Simulation of ecotoxicological effects of perchlorate and hexavalent chromium combined pollution in the aquatic ecosystem

Objective To investigate the ecotoxicological effects of ClO₄⁻ and Cr⁶⁺on the aquatic ecosystem under combined pollution conditions.

Method The aquatic ecosystem was constructed, Eichhornia crassipes, Daphnia carinata and Pomacea canaliculata with the same growth conditions were added, respectively, and exposed to water with different concentrations of ClO₄⁻ and Cr⁶⁺ and their combined pollution. The ecotoxicological effects of ClO₄⁻ and Cr⁶⁺ on E. crassipes, D. carinata and P. canaliculata under single and compound conditions were studied.

Result With the increase of exposure time, the population of D. carinata increased first and then decreased. The 0.02 mg·L⁻¹ Cr⁶⁺ promoted the growth of D. carinata, while 200 mg·L⁻¹ ClO₄⁻, 0.20 mg·L⁻¹ Cr⁶⁺ and their combined pollution inhibited the growth of D. carinata. The 0.02 mg·L⁻¹ Cr⁶⁺ had little effect on the growth of P. canaliculata; Howerver, single ClO₄⁻ (20 and 200 mg·L⁻¹) and 0.20 mg·L⁻¹ Cr⁶⁺ as well as their combined pollution treatment groups had significant inhibitory effects. The contents of ClO₄⁻ and Cr⁶⁺ in each organ of E. crassipes increased with the increase of pollutant concentration in water. Under the same concentration of pollutant, the order of ClO₄⁻ content in all organs was leaf > stem > root, the order of Cr⁶⁺ content was root > stem > leaf. The contents of ClO₄⁻ in D. carinata and P. canaliculata were lower than that in E. crassipes.

Conclusion Both single and combined pollution of ClO₄⁻ and Cr⁶⁺ cause toxic effects on organisms in aquatic ecosystems. E. crassipes has strong absorption ability to ClO₄⁻ and Cr⁶⁺, with ClO₄⁻ mainly concentrated in leaf, and Cr⁶⁺ in root. The absorbing abilities of D. carinata and P. canaliculata to ClO₄⁻ were weaker than that of E. crassipes.