Occurrence and risks of antibiotics in the coastal aquatic environment of the Yellow Sea, North China Ruijie Zhang a, b , Jianhui Tang b , Jun Li a , Zhineng Cheng a , Chakra Chaemfa a , Dongyan Liu b , Qian Zheng a , Mengke Song a , Chunling Luo a , Gan Zhang a, b, ⁎ a State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China b Key Laboratory of Coastal Environmental Process, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai 264003, China HIGHLIGHTS ► Some antibiotics were ubiquitous in coastal seawater of the Yellow Sea, North China. ► Higher concentrations and spatial variations were presented in the semi-enclosed bay. ► Lower concentrations and spatial variations were presented in the open bays. ► Source of the antibiotics in the different bays varied largely. ► Parts of the antibiotics in one bay posed high ecological risks to some organisms. abstract article info Article history: Received 8 May 2012 Received in revised form 8 February 2013 Accepted 9 February 2013 Available online xxxx Keywords: Antibiotics Seawater Jiaozhou Bay Source apportionment Risk assessment Eleven antibiotics in three different categories were investigated in two types of coastal bays (a semi-enclosed bay and an open bay) of the Yellow Sea and in fresh water (rivers and sewage treatment plants [STP] effluents) that discharged into the bays. The results revealed the presence of three predominant antibiotics: dehydration erythro- mycin, sulfamethoxazole and trimethoprim. These antibiotics were detected in the seawater and fresh water with concentrations of b 0.23–50.4 ng L -1 and b 0.25–663.1 ng L -1 , respectively. In terms of the regional distribution of the compounds within the two types of bays, higher concentrations (b 0.23–50.4 ng L -1 ) and higher spatial variations (coefficients of variation: 98%–124%) were found in the semi-enclosed Jiaozhou Bay due to the poor water-exchange ability and to fresh-water inputs through rivers and/or STP effluents. In contrast, lower concentra- tions (b 0.23–3.0 ng L -1 ) and lower spatial variations (coefficients of variation: 36%–75%) were present in the open Yantai Bays due to the strong water-exchange with the open sea. The source apportionment suggested that 1) fresh-water inputs were the primary source of macrolides in the coastal water, and 2) mariculture affected the relative pollution levels of trimethoprim, sulfamethoxazole and sulfathiazole in the bays. In addition, a risk as- sessment based on the calculated risk quotient (RQ) showed that the dehydrated erythromycin, sulfamethoxazole and clarithromycin detected at most of the sampling sites in Jiaozhou Bay could pose high (RQ>1) risks to the most sensitive aquatic microorganisms, such as Synechococcus leopoliensis and Pseudokirchneriella subcapitata, whilst in the Yantai Bays, the compounds could pose medium risks (1 ≥ RQ>0.1) to the same aquatic microorganisms. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Antibiotic residues are new pollutants in the environment. These compounds can cause ecological harm to organisms and promote antibiotic-resistance genes in bacterial populations (Eguchi et al., 2004; Kummerer, 2004). Antibiotic residues are widely present in faeces, medical waste, soil and all types of aquatic environments due to the extensive and long-term use of antibiotics in human therapy and veterinary medicine as well as in promoting the growth of animals in livestock production (Kummerer, 2009). Terrestrial antibiotic residues could be transported to marine environments via riverine inputs (Jia et al., 2011; Zhang et al., 2012b; Zou et al., 2011) and sewage treatment plant (STP) effluents (Gulkowska et al., 2007; Minh et al., 2009). These antibiotics and/or the residues used in mariculture (Jia et al., 2011) cause various degrees of antibi- otic pollution in the coastal environment. For example, as shown in Table 1, the maximum concentration (c max ) of roxithromycin (RTM) was up to 630 ng L -1 in Bohai Bay (Zou et al., 2011) of the Bohai Sea (BS), China, the c max of trimethoprim (TMP) was up to 330 ng L -1 in Laizhou Bay (Zhang et al., 2012b) of the BS, the c max Science of the Total Environment 450-451 (2013) 197–204 ⁎ Corresponding author at: No. 511 Kehua Street, Tianhe District, Guangzhou, Guangdong Province, China. Tel.: +86 20 8529 0805; fax: +86 20 8529 0317. E-mail address: zhanggan@gig.ac.cn (G. Zhang). 0048-9697/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.scitotenv.2013.02.024 Contents lists available at SciVerse ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv