基于RSM及SEM的水体自净多因素交互作用评估OA

[Objective]This study investigates the synergistic and antagonistic effects of multiple factors on water self-purification capacity and examines self-purification efficiency of water under the combined influence of multiple factors,aiming to overcome the limitations of previous studies and provide new quantitative evidence for understand-ing water self-purification capacity in complex aquatic environments.[Methods]To investigate the interactions a-mong multiple factors affecting water self-purification capacity,orthogonal experiments were conducted on water samples collected from the northwest side of a lake in Wuhan,which was affected by mixed pollution from domestic sewage and industrial wastewater and contained a microbial community.The orthogonal experiment results were ana-lyzed using a combination of response surface methodology(RSM)and structural equation modeling(SEM)to re-veal the nonlinear interaction mechanisms among typical influencing factors,including meteorological conditions,pollutant concentration background values,and biological activity.[Results]The results of orthogonal experiments showed that water self-purification efficiency(η),nitrification rate(rN),and oxygen mass transfer efficiency(KLa)of water all varied nonlinearly across experimental groups,with maximum values observed at approximately temperature(T)=25℃,dissolved oxygen concentration(DO)=6 mg/L,flow rate(v)=0.1 m/s,microbial a-bundance(M)=5×107 CFU/mL,and chemical oxygen demand(C)=100 mg/L.RSM analysis indicated that at the optimal parameter combination(T=24.8 ℃,DO=5.9 mg/L,v=0.27 m/s,C＜100 mg/L,and M=4.7×107 CFU/mL),η significantly increased to 83.24％,rN exceeded 1 mg/(L·h),and KLa reached its maximum.In ad-dition,in the binary factor interactions,the most significant interaction term was T× DO,with a synergistic contri-bution of 45.52％.SEM path analysis showed that v and T influenced the water self-purification process through both direct effect and indirect effect.Paths:v→DO→η;v→DO→Mi(microbial activity,including rN and M)→η;T→DO→η;T→Mi→η;T→DO→Mi→η,where the direct effect of v on water self-purification process was 0.41,and the indirect effect was 0.25;and the direct effect of T on water self-purification process was 0.35,and the indirect effect was 0.25.The total effect of T and v on water self-purification process increased by 0.25 compared with the direct effect of each factor alone.[Conclusion]The results confirm that there is a synergistic amplification mecha-nism and significant threshold effects among different environmental influencing factors.Binary factor interactions not only show significant effects,but also factors originally negatively correlated with water self-purification capacity can significantly reduce their inhibitory influence on water self-purification efficiency after complex interactions with other factors.Additionally,factors such as flow rate and temperature affect the water self-purification process both directly and indirectly through their effects on other influencing factors.These findings provide a new quantitative basis for evaluating water self-purification ability and its controlling factors in complex aquatic environments.