| The land that carries the social activities of human beings is the foundation of the development of human society and is closely related to our lives.With the rapid economic and social development,land has become an increasingly important resource,so the legal protection and proper use of land resources have become more and more important.Land quality is a comprehensive attribute of land,which reflects the influence of natural factors and human activities on the land.Through the geochemical evaluation of the land quality,the content level and spatial distribution of the beneficial and harmful elements in the soil,as well as the comprehensive level of the land quality can be obtained.Understanding the details of the land quality in the study area is of great significance to land use planning,environmental protection and sustainable development.In this paper,310 soil samples,19 irrigation water samples,and 10 rock samples were collected from a typical blood orange base in Chongqing.Analyze soil p H(p H value)and soil organic matter content level;Analysis of nitrogen(N),phosphorus(P),potassium(K),calcium(Ca),magnesium(Mg),sulfur(S),silicon(Si),copper(Cu),zinc(Zn),iron(Fe)The abundance and deficiency of soil nutrients such as manganese(Mn),boron(B),molybdenum(Mo),and chlorine(Cl);Analyze the pollution of heavy metal elements such as copper,zinc,cadmium(Cd),mercury(Hg),arsenic(As),lead(Pb),chromium(Cr),nickel(Ni)and other soil pollution;And analyze the enrichment characteristics of soil elements in rock-soil.Use the land use status map of the third national land survey as the evaluation unit map to carry out geochemical evaluation and analysis of land quality.Thus,the area ratio and spatial distribution of the environmental geochemical grade of irrigation water,the comprehensive grade of soil nutrient geochemistry,the comprehensive grade of soil environmental geochemistry,and the comprehensive grade of soil quality geochemistry are obtained.The evaluation results provide a scientific basis and decision-making reference for agricultural structural adjustment,regional planning,and comprehensive development.The main findings are as follows:(1)The results of the geochemical evaluation of the irrigation water environment show that the p H,copper,zinc,cadmium,lead,chromium,selenium,total mercury,total arsenic,chloride,and fluoride content of the irrigation water are all lower than the standard limit values.The comprehensive geochemical grade of the irrigation water environment is first,indicating that the irrigation water in the study area is not polluted and the irrigation water environment meets the quality standards and can meet the daily irrigation needs.(2)The study area is dominated by acid soil(5.0≤p H<6.5),accounting for 61.91%of the total area;The second is neutral soil(6.5≤p H<7.5),accounting for 27.69% of the total area;Alkaline soil(7.5≤p H<8.5)and strongly acidic(p H<5.0)soils are less distributed,accounting for 7.63% and 2.77% of the total area respectively,and there is no strong alkaline soil(p H≥8.5).The soil organic matter geochemical grade is mainly grade four(relatively lacking),accounting for 80.92% of the total area;Followed by the fifth class(lack),accounting for 14.52% of the total area;The third class(medium)only accounts for 4.56% of the total area;There is no first-class(rich)and second-class(richer)distribution.(3)The results of soil nutrient element content levels show that: The proportion of soil nitrogen deficiency(N≦1g/kg)is 73.86%;The proportion of soil phosphorus deficiency(P≦0.6g/kg)is 49.59%;The proportion of soil potassium deficiency(K≦15g/kg)is 15.41%;The proportion of soil calcium deficiency(Ca O ≦1.16%)is62.39%;The proportion of soil magnesium deficiency(Mg O≦1.20%)is 23.4%;The proportion of soil sulfur deficiency(S≦219mg/kg)is 59.81%;The proportion of soil copper deficiency(Cu≦21mg/kg)is 36.42%;The proportion of soil zinc deficiency(Zn≦62mg/kg)is 33.23%;The proportion of soil iron deficiency(Fe2O3≦4.15%)is26.34%;The proportion of soil manganese deficiency(Mn≦500mg/kg)is 39.29%;The proportion of soil lack of boron(B≦45mg/kg)is 83.93%;The proportion of soil lack of molybdenum(Mo≦0.55mg/kg)is 98.27%.(4)The content of heavy metals Cu,Zn,Cd,Hg,As,Pb,Cr,Ni in soil pollution is20.67±5.84mg/kg,67.66±18.28mg/kg,0.22±0.07mg/kg,0.06±0.04mg/ kg,3.72±1.55mg/kg,25.59±2.36mg/kg,64.67±11.06mg/kg,25.95±7.96mg/kg.The soil Cu,Zn,Hg,As,Pb,Cr,Ni content of geochemical grades are all first-class(clean);The geochemical grade of soil Cd content has a small amount of second-class(light pollution),accounting for 5.33% of the total area,and the rest are first-class(clean),accounting for 94.67% of the total area.(5)Enrichment characteristics of soil elements in paddy field: N is strong enrichment;Si and Mo are weakly enriched;S and B are normal;P,K,Mg,Cu,Zn,Fe are weakly depleted;Ca and Mn are strongly depleted.The enrichment characteristics of dry land soil elements: N is strong enrichment;Si and Mo are weakly enriched;P and B are normal;K,Mg,S,Cu,Zn,Fe are weakly depleted;Ca and Mn are strongly depleted.The enrichment characteristics of orchard soil elements: N is strong enrichment;Si and Mo are weakly enriched;P,K,Mg,S,Cu,Zn,Fe,B are weakly depleted;Ca and Mn are strongly depleted.Enrichment characteristics of overall soil elements in the study area: N is strong enrichment;Si and Mo are weakly enriched;P,S,B are normal;K,Mg,Cu,Zn,Fe are weakly depleted;Ca and Mn are strongly depleted.(6)The soil nutrient and geochemical comprehensive grade results show that: The main categories are fourth-class(relatively lacking)and third-class(medium),accounting for 46.07% and 39.68% of the total area;The second-class(richer)accounted for 8.49% of the total area;The fifth grade(lack)accounts for 5.76% of the total area;There is no first-class(rich)distribution.The comprehensive grading results of soil environmental geochemistry show that: Mainly first-class(clean),accounting for 94.67% of the total area;Second-class(light pollution)accounted for 5.33% of the total area;There is no distribution of third-class(light pollution),fourth-class(medium pollution),and fifth-class(severe pollution).The soil quality geochemical comprehensive grade results show that: Mainly third-class(medium),accounting for50.62% of the total area;Followed by the second class(good),accounting for 37.43%of the total area;First-class(high-quality)accounts for 6.20% of the total area;The fourth class(bad class)accounts for 5.76% of the total area;There is no fifth-class(inferior)distribution. |
