宁夏南部山区葫芦河流域土壤地球化学特征及影响因素分析

Geochemical characteristics and influencing factors of soil in Hulu River Basin in the southern mountainous region of Ningxia

基于宁夏固原地区土地质量地球化学调查数据资料,采用数理统计方法研究了表层土壤30项元素(指标)的背景值,对比分析了不同成土母质(岩)和土地利用类型元素空间分布特征和富集贫化规律,进一步采用主成分分析法从元素组合特征的角度分析了制约元素分布特征的因素。结果表明:研究区土壤中亲铁元素(Ni)、亲钨元素(Mo)、碱(土)金属元素(Na_(2)O、MgO、CaO)及卤族元素(I、F)、亲铜元素(As)含量高于全国背景值,Hg、Se、有机质、N、Pb等亲生物元素与全国背景值相比相对贫化。成土母质(母岩)是土壤元素含量特征的主要控制因素,在成土过程中,自然及人为影响造成了部分元素的贫化富集。N、Mo、I、有机质、S等受红土母质和其母岩控制明显,Ca^(2+)、Na^(+)则在水动力影响下造成风化淋失。河谷平原土壤元素含量介于红土和黄土母质之间,在表生环境下易溶于水的Na_(2)O、K_(2)O、Cl在水动力的作用下于河口、河谷地带富集,P、Hg、Se、Mo则受人为干扰出现局部富集。因子分析表明,成土母质(岩)、成土过程中的风化、淋滤、生物富集等作用及人类生产活动共同影响着研究区表层土壤的背景值特征。该研究成果可为区域资源环境评价提供基础地球化学信息。

Based on the data derived from the geochemical survey of land quality in the Guyuan region,Ningxia,this study studied the background values of 30 elements(indicators)in the surface soil using mathematical statistics.This study compared the distribution and enrichment(or dilution)characteristics of elements in different parent materials(parent rocks)and land use types and further analyzed the factors restricting the distribution of the elements from the perspective of element association characteristics using the principal component analysis method.The results show that the contents of iron-philic element Ni,tungsten-philic element Mo,alkaline(earth)metal elements Na_(2)O,MgO,CaO,halogen elements I,F,and copper-philic element As were all higher than corresponding national background values,while the contents of the biophilic elements such as Hg,Se,organic matter,N,and Pb were lower than corresponding national background values.Parent materials(parent rocks)were the main factor controlling the characteristics of element contents in soil.In the process of soil formation,natural and man-made influences have caused the enrichment or dilution of some elements.N,Mo,I,organic matter,and S are significantly controlled by the laterite parent material and their parent rocks,and the erosion of Ca^(2+) and Na^(+) causes weathering and leaching due to hydrodynamic effects.The element contents in the soil in the river valley plain were between those of laterite and those of loess parent material.In a supergene environment,Na_(2)O,K_(2)O,and Cl,which are prone to dissolve in water,are rich in estuaries and valleys due to hydrodynamic action.P,Hg,Se,and Mo elements are locally rich due to human interference.The factor analysis shows that parent materials(parent rocks),weathering,leaching,and bioaccumulation in the process of soil formation,and human production activities all affect the background values of the surface soil in the study area.The study results will provide basic geochemical information for the assessment of the regional resources and environment.