake dynamics of NaPCP onto Carassius auratus, where the Carassius auratus were exposed to NaPCP solution with four different initial concentrations (300, 600, 750, 900 mu g.L-1) for 96 hours, and water samples were extracted for analysis of concentrations of NaPCP. Variations of the accumulative death of the fish with time, accumulative uptake contents per unit body weight and uptake rates of NaPCP by Carassius auratus were monitored in the experiment. The experimental results reveal that the accumulative death rates of the fish increased with increasing NaPCP concentrations, presenting a doses-effect relationship. While those in the control group were almost constant with time, the NaPCP concentrations in the experimental groups decreased quickly in the first 12 hours, and thereafter varied slowly, approaching steady values by the end of the tests. The accumulative uptake contents of NaPCP per unit body weight of fish were found to increase quickly in the very beginning, and thereafter slowly on approaching a steady state, and at the same exposure time they would increase with increasing initial NaPCP concentrations. The uptake rates of NaPCP by Carassius auratus were found to be higher in the very beginning and thereafter to decrease quickly toward zero, which was approached after 8 hours compared with the earlier stage values. It was also found that a higher initial NaPCP concentration could lead to a greater uptake rate of NaPCP by Carassius auratus.