## 4 Conclusions  
In this study, the occurrence and distribution of 110 PhACs in snow near the JZB were investigated for the first time, and the possible sources and potential risks were estimated. A total of 38 substances were detected in snow with concentrations at the ng/L level, including sulfadiazine, sulfararazine, sulfaromonotheroxine, sulfarameter, sulfamethoxypyridazine, sulfamethoxazole, norfloxacin, pefloxacin, oxolinic acid, roxithromycin, josamycin, tilmicosin, cefixime, cefetamet pivoxyl, desacetylcefotaxime, cefamandole, ceftiofur, cephalosporonium, tetracycline, dimetridazole,ronidazole, 5-chloro-1-methyl-4-nitroimidazole, 5-nitrobenzimidazole, flunixin, piroxicam, indomethacin, tolbutamide, prednisone, methylprednisolone 21-acetate, fludrocortisone 21-acetate, budesonide, triamcinolone diacetate, fluocinonide, chloradinone acetate, trenbolone, lorazepam, nitrazepam, and salbutamol. All these contaminants were detected for the first time in snow. Antibiotics (92.33%) and hormones (5.87%) were the dominant compounds in JZB snow. Snow deposition has a direct scavenging effect on air pollutants. As a whole, the PhACs concentration in snow at JZB was higher than that in the seawater of JZB. Additionally, snowfall can effectively remove PhAC pollutants in the atmosphere and has an important significance in adjusting the PhAC concentration in the air. The residual PhACs in the snow in JZB mainly come from local pollutant emissions in Qingdao, followed by remote transmission of PhACs. A total of 14 PhACs (chloradinone acetate, trenbolone, indomethacin, sulfararazine, desacetylcefotaxime, sulfaromonotheroxine, nitrazepam, tilmicosin, prednisone, budesonide, triamcinolone diacetate, sulfameter, lorazepam, and tetracycline) came from local pollutant emissions, while salbutamol, nonidazole, and oxolinic acid came from remote transmission. The results of PCA-MLR source analysis show that the proportions of the drugs used for animals and humans in the accumulated snow samples in JZB to the snow samples at all JZB offshore sampling points were relatively high, at 46.00% and 40.16%, respectively. An environmental risk assessment revealed that tetracycline could present high ecological risk to relevant algae and invertebrates, and sulfamethoxazole might pose a medium risk to algae. Therefore, we need to strengthen the control of the use of human and veterinary drugs, improve the capacities of sewage treatment plants to process drug residue, and process animal excrements in a more scientific way, with the goal of decreasing the concentrations of human medicines and veterinary drugs in the environment.  
Figure 6: Risk quotients (RQs) for the PhACs detected in the surface seawater of JZB.  
Supplementary Materials: The following are available online at [[http://www.mdpi.com/2076-3417/9/6/1078/s1](http://www.mdpi.com/2076-3417/9/6/1078/s1)]([http://www.mdpi.com/2076-3417/9/6/1078/s1](http://www.mdpi.com/2076-3417/9/6/1078/s1)).
* **Author Contributions:** [PERSON] and [PERSON] conceived and designed the experiments; [PERSON], [PERSON], [PERSON], and [PERSON] performed the experiments and analyzed the data; [PERSON] and [PERSON] wrote the manuscript; all authors discussed the results and edited the manuscript.
* **Funding:** This study was supported by the Fund of the Key Science and Technology Innovation Program Supported by Shandong Province and Qingdao National Laboratory for Marine Science and Technology (Grant No. 2018 SDKJ0504-1), the National Natural Science Foundation of China (Grant No. 41676068) and the Development of Instrument & Equipment Function and Technical Innovation Project of CAS (Grant No. HYQY-GNKF2016-1-2).
* **Conflicts of Interest:** The authors declare no conflict of interest.