Study On Distribution And Release Law Of Nitrogen And Phosphorus In Nanhe River Basin Of Qionglai City

Rivers are the necessary material basis for people’ s life.The quality of river water affects people’ s quality of life to some extent.Sediments are the main source of water pollution,in which nutrients,heavy metals and other pollutants are stored.Therefore,in order to find out the distribution law of nitrogen and phosphorus in the overlying water of the river and the law of nitrogen and phosphorus release from sediments,taking the Qionglai section of the Nanhe River Basin as the research object,the Nanhe River Basin in Qionglai City was analyzed through water quality evaluation methods,water quality model construction and indoor water sample experiments.The relationship between the water quality,nitrogen and phosphorus distribution,environmental factors and the release of nitrogen and phosphorus nutrients from sediments.The research results provide a basis for pollution control and ecological protection in the Nanhe River Basin in Qionglai City.The main findings of this study are as follows:(1)Aiming at the water quality problems of the Nanhe River Basin in Qionglai City,through the single-factor evaluation method,the comprehensive evaluation index method,and the comprehensive evaluation of fuzzy mathematics,it is concluded that the nitrogen and nutrients in the sewage plant’s sewage outlet are seriously exceeding the standard,the junction of the Xinkai River and the Nanhe River is seriously polluted by the phosphorus and nutrients,and the watershed is seriously polluted.The chemical oxygen demand of the samples was lightly or moderately polluted;the nitrogen and phosphorus pollution levels of other sampling points were lightly or heavily polluted.By comparing the results of each method,the singlefactor evaluation method is simple to calculate but the accuracy of the results is not high;the comprehensive evaluation index method comprehensively considers the influence of a single factor,and the accuracy is higher than that of the single-factor evaluation;the fuzzy mathematics comprehensive evaluation method considers the weight of the factors,the calculated results are consistent with the actual.(2)According to MIKE 21,the hydrodynamic-water quality model was constructed,and the time distribution law of chemical oxygen demand,total nitrogen,total phosphorus and ammonia nitrogen was analyzed and studied on the four entry sections of the Nanhe River Basin in Qionglai City.The change trend of the four indicators is roughly the same,and the lowest is in September,and the water quality of the mulberry orchard interface is better than the other three.At the same time,the temporal and spatial distribution of nitrogen and phosphorus nutrients in the Nanhe River Basin of Qionglai City was analyzed.And the nutrient salt concentration is high in the easily blocked places,which will greatly affect the safety of downstream water intake when upstream sewage and sewage outfall sewage converge.(3)Using indoor nitrogen and phosphorus release simulation experiments,the three environmental factors of temperature,p H and dissolved oxygen were used to study the release law of nitrogen and phosphorus in sediments.The results showed that the nitrogen and phosphorus release intensity of sediments was positively correlated with temperature and negatively correlated with dissolved oxygen,p H can promote the release of nitrogen and phosphorus in acidic and alkaline environments;and through the curve fitting of environmental factors and nitrogen and phosphorus release intensity through SPSS,the optimal simulation of the release intensity of different nitrogen and phosphorus nutrients and environmental factors is obtained.The composite curve is a quadratic or cubic relationship;finally,MATLAB is used to analyze the relationship between the interaction of environmental factors and the release of nitrogen and phosphorus from sediments,and it is concluded that the interaction of dissolved oxygen and temperature,dissolved oxygen and p H has reached a significant level on total nitrogen release;temperature and p H The effective combination of the two has a significant effect on the release of total phosphorus;the interaction of dissolved oxygen and temperature,temperature and p H has a significant effect on the release of ammonia nitrogen,and the interaction of temperature,p H and dissolved oxygen has a significant effect on the release of nitrogen and phosphorus from sediments at different levels.