## 1 Introduction  
Pharmaceutically active compounds (PhACs) are widely used in human disease treatment, animal breeding, and aquaculture husbandry to prevent or treat human and animal diseases [1]. Antibiotics, analgesics, steroids, antidepressants, antipsychotics, and stimulants are among the arrays of PhACs. However, PhACs are not entirely absorbed by organisms, and a major fraction is excreted in parent or metabolite form through urine and feces [2; 3]. As emerging organic pollutants, PhACs in the environment can be toxic to certain aquatic organisms and induce antibiotic resistance due to their large production volumes, pseudo persistence, bioaccumulation, and potential ecotoxicity [4; 5]. In addition, long-term exposure to low concentrations of PhACs brings about tremendous risks to both the ecological environment and humans. PhACs poison the microflora or lower organismswith the same or similar target organ after entering the environment. The microflora and lower organisms are the basis of the ecological system; thus, the destruction of these components is devastating to the entire ecological system, may cause changes to the carbon recycling processes and the ecological environment, and eventually will impact the health of humans [6].  
The PhACs in the environment have also recently attracted much attention throughout the world. PhAC contamination has been reported in many countries, such as Spain [7], the USA [8], Malaysia [9], Germany [10], Cyprus [11], France [12], Canada [13], and India [14]. However, few PhACs have been regulated as contaminants worldwide [13]. PhACs have been detected in different environmental samples, including rivers [15], lakes [16], wastewater [17], soils [18] and sediments [19]. However, the existence of PhACs in snow has not been reported. PhACs in the snow can enter the water and soil ecosystem directly or indirectly. Snowfall is an important way to remove organic pollutants from the air and constitutes an important source of organic pollutants in water [20]. In general, PhACs are designed to cause specific effects even at low concentrations, and long-term exposure to low doses of these compounds can cause adverse effects to ecosystems [6].  
Jiaozhou Bay (JZB) (N35\({}^{\circ}\)38\({}^{\circ}\)-36\({}^{\circ}\)18\({}^{\prime}\), E120\({}^{\circ}\)04\({}^{\prime}\)-120\({}^{\circ}\)23\({}^{\prime}\)) is a typical semi-enclosed bay that is surrounded by the city of Qingdao (Figure 1). The degree of water exchange in the bay is far lower than that in the open sea, and the bay is easily influenced by rainfall, snowfall, and terrestrial input from rivers [21; 22]. The occurrence of quinolone antibiotics and ciprofloxacin has been reported in the seawater in this area, revealing that JZB is polluted by PhACs [23]. Therefore, 110 commonly used PhACs were selected for this study based on the known drugs used in China, including hormones, hypoglycemic substances, antibiotics, diazepam, nonsteroidal anti-inflammatory drugs, and antiviral drugs, to investigate the characterization and source of PhACs in the snow at nearshore locations in JZB in North China. In addition, the preliminary potential ecological risk was evaluated for those PhACs in JZB.  
Figure 1: Locations of the sampling sites.  
The results will help us gain insight into the chemical characteristics, source apportionment, and ecological risk of PhACs in the snow near JZB, and provide basic data support for further research on migration, transformation mechanisms, and other basic theoretical studies of PhACs.