Study On The Sensitivity Of Ostracods To Uranium And Cadmium

Ostracods are widely used as indicator organisms in environmental risk assessment,but they are rarely reported in mine environmental monitoring and assessment.Both uranium and cadmium are important pollutants in the development of uranium mines and pose a serious threat to the environment and ecological health.Therefore,in this paper,two ostracods（Cypridopsis vidua and Heterocypris sp.）,which are widely distributed and easy to collect and cultivate,are used as test organisms,and uranium and cadmium are used as target poisons to study their sensitivity levels.First,carry out the indoor acute toxicity experiment,first carry out the acute exposure experiment of uranium and cadmium on the ostracod,and carry out the experiment on the model organisms Daphia magna,Brachydanio rerio,Cyprinus carpio.Compare the obtained experimental data to determine the sensitivity level of ostracod to uranium and cadmium.In order to further explore the interaction between uranium and cadmium,two methods of direct equipartition ray（Equ Ray）and equivalent-effect concentration ratio（EECR）were used to mix uranium and cadmium,and C.carpio was used for experiments.The experimental data obtained is based on the concentration price model（CA）and the independent action model（IA）to judge their interaction mode.In addition,physical and chemical analysis and evaluation of ostracod toxicity were conducted on water samples collected from a uranium mine pit and tailings near the water system in northern Guangdong,in order to explore the sensitivity of ostracods to actual pollutants of uranium and cadmium.The main conclusions of the thesis are as follows:（1）The 96-hour lethal concentration(96-h LC₅₀)of C.vidua for uranium is 6.205 mg/L,the 96-hour LC50 for cadmium is 0.054 mg/L;the 96-hour LC₅₀of H.sp.for uranium is 7.153 mg/L The 96-h LC₅₀for cadmium is0.152 mg/L.Based on U-96 h-LC₅₀,the uranium sensitivity sequence is:C.vidua>H.sp.>D.magna>C.carpio>B.rerio;based on Cd-96h-LC₅₀,the cadmium sensitivity sequence is:C.vidua>H.sp.>D.magna>C.carpio>B.rerio.According to the comparison between the CRC obtained by the joint toxicity experiment and the CA and IA reference model predicted CRC,the binary mixture of uranium and cadmium showed obvious antagonism.（2）According to the physical and chemical analysis of the pit mouth and the water system near the tailings of a uranium mine in northern Guangdong,it can be seen that according to the single factor index method,the uranium pollution level of the pit mouth water system is shown to be severely polluted in the tailings pond.Both are low and only show severe pollution at K3,but the high P_ivalue in the tailings pond seriously pollutes the water environment;according to the potential risk index method,both uranium and cadmium pollution seriously exceed the highest risk assessment level,showing extremely strong risk.In the ostracod toxicity assessment of the collected waters,it was found that ostracods were sensitive.C.vidua and H.sp.had much higher mortality at the origin of the most polluted pit mouth and tailings pond than the other less polluted points.Water sample.The mortality rate decreases with the decrease of uranium and cadmium concentration.C.vidua is more sensitive to uranium and cadmium pollution than H.sp.,which is consistent with the results of previous indoor experiments.