Long-term impact of 11 years' typical agricultural discharges on agricultural non-point source pollution loss and its environmental threat to a coastal city of yellow sea, qingdao, east china

Long-term fertilization and livestock farm wastes discharges aggravate water eutrophication via agricultural non-point source pollution (ANSP) process. The ANSP loss load is hard to quantify due to the complexity and randomness, especially in coastal cities. This study quantified the ANSP loads response to the 11 year-long fertilization and livestock sewage discharges in a typical coastal city of the Yellow Sea, Qingdao, East China. The agricultural non-point loss load coefficient K was introduced to evaluate the environmental threat (ET) of the ANSP. The results showed that the loss loads of nitrogen and phosphorus respectively were 10-80 kg/ha and 1-20 kg/ha after 11 years' fertilization. The ANSP loss loads induced by livestock sewage discharges of BOD5, COD, total phosphorus and total nitrogen were 2-35 kg/ha, 3-35 kg/ha, 1-15 kg/ha and 2-18 kg/ha, respectively. The long-term fertilization and livestock sewage discharges respectively induced the K values of ANSP to exceed 80 in six and five of 9 districts in Qingdao, indicating serious ET. The ANSP potentially had more serious agri-environmental threat to the main agricultural producing areas along the Dagu River Basin of the Jiaozhou Bay. The results provide basic information for the ANSP of the Jiaozhou Bay and the methods used in this study should be applied in similar agricultural and coastal cities.