Characteristics And Environmental Significance Of Dissolved Organic Nitrogen In Plateau Lakes

Plateau lakes present different characteristics with plain lakes in many aspects because of their unique geographical environment.A comprehensive and in-depth study of plateau lakes is of great significance for their environmental protection.As an important component of the organic and nitrogen in the lake,DON plays a vital role in the evolution of the lake.In this study,Ultraviolet-visible spectroscopy(UV/Vis)and excitation-emission matrix fluorescence combined with parallel factor analysis(the EEM-PARAFAC model)were used for the characterization of the components and structure of the dissolved organic nitrogen(DON)in the overlying water of three typical lakes from Yunnan Plateau,China.And FT-ICR-MS technology is used to analyze the molecular level of the sediment DON.Components S2 identified by the PARAFAC model were highly prevalent in plateau lakes but rarely appeared in plain lakes.To be noted,we found that with the decrease of eutrophication level,relative abundance of S2 presented significance increase,the relative abundance of S2 can be used as an indicator of lake trophic status.The cultures experiment was conducted to compare the bioavailability of bacteria and algae to sediment DON.Bacteria and algae could only change the content of DON components without changing their species.This study represents the first attempt to use FT-ICR-MS in the compositional characterization of molecular-level DON in lake sediments.The results showed large numbers of N-containing compounds.With a van Krevelen diagram,most sediment DON structures were identified as lignin components(68%of the total).At present,the state of sediment in Erhai is relatively stable,but in the long run there is a greater risk of nutrient release.