Study On Spatial Variation Of Soil Nutrients And Heavy Metals In Middle Of Yaodu District Based On GWR Model

Taking Yaodu area of Linfen central region as the study area,using classical statistics to the combination of statistical and GIS method,in the full investigation field information widely collected data on the basis of understanding,focusing on Yaodu central area and heavy metal spatial variation of soil nutrients and influencing factor two aspects were studied based on SPSS,ArcGIS software platforms.The main conclusions are as follows:(1)The contents of soil nutrients and heavy metals were different in different functional areas.Difference in soil nutrient content:The soil nutrient content in the industrial area was generally low,but AK content was the highest;The soil nutrient content in the park was in the middle level,and the AK content was the lowest;The contents of soil nutrients were relatively high in the cultural and educational areas,with SOM and TN contents being the highest;Soil nutrient content in suburban farmland was in the middle level,but AP content was the highest.Difference of heavy metal content in soil:The contents of Pb,Cr,Mn and Cu were the highest and the contents of Cd were the lowest;The content of Pb and Cr was the lowest,and the content of Zn and Ni was the highest;The heavy metal content in the park is generally low,and the contents of Zn,Mn,Ni and Cu are all lower than those in cultural and educational areas and industrial areas,only Cd content is higher.According to the second national soil nutrient classification standard,SOM,TN,AP,AK,HN,Avail-Zn,Avail-Mn,Avail-Cu contents in suburban farmland are level four,level three,level two,level one,level four,level four,level three,level four,the contents of soil AP,HN,AK and Avail-Cu are high.(2)There was a certain correlation between soil nutrients and heavy metals.In the cultural and educational areas,soil pH has a highly significant negative correlation with TN,SOM,Zn,Mn and Cu,and a significant negative correlation with soil AP.Soil SOM content has a positive correlation with AP,Zn and AK;In the park leisure area,SOM content of soil ispositively correlated with AK and Cd;In the suburban farmland soil SOM were very significant positive correlation with HN,AP,soil TN content and SOM,HN,AP were very significant positive correlation,both HN were very significant positive correlation with AP,AP and AK,the Avail-zinc,were very significant positive correlation,the Avail-Cu AK and the Avail-Mn were very significant positive correlation,the Avail-Cu,the Avail-zinc and the Avail-Mn were very significant positive correlation,the Avail-Cu,the Avail-Mn were very significant positive correlation with the Avail-Cu.In addition,the soil Pb,Zn,Cu and Cd in the three functional areas are positively correlated.(3)Elevation,slope,slope direction,NDVI,dist-road and dist-river have significant effects on soil nutrient content.SOM average content increased with the increase of altitude,while TN average content first decreased with the increase of altitude,and then increased slightly to about 650 m.TN and SOM contents in soil have an obvious linear relationship with the slope,which decreases with the increase of the slope.However,AK can be directly absorbed by plants in the soil because it is greatly affected by crops,parent material of soil and other factors,so it is not affected by the slope.In the relationship with slope direction,soil TN presents an obvious linear relationship,that is,the more sunny the land,the higher the TN content.(4)The spatial variation of soil nutrients and soil pH were significant.The TN,SOM,AP and AK of soil in the study area are normally distributed after Log,box-cox,box-cox and Log transformation respectively.The general Kriging method was used to set different parameters for the function fitting of soil nutrients.Finally,the optimal model of pH was determined to be the exponential model,while the optimal models of TN,SOM,AP and AK were all Gaussian models.The pH value of the soil is generally alkaline,ranging from 7.2to 8.3,with a small span.The pH value around the urban area of Yaodu district is relatively high(higher than 7.9).The pH value in the west of Duandian township and the northeast of Yaomiao town is also relatively high.SOM content of soil is higher on both sides of Fen river,and generally presents the law of decreasing from west to east and lowest industrial area.The distribution law of soil TN content is similar to the distribution law of SOM content,which is also higher in the west and lower in the east,and the high value area appears in the culturaland educational area.Soil pH,SOM,TN and AK contents in the study area generally show a law of middle high,surrounding low,especially in the southeast and southwest regions where soil nutrient contents are relatively low.The variation coefficient of soil pH and nutrient is AP>TN>SOM>AK>.Except pH,other soil nutrients all reach a strong variation level.(5)GWR model analysis of soil pH and nutrient contents.In the GWR model analysis,the bandwidth selection was compared with the AIC method and the CV method respectively.It was found that the model fitting degree obtained by the AIC method was higher than that by the CV method,and the residual error was small.The adjusted AIC method was more suitable for the observation data.The effect of NDVI on soil pH was negatively correlated on the whole and gradually weakened from west to east in a belt;The influence on SOM is positively correlated,which has a great influence in the eastern part of Wei town,a small part of the eastern part of Tumen town and the urban area of Yaodu district;The impact on TN is positive correlation between cultural and educational areas and industrial areas,but negative correlation between most areas of Jiade township and the eastern part of Wu town;There was a positive correlation between AP and AK,especially in Wei village.The effect of dist-road on soil pH was negatively correlated and gradually increased from southwest to northeast in a belt;The influence on SOM is positively correlated with the eastern part of Tumen town.The influence on AP was positively correlated in the southeast of the study area and the east of Tumen town,while negatively correlated in the park green land and wendiocese.The overall effect on soil AK was positively correlated.The effect of dist-river on soil pH was positively correlated and gradually increased from northwest to southeast in a zonal manner.The effect on SOM and TN was positively correlated on the whole,but the correlation was weak near Yaomiao town and in the southeast of the study area.The effect on soil AK is obviously positive correlation in the vicinity of main river course of Fen river and Duandian township,but negative correlation in the east and west sides.