ASSESSMENT OF THE COMBINED TOXICITY OF ALUMINUM SALTS ON MULTI-TROPHIC AQUATIC ORGANISMS IN THE CHISHUI RIVER

The discharge of tailwater from distilleries in the Renhuai section of the Chishui River has led to the detection of characteristic ions in the water body, including Al³⁺ (0.028—0.215 mg/L), \rmSO^2-_4 (75.7—177 mg/L), Na⁺ (7.33—85.8 mg/L), and Cl^- (7.75—65.0 mg/L). To clarify the ecological risk level, this study established an exposure system based on the detected environmental concentrations, using aluminum sulfate (Al₂(SO₄)₃), aluminum chloride (AlCl₃), and sodium sulfate (Na₂SO₄). The toxicity effects on aquatic organisms across different trophic levels were systematically assessed using Chlorella vulgaris, Daphnia magna, Gobiocypris rarus, and Myxocyprinus asiaticus as test species. Acute toxicity tests showed that the 72h-EC₅₀ of single aluminum salts for C. vulgaris (13.89—45.55 mg/L), the 48h-LC₅₀ for D. magna (27.36—33.25 mg/L), and the 96h-LC₅₀ for G. rarus (20.52—33.25 mg/L) were all significantly higher than the environmental concentrations of Al³⁺, indicating no acute lethal risk at current levels. However, chronic exposure to sublethal concentrations of aluminum salts (13.69—34.22 mg/L) significantly delayed reproduction in D. magna, inhibited fish growth, and interfered with their phototactic behavior. Concurrently, significant alterations in Na⁺/K⁺-ATPase activity and oxidative stress responses were observed, demonstrating that subchronic physiological disturbances constitute the core risk.