[Distribution Characteristics of Urea and Constitution of Dissolved Nitrogen in the Bohai Sea and the Huanghai Sea in Spring].

Based on the investigation of the Huanghai Sea and the Bohai Sea in Spring( April to May) of 2014, the concentrations of urea and inorganic nitrogen were determined respectively by diacetyl monoxime-Semicarbazide Hydrochloride method and Spectrophotometric method. The distribution of urea and the component of dissolved nitrogen were analyzed. The influencing factors of urea were also discussed. The results showed that the concentration of urea in the Bohai sea and the Huanghai sea ranged from 0.21-2.17 μmol x L(-1), and the average concentration was (0.84 ± 0.20) μmol x L(-1). Urea was an important component of the dissolved organic nitrogen (DON) and accounted for 7.90% of DON. In the investigated area, the average concentration of urea in the north Huanghai sea was the highest, and that in the south Huanghai sea was the lowest. The concentration of urea in the Huanghai sea gradually reduced from inshore to offshore. The areas with high concentrations of urea were near the coastal cities like Qingdao and Dalian where have high population density. The concentration of urea in Bohai sea gradually increased form inshore to offshore, this result indicated that the river input was not the primary source and this might be caused by adsorption of colloid flocculation.