[Distribution and Burial Characteristics of Nitrogen Forms in Sediment of Dianchi Lake During Last Century].

In order to analyze the composition, distribution and burial characteristics of nitrogen in sediments of Dianchi Lake in the last hundred years, 6 sediment cores were sampled in July 2014 to determine the contents of different nitrogen species and sedimentary age sequence. The integrated results demonstrated a high content of total nitrogen in sediments ranging from 1263.68-7155.17 mg·kg. The contents of nitrate nitrogen and ammonium nitrogen were low, which were 10.00-144.00 mg·kgand 9.20-146.50 mg·kg, respectively. Organic nitrogen was the main component in the sediments, ranging from 255.80 to 5644.25 mg·kg, composing a large average percentage of 91.26%. In addition, the nitrogen pollution of sediment in Dianchi Lake has reached a high level and is becoming serious since 1970s, which surged in the late 1990s. The spatial difference of total nitrogen was obvious, with comparably the most in the south, less in the north and least in the center. The average deposition rate was changing from 0.092 g·(cm·a) to 0.187 g·(cm·a) in the last 100 years and increased first, then declined, finally showed a slight upward trend over time. The burial rate of total nitrogen in sediment increased over time and almost grew up straightly after 1990,which decreased from the south to the north of Dianchi Lake in space. It was estimated that the reserves of total nitrogen, organic nitrogen, nitrate nitrogen, ammonium nitrogen in the sediment were 92139.15 t, 86745.62 t, 2464.16 t, 2929.37 t, respectively, from 1900 to 2014.