Abstract:
According to the survey of sea water of 56 stations for the adjacent waters of the Yellow River estuary in October of 2014, the characteristics of nutrients distribution were analyzed, and the level of eutrophication and organic pollution situation was evaluated. The results showed that due to the influence of runoff of the Yellow River, the horizontal distribution of both surface layer and bottom layer of DIN showed a decreasing trend from nearshore area to offshore area, especially the highest value appeared in the waters of the Yellow River estuary. Also there was significant negative correlation between DIN and salinity. However, the horizontal distribution of surface layer of PO
4-P showed an increasing trend from nearshore area to offshore area, while the bottom layer of PO
4-P was well distributed. And there was not significant correlation between PO
4-P and salinity. It was indicated that the main source of PO
4-P was not mainly from the runoff such as Yellow River, but interrelated to the regeneration of the decomposition and mineralization of organic materials, the blooms of phytoplankton, and the delivery upwards of PO
4-P from the surface seabed sediments and so forth. Based on the structure of nutrient salts, the ratio of N/P in the survey area was higher than Redfield ratio, where P was relatively lack compared to N. Based on the horizontal distribution of the ratio of N/P and the density of phytoplankton, too higher ratio of N/P may result in the growth of phytoplankton limited by a relatively low content element, so as to a low density of phytoplankton. According to the results of eutrophication index and organic pollution index, it was in the nutrition status in the survey area of Yellow River estuary in autumn of 2014, where DIN should be the main factor of eutrophication of sea waters of the Yellow River estuary. The grade of organic pollution of the survey area belonged to the second level, which showed that the survey area started to be polluted by organic materials.