Temporal And Spatial Distribution Of Nitrogen And Phosphorus And Pollution Loads From Internal And External Sources In Lugu Lake

Lugu Lake is one of the lakes with the best water quality in my country and plays an important role in the regional ecological environment and economic development.Due to the imbalance of local environmental management and the damage of sewage collection pipe network,the total amount of pollutants entering the lake has increased.In this study,the pollutants entering the lake were taken as the research object,and the temporal and spatial changes of total nitrogen and total phosphorus in Lugu Lake were studied.Through the indoor release experiment of total nitrogen and total phosphorus concentration,the law of nitrogen and phosphorus release in sediment and plant decay and decomposition process was explored,and endogenous nitrogen and phosphorus loads were estimated.Combined with exogenous pollution in the watershed,an improved output coefficient model was established,and the model was used to estimate exogenous nitrogen.Phosphorus load.The result is as follows:The evaluation of the water quality of Lugu Lake shows that there are obvious temporal and spatial differences between the two periods of high and dry periods of Lugu Lake.The results of sediment monitoring show that the time distribution of total phosphorus,total nitrogen and total organic matter content is opposite to that of water quality.The indoor static experiments of endogenous sediments show that the release laws of total nitrogen and total phosphorus are similar,both have a trend of rising first and then falling under the condition of constant water exchange.After the water exchange rate is accelerated,the monitoring concentrations of total nitrogen and total phosphorus are Although there was a decrease,the release rate was significantly increased.At the end of the experiment,the total nitrogen release calculated was 527.89 mg,and the total phosphorus was 82.45 mg.The estimated total nitrogen and total phosphorus releases from the grass bottom mud were 667.9 t/a and 41.8 t/a,respectively.The release experiment of emergent plants in water immersion and decay showed that the nitrogen and phosphorus release laws of the four emergent plants were different,but the general trends were similar.The total nitrogen release flux was 612.32 mg and the total phosphorus was 159.08 mg.Total nitrogen 0.8174 t/a,total phosphorus 0.2015 t/a.Regarding the estimation of exogenous nitrogen and phosphorus load,this study introduces the topographic influence factor,rainfall erosivity factor and lake entry coefficient to improve the classic output coefficient model,which is verified with the measured lake value.The error of the result is within the credible range,indicating the improvement.The method is feasible to a certain extent,and the final results show that the exogenous total nitrogen load into the lake is 354.34 t/a,and the total phosphorus load is30.84 t/a.