Objective The aims were to explore the spatial distribution characteristics and influencing factors of soil selenium (Se) content in Hancheng, Shaanxi Province, in order to provide theoretical basis and practical guidance for rational development and utilization of soil Se resources, protection of regional ecological environment safety and residents' health.

Methods The Se contents in soils at different depths in Hancheng, Shaanxi Province, was detected, and the spatial distribution and influencing factors of Se contents in different soil types, land use types, terrain gradients and landforms were analyzed by statistical methods.

Results The Se contents in the surface soils of Hancheng were more enriched than that in the middle soil and deep soil, with obvious surface accumulation. The average level of Se content in soil was a moderate state, which was 0.87 times of the national average level and 2.17 times of Shaanxi Province. Some areas of Hancheng belonged to high Se area. Among different soil types, alluvial soil and neutral coarse bone soil had the highest Se content in each soil layer, and the Se content in drab soil was the lowest in the surface soil, while the Se content of calcareous stony soil was the lowest in the middle and deep soil. In different land use types, Se content showed obvious distribution characteristics. In the surface soil, the Se content of grassland was the highest, and that of irrigated land was the lowest. The Se content of grassland in middle and deep soil was the lowest, and the difference of Se content among other land use types was not significant. It was worth noting that the Se content of grassland soil decreased sharply with the increase of soil depth. The Se content of surface layer was 3.5 times that of middle layer and 5.8 times that of deep layer. There was no significant change in soil Se content in different terrain slope. Among the different landform types, the Se contents in the surface soil valley terrace and loess tableland were the highest, and the difference between the middle soil and the deep soil was less and less.

Conclusion The distribution characteristics of soil Se content in Hancheng were different in soil types, land use types and different geomorphic types. In the different terrain slopes, the difference was very small. Soil Se content was the result of the combined effect of soil type, land use type, topography and other factors.