Objective To evaluate the toxicity of uranium tailings leaching liquid (UTLL) on zebrafish (Danio rerio) and provide scientific basis for assessment on uranium tailings hazard and potential environmental risk.
Methods Flame atomic absorption was used to measure the concentrations of heavy metals in UTLL. Uranium was determined by spectrophotometry using TRPO-cyclohexane/2-(5-bromo-2-pyridylazo)-5-diethyl-amino phenol. Other compositions of UTLL were analyzed according to the relevant international standards. Zabrafish were treated with 0.05%, 0.25%, 0.50%, and 1.00% UTLL for 7 d. Changes in the activities of superoxide dismutase (SOD), catalase (CAT), Na+-K+-ATPase and content of malondialdehyde (MDA) in the tissues of muscle, gill, liver of zebrafish samples were analyzed, respectively.
Results The concentration of uranium in the UTLL was 0.0628 mg/L, which was nearly four times of the limits prescribed in World Health Organization's provisional drinking water guideline. After exposure for 7 d, the activity of SOD was decreased significantly in the three sampled tissues at the designed concentrations (P<0.05); however, it increased at the low concentrations in the tissue samples of muscle and liver (P<0.05), indicating that the activity of SOD may exhibit both time-response and concentration-response relationships. The CAT activity was reduced in the gill samples after exposure in a dose-dependent manner (P<0.05), and the highest inhibition rate was 84.8%, which suggested early oxidative stress in the gill tissue. The activity of Na+-K+-ATPase was decreased along with the concentration of UTLL increased (P<0.05), while the MDA concentrations displayed an increasing tendency.
Conclusion The hazard of UTLL to organism may be mainly caused by the toxicity of uranium. Decreasing the level of oxidative stress injury may be one of the effective targets for preventing poisoning from UTLL.
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