东北地区典型湖沼沉积物溶解态有机质组成特征及来源解析:以库里泡为例

Composition characteristics and source tracing of dissolved organic matter of lacustrine sediment in northeastern China:A case study of Lake Kulipao

溶解态有机质(DOM)是湖泊沉积物的重要组分,解析DOM的组成和来源对于深入理解湖泊有机质生物地球化学循环及控制水体富营养化具有重要意义。本研究于2021年5月和8月采集了大庆市库里泡表层及柱状沉积物、泡内水生物(浮游藻类、挺水植物和沉水植物)、岸边土壤、陆生C3和C4植物、禽畜粪便以及城镇污水等样品,分析了样品DOM的稳定同位素(δ^(13)C和δ^(15)N)组成及三维荧光光谱特征,并利用IsoSource软件计算了不同来源样品对沉积物DOM的贡献率。结果显示:(1)库里泡内表层沉积物DOM的δ13C和δ15N组成存在季节性差异,5月δ^(13)C和δ^(15)N均值分别为-25.54‰和9.02‰,8月分别为-26.81‰和8.40‰。(2)库里泡内柱状沉积物DOM的δ^(13)C和δ^(15)N组成在垂直方向存在差异,表层(0~3 cm)δ^(13)C和δ^(15)N均值分别为-26.58‰和9.04‰,深层(3~30 cm)均值分别为-25.40‰和10.61‰。(3)表层沉积物DOM的三维荧光组分存在季节性差异。5月以类腐殖质荧光组分为主,占比为87.89%,HIX和BIX分别为6.27和0.67;8月蛋白类荧光组分占比为49.58%,HIX和BIX指数均值分别为1.72和0.87。(4)5月表层沉积物DOM外源输入占比为61%,以土壤(21.40%)和城镇污水(18.08%)为主;而8月内源贡献占比稍高(55.10%),且以挺水植物为主(48.68%)。(5)柱状沉积物(0~30 cm)不同深度DOM来源组成相近,主要为城镇污水、沉水植物/藻和挺水植物,贡献率均值分别为42.13%、25.07%和18.53%。整体上,库里泡沉积物DOM来源主要受到流域内人类活动及气候特征的影响,本文研究结果有利于加深对我国东北地区湖泊沉积物有机质迁移转化及累积规律的认识。

Dissolved organic matter(DOM)is one of the important components in lake sediment.Identifying the composition and sources of sediment DOM exerts great significance on the understanding of carbon biogeochemical processes and the eutrophication control of lake.To trace the source of sediment DOM in Lake Kulipao,samples of sediment and potential sources were collected in May and August 2021,including surface and core sediment samples,phytoplankton,macrophytes,C3 and C4 plants,livestock manure and treated effluent.Stable isotope(δ^(13)C andδ^(15)N)and fluorescence spectroscopy were applied to characterize the DOM composition of sediment and source samples.Furthermore,contribution rates of different sources to surface and core sediment DOM were calculated using IsoSource software.The calculation results showed that:(1)δ^(13)C andδ^(15)N of DOM in surface sediment differed in May(average values of-25.54‰and 9.02‰)and August(average values of-26.81‰and 8.40‰).(2)δ^(13)C andδ^(15)N of DOM in core sediment differed in depth,with average values of-26.58‰and 9.04‰in depth of 0-3 cm and-25.40‰and 10.61‰in depth of 3-30 cm.(3)Fluorescence components of surface sediment DOM were dominated by humic-like component(87.89%)in May,with HIX and BIX values of 6.27 and 0.67.In August,protein-like component increased to 49.58%with HIX and BIX values of 1.72 and 0.87.(4)Source analysis showed that allochthonous DOM(61%)dominated in surface sediment in May,with soil and treated effluent proportions of 21.40%and 18.08%,respectively.In August,proportion of autochthonous DOM increased to 55.10%,with a high contribution of emergent macrophyte(48.68%).(5)The DOM sources of core sediment showed no significant variation with depth,with treated effluent,submerged plant/algae and emergent macrophyte dominating the DOM with proportions of 42.13%,25.07%and 18.53%,respectively.In a whole,sources of sediment DOM in Lake Kulipao were mainly related to the human activities and climate features.This study can potentially improve the understanding of DOM accumulation and transportation in northeast watersheds of China.