# Antibiotics in Groundwater and River Water of Bialka--A Pristine Mountain River
## 3 Results  
A total of 24 antimicrobial agents were monitored within this study, out of which 16 were detected above the LOD of the method (Table 1). The examined water samples differed in terms of the expected anthropogenic pressure, understood as the proximity to households, hotels, tourist infrastructure and livestock-associated pressure. Figure 2 presents the frequency of detection of antibiotics (only those above LOQ are shown in this figure) in the water samples, divided into three groups: groundwater (GW), river water (RW) and river water collected by the discharge from the sewage treatment plant (STP). The overall frequency of detection for all antimicrobial agents examined in this study is shown in Table 1. While looking at the overall frequency of detection, clindamycin was most frequently detected (63.16% of samples), followed by erythromycinycin (59.65%), ofloxacin and trimethoprim (57.89%) and sulfamethoxazole (50.88%). While looking at Figure 2, it can be noticed that these five antimicrobials are also the five most frequently detected in STP, RW and GW samples but in varying order. In descending order of detection frequency, these antimicrobials can be arranged as follows: STP--ofloxacin, trimethoprim (100%) > erythromycinycin, clindamycin (90%) > sulfamethoxazole (80%); RW--clindamycin (63%) > ofloxacin, erythromycinycin (53%) > trimethoprim (50%) > sulfamethoxazole (45%); GW--erythromycin (67%) > trimethoprim, sulfamethoxazole (50%) > clindamycin, ofloxacin (33%). On the other hand, gentamicin (aminoglycososide), amoxicillin, aztreonam, cefuroxime, cephalozolin (\(\beta\)-lactams), tylosin (macrolide), rifampicin (ansamycin) and enrofloxacin (fluoroquinolone) were not detected at all in this study. The antimicrobial agents, the concentrations of which were higher than the LOD and/or LOQ of the UHPLC/MS/MS method but with the least frequently detected, belonged to the group of \(\beta\)-lactams and these were: ceftazidime and piperacillin (1.75%), cefamandole (3.51%) and ampicillin (5.26%). As shown in Table 1, none of the examined antimicrobials were detected in one of the groundwater samples (GW1) collected in the Tatra Mountains (Tatra National Park). However, the second groundwater samples (GW2), also collected in the TNP but much closer to households and located below mountain shelters, was not as clean: as many as seven antimicrobial agents were detected in this sample: cefoxitin, erythromycin, ofloxacin, clindamycin, vancomycin, trimethoprim and sulfamethoxazole. The highest number of antimicrobial agents was detected by the STP (14 detected and 13 detected in the amounts exceeding the LOQ, which allowed precise assessment of their concentration). This sample was also characterized by the highest mean and maximum concentrations of all antimicrobials, except ceftazidime (the highest mean and max. concentration of this antibiotic were recorded in the RW4 sample, located c.a. 3 km downstream of the STP). What can also be observed while looking at Table 1 is that the total concentrations of antimicrobial agents detected vary considerably, from 19.68 ng/L for ampicillin (\(\beta\)-lactam) to 6063.25 ng/L for oxytetracycline (tetracyclines). Oxytetracycline is also the antibiotic whose maximum concentration was the highest out of all examined antibiotics (1819.07 ng/L by the STP). Figure 3a-f show the differences in the total concentrations of antibiotics between the examined sites. The total concentration of antimicrobial agents varied from 17.94 ng/L for the river water upstream of the STP (RW2) to 7593.37 ng/L by the STP. The total concentration of antibiotics in groundwater (GW2) was 27.92 ng/L. Interestingly, the share of total concentration of vancomycin in all antimicrobials is very high in the GW and RW samples that are not subjected to high anthropogenic pressure--even 64.38% (17.91 ng/L) in GW and 53.31% (21.83 ng/L) in RW1 (Figure 3a-f).