云南洱海表层沉积物中C_(25)高支链类异戊烯烃(HBIs)的特征及其生物地球化学指示意义  

Characteristics and biogeochemical implications of C_(25) highly branched isoprenoids(HBIs)in surface sediments of Lake Erhai in Yunnan Province

作　　者：蔡璐依 张灿 何毓新[1] Cai Luyi;Zhang Can;He Yuxin(School of Earth Sciences,Zhejiang University,Hangzhou 310027,P.R.China;State Key Laboratory of Lake Science and Environment,Nanjing Institute of Geography and Limnology,Chinese Academy of Sciences,Nanjing 210008,P.R.China)

机构地区：[1]浙江大学地球科学学院,杭州310027 [2]中国科学院南京地理与湖泊研究所湖泊与环境国家重点实验室,南京210008

出　　处：《湖泊科学》2023年第3期922-933,共12页Journal of Lake Sciences

基　　金：国家自然科学基金项目(41877332,42073071和42007401)资助。

摘　　要：C_(25)高支链类异戊烯烃(C_(25) HBIs)通常被认为是指示硅藻的生物标志化合物,近年来在长江下游湖泊沉积物中被广泛检出。尽管云南湖泊分布广泛,但尚未有C_(25) HBIs检出的相关报道。本研究通过分析洱海不同湖区表层沉积物,首次指出其存在C_(25) HBIs化合物,并通过分析不同C_(25) HBIs化合物的空间分布特征解析其生物地球化学指示意义。结果显示,洱海表层沉积物中存在C_(25:1)HBI和C_(25:2 )HBI化合物,但均未检测到同分异构体。洱海沉积物中C_(25) HBIs浓度为11.18μg/g(TOC),显著高于富营养化的太湖,与澄湖相当。C_(25:1)HBI浓度表现出南高北低的空间分布特征,而C_(25:2 )HBI浓度则相反,因此C_(25:1)HBI可能表征了洱海南部湖区的优势硅藻。在C_(25:2 )HBI浓度较低(<0.4μg/g)的沉积物中,C_(25:1)HBI和C_(25:2 )HBI呈现微弱正相关,而部分浅水区域的沉积物则表现出C_(25:2 )HBI浓度高(>0.4μg/g)但C_(25:1)HBI浓度低的现象。不同湖区沉积物中C_(25) HBIs浓度与总有机碳和总氮含量的关系存在差异:(1)北部湖区C_(25:1)HBI与TN含量呈负相关,可能表明C_(25:1)HBI生源硅藻受到洱海北部农业活动和氮磷肥大量输入的限制。(2)中部湖区C_(25:1)HBI和C_(25:2 )HBI浓度均与湖泊富营养化水平呈微弱正相关,但与总有机碳含量不存在相关性,说明C_(25) HBIs的生源硅藻受控因素相对复杂。(3)南部湖区C_(25:1)HBI浓度和总有机质含量变化一致,和总氮含量呈较强的正相关关系,而C_(25:2 )HBI浓度与湖泊总生产力和富营养化水平的相关性均较弱。综上研究发现,洱海的C_(25:1)HBI浓度可以指示洱海南部湖区的优势硅藻和富营养化程度,这与长江下游湖泊现象不同;C_(25:2 )HBI可能有较多来源,除了和C_(25:1)HBI相似来源的硅藻以外,还包含某些适于生存在浅水环境的硅藻,因此C_(25:2 )HBI受水文条件控制强烈。C_(25) highly branched isoprenoids(HBIs)are generally regarded as biomarkers signaling diatoms and have been widely detected in lakes in the lower-middle reaches of the Yangtze River recently.The lakes in Yunnan Provinces are rich and diverse in diatoms,whereas the reports on C_(25) HBIs still very limit.In this study,we first detected C_(25:1)HBI and C_(25:2 )HBI in sediments of Lake Erhai,and further revealed the potential biogeochemical significance of C_(25) HBIs by comparing the spatial differences of the proxy and other underlying factors such as TOC,TN,water depth,etc.The isomers of both C_(25:1)HBI and C_(25:2 )HBI were not detected in all surface sediments in Lake Erhai.The concentration of C_(25) HBIs was 11.18μg/g(TOC),which was much higher than those in eutrophic Lake Taihu and similar with those in Lake Chenghu.The concentration of C_(25:1)HBI increased from the north to the south in Lake Erhai,while inverse trends for the concentration of C_(25:2 )HBI.C_(25:1)HBI in Lake Erhai might come from certain predominant diatoms in the southern lake.In sediments with lower concentration of C_(25:2 )HBI(<0.4μg/g),there existed a weak positive correlation between C_(25:1)HBI concentration and C_(25:2 )HBI concentration,while in some shallow areas,the concentration of C_(25:2 )HBI was high(>0.4μg/g)and the concentration of C_(25:1)HBI was low.Besides,the correlation between C_(25) HBIs concentration and TOC/TN displayed distinct spatial differences.In the northern part of Lake Erhai,C_(25:1)HBI-sourced diatoms might be inhibited by a large amount of nitrogen and phosphate fertilizer inputs related to agricultural activities.In the central part of Lake Erhai,the concentration of C_(25) HBIs showed a weak positive correlation with TN,but no correlation with TOC,indicating that the underlying control factors of the C_(25) HBIs-sourced diatoms were relatively complex.In the southern part of Lake Erhai,a strong positive correlation could be observed between C_(25:1)HBI concentration and TN,and between C_(25:1)HBI

关 键 词：洱海 表层沉积物 高支链类异戊烯烃 硅藻 富营养化 水深 

分 类 号：X524[环境科学与工程—环境工程] P593[天文地球—地球化学]