Ammonia nitrogen adsorption and release characteristics of surface sediments in Dianchi Lake, China

To determine the ammonia nitrogen adsorption and release characteristics of surface sediments in Dianchi Lake, 36 surface sediment (0-10 cm) samples were collected in 2013. Results showed that compared with other lakes in China (e.g. Erhai Lake and Taihu Lake), Dianchi Lake had high levels of ammonia nitrogen (NH4 (+)-N) adsorption capacity, release rate and release capacity. The ammonia nitrogen release risk of Dianchi sediments was relatively high. Comparison of the equilibrium ammonium concentration (ENC (0)) in surface sediments and the ammonium contents in the overlying water of Dianchi Lake indicated that ENC (0) was high for most lake sections. Therefore, the sediments of Dianchi Lake would be a pollution source, and ammonia nitrogen release risk was high because the surface sediments of Dianchi Lake were heavily contaminated with nitrogen. The total nitrogen (TN) and NH4 (+)-N contents of the sediments of Dianchi Lake greatly influenced the ammonia nitrogen adsorption-release process. Aside from TN, nitrogen fractions should also be studied when assessing pollutant release risk from lake sediments. NH4 (+)-N was the main fraction of nitrogen released from sediments, which was highly significant when evaluating sedimentary release capacity. The sedimentary release capacity and release potential of nitrogen provided important information to assess release risks.