洱海表层沉积物溶解性有机氮生物有效性

选取9个洱海表层沉积物样品,提取了DON(溶解性有机氮)进行生物矿化培养,测定了培养过程中各形态氮含量,并运用三维荧光技术研究了DON结构变化. 结果表明:①洱海沉积物中w(DON)范围为43.52~214.71mg/kg,平均值为115.19mg/kg,DON主要由类蛋白和类腐殖质类物质构成,并且以类蛋白为主；②洱海沉积物中DON生物有效性为1.21%~72.77%,平均值为33.23%,生物可利用量平均值为50.22mg/kg；DON生物有效性空间差异明显,北部和南部较高,而中部较低；③洱海生物自身产生及形成的DON主要由类酪氨酸组成,其中有小部分类腐殖质可被生物利用,这是由于类色氨酸和类酪氨酸共存可提高DON类腐殖质生物有效性. 此外,w(DON)占w(TDN)(TDN为可溶性总氮)的比例是影响DON生物有效性的重要因素,w(DON)/w(TDN)越高,类腐殖质及类酪氨酸含量越低,沉积物中DON生物有效性越高. 可见,DON对湖泊富营养化有重要影响,控制洱海富营养化,不仅需要关注沉积物中的w(TN),也应关注w(DON)及DON组成特征. 

Bioavailability of Dissolved Organic Nitrogen in the Surface Sediments of Erhai Lake

Nine surface sediment samples from Erhai Lake were selected to extract dissolved organic nitrogen (DON) for the biomineralization incubation experiment. Different forms of nitrogen content were measured and the three-dimensional fluorescence of DON was applied in combination with the excitation-emisson matrix spectrum during the process of incubation. The results indicated that:① Contents of DON in sediments ranged in 43.52-214.71mg/kg with the average of 115.19mg/kg, mainly being consist of a class of proteins and humic, and like protein-based. ② The bioavailability of DON in surface sediments from Erhai Lake was 1.21%-72.77% with its average of 33.23%; The content was 50.22mg/kg and this showed a obvious spatial difference which was higher in the northern and southern of Erhai Lake, and lower in central lake. ③ The class of tyrosine composition was the dominant component of autochthonal DON in sediments, and some humic of DON can be bioavailable, as it promoted biological effectiveness by class of tryptophan and tyrosine. Moreover, the proportion of DON in TDN is an important factor of DON bioavailability. The higher the value of DON/TDN, the lower the content of a class of humic and tryptophan, the higher the bioavailability of DON in samples. Therefore, since DON is an important active component of TN in sediments, what should be paid attention to is not only TN in sediments, but also DON and its compositions for controlling of the Erhai Lake eutrophication.