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Abstract Longjinghu Lake is a new deep lake based on the original channel with an artificial dam. Before comprehensive improvement, the sewage discharged into Longjinggou upstream is the main source of exogenous nitrogen of Longjinghu Lake. The paper aimed to investigate the space distribution characteristic of nitrogen forms and demonstrate the processes of nitrogen migration and transformation. According to the depth of water and aging age of sediments, sediment samples were collected from the three sampling regions including original channel, bottom region and slope of newly submerged area. Concentration of different nitrogen forms in the overlying water, interstitial water of sediment cores and total nitrogen in the surface sediment were analyzed. The results showed that there were existed similar speciation distribution trends of total nitrogen, ammonia nitrogen, and dissolved organic nitrogen in the above samples, and the distribution were: original channel > bottom region> slope area, which similar to the change trend of water depth. The average concentration of total nitrogen, ammonia nitrogen, dissolved organic nitrogen in the sediment interstitial water were 33.59, 14.62, 18.06mg/L and 23.01, 8.39, 13.75mg/L and 8.57, 2.81, 5.45mg/L respectively. The concentration change significantly along the slope and higher than that of overlying water, has great release potential. The average content of total nitrogen in the surface sediments from the original channel and the bottom region of newly submerged area were 3789 and 2984mg/kg respectively which was obviously higher than that of slope zone with the concentration of 1287mg/kg. The results could provide fundamentals for the prediction of internal load and the control of inner source pollution.
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Received: 06 March 2015
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