| In order to study the mutation characteristics, trend and influence factors of CODMn, the Mann-Kendall test was used to study the trend and mutation characteristics of CODMn, and the relationship between main hydrological factors, economic and social indicators and CODMn was analyzed by SPSS software. The results showed that CODMn at Haikou section of Fuxian Lake showed a significant increasing trend, with an average annual increase of 0.027 mg/L from 1992 to 2021, and the concentration was close to 2.0 mg/L in recent years. CODMn mutated three times during the study period, with insignificant mutation in 1994 and 1996, and extremely significant mutation in 2021. The water level of Fuxian Lake experienced a changing process of rising, leveling off, falling, rising and falling. The average annual evaporation was about 1.4 times of average annual precipitation, and the water level showed a decreasing trend when the evaporation-precipitation ratio was high. Population density, evaporation and water level can explain 65.0% of the variation of CODMn at Haikou section of Fuxian Lake. Population density and evaporation are positively correlated with CODMn, while water level is negatively correlated with CODMn. Population density, evaporation and water level are the main influence factors.The greatest one is population density. |
