Analysis And Variation Characteristics Of Pollution Sources In Wangbeng Interval Of Huaihe River Basin

In this study,Wangbeng interval in Huaihe River Basin was taken as the research unit,and the water and soil in the unit were taken as the main research objects.Through the comprehensive use of various research methods such as water chemical analysis,carbon,nitrogen and oxygen stable isotope technology and multi-model calculation,the current situation and spatial-temporal distribution law of the main water pollution in the basin were analyzed.The qualitative and quantitative analysis of nitrate pollution in the water body of the study area was carried out by using the characteristic values ofδ¹⁵N andδ¹⁸O double stable isotope combined with the stable isotope mixing model SIAR and Iso Source model,and the source and current situation of nitrate pollution in Wangbeng interval in Huaihe River Basin were explored.Identify the key pollution sources and the contribution rate of pollution sources;on the other hand,according to the land use types and soil depth,the distribution and migration characteristics of soil organic carbon in the basin were analyzed,and isotope technology was applied to the soil.The source of sediment organic carbon in the study area was analyzed and the contribution rate of pollution sources was calculated.The following conclusions are drawn from the above research:（1）The nitrate content of water in the study area is generally higher than that of ammonia nitrogen,and most water bodies are greatly affected by domestic sewage and agricultural wastewater,which reflects that the impact of human activities on surface water cannot be ignored;（2）Combined with the general situation of the study area,the pollution sources are divided into five categories:manure wastewater（MS）,soil source（SN）,atmospheric deposition（AP）,agricultural fertilizer source（FS）and litter source（DF）.NO₃^--N source was qualitatively identified by NO₃^--N nitrogen and oxygen isotopes.It is preliminarily concluded that the main sources of NO₃^-in the middle section of Wang Bengbu section and the north and south coast of Huaihe River Basin are soil,agricultural fertilizer,litter and manure sewage,and atmospheric deposition and litter are secondary sources of nitrate pollution in water.The isotope mixing model（SIAR）was used to quantitatively analyze the source of nitrate.The results showed that the NO₃^-in the water bodies of Huaihe River,Nihe River,Chengdong Lake and Pihe River mainly came from atmospheric deposition（AP）and soil source（SN）,and the contribution rates were 16.49%～37.83%and 48.35%～73.15%,respectively.NO₃^-in Yaogou water body,Anfengtang water body and intercepting channel water body mainly comes from manure sewage（MS）,litter（DF）and agricultural chemical fertilizer（FS）,with contribution rates of 18.60%–35.13%,24.13%–25.43%and 31.07%–52.92%,respectively.The difference of NO₃^-source contribution ratio in Yinghe waterway is small;（3）The IsoSource model was used to calculate the contribution rate of pollution sources to the water body in the study area.The NO₃^-in the water body of Huaihe River,Nihe River and Chengdong Lake was mainly derived from atmospheric deposition（AP）and soil source（SN）,with the contribution rates of 27.4%–49.3%and 28.8%–59.3%,respectively.The NO₃^-in the water body of Pihe River was mainly derived from soil source and manure sewage source,with the contribution rates of 70.3%and 11.0%,respectively,NO₃^-in Yaogou water body,Anfengtang water body and intercepting channel water body mainly comes from manure and fertilizer wastewater（MS）,litter（DF）and agricultural chemical fertilizer（FS）,and the contribution rates are 27.4%–49.3%and 28.8%–59.3%,respectively.There is little difference in the contribution rate of NO₃^-source in Yinghe waterway water body,which is consistent with the calculation results of SIAR model.The correlation analysis showed that there was a certain nitrification in the water bodies of Huaihe River,Pihe River and the main ditch-kiln ditch in the study area.Principal component analysis showed that the content of nitrate in Huaihe River,Nihe River and Yaogou water was high,the content of ammonia nitrogen in Huaihe River and Nihe River water was high,and the nitrogen pollution in Huaihe River and Nihe River was serious.（4）The soil of different types and depths in the study area were analyzed.The results showed that the soil was mostly neutral acidic soil.The contents of soil organic carbon（SOC）and total nitrogen（TN）were 9.39～54.27 g/kg and 3.40～34.60 mg/L,respectively.The soil organic matter had a high degree of humification.Among the three sampling points in the stratified sampling,the SOC content at point G1 did not show a significant upward or downward trend with the increase of soil depth.With the increase of soil depth,the SOC content at point G2 first decreased significantly,and then increased rapidly,and then decreased rapidly and gradually stabilized with the increase of soil depth.The SOC content at point G3 increased to a certain extent in the soil depth of 0–10 cm,and then decreased significantly from about 10 cm;（5）The distribution of carbon isotope under different land use types and depths was analyzed and calculated based on stable carbon isotope technology and SIAR mixed model.The results showed that the average value of carbon isotope was forest soil（-26.10‰）>grassland soil（-26.72‰）>farmland soil（-27.21‰）>floodplain soil（27.37‰）;the variation characteristics of soil carbon isotope in different soil depths are that the soil carbon isotope value has a significant increase trend with the increase of soil depth.The carbon isotope ranges from-28.82‰to-22.84‰,with an average of-27.08‰;the contribution rates of different land use types to sediment organic carbon were ranked as follows:farmland soil>floodplain soil>woodland soil>grassland soil.The contribution of soil to sediment organic carbon decreased with the increase of soil depth.Figure[53]table[15]reference[104]...