Due to the unique hydrogeological environment of karst areas, pollutants are more likely to enter the soil and water, showing a special migration and transformation behavior. In this work, the binding behaviors between strontium (Sr²⁺) and dissolved organic matter (DOM) extracted from soil under the influence of pH and Ca²⁺ in a typical karst area were investigated by applying three-dimensional fluorescence spectroscopy combined with parallel factor analysis (EEM–PARAFAC) and two-dimensional correlation analysis (2D-COS) of synchronous fluorescence spectra (SF). The results show that DOM extracted from soil was dominated by tryptophan-like and tyrosine-like materials (77% in total). Two-dimensional COS of SF showed that the tryptophan-like substance in DOM extracted from soil preferentially bound to Sr²⁺. When the pH was 7, the binding coefficient (logK_a) of the four DOM components ranged from 2.69 to 4.04, which was more conducive to the binding of DOM extracted from soil and Sr²⁺ than under acidic and alkaline conditions. Ca²⁺ in soil weakened the binding of DOM extracted from soil to Sr²⁺ by competing for binding sites and changing the molecular surface potential. This research is helpful for acknowledging the migration and transformation of Sr²⁺ and offers a reference for groundwater protection in karst areas.

Subterranean karst caves are windows into the terrestrial subsurface to deconstruct the dimensions of mycobiome fingerprints. However, impeded by the constraints of remote locations, the inaccessibility of specimens and technical limitations, the mycobiome of subterranean karst caves has remained largely unknown. Weathered rock and sediment samples were collected from Luohandu cave (Guilin, Southern China) and subjected to Illumina Hiseq sequencing of ITS1 genes. A total of 267 known genera and 90 known orders in 15 phyla were revealed in the mycobiomes. Ascomycota dominated all samples, followed by Basidiomycota and Mortierellomycota. The sediments possessed the relatively highest alpha diversity and were significantly different from weathered rocks according to the diversity indices and richness metrics. Fifteen families and eight genera with significant differences were detected in the sediment samples. The Ca/Mg ratio appeared to significantly affect the structure of the mycobiome communities. Ascomycota appeared to exert a controlling influence on the mycobiome co-occurrence network of the sediments, while Ascomycota and Basidiomycota were found to be the main phyla in the mycobiome co-occurrence network of weathered rocks. Our results provide a more comprehensive dimension to the mycobiome fingerprints of Luohandu cave and a new window into the mycobiome communities and the ecology of subterranean karst cave ecosystems.