| With the improvement of agricultural intensive management,non-point source pollution had gradually become the key target of prevention and control of water environment pollution in our country,and its control and governance could not be delayed.The riparian zone was a place where human activities were intensive,and changes in its landscape type composition and spatial layout could affect the biogeochemical cycle process to varying degrees,thereby changing the production and output of non-point source pollutants,causing changes in water quality.Therefore,it was of great significance to explore the impact of changes in the riparian landscape characteristics of the river basin on water quality,to control the source pollution and to protect the water environment quality.As an important grain production base in China,the Dongting Lake Basin has been continuously deteriorating due to the same season of rain and heat,abundant precipitation and agricultural non-point source pollution.At the same time,the developed water system in the basin caused the complex and diverse characteristics of the riparian landscape pattern,and had an important impact on the migration,storage and transformation of pollutants.Therefore,we selected the typical source agricultural watershed of Dongting Lake—Jinjing River Basin in Changsha as the research object in this study.Based on the extraction of remote sensing image information and the long-term positioning monitoring data of river water quality in the basin,the landscape pattern change characteristics of the riparian zone and the temporal and spatial variation characteristics of nitrogen and phosphorus in the river basin were analyzed;And through redundancy analysis and variance decomposition analysis,the riparian zone range and the most important core landscape index which had a significant impact on nitrogen and phosphorus concentration were identified;To clarify the relationship between the landscape pattern characteristics of different levels of optimal riparian width and the concentration of nitrogen and phosphorus in rivers in different hydrological seasons;Finally,change point analysis was further used to quantify the threshold range of the core landscape index that caused the sudden change of phosphorus concentration in the river during the wet season and the flat and dry season,attempting to provide a scientific theoretical basis for the prevention and control of non-point source pollution in the river basin from the perspective of landscape planning.The main conclusions of this study were as follows:(1)Landscape pattern characteristics of the riparian zone in Jinjing River Basin:During the study period,the residential land and other areas in the river basin increased significantly,and there was a dynamic balance between woodland and farmland.With the increasing width of the riparian zones,there are significant spatiotemporal differences in landscape composition and spatial configuration.(2)Characteristics of nitrogen and phosphorus of river quality in the basin:During the research period,the N output form of rivers in the study area was mainly dissolved inorganic nitrogen,while the output form of P was mainly dissolved inorganic phosphorus.There are significant spatial and temporal differences in nitrogen and phosphorus pollution between different sub-basins.The concentration of N and P is significantly higher in the dry season than in the wet season,and the comprehensive pollution index of some sub-basins is high,and the pollution is more serious.(3)Influence of riparian landscape pattern in Jinjing River Basin on river nitrogen and phosphorus:300 m farmland patch dispersion index(SPLITfarmers)and 400 m residential maximum patch area index(LPIresidence)are the key width and the main core landscape index affecting the change of river nitrogen and phosphorus concentration during wet and dry season.Moreover,when SPLITfarmers are>15.76 and LPIresidence are<28.8%,the probability of river P pollution can be reduced. |
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