A Study on Distribution Characteristics of Dissolved Organic Nitrogen (DON) in the Sediments of Lake Shankou

The contents and distribution characteristics of dissolved organic nitrogen (DON) and free amino acids (FAA) from the 14 sediments of Lake Shankou, a typical mountain lake in northeast region were studied. The results indicated that the DON contents ranged from 124.41 to 560.17 mg/kg, averaged 304.78 mg/kg, comprising 45.25% of total dissolved nitrogen (TDN) and 5.27% of total nitrogen (TN) in Lake Shankou. The contents of FAA varied from 9.21 to 18.53 mg/kg (mean content, 12.19 mg/kg), comprising 4.35% of DON, 1.91% of TDN and 0.22% of TN, respectively. The DON molecular fraction results indicated that and low molecular weight DON and SUV254 with MW <1 ku about was the dominating fraction at the sampling stations, and high molecular weight DOC with MW >30 ku was the dominating fraction. The DOC/DON ratio results indicated that the small MW fractions(<1 ku) at station 2 which located at downstream of Lake Shankou derived from natural organic matters in sediments and allochthonous sources in water column, and the high MW fractions(>30 ku) at station 2 were mainly from external input in water. The DOC/DON ratios of the small MW fractions(<1 ku) and high MW fractions(>30 ku) at stations 8 and 13 were much low, implying their sources mainly from autochthonous contribution.