Study On The Influence Of Soil Water Loss Under Different Land Uses On Nitrogen Output In Chishui River Basin

As the first tributary of the upper reaches of the Yangtze River,the Chishui River has no dam-building primary tributaries.Its main stream,most of its tributaries still maintain natural communication with the Yangtze River.The special geographical environment provides a good living space for many rare animals,plants.Environmental protection is of great significance.In view of the current situation of non-point source nitrogen pollution in the Chishui River Basin,this study uses the Chishui River Basin as the research area,lays up nitrogen sampling points.Based on the land use types of the Chishui River Basin sub-basin,combined with the sampling data of the sub-basin,the mainstream section of the Chishui River Basin.Analyze the characteristics of nitrogen output,study the impact of land use types on nitrogen output,in order to provide a theoretical basis for the control,management measures of non-point source pollution in the Chishui River Basin.The main findings are as follows:?1?Analysis of the land use structure of the Chishui River sub-basin,the results show that the Chishui River sub-basin is dominated by the“sink”use type,the proportion of forest area is 67.6%,of which the proportion of forest area is larger in the downstream area,reaching 89.2.%.The“source”use type is mainly cultivated shrub grass.The sum of the area ratio of cultivated shrub is 14.95%,the“source”use type is mainly concentrated in the middle upper reaches,with an area ratio of 19.95%.?2?Sampling the Chishui River Basin in January 2017 August 2017 to analyze the nitrogen concentration.The results show that the nitrogen output of the Chishui River Basin is mainly NO₃^--N,the NO₃^--N/TN is above 67%.In terms of output characteristics,in the space,the main stream the tributary show the same trend,the trend of the main stream is more obvious.The upper part of the Chishui River Basin has the highest TN NO₃^--N,the difference of NH₄⁺-N distribution is relatively small.In time,all the sampling points of the main stream during the wet season TN NO₃^--N are higher than the dry season.The tributary is upstream,the output concentration of TN NO₃^--N in the wet season is higher than that in the dry season;in the middle reaches,the output concentration of TN NO₃^--N in the wet season is lower than the dry season;in the downstream,the TN NO₃^--N in the wet season The N output concentration is slightly lower than the dry season.Most of the NH₄⁺-N in the dry stream dry season is higher than the wet season.Most of the NH₄⁺-N in the tributary period is higher than the dry season.?3?Correlation analysis between use nitrogen output concentration,the results show that the tributary use structure is the main factor affecting the spatial difference of TN NO₃^--N output concentration,the forest plays a significant role of“sink”.Significant"source"effect.At different time scales,the use structure has different effects on the output concentrations of TN NO₃^--N.The impact of cultivated construction on the output of TN NO₃^--N during the wet season is significant in the dry season.?4?Comprehensive analysis of use nitrogen output coefficient.The results show that the TN output coefficient of cultivated is 10.54mg/L,the TN output coefficient of shrub grass is 6.03mg/L,the total nitrogen output coefficient of forest is 1.54mg/L.The study on the pollution load of the Chishui River Basin shows that when the difference between the proportion of the area of the“sink”in the Chishui River Basin,the area ratio of the“source”use type is within 15%,the difference between them is 1%,the non-point source pollution is reduced by 2.00 mg/L.