| This paper mainly studies on the typical wetlands in the pearl river estuarine region and the existing form of nitrogen and it's denitrification in surface and subsurface sediments from the Qi'ao islands; This article also researches on the existing form of phosphorus in sediments, phosphate adsorption kinetics characteristics onto the sediments and its sorption isotherms. Then, it discusses the physical and chemical characteristics of the sediments and the influence on the phosphate adsorption characteristics by overlying water salinity. It comes to the conclusions that:By determining the existing form of nitrogen in sediments and between sediments of the Qi'ao island, we finds out that the content of TN in sediments is 973～1147mg/kg or 1025～1127mg/kg. The content of inorganic nitrogen in TN is NH4+-N>NO3--N>NO2--N. The content of NH4+-N accounted for above 85% of the total inorganic nitrogen, and above 96% in total nitrogen is organic nitrogen. Organic nitrogen holds a larger proportion of total nitrogen in sediments and in the interstitial water, while inorganic nitrogen accounts for a smaller proportion. NH4+-N occupies a larger proportion of inorganic nitrogen.It comes to a conclusion from the experiment of "Effect of salinity on NH4+ exchange behavior at the sediment-water interface": NH4+ goes into water from the sediments when the salinity changes from 1% to 3‰; and NH4+ backs into the sediments from water when the salinity changes from 3%o to 6%o. The experiment shows the average of denitrification intensity of Qi'ao island light land and mangrove is 276.2 mg·kg-1·h-1 and 237.5 mg·kg-1·h-1. The denitrification intensity of the surface and subsurface is averagely 250.7mg·kg-1·h-1 and 263.0mg·kg-1·h-1. Through this data we find that the mangrove has much greater denitrification intensity than the light beach does. We also find that the intensity of the subsurface is apparently stronger than the surface.The average content of TN of the sampling points changes from 527.18μg/g to 748.89μg/g. Among the content of TN in Xiahengli, Shanghengli and the junction between Hengli and Jiaomen, Xiahengli is lowest, which is 527.18μg/g, and the junction between the Hengli and Jiaomen highest 748.89μg/g, and Shanghengli is 642.91μg/g. The forms of inorganic phosphorus in the sampling points mainly exist on the binding form of calcium and phosphorus which accounts for about 60% of the inorganic phosphorus. It shows by the vertical distribution of phosphorus in sediments that the existing forms of phosphorus in core sediments from the Shanghengli and Xiahengli are both mainly the binding form of calcium and phosphorus; Ca-P>Org-P>Fe/Al-P>Lsor-P. The forms of phosphorus in Hengli and in the junction between the Hengli mainly exist on the organic phosphorus which accounts for about 40% of TP, Org-P>Ca-P>Fe/Al-P>Lsor-P.Phosphate adsorption characteristics onto the sediments meet the Langmuir equation. The adsorption mainly happens in 11 h, and comes to a balance in 24h. Phosphorus adsorption rate of sediments comes to a maximum in 0-0.5h. The sediments in Xiahengli have the strongest phosphorus adsorption capacity; the phosphorus adsorption capacity of sediments in Xiahengli and in Shanghengli is relatively parallel, but the phosphorus adsorption products of the surface sediments in Shanghengli are more stable. The adsorption characteristics have the positive correlation with the size of particles and the content of organic carbon.
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