| This research paper explores the degree of soil development in the Luhuo River Valley of the Xianshui River.10 soil profiles from different elevations and multiple terraces were selected as the research objects.Through field profile descriptions and indoor physical and chemical property analysis,the sources of soil materials and weathering development characteristics were discussed.Furthermore,the systematic classification status was identified by diagnostic layers and diagnostic characteristics.t provides theoretical basis for land development and utilization in this area.The following research results were obtained.（1）Basic physical and chemical properties of the soil in the study area.The dry color of the soil is mainly brown and yellow-brown,while the wet color is mainly turbid yellow-brown and dark brown.The texture of the soil is mainly loam and sandy loam.The frequency-dependent magnetic susceptibility of the soil is between 6.7%and 10.9%.The loss on ignition of the soil is between 5.14%and 10.83%.The p H value of the soil in the study area is between 5.72 and 8.35,and the equivalent calcium carbonate content is between0 and 79.63 g/kg,except for the two profiles with the highest altitude,which are acidic or neutral.The other profiles are alkaline,and the bottom of the profiles shows strong hydrochloric acid reaction and high calcium carbonate content.The organic carbon content is between 1.48 and 29.60 g/kg,and the organic carbon content is generally high in the surface layer of each profile.The total nitrogen content is between 0.24 and 2.61 g/kg,and both decrease gradually with increasing depth.The cation exchange capacity（CEC）ranges from 8.42 to 19.05 cmol（+）/kg.The available phosphorus content ranges from 1.25 to 8.07mg/kg,which is generally low and decreases gradually with depth.The free iron content is between 7.63 and 24.98 g/kg,and the percentage of free iron ranges from 14.78%to 42.63%,with an average of 23.92%.there are significant differences between the soil profiles,but the variation within each profile is relatively small.（2）Geochemical properties of the soil in the study area.The major constituents of the Luhuo soil are Si O2,Al2O3,and Fe2O3,and their sum exceeds 79%.The relative migration order of the major elements varies among the soil profiles.The CIA value of the soil in the study area ranges from 61.22 to 69.80.The Na/K ratio ranges from 0.60 to 1.30.The leaching coefficient ranges from 0.35 to 0.45.The base saturation ratio ranges from 0.13 to 0.23.The residual index ranges from 2.30 to 3.62.The total rare earth element content ranges from180.80 to 236.99 mg/kg,and the Eu/Eu*ratio ranges from 0.55 to 0.64,the La N/Yb N ratio ranges from 9.59 to 13.21,the Gd N/Yb N ratio ranges from 1.68 to 2.23,and the La N/Sm Nratio ranges from 3.70 to 4.09.The distribution pattern of rare earth elements in the Luhuo soil is highly consistent,showing enrichment of light rare earth elements and depletion of heavy rare earth elements in all soil profiles.（3）Study on the pedogenetic features and provenance of the soil in the study area.The scatter plot of the constant and rare earth element characteristics of the Luhuo soil profile compared with windblown sediments from other areas shows that the Luhuo soil has a different source area from the Chengdu clay source area.The Luhuo soil profile may have a similar source area as the Luochuan loess and the Zhenjiang Xiashu soil.The A-CN-K ternary diagram indicates that the soil in the study area（with weak weathering degree）is closer to the Luochuan loess than the Chengdu clay,the Zhenjiang Xiashu soil,and the ancient soil in Luochuan.（4）Soil type identification in the research area.In Chinese Soil Taxonomy（CST）,10soil profiles in the research area belong to 4 orders as such as Argosols,Isohumisols,Cambosols and Primosols,4 Suborders,4 Groups and 4 Subgroups of Typic Hapli-Udic Argosols,Typic Hapli-Udic Isohumosol,Typic Hapli-Ustic Cambosols and Typic Aqui-Alluvic Primosols. |
