Spatial Distribution Characteristics of Nitrogen and Phosphorus in Sediments of Coastal Wetlands

Taking the typical coastal wetlands in the Yellow River Delta as the research object, (i) three parallel strips A1, A2 and A3 were set up along the vertical coastline in the newborn wetland at 60 km south of the Dongwenliu Management Station in the Yellow River Delta Nature Reserve. (ii) Sample plots B (Phragmites communis area), C (Suaeda glauca area), and D (Tamarix chinensis area) were set up near the field ecological station of the coastal wetlands. Through collecting sediment samples and measuring nitrogen and phosphorus contents, the spatial distribution characteristics of nitrogen and phosphorus in sediments of coastal wetlands were studied. Following results were obtained. (i) The concentration of TN in the 0-20 cm surface sediments of the coastal wetlands in the Yellow River Delta was in the range of 130-695 mg/kg, the concentration of TP was in the range of 589-778 mg/kg, and the average content of TN and TP was 372.18 and 660.82 mg/kg respectively. (ii) From the remote coastal area of the Yellow River to the near coastal area, the horizontal distribution of TN in the sediments was different at each level, and the TN content in the surface sediments gradually decreased; the content of TP generally increased. (iii) At the profile level, the content of TN and TP generally showed a trend of decreasing gradually from the surface layer and tending to be stable, and the peak appeared at the outermost layer. (iv) In the sediments under different vegetation cover, TN was more evenly distributed on each profile, and the distribution of TP on each profile was different. TN showed the largest distribution in the 0-20 cm surface sediments in the T. chinensis area, while TP had the largest distribution in the 80-100 cm bottom sediments in the T. chinensis area.