洱海水-陆界面溶解性有机氮组成结构及生物有效性-以永安江为例

利用紫外与三维荧光光谱技术，研究了洱海水-陆界面溶解性有机氮(DON)组成结构及生物有效性特征，并探讨了其对湖泊水质影响。结果表明：(1)水-陆界面经由永安江输入洱海DON浓度在0.25～1.39 mg·L-1之间，从河流到湖内以夏秋两季DON浓度较高；经由永安江输入洱海DON负荷量在0.48～2.34 t之间，其中以夏季DON负荷量最高，表明经由入湖河流输入洱海的DON对洱海水质影响潜在风险较大，尤其夏季明显。(2)水-陆界面经由永安江输入洱海的DON组成主要以类腐殖质物质为主，永安江沿程到湖内衰解特征明显且生物有效性为15.27%，而类蛋白和可溶性微生物代谢产物则出现不同程度累积，累积率分别为42.00%和20.68%；DON组分的分子腐殖化程度经由永安江到洱海湖内呈渐降趋势且降低了14.97%。同时，分子芳香环取代基从以脂肪链为主逐渐向以羰基、羧基、羟基、酯类为主转变，尤其在夏季表现明显。(3)水-陆界面经由永安江输入洱海DON组成特征参数(P_{(Ⅲ+Ⅴ, n)}/P_{(Ⅰ+Ⅱ, n)}和A₂₅₃/A₂₀₃值)与其不同形态氮含量显著相关(R2=0.64～0.74, P<0.1，P<0.05)，即永安江输入洱海DON结构影响其生物有效性；水-陆界面DON不同结构特征参数与水质呈显著正相关(R=0.82～0.96, p<0.05，p<0.01)，表明水-陆界面经由永安江入湖DON组成结构及生物有效性对洱海水污染有一定贡献，尤其在夏季受陆源等人类活动影响较大时，影响更为突出；由此可见，洱海水-陆界面经由永安江入湖DON组成结构变化(如P_{(Ⅲ+Ⅴ, n)}/P_{(Ⅰ+Ⅱ, n)}，A₂₅₃/A₂₀₃)可在一定程度上反映洱海水质状况。

The Composition,Structure and Bioavailability of Dissolved Organic Nitrogen (DON) in the Water-Land Interface from Erhai Lake:A Case Study in Yongan Revier

The composition,structure and bioavailability characteristics of dissolved org anic nitrogen (DON) in the water-land interface of Erhai Lake were studied by u sing fluorescence and UV-vis absorbance.Moreover,the effect on water qualit y was also discussed.Results showed that:(1) The DON concentration of the wa ter-land interface from Erhai Lake via Yongan River was between 0.25 and 1.39mg·L-1,and the DON concentration were relatively high by summer and au tumn from the inflow river input into the Erhai Lake.The loading of DON into t he Erhai Lake by Yongan River between 0.48 and 2.34 t,and it was relatively high in summer,suggesting that the potential risk for impact on the water qual i ty of Erhai Lake was relatively large by the inflow river into the Erhai Lake,especially in the summer.(2) The DON mainly comprised humic-like substances in the water-land interface from the Yongan river flow into the Erhai Lake,showin g the decrease by the microbial degradation with 15.27％,however,aromatic proteins-like and dissolved metabolites of the microorganisms were accumulated by 42.00％ and 20.68％,respectively to some extent.In addition,the humificat ion degree of DON was gradually decreased by 14.97％ via Yongan River into Erhai Lake.Moreover,the substitution groups in the aromatic rings of DON showed tha t the transformation of mainly contained aliphatic chains to carbonyl,carboxyl,hydroxyl and esters from inflow river into Erhai Lake,particularly in the summ er;(3) The composition characteristic parameters of DON (P(Ⅲ+Ⅴ,n)/P(Ⅰ+Ⅱ,n),A253/A203) was positively correlated wit h the contents of the different nitrogen (N) forms (R2=0.64～0.74,p<0.1,p<0.05) in the water-land interface from Erhai Lake via Yongan ri ver,that was,the structure affect their bioavailability;the different stru ctural characteristic parameters of DON in the water-land interface from Erhai Lake had a significant positive correlation with water quality(R=0.82～0.96,p<0.05,p<0.01),indicating that the composition,structure and bioav a ilability of DON had contributed to the water pollution in the water-land inter face from the Yongan river input into the Erhai lake,especially being greatly af fected by the terrestrial pollution such as human activity in summer.Therefore,the change of composition and structure of DON (such as P(Ⅲ+Ⅴ,n)/P(Ⅰ+Ⅱ,n),A253/A203) in the water-land interface from th e Yongan river into lake could reflect the condition of the water quality of Erh ai Lake to some extent.