Investigation of inorganic nitrogen and active phosphorus contents in Pearl River Estuary

Vertical profiles of inorganic nitrogen and active phosphorus and other chemical parameters were taken in spring and autumn from 2003 to 2005 in the eight channels of Pearl River in order to analyze the status and characteristics of eutrophication. The result showed that in these three years, NO₃^--N is the main form of inorganic nitrogen in most area. The contents of inorganic nitrogen are between 1.986 to 5.070 mg·L^-1 in the Estuary. The contents of inorganic nitrogen in Humen (one of the Pearl River channels) and Jitimen are much higher than those of the other channels of the Pearl River, and Hengmen and Modaomen are obviously the lowest in these eight channels. The concentrations of active phosphorus are much lower than the first grade of seawater quality standard in this area. The situation of eutrophication becomes worst in the Estuary.