工业尾水排放对鸳溪河鱼类养殖影响的对比研究OA

Taking the discharge outlet of treated tailwater from the Second Sewage Treatment Plant of Gaojie Park in Yibin High-tech Zone as the research site,this study selected the upstream(unaffected by tailwater),midstream(tailwater mixing area)and downstream(fully mixed tailwater area)of the Yuanxi River as water sources to carry out a comparative polyculture experiment of fish.The experimental fish species included common carp,grass carp,koi,yellow catfish,and topmouth culter,with a culture period of 90 days.Water quality indicators(temperature,dissolved oxygen,pH,ammonia nitrogen,nitrite nitrogen,salinity,and total dissolved solids),fish growth per-formance,muscle nutritional composition,muscle quality,heavy metal content,antioxidant enzyme activity,diges-tive enzyme activity,blood biochemical indexes,and tissue structure were monitored.The results showed that the water temperature in the midstream and downstream was higher and rose in parallel with several other water-quality parameters(TDS,ammonia nitrogen),and was temporally associated with improved growth performance;however,the independent contribution of temperature could not be isolated from these co-varying factors in the present design;all monitored water quality indicators met the requirements for fish culture.The final body weight of common carp in the midstream and downstream groups was significantly higher than that in the upstream group(P<0.05),while no significant differences were observed in most other growth indexes.Muscle cadmium content increased significantly downstream(P<0.05),and the bioconcentration factor(BCF)remained closely similar between the upstream and downstream groups(80.0 vs.77.8);this constancy indicates that muscle cadmium tracked the ambient water concen-tration in a linear,dose-dependent manner rather than reaching a safe plateau,and should be interpreted as a signal warranting continued monitoring rather than as evidence of safety.Muscle nutrition and flesh quality were within standard limits,and no statistically significant differences were found in enzyme activities or tissue structure,although the limited histological sample size(n=12 per group)constrained the statistical power to detect subtle effects.The findings indicate that,within the 90-day observation period and at the tailwater concentrations studied,no acute tox-icity or overt growth inhibition was observed;however,given the linear cadmium accumulation pattern,the confound-ed temperature effect,and the limited power of the histological comparisons,the current evidence supports only a conclusion of"no detectable short-term adverse effect under the conditions tested,"and is insufficient to support broader claims regarding the long-term feasibility of using this tailwater as a supplementary water source.Continued,longer-term ecological monitoring is recommended to evaluate cumulative and multi-generational risks.