广东乳源典型富硒区土壤硒元素地球化学特征及其影响因素探讨

以广东省乳源瑶族自治县富硒（Se）土壤为研究对象，依据研究区422件表层土壤调查数据，探讨研究了土壤中不同要素下Se元素含量的地球化学特征、空间分布特征及其影响因素。研究结果表明：研究区土壤Se元素平均含量为0.65 mg·kg－1，分别是韶关市背景值、广东省背景值和全国丰度的1.97、2.71和2.95倍。富硒土壤主要分布在研究区的中西部地区，共圈定2061.31 km2富硒土壤，占研究区总面积的89.66%。不同土地利用类型下，Se含量整体呈现为林地＞园地＞草地＞耕地。研究区土壤Se元素富集主要受到成土母质的控制，土壤中Se含量最高的成土母质类型为泥质岩类风化形成的土壤，富硒率为93.33%；其次受到研究区内表生地球化学作用及S、N等元素的吸附固定作用影响，有利于土壤Se元素的富集。研究区土壤中Se与pH呈显著的负相关关系，即pH值越低，Se含量越高。这些认识有利于对当地富硒土地资源的合理规划利用提供一定科学依据，具有较好的农业经济意义。

Selenium-rich soils in the area of Ruyuan,Guangdong, China: Se geochemistry and evaluation of factors controlling Se enrichment

A survey of 422 surface soil samples in the Ruyuan Yao Autonomous County of Guangdong Province was done to determine the geochemistry and spatial distribution of Se, and to evaluate factors that could influence Se distributions in soils in the study area. Results showed that the average content of Se in soil of the study area was 0.65 mg·kg－1, which was 1.97, 2.71 and 2.95 times that of the background values of Shaoguan City, Guangdong Province, and the national average, respectively. The selenium-rich soil is mainly distributed in the central and western regions of the study area, and a total area of 2061.31 km2 of selenium-rich soil is delineated, accounting for 89.66% of the total study area. Soil Se concentrations vary by land use type: forest land > garden land > grassland > cultivated land. The enrichment of Se in the soil of the study area is mainly controlled by the parent material. The type of parent material with the highest soil Se content is soil formed by the weathering of argillaceous rocks, where soil selenium is enriched 93.33% relative to parent rock. Secondly, it is affected by the supergene geochemistry and the adsorption and fixation of S, N and other elements in the study area, which is conducive to the enrichment of Se in soil. There was a significant negative correlation between Se and pH in the soil of the study area, that is, the lower the pH value, the higher the Se content. These insights provide a scientific basis for the rational planning and utilization of local selenium-rich land resources, especially for considering agricultural land uses. Se can provide an essential nutrient or adversely affect crops, depending on Se concentrations and chemical form.