The Research Of Basic Soil Characteristics Of Farmland In The Lower Reaches Of The Biliu River And Heavy Metal Pollution

The village in the lower reaches of the Biliu River has a long history of leeches farming.Antibiotics,hormones and other drugs,feeds,and excreta used in leeches may pollute the water and farmland downstream of the Biliu River.Based on this,this paper takes the farmland soil in the lower reaches of the Biliu River as the research object,and based on field surveys and experimental results of 25 soil samples,the basis for the determination of soil physical,chemical,and heavy metal contents in the soil of the Lower Yellow River is determined.On top of this,further evaluation was made on the status of heavy metal pollution in farmland soils,in order to investigate whether the limping cages discharged from the leeches of the study area are related to heavy metal pollution in the farmland soil downstream of the Biliu River.The main research conclusions are:（1）The ratio of clay in the 0-20cm layer of farmland in the lower reaches of the Biliuhe River is 0.60%-4.76%,with an average of 3.10%;the proportion of the powders is5.03%-40.49%,with an average of 21.92%;From 54.75%to 94.37%with an average of74.98%,the farmland soil in the study area was sandy loam soil.In September and October,the farmland soil temperature in the downstream of the Biliu River was 13.6-27.83°C with an average of 21.12°C.The coefficient of variation of the 25 sampling points of farmland soil physical properties all belong to moderate variation,indicating that there are obvious spatial differences in soil physical properties in the lower reaches of the Biliu River.（2）The pH value of the 0-20cm layer of farmland in the lower reaches of the Biliuhe River varied from 4.74 to 6.47 with an average of 5.74;the organic matter in the farmland soil was from 18.21 to 66.64 g/kg,with an average of 42.52 g/kg."Feng"grade;conductivity is33.57⁶09.33us,the average value is 190.4us;salt content varies between 16.73⁹96.00ppm,the average value is 126.08ppm.From the viewpoint of the abundance of oxides,the content of SiO2 in farmland soil is high,the content of CO₂ and Al₂O₃ is relatively high,and the contents of Fe₂O₃,K₂O,Na₂O,CaO,and MgO are also considerable.From the perspective of element abundance,K in farmland soil The content of Fe and Fe is very high,and the contents of C,N,Ca,and Mg are also high.The coefficient of variation of 25 farmland soil chemical properties at 25 sampling points is weak,moderate or strong,indicating that there are spatial differences in soil chemical properties in the lower reaches of the Biliu River.（3）The mean values of Cr,Cu,Zn,As,Ni,and Pb in the 0-20cm layers of farmland in the lower reaches of the Biliuhe River exceed the soil background values in Dalian,indicating that heavy metals accumulate in the farmland soil in the study area.The degree of accumulation is Ni>Zn>Cu>Cr>As>Pd.The contents of Cr,Cu,Zn,and As in the larvae removed from the leech breeding industry in the study area were respectively 20.51,3.95,32.70,and 6.74 times the background value of the soil in Dalian.This does not rule out the leech breeding industry for the Biliu River.The accumulation of heavy metals in the soil of the downstream farmland has a certain contribution.（4）The evaluation of single pollution index method showed that the pollution degree of farmland soil in the lower reaches of the Biliu River by six heavy metal elements from high to low was Cr>Ni>Zn>Cu>As>Pd,among which Cu and Zn were moderately polluted,Cr and Ni are heavy pollution;evaluation of the Nemero index method shows that the farmland soil in the study area is heavy metal heavy pollution;the gray cluster method evaluation shows that 6 out of the 25 soil samples in the study area are clean grade.Among them,19 were moderately polluted;the potential harm levels of six heavy metal elements on farmland soil downstream of the Biliu River were Ni>As>Cu>Pd>Zn>Cr.Based on the comprehensive analysis,the heavy metal pollution in the soil of farmland in the lower reaches of the Biliu River is relatively serious,but its potential ecological damage is lighter.