[Compositional Characteristics of Sediment Dissolved Organic Nitrogen in Typical Lakes and Its Relationship on Water Trophic Status].

UV-Vis absorbance, fluorescence, and Gas Chromatography Mass Spectrometry (GC-MS) were applied to the comparative study on sediment dissolved organic nitrogen (DON) in five typical lakes (Erhai lake, Dianchilake, Poyang lake, Wuhan Dong lake, and Taihu lake) in different lake regions with different nutrition status, revealing the relationship between structural and compositional characteristics of sediment DON and trophic level of lakes. The obtained results showed that: ①Structure of lake sediment DON in Yungui Plateau region is more stable, compared with those in Eastern Plain region, indicating its lower bioavailability. ②In Yungui Plateau region, the source and compositional characteristics of sediment DON weremore complex in Dianchi lake (a seriously polluted lake), and its sediment DON bioavailabilitywas relatively higher. While, with respect to the less polluted Erhai lake, the source of sediment DON is more simple with a higher stability in DON structure and composition, which is beneficial for maintaining its good water quality. ③In Eastern Plain region, nutrition status of Taihu lake was similer to Donghu lake. The structure and composition of sediment DON was complex. But the lower aromaticityand fewer Aromatic ring substituents abundance made their relatively weak nutrient retention ability, posing risk to water quality. With regard to Poyang Lake, the structure and composition of sediment DON was relatively simple, but nutrient retention ability was relatively strong, which played a positive role in maintaining good water quality. ④P(Ⅲ+Ⅴ, n)/P(Ⅰ+Ⅱ, n) values(the content ratio of humic-like substanceto protein-like substances)were in sequence of Dianchi Lake (33.14)>Erhai Lake(21.49)>Taihu Lake(9.06)>Donghu Lake(7.04)>Poyang Lake(4.83), while E(4)/E(6) values (the ratio of UV-Vis absorbance at 465 and 665 nm) were in sequence of Dianchi Lake (27.00)>Donghu Lake(6.65)>Poyang Lake(5.47)>Taihu(3.50)>Erhai Lake(2.31). In addition, P(Ⅲ+Ⅴ, n)/P(Ⅰ+Ⅱ, n) and E(4)/E(6) valueswere positively correlated with thecontents of the different nitrogen (N) forms in the sediments. The above information suggested that P(Ⅲ+Ⅴ, n)/P(Ⅰ+Ⅱ, n) and E(4)/E(6) values exhibited good discrimination degree among different trophic status lakes, and they were considered to indirectly indicate the nutrition levels of lakes to a certain extent.