Research on the Release Potential of Ammonia in the Estuarine Wetland Sediments of Erhai Lake

After running for ten years, the nitrogen content in the sediments of Luoshijiang Estuarine Wetland increased continuously, and there was great release risk. In order to explore the spatial-temporal distribution characteristics of nitrogen in the overlying water and sediment of the wetland, on-site investigation and monitoring were carried out. A 5-day laboratory simulation experiment was carried out by using the method of continuous flow culture of the original column samples to study the variation features and influencing factors of release flux of NH₄⁺-N in wetland sediments. The results show that: (1)The concentrations of TN and NH₄⁺-N were quite high and ranged from 3.11 to 5.13 and from 0.32 to 0.62 mg·L^-1, respectively, which both showed a decreasing trend from inlet to outlet of the wetland. The contents of TN and NH₄⁺-N in the surface sediments ranged from 1 264.83 to 2 554.48 and from 13.56 to 63.42 mg·kg^-1, respectively, which showed that the contents in inlet were higher than those in other monitoring points. (2)The release fluxes of NH₄⁺-N in the sediments of Luoshijiang Estuarine Wetland were in the range of 270.60 to 747.58 mg·m^-2·d^-1 with the average value of 482.95 mg·m^-2·d^-1, and the wetland sediments mainly acted as the release source of NH₄⁺-N. During the experiment of 5-day continuous flow cultivation, the release flux of NH₄⁺-N in wetland sediments showed a trend of first decreasing and then increasing, and reached the lowest value on the third day of the experiment. The results could provide scientific basis for the design and management of artificial wetland restoration in Erhai Lake Catchment.