Spatial Distribution Characteristics Of Surface Water Quality In The Ogan-kucha River Oasis And Its Relationship With Landscape Pattern

In recent years,the study of landscape pattern in arid areas has become increasingly mature.With the deepening and systematization of the research,the relationship between landscape pattern and water chemical characteristics has been paid much attention by researchers.The parameters of water chemical characteristics will also have a certain impact on the landscape pattern.Therefore,studying and revealing the relationship and mutual influence between landscape patterns and hydrochemical characteristics in arid regions is conducive to the harmonious development of social economy and ecological environment in arid regions.First of all,this paper selects two water sample data in 2016 and 2017,preprocesses them and evaluates the water quality of the research area.Secondly,the remote sensing data of 2017 gaofen-1（gf-1）were selected and classified into five types including forest-grassland,water area,cultivated land,construction land and unused land.With the actual water sampling point as the center,buffer areas of 100m,200m,300m,400m,500m and 1000m are made.The landscape pattern characteristics of weiku oasis in different buffer areas were analyzed from two levels of landscape and type.Finally,the relationship between landscape pattern and water quality index in weiku oasis was further analyzed by means of RDA.Our study mainly draws the following conclusions:1.Landscape pattern analysis（1）From the perspective of land use landscape structure and spatial distribution,cultivated land and unused land are the main types of land use landscape in Wei-Ku oasis,of which cultivated land is mainly distributed in the central area of Wei-Ku oasis,and unused land is mainly distributed in Around the Wei-Ku Oasis.Construction land is scattered within the oasis;（2）From the results of landscape level analysis,it can be seen that the complexity,fragmentation,spatial heterogeneity,and land use abundance of the landscape in the 100m buffer zone are the lowest,and the complexity and fragmentation of the landscape vary with the buffer.The area radius increases.When the buffer radius increases to 1000m,it reaches the highest.The balance of human activity in the six buffer zones.The dominant patch type in the landscape has good connectivity within200m.2.Water quality evaluation of Weiku Oasis（1）The p H changes in irrigation water,alkali drainage channel and groundwater are not large,and the changes in conductivity and salinity are relatively large.Among cations,Na⁺have the most obvious changes,and among anions,Cl^-ions have the most obvious changes.The average water quality of the alkali drainage channel is higher than that of irrigation water and groundwater.The overall p H is weakly alkaline;the conductivity and salinity of the alkali drainage channel are the highest;the average value of the eight major ions is the highest in the alkali drainage channel and the smallest in the groundwater.Compared with 2016,the water quality of the study area in2017 was relatively unstable relative to the internal structure.The overall cation content is Na⁺>Mg²⁺>Ca²⁺>K⁺,and the overall anion content is SO₄^2->Cl^->HCO₃^-.（2）According to the comprehensive pollution assessment results of heavy metals,the pollution levels of Cu,Zn,Hg,As,COD,and TP in the Weigan River,Kuqa River,Tarim River,Kizil River,and reservoirs are all within the clean range,and the pollution level All are within the clean range.The pollution levels of Cr in the Tarim River,Kyzyl River and the reservoir are all within the clean range,and the pollution level in the Weigan River and Kuqa River exceeds the warning level on average.The pollution level of Pb in Weigan River is within the standard limit.The pollution levels of p H in the Weigan River,Kuche River,Kyzyl River,and reservoirs are all within the clean range,and the pollution level in the Tarim River exceeds the warning level.（3）The carcinogenic risk order of each sampling area is:Kuche River>Tarim River>Weigan River>Reservoir>Kizil River.Cr and As should be the priority pollutants in the study area.（4）The distribution of water quality and salinity in the study area exhibits a bipolar concentration and has a strong spatial autocorrelation.The high-value accumulation areas of water quality are gradually concentrated with the increase of the buffer distance,and the low-value areas are spatially continuous,and the spatial distribution pattern remains basically stable.There were no high and low concentration areas and low and high concentration areas in the study area.3.Relationship between landscape pattern and water quality characteristics（1）Relationship between land use landscape type and water quality:Within the100m buffer range,the correlation between the landscape index and water quality index of cultivated land and construction land is relatively high.The correlation between construction land and water area reached the highest within the buffer area of??300m;within the buffer area of 400m,500m and 1000m,the correlation between forest and grassland and water quality indicators was high,and it gradually increased with the increase of the buffer distance,and was within 1000m The amount of interpretation of the buffer range features reached the highest.In terms of landscape types,the impacts of cultivated land and unused land in the 100-1000m buffer range on water quality showed a trend of decreasing first and then increasing.The amount of forest grassland interpretation in different buffer zones is above 80%,of which the1000m buffer range reaches the highest.The impact of construction land landscape on water quality shows a tendency to decrease with increasing distance;（2）The relationship between type level and water quality:from different buffer ranges,within 100m and 200m buffer range,PLAND index plays a key role in water quality change;in 300 range,PD index has the most obvious effect on water quality change;400m buffer range Inside,the interpretation of the ED and AI indexes is greater than other indexes;when the buffer radius is greater than 400m,the interpretation of each landscape index shows a clear downward trend,indicating that the impact of the landscape index on the water quality index is more intense in the buffer range of100-400m.From the perspective of different land use landscapes,within 100m range,the PLAND index in cultivated land has the strongest correlation with NH₃-N,ED index and Zn;within the 200m and 300m buffer range,the water area landscape and water quality indicators show negative Correlation,the landscape index of construction land has a strong positive correlation with NH₃-N and TN.These two phenomena are more significant when the buffer distance increases to 300m;the correlation between the cultivated land landscape index and HCO₃^-is opposite at 200m and 300m,Indicating that there is a scale effect of HCO₃-concentration;within the 400m buffer range,the forest grassland landscape index has a high correlation with the water quality index,of which the forest grassland AI index has the highest correlation with Zn,ED and S0₄^2-,PLAND and HCO₃^-;Within the buffer range,there is a strong correlation between the AI and PD indexes of forest and grassland and Zn,no correlation with HCO₃^-,and a better negative correlation with TN;the correlation between PLAND and HCO₃^-gradually increases;to 1000m buffer Range,the forest grassland has the highest correlation with water quality,of which the PLAND index has the strongest positive correlation with Zn,but has a negative correlation with NH₃-N and TN;（3）Within the 100m buffer range,IJI has a strong positive correlation with Zn,but has a significant negative correlation with TN;within the 200m buffer range,ED has a positive correlation with NH₃-N,SHDI and HCO₃-,and the correlation Significantly higher than other indexes;LPI and Zn,COHESIONI and NH3-N have a significant negative correlation;within the 300m buffer range,ED and HCO₃-,PD and S0₄^2-,SHDI and NH₃-N have the highest positive correlation;PD The negative correlation with TN is strong;when the buffer radius is increased to 400m,SHDI has the strongest positive correlation with HCO₃^-,S0₄^2-,LPI and TN,and LSI,PD,ED have a negative correlation with TN,and these indexes are related to Zn,NH₃-N and COHESION are not significantly correlated with Zn;in the 500m buffer range,SHDI and HCO₃^-,S0₄^2-,LPI and TN,CONTAG and NH₃-N are positively correlated,and the correlation is strongest;ED,LSI,PD and TN is obviously negatively correlated and has no correlation with Zn and NH₃-N;1000m buffer range,the relationship between landscape index and water quality is LJI and Zn,and COHESION and NH₃-N are highly correlated;except LPI and COHESION,other indexes are all There is a negative correlation with TN and NH₃-N;...