Sediment records of highly variable mercury inputs to mountain lakes in Patagonia during the past millennium
Sediment records of highly variable mercury inputs to mountain lakes in Patagonia during the past millennium
复制标题
过去千年巴塔哥尼亚高山湖泊汞输入变化很大的沉积物记录
DOI：
10.5194/acp-10-3443-2010
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发表时间：
2009
影响因子：
6.3
通讯作者：
M. Arribére
中科院分区：
文献类型：
--
作者：
S. Guevara;M. Meili;A. Rizzo;R. Daga;M. Arribére
抽象。位于阿根廷北方巴塔哥尼亚安第斯山脉保护区的Nahuel Huapi国家公园，其原始湖泊生态系统中的汞含量较高，这促使人们对汞的循环和来源进行进一步调查。在这里，我们报告汞记录在沉积序列，以确定在过去的千年大气来源。除了全球迁移和沉积之外，由于公园位于南部火山带，因此与火山活动相关的当地排放是一个潜在的大气汞源。两个沉积物芯提取Toncek湖，一个小的，高海拔的系统，主要反映与大气的贡献，和莫雷诺湖Oeste，一个更大，更深的湖，有一个扩展的分水岭，主要由原生森林覆盖。根据210 Pb和137 Cs剖面对沉积序列进行了定年。此外，火山灰层进行了鉴定和地球化学特征的年代应用，并调查任何关联的火山喷发与汞记录。沉积物中的汞浓度进行了测量沿着与其他32种元素，以及有机质，亚化石摇蚊，和生物硅。观测到的背景汞浓度，从具有较低值的序列域确定，范围为50至100 ng g−1干重（DW），而表层达到200至500 ng g−1 DW。然而，除了这一传统模式之外，两个层序中的两个深层区域汞含量急剧增加，达到400至650 ng g−1 DW;上部区域的汞含量可追溯到18至19世纪，下部区域的汞含量大约在13世纪。这些浓度不仅在本剖面中有所升高，而且比在其他淡水沉积物中测定的背景值高出许多倍，汞通量也是如此，通切克湖的汞通量达到120至150 μg m−2 y−1。汞浓度和有机质，亚化石摇蚊，生物硅，或确定的其他元素的含量之间没有相关性。然而，明显增加的汞浓度观察到直接以上一些火山灰层，这表明与火山活动。长期火灾可能是另一个潜在的大气来源，因为早期的汞峰值与报告的木炭峰值相吻合，而较高的汞峰值与树木年轮数据和历史记录中长期森林火灾的证据相吻合。
Abstract. High Hg levels in the pristine lacustrine ecosystems of the Nahuel Huapi National Park, a protected zone situated in the Andes of Northern Patagonia, Argentina, have initiated further investigations on Hg cycling and source identification. Here we report Hg records in sedimentary sequences to identify atmospheric sources during the past millennium. In addition to global transport and deposition, a potential atmospheric Hg source to be considered is the local emissions associated with volcanic activity, because the Park is situated in the Southern Volcanic Zone. Two sediment cores were extracted from Lake Toncek, a small, high-altitude system reflecting mainly direct inputs associated with atmospheric contributions, and Lake Moreno Oeste, a much larger and deeper lake having an extended watershed covered mostly by native forest. The sedimentary sequences were dated based on both 210Pb and 137Cs profiles. In addition, tephra layers were identified and geochemically characterized for chronological application and to investigate any association of volcanic eruptions with Hg records. Hg concentrations in sediments were measured along with 32 other elements, as well as organic matter, subfossil chironomids, and biogenic silica. Observed background Hg concentrations, determined from the sequence domains with lower values, ranged from 50 to 100 ng g−1 dry weight (DW), whereas the surficial layers reached 200 to 500 ng g−1 DW. In addition to this traditional pattern, however, two deep domains in both sequences showed dramatically increased Hg levels reaching 400 to 650 ng g−1 DW; the upper dated to the 18th to 19th centuries, and the lower around the 13th century. These concentrations are not only elevated in the present profiles but also many-fold above the background values determined in other fresh water sediments, as were also the Hg fluxes, reaching 120 to 150 μg m−2 y−1 in Lake Toncek . No correlation was observed between Hg concentrations and the contents of organic matter, subfossil chironomids, biogenic silica, or the other elements determined. However, distinctly increased Hg concentrations were observed immediately above some tephra layers, suggesting a link to volcanic events. Extended fires might be another potential atmospheric source because the earlier Hg peaks coincide with reported charcoal peaks, whereas the upper Hg peaks coincide with evidences of extended forest fires from tree-ring data and historical records.