Toxic Effects Of Daphnia Magna To Polluted Water By Cadmium After Treatments With Aluminum Chloride

In recent years, sudden heavy metal pollution break out frequently, and theecological environment is threatened severely, then damaged aquatic organisms andhuman health. Cadmium pollution is common in the heavy metal pollutions,aluminum salt flocculants has become the common adsorbent and using on a largescale in the sudden pollution of heavy metals, however, the residual aluminum andcadmium in sediments might exist in environment for a long time and polluteenvironment again. Therefore, research the ecological toxicity effects of aluminumchloride treat the water polluted by cadmium has practical significance.The research adopts Daphnia magna as the model organism, and studied threeaspects include acute toxicity, chronic toxicity and genetic toxicity by static bioassaytest, in order to analysis toxic effects the water polluted by cadmium and then treatedby aluminum chloride of Daphnia magna. The study investigated the molting times,number of neonates and the length during the process of growth and development ofDaphnia magna, to provide theoretical for cadmium pollution emergency treatmentand sediments disposal.The results of acute toxicity experiment showed that the LC50-48hof CdCl₂andAlCl₃are0.064mg/L and16.82mg/L respectively. Cd-Al shows antagonistic effect incombined effects about Daphnia magna. In the concentration of1TU, the survivalrate in the ratio of Cd:Al at10:0and0:10is lower than the group of7:3,5:5and3:7,and the lowest acute toxic effects appear in the ratio of Cd:Al at5:5（0.032mg/Lå’Œ8.4mg/L）.The results of chronic toxicity in different concentration about Cd-Al showedthat the molting times and the length is no significant difference compared with thecontrol group in0.01TU, and in0.05TU and0.1TU, the molting times and the lengthshowed very significant difference compared with the control group in21-days. The all results suggested that the inhibitory effects more and more serious with thegrowing concentration, but the effects of growth and development is almost nosignificant difference among different proportions of Cd-Al.In the concentration of0.01TU,0.05TU and0.1TU, the genetic toxicity ofDaphnia magna suggested that the offspring affected severely when they exposure inthe cadmium polluted water treat by aluminum chloride. This may because of thebioaccumulation in Daphnia magna about Cd and Al, and the offspring be affectedgradually enhanced. So the Cd can remove from the sediments into the water, andlead to persistent damage.The research assessed the cadmium polluted water which treated by aluminumchloride, however, we need further research the dynamic process about adsorption,release and migration of Cd and Al in water and sediments, and the inhibitorymechanisms of growth and development, in order to achieve the practical application.