Distribution characteristics, influencing factors and eco-environmental impact of soil germanium in Western Liaohe River Basin

This paper is the result of ecological geological survey engineering.

Objective Germanium element (Ge) has important biological and industrial application prospects.

Methods Based on the multi−target regional geochemical survey results in the Liaohe River Basin, the global Moran index, semi−variance analysis, and anthropogenic environmental enrichment coefficient were used to study the spatial distribution characteristics of surface and deep soil Ge in the Western Liaohe River Basin. Random forest was used to calculate the explanation degree and importance ranking of geological and environmental factors on soil Ge.

Results The average Ge content of surface and deep soil in the Western Liaohe River Basin is 1.10 mg/kg and 1.08 mg/kg respectively, and the average Ge content of surface and deep soil in the upstream is 1.46 mg/kg and 1.41 mg/kg respectively, the average Ge content of the downstream surface layer and deep soil is 1.07 mg/kg and 1.05 mg/kg respectively. Overall, there is little difference between the surface layer and the deep layer, but the upstream layer is significantly larger than the downstream layer. The global Moran index shows that the spatial distribution of surface and deep soil Ge has obvious spatial autocorrelation. Semi−variance results show moderate and strong spatial autocorrelation in the upper and lower surface and deep soils. The distribution of areas with high Ge content in surface and deep soils is basically the same. In the land quality geochemical grade classification of surface soil Ge content, deficiency accounts for 88.4% and is mainly distributed in the downstream area. The areas of medium, relatively rich and rich account for 9.8% in total. Germanium is relatively concentrated in the upstream area. The results of the man−made environment enrichment coefficient show that the upstream area is mainly affected by natural factors and slight human activities; the downstream area is more significantly affected by human activities. The results of the random forest model showed that influencing factors such as soil physical and chemical property indicators, soil parent rock, altitude, soil type, and land use type explained 68.5% and 56.1% of Ge in surface and deep soil in the study area respectively; the ranking of importance shows, the soil−forming parent rock ranks first in importance, elements such as Ti, TFe₂O₃, Zn, Cr and Mn are at the forefront, altitude and soil type are more important, while land use type and soil pH are less important.

Conclusions Different soil physical and chemical property indicators, soil−forming parent rock, altitude, soil type, and land use type in the study area all cause significant differences in the Ge content of surface and deep soils, as well as upper and lower surface and deep soils. The soil Ge in the upper reaches of the study area is richer than that in the lower reaches, which is more suitable for the development of Ge−rich agricultural products and Ge−rich agriculture.