Influx and concentration of triazine pesticides in the Amaterska cave system, Moravian Karst, Czech Republic

The aim of this study was to detect three triazine pesticides and their metabolites in the drip water and the sediment of the Amaterska cave system. Diversity of the bacterial community in the sediment was also assessed, and the potential role of bacteria in degradation of these pesticides was evaluated. Triazines and their metabolites were analyzed in the soil, drip water, and sediment of the Amaterska cave system area in seven sampling sites (S1-S7) based on the above ground cover that included forest, permanent grassland, and agriculture cropland. The bacterial community in the cave sediments (S1-S6) was also analyzed using the Illumina sequencing of the V3 and V4 regions of 16S rDNA. Triazines were present in the soil and drip water in all sites below grassland and agricultural land but not under the forest area. Only atrazine metabolites were detected in the surface soil. In contrast, atrazine was detected in all cave sediments regardless of above ground cover, and this is likely due to the occasional alluvial influx. The overall prevalence of bacteria potentially capable of atrazine degradation in the cave sediment ranged from 13.4 to 64.0% of the entire bacterial community. The concentrations of atrazine in the cave sediment were 16 to 70 times higher than in those in drip water. High concentrations of atrazine in the cave sediment indicate a slow degradation rate of triazines in the cave likely due to low temperatures and absence of photolysis. The main source of atrazine in the Amaterska cave system is likely not drip water but the alluvial influx. Bacteria potentially capable of triazine degradation in the cave sediment were detected; however, their role in this process remains to be investigated.