中文摘要：

北江是发源于湖南（武水）和江西（浈水），汇于广东韶关，流经广东全境并人海的三大河流之一。为了解整个北江抗生素污染情况，共设置44个采样点，并采集了河水及部分沉积物样品，较全面地分析了各样品中12种典型抗生素含量并初步探究了其污染来源。研究发现，包括北江源头在内的全河段均有抗生素的检出，5类抗生素在表层水和沉积物中的平均浓度分别为77．8ng·L。和3．6ng·g-1其中，大环内酯类污染最为严重，其含量范围为11．7～114．6ng·L-1和0~435．3ng·g-1，远高于其他类抗生素。表层水中磺胺类的磺胺甲恶唑和氯霉素类的检出率达100％，其中以磺胺甲恶唑（14．7ng·L-1）和阿奇霉素（25．0ng·L-1）为主，而沉积物中以阿奇霉素（35．9ng·g-1）、氧氟沙星（5．4ng·g-1）和四环素（3．3ng·g-1）为主。由于流域污染源种类和数量不同，各抗生素在北江中的分布也存在差异。表层水中抗生素含量水平表现为下游高于上中游，在沉积物中则主要集中于中、下游之间河段。这反映了人类活动强度对北江抗生素污染的直接影响。

英文摘要：

The Beijiang River is one of the three major rivers which flow across the Pearl River Delta Region, south- em China. It serves one of the most densely urbanized regions in China and was heavily impacted by agricultures and aquacultures in recent 30 years. As emerging pollutants, there are less complete database on antibiotics and their pol- lution sources in the river environments. To gain insight into the occurrences, distributions and possible sources of antibiotics in the whole Beijiang River, 44 water samples and 23 sediment samples were collected along the river from source to estuary. Total 12 common antbiofics including 4 sulfonamides （sulfadiazine, sulfamethazine, sulfame- thoxazole and sulfacetamide）, 2 quinolones （norfloxacin and ofloxacin）, 4 macrolides （roxithromycin, erythromycin, azithromyein and clarithromycin）, chloramphenicol and tetracycline were investigated in these samples. The selected compounds in the samples were pretreated using solid phase extraction （SPE） followed by the determinations of high performance liquid chromatography-tandem electrospray ionization mass spectrometer （HPLC-MS/MS）. The results showed that most of the antibiotics could be detected in all the samples including those from headwater areas less im- pacted by human activities indicating that the antibiotics were ubiquitous in the environments of the Beijiang River. The average concentrations of all antibiotics were 77.8 ng.L-1 in the surface water and 3.6 ng.g-1 in the sediments, re- spectively. The macrolides were the dominant pollutants with their concentration ranging from 11.7 to 114.6 ng.L-1 in the surface water and 0~22.8 ng.g-1 in the sediments, followed by quinolones （0-113.1 ng.L-1, 0-47.1 ng-g-1） and sulfonamides （6.7~41.5 ng.L-1, 0-1.3 ng. g＇]）. Generally, there were higher levels of antibiotics detected in the water samples adjacent to downstream and in the sediment samples between mid- and downstream than those in the up- stream fiver. The total concentrations of most of the s