## 3 Results and Discussion
### Composition Characteristics of Pharmaceuticals in Snow
#### 3.1.1 Antibiotics  
Antibiotics are one of the most commonly used classes of pharmaceuticals and are commonly detected in marine environments [30; 31]. China's shelf seas have been previously reported to be impacted by antibiotics [32]. In this study, 23 out of the 59 screened antibiotics were detected at the 19 sampling stations. Six out of the 15 screened sulfonamides were detected: Sulfadiazine, sulfarenzine, sulfamonomethoxine, sulfameter, sulfamethoxypyridazine, and sulfamethoxazole. The concentrations of sulfamonomethoxine, sulfameter, and sulfamethoxypyridazine were above the LOQ in all samples with a frequency of detection of 100%, and these concentrations ranged from 0.55-0.58 ng/L, 0.45-2.17 ng/L, and 0.45-0.65 ng/L, respectively, indicating the widespread distribution of these compounds. Sulfadiazine and sulfarenzine were detected sporadically at low concentrations in the ranges of ND-0.20 and ND-0.08 ng/L, respectively. Sulfamethoxazole exhibited low detection frequencies of 5.26% and a maximum concentration of 3.95 ng/L. The mean concentrations of sulfadiazine and sulfamethoxazole in snow in this research were 0.08 and 0.21 ng/L, respectively, which are equivalent to the concentrations in the seawater of JZB [33] and lower than the concentrations in other surrounding sea areas, such as Laizhou Bay, Liaodong Bay, and Bohai Bay [34]. Three out of the 10 screened quinolones were detected: Norfloxacin, pefloxacin, and oxolinic acid. Oxolinic acid was detected with a frequency of detection of 52.63% in the range of ND-0.27 ng/L. Norfloxacin, along with pefloxacin, was detected at high levels (ND-11.50 and ND-6.43 ng/L, respectively) with a frequency of detection of 10.53%. Norfloxacin and pefloxacin are used primarily as human medicine, and their medical consumption is relatively high in China [35]. Norfloxacin and pefloxacin exhibited low concentrations and detection frequencies because they have short half-lives. We previously reported that the norfloxacin concentration in the seawater of JZB was within the range of ND-0.6 ng/L [23]. The norfloxacin concentration in the snow near the shore of JZB was higher than that in the seawater of JZB. Three out of the 5 screened macrolides were detected: Roxithromycin, josamycin, and tilmicosin. Roxithromycin had a frequency of detection of 94.74% in the range of ND-0.60 ng/L, indicating its widespread distribution. Josamycin and tilmicosin were detected sporadically at low concentrations in the ranges of ND-0.11 and ND-2.64 ng/L, respectively. High levels of erythromycincin and roxithromycin were determined by [PERSON] et al. in the seawater of Victoria Harbour at concentrations up to 1900 and 47 ng/L, respectively [36]. The main reasons why the concentration of roxithromycin was lower in the snow sample from JZB than in the seawater may be the massive usage amount and relatively high boiling point of roxithromycin, which is a new generation of macrolide antibiotics and very difficult to volatilize in the natural environment. The concentration of josamycin in Tunisia coastal waters was measured to be 0.8 ng/L [37]. Josamycin and tilmicosin are rarely reported in seawater and have not been reported in the coastal waters of China. Six out of the 15 screened cephalosporporins were detected: Desacetylcefotaxime, cephalonium, cefixime, cefetamet pivoxyl, cefamandole, and ceftiofur. Desacetylcefotaxime and cephalonium were identified at frequencies of detection above 70% in the ranges of 16.20-101.00 and ND-5.61 ng/L, respectively. Desacetylcefotaxime mainly comes from the metabolism of cefotaxime; it has relatively weak antimicrobial activity, but its half-life period is longer and more stable than that of cefotaxime. Desacetylcefotaxime was the primary cephalospororin-contaminated drug in snow. The frequency of detection of cefixime, cefetamet pivoxyl, cefamandole, and cephalosporporins was 5.26%, the mean concentration of ceftiofur was 1.43 ng/L, and the concentrations of the other three types were less than 1 ng/L.