Geochemical characteristics of strontium and development potential of strontium−rich ecological industry in Chengde, Hebei

This paper is the result of hydrogeological survey engineering.

Objective It is of great significance to the establishment of strontium−rich soil standards and the development of strontium−rich ecological industries to clarify the abundance, sources, and migration patterns of strontium in the bedrock − regolith −soil−plant continuum system.

Methods The geochemical baseline values of the strontium in topsoil of the Chengde region and the Hongqi−Damiao small catchment were determined using the reference element method. Multivariate statistical analysis, GIS methods, chemical depletion fraction (CDF), bioconcentration factor (BCF), electron probe microanalysis, and in−situ microanalysis were systematically conducted to elucidate the abundance, spatial variation, migration and accumulation characteristics of strontium in bedrock−regolith−soil layers of different geological formations, different types of water and plant samples, as well as to identify the host minerals of strontium in bedrock and the causes of geochemical anomalies of strontium in Chengde City. The development potential of strontium−rich ecological industry in Chengde was evaluated combining the current research status of strontium−rich ecological industry at home and abroad with the ecological resource endowment of Chengde City.

Results The geochemical baseline value of the strontium in topsoil from the Chengde region and the Hongqi−Damiao catchment was 206.87−216.49 mg/kg, and 241.69−260.51 mg/kg, respectively. The average Sr content in the topsoil of Chengde was 514.59 mg/kg, with 59.05% and 68.10% of topsoil samples exceeding the geochemical baseline value of the entire region and the Sr background value of Soil Layer A in China. The average Sr content in the bedrock of the Chengde region was 546.57 mg/kg, and the Sr−rich host minerals were identified as pyroxene, olivine, apatite, calcium feldspar, and hornblende. The leaching−loss intensity of strontium during the chemical weathering process of anorthosite, plagioclase gneiss, and granite was relatively higher than that of other geological formations. The spatial variation of strontium abundance in bedrock exhibited good spatial coupling with regional tectonic framework. The uplifting and thinning of the continental crust in the North China Craton led to the upwelling of Sr−rich Archean metamorphic basement materials between the Fengning−Longhua and the Damiao−Niangniangmiao deep faults. Consequently, the Damiao anorthosite rock mass, Hercynian intrusive rocks, volcanic rocks, and Archean metamorphic basement formed by the mixing and crystallization separation of basic magma and continental crust along the deep fault belt are enriched in strontium. The water samples in the Luanhe River Basin, well and spring water samples in Hongqi−Damiao catchment with Sr²⁺concentration higher than 0.4 mg/L accounted for 58.08%, 81.61% and 53.57% respectively, and the average Sr²⁺concentration of geothermal water and hot spring samples was 0.78 mg/L. The average Sr content of 34 economic crops ranged from 0.77 to 26.60 mg/kg, of particular note was that the Sr content of Scutellaria baicalensis was 15.94−116.51 mg/kg, which was significantly higher than other producing areas in China.

Conclusions Chengde possesses prominent advantages in strontium−rich water and soil resources, and its geographical−indication products and authentic Chinese herbal medicines exhibit distinct strontium−rich characteristics. The strontium−rich ecological industry in Chengde—including drinking mineral water, geothermal health industries, beverage and wine production, characteristic ecological agriculture, organic green foods, agricultural and sideline products, and authentic Chinese herbal medicine derivatives—holds significant development potential.