Compositional changes in sediments of subalpine lakes, Uinta Mountains (Utah): evidence for the effects of human activity on atmospheric dust inputs
Compositional changes in sediments of subalpine lakes, Uinta Mountains (Utah): evidence for the effects of human activity on atmospheric dust inputs
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DOI：
10.1007/s10933-009-9394-8
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发表时间：
2010-06
影响因子：
2.1
通讯作者：
R. Reynolds;Jessica S. Mordecai;J. Rosenbaum;M. Ketterer;M. Walsh;K. Moser
中科院分区：
文献类型：
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作者：
R. Reynolds;Jessica S. Mordecai;J. Rosenbaum;M. Ketterer;M. Walsh;K. Moser
犹他州东北部尤塔山脉马歇尔湖和隐湖沉积物中含有大气矿物粉尘沉积的记录，这是由湖泊沉积物的矿物学和地球化学特征与流域前寒武纪碎屑岩的差异所揭示的。在跨越一千多年的岩心中，成分的最大变化发生在过去大约140年里。与矿床相关的许多元素（Ag、As、Bi、Cd、Cu、In、Mo、Pb、S、Sb、Sn和Te）在湖泊沉积物中增加，深度高于约公元1870年。这些金属来自尤塔山脉西部矿区的来源表明：(1)尤塔山脉缺乏这些金属的开采和冶炼，(2)隐藏湖定居后沉积物中大多数这些元素的浓度低于马歇尔湖，马歇尔湖更接近采矿地区和犹他州中北部被称为瓦萨奇锋的密集城市化部分。(3)沉积物中Pb同位素组成与瓦萨奇前缘可能熔炼过的矿石同位素组成的对应关系。湖泊沉积物中铜的主要来源可能是马歇尔湖以西110公里处的宾厄姆峡谷露天矿。根据大约自公元1900年以来美国西部工业活动的广泛增加，在瓦萨奇前线之外可能还有许多其他金属来源。在大约公元1945年以来沉积的沉积物中，根据239+240Pu活性估计，Mn、Fe、S和其他氧化还原敏感金属浓度的增加可能部分是由于与氧化还原变化相关的成岩作用。然而，我们的结果表明，这些元素的增加也与大气输入有关，因为它们的大量增加几乎与粉砂级含钛碎屑磁铁矿的突然增加一致。这种磁铁矿被解释为大气尘埃的组成部分，因为它不存在于集水区的基岩中。大约公元1950年以后沉积的沉积物中磷的富集似乎主要是由大气输入引起的，可能来自农业肥料和含磁铁矿的土壤。
Sediments in Marshall and Hidden Lakes in the Uinta Mountains of northeastern Utah contain records of atmospheric mineral-dust deposition as revealed by differences in mineralogy and geochemistry of lake sediments relative to Precambrian clastic rocks in the watersheds. In cores spanning more than a thousand years, the largest changes in composition occurred within the past approximately 140 years. Many elements associated with ore deposits (Ag, As, Bi, Cd, Cu, In, Mo, Pb, S, Sb, Sn, and Te) increase in the lake sediments above depths that correspond to about AD 1870. Sources of these metals from mining districts to the west of the Uinta Mountains are suggested by (1) the absence of mining and smelting of these metals in the Uinta Mountains, and (2) lower concentrations of most of these elements in post-settlement sediments of Hidden Lake than in those of Marshall Lake, which is closer to areas of mining and the densely urbanized part of north-central Utah that is termed the Wasatch Front, and (3) correspondence of Pb isotopic compositions in the sediments with isotopic composition of ores likely to have been smelted in the Wasatch Front. A major source of Cu in lake sediments may have been the Bingham Canyon open-pit mine 110 km west of Marshall Lake. Numerous other sources of metals beyond the Wasatch Front are likely, on the basis of the widespread increases of industrial activities in western United States since about AD 1900. In sediment deposited since ca. AD 1945, as estimated using239+240Pu activities, increases in concentrations of Mn, Fe, S, and some other redox-sensitive metals may result partly from diagenesis related to changes in redox. However, our results indicate that these elemental increases are also related to atmospheric inputs on the basis of their large increases that are nearly coincident with abrupt increases in silt-sized, titanium-bearing detrital magnetite. Such magnetite is interpreted as a component of atmospheric dust, because it is absent in catchment bedrock. Enrichment of P in sediments deposited after ca. AD 1950 appears to be caused largely by atmospheric inputs, perhaps from agricultural fertilizer along with magnetite-bearing soil.