Keywords: 
• antibiotics emissions /
• small watershed /
• ecological risk /
• tetracyclines

Abstract: Environmental pollution problems are increasing seriously due to over utilizations and emissions of antibiotics. Estimations of antibiotic emissions are key index on evaluation of antibiotic pollution level in river basin. However, there is a lack of well-founded and commonly accepted estimation method of antibiotics emissions. In this study, an estimation method for typical antibiotics emissions in small watershed is established based on Meijiang River Basin. Emissions of tetracycline antibiotics (TCs), which released into different environment phases, were calculated, and main sources of TCs were analyzed, respectively. The results showed that the total emissions of TCs in Meijiang River Basin were 8 558.06 kg in 2016, and their distribution varied with population and breeding density in different districts, in which Meijiang Town had the largest emissions up to 1 224.4 kg. The emissions of four TCs types in the river basin ranked in the following order: doxycycline>oxtetracycline>tetracycline>chlortetracycline. Affected by emission sources, emission paths, and other factors, TCs were mainly released into soil phase and water phase. TCs detected in the soil phase were mainly from pig and sanhuang chicken manure, and TCs detected in the water phase were mostly from human and pig manure. The result indicates that TCs pollution in Meijiang River Basin may cause potential ecological risk, and therefore the management of antibiotics utilization should be enhanced. This research could provide a very effective method for the estimation of antibiotics emissions in small watersheds of China, as well.