【作者】 袁林喜；

【导师】 孙立广；

【作者基本信息】 中国科学技术大学 ， 环境科学， 2010， 博士

【摘要】 为了加强南北极对比研究,更好地了解极地生态环境演化对全球变化的响应,完善极地无冰区生态地质学这个全新研究领域的理论体系,我们在北极典型岛屿斯瓦尔巴群岛的新奥尔松地区开展了相关研究；同时为了拓展生态地质学的研究范围,探讨更多的生态地质学问题,我们在中国东海的典型岛屿舟山群岛上也开展了相关研究。本文以北极斯匹次卑尔根岛的新奥尔松古海蚀凹槽沉积剖面和浙江舟山群岛古木堆积潮间带为研究材料载体,运用年代学、沉积学、元素地球化学、同位素地球化学、古生态学、地质微生物学、微生物成矿学等多学科交叉的理论和方法,分别分析了北极古海蚀凹槽沉积物的年龄、地球化学元素含量、有机碳氮同位素、无机碳酸盐碳氧同位素、粒度、Hunter白度。和浙江古木堆积潮间带的元素地球化学特征、渗漏水系统的微尺度特征、潮间带物质的硫同位素、潮间带铁锰矿物的微区特征,结合多元统计分析的数学处理方法,对北极新奥尔松古海蚀凹槽和浙江舟山群岛古木堆积潮间带进行了综合生态地质学问题研究,主要结论如下：(一)结合对北极新奥尔松古海蚀凹槽沉积物来源的识别和沉积物形成时间的确定,发现早在距今9400年,海鸟就已经登陆王湾,并在王湾生活繁衍。这是对北极新奥尔松全新世海鸟历史研究的首次报道,为进一步研究和认识北极斯瓦尔巴海鸟的生态历史具有重要意义；(二)通过对北极新奥尔松古海蚀凹槽中保存的贝壳残体的贝壳文石氧同位素组成的分析而重建了9,400 yr BP的环境水温为-0.52～+4.78℃,比现代环境水温高约1度；而贝壳的大量同时死亡很可能是发生在9,400 yr BP的突然降温事件导致的。而这次事件很可能是由减弱的太阳辐射驱动,通过温盐环流等正反馈放大,并最终导致高北极海表面温度急剧下降。这次短暂而明显的降温事件不仅在格林兰、北大西洋、阿尔卑斯、东欧等北半球广泛存在,而且在低纬地区、南半球,甚至是遥远的南极也有记录,表明9,400 yr BP突然降温事件很可能是广泛存在的；(三)AMS14C定年建立了北极新奥尔松古海蚀凹槽沉积70.118 cm段的年代学,探讨了该层位的沉积模式,并提取了代表鸟粪的标型元素组合,重建了海鸟种群数量变化历史。结果显示,海鸟自距今9400年登陆新奥尔松至距今1860年期间,其种群数量经历了2个主要阶段：(Ⅰ),登陆之初,海鸟种群数量逐渐增长,在距今7650年左右达到最大种群数量；(Ⅱ),随后的5800年时间里,海鸟种群数量经历了3次剧烈波动：7650-6280 yr B.P.、6280-4580 yrB.P.、4580-2540yr B.P.。进一步对比发现,海表面温度(SST)并不是斯瓦尔巴群岛海鸟生态的显著性限制因素,北大西洋气候,尤其是高尔夫湾流的变化会对海鸟生态形成决定性的影响；(四)北极新奥尔松古海蚀凹槽沉积10-70 cm段的砾石堆积是小冰期(LIA)冰进的产物。0-10 cm段是小冰期(LIA)冰退之后的20世纪以来的现代沉积物,与新奥尔松地区的人类活动有关；(五)对中国舟山群岛古木堆积潮间带的现代微生物成矿学研究,发现埋藏古木产生的腐殖质／有机酸为嗜中性铁氧化菌Leptothrix ochracea和Gallionella ferruginea、硫酸盐还原菌生长提供了理想的生存条件；铁氧化菌的矿化产物主要为隐晶质的水铁矿,并且铁氧化菌矿化过程经历不同阶段,即从细胞壁表面矿化、细胞内部部分矿化直至整个细胞完全被矿化,其对环境中的金属元素的生物地球化学循环产生重要的影响；硫酸盐还原菌在该潮间带环境中的大量存在,并参与了Fe-S循环过程、进行了生物诱导下的胞外成矿作用；(六)对中国舟山群岛古木堆积潮间带的Fe-Mn氢氧化物包被胶结现象研究显示,其中,黄红色包被物的主要矿物组成为水铁矿和针铁矿,黑色包被物的主要矿物组成为层状水锰矿和水合软锰矿,而且Fe/Mn元素在这些包被物中均匀分布。扫描电镜揭示黄红色包被物中的矿物是以球状体和球状集合体形式存在的,同时大量杆状菌群落和菌席也被观察到；黑色包被物中的矿物是以微小的锯齿形盘状晶体排列成不规则蜂窝状结构,而且,最初的Mn氢氧化物沉淀-水合软锰矿晶体在结核状胶结物中被观察到,呈椭球状。同时在黑色包被物中也发现大量细菌残体存在。细菌很可能在Fe-Mn氢氧化物包被物形成过程中扮演了重要的角色。微量金属元素分布结果显示,这些Fe-Mn包被物显著吸附Sc, V, Cr, Co, Ni, Cu, Zn, Ba,尤其是Co和Ni,可以作为潜在的环境生物修复材料。Fe-Mn包被物具有显著的PAAS标准化MREE富集的配分模式,揭示了其经历了两个连续的形成过程：(1)堆积古木通过发酵作用释放大量腐殖酸,腐殖酸作用于基岩释放大量Fe-Mn矿物,这些Fe-Mn矿物以腐殖酸络合态的形式被地下水系统运移至潮间带,与海水混合,发生絮凝作用,但这个过程并不发生显著的REE分馏；(2)絮凝过程中或絮凝之后,海水中的MREE优先吸附到沉淀形成的Fe-Mn氢氧化物中,导致形成的Fe-Mn包被物富集MREE。本研究对于Fe-Mn氢氧化物包被的微区特征的认识,以及潮间带、浅海等环境下的Fe-Mn循环过程及其REE和微量金属元素的行为的理解具有重要的意义。更多还原

【Abstract】 To compare between Antarctica and Arctic, to better understand the evolution of the polar environment and its respond to global change, and to promote the theoretical system of ecological geology in polar ice-free areas, we carried out studies in Spitsbergen, Svalbard. Meanwhile, to expand the study scope of ecological geology, we performed related researches in Zhoushan Archipelago, Zhejiang.In the present dissertation, a paleo-notch sediment profile with a 118 cm length was sampled in Ny-Alesund, Spitsbergen, Arctic, and samples in a special intertidal zone influenced by buried ancient wood were collected in Zhoushan Archipelago, Zhejiang. Then, analysis, including chronology, sedimentology, geochemistry, isotopic geochemistry, palaeoecology, Geological microbiology, microbial mineralization, were performed on those samples. Main conclusions are listed as follows:(1) The identification of sediment sources and the deposited age indicate that seabirds have inhabited Ny-Alesund since 9,400 yr B.P. after Kongsfjorden was completely deglaciated. This is the first report on Holocene seabird occupation on Ny-Alesund and it provides the foundation for understanding the ecological history of seabirds in Svalbard in Holocene;(2) The calibrated aragonite isotopic temperature equation was established for Ny-Alesund based on comparing theδ18O profiles of shell fragments in paleo-notch sediments and modern mollusks. The paleotemperature range was reconstructed as-0.52～+4.78℃, warmer than today by about 1℃. Moreover, the mortality of the fossil mollusks was very likely caused by an abrupt cooling event at about 9,400 yr B.P., which was inferred from reduced insolation, weakened thermohaline circulation (THC), and abrupt decreased SST. This abrupt cooling event might extensively occur.(3) AMS14C chronology was established for the 70-118 cm unit in paleo-notch sediments, and the bio-element cluster was extracted to reconstruct the historic seabird populations. The historic seabird populations experienced obvious fluctuations during 9400-1860 yr BP:(Ⅰ) at the beginning of landing, the seabird populations gradually increased, and reached the maximum at about 7650 yr BP; (Ⅱ) in the subsequent 5800 years (7650-1860 yr BP), the seabird populations intensively fluctuated during 7650-6280 yr BP,6280-4580 yr BP, and 4580-2540 yr BP. Moreover, the fluctuations of historic seabird populations were dominated by North Atlantic climate change, not SST; (4) The gravel accumulation in 10-70 cm unit in paleo-notch sediments was caused by LIA; The sediments in 0-10 cm unit was related with anthropogenic activities in Ny-Alesund, Arctic;(5) The modern microbial mineralization study in the intertidal zone influenced by ancient wood revealed that neutrophilic iron-oxidizing bacteria (Leptothrix ochracea, Gallionella ferruginea) and sulfate reduction bacteria (SRB) extensively existed in the intertidal zone. The biomineralization product of neutrophilic iron-oxidizing bacteria is ferrihydrite, a poorly ordered iron oxide. The mineralization process of the iron oxidizing bacteria undergoes different stages, from extracellular mineralization, intracellular mineralization to the whole cell mineralization, and these bacteriogenic iron oxides (BIOS) obviously affected the fate of metal ions there. The SRB were involved in Fe-S cycle to induce extracellular biomineralization.(6) Microscale analysis methods were employed to study the nanoscale characterization and trace element distributions in the stratified sediments and the concretions in the special intertidal zone, Zhoushan Archipelago, Zhejiang. Light microscopy, scanning electron microscopy (SEM) and backscattered electron imaging (BSE) revealed that these samples were composed of different coatings on sand grains. The main mineral compositions of coatings are ferrihydrite and goethite for the yellowish-red parts, and birnessite and vernadite for the black parts using X-ray powder diffraction (XRD). SEM observations show bacteriogenic products and bacterial remnants extensively occurred in the coatings, indicating that bacteria likely played an important role in the formation of Fe-Mn oxyhydroxide coatings here. PAAS-normalized middle rare-earth-element (MREE) enrichment patterns were characterized by the coatings, which were caused by two subsequential processes:(1) preferentially release of Fe-Mn from the beach rocks by fermentation of ancient woods and colloidal flocculation in the mixing water zone; (2) preferentially adsorption of MREE by Fe-Mn oxyhydroxides from the seawater. The chemical results indicate that trace metals of the coatings are enriched with Sc, V, Cr, Co, Ni, Cu, Zn, Ba, particularly for Co, Ni, implying significant implications for environmental bioremediation. Furthermore, the formation model for these Fe-Mn oxyhydroxide coatings was proposed. These findings in the present study provide a sight in the nannoscale features of Fe-Mn oxyhydroxide coatings and the Fe-Mn biogeochemical cycles involved buried organic matters in the intertidal zone or shallow coast.更多还原