Three North African dust source areas and their geochemical fingerprint
Three North African dust source areas and their geochemical fingerprint
复制标题
DOI：
10.1016/j.epsl.2020.116645
复制
发表时间：
2021-01-15
影响因子：
5.3
通讯作者：
Wilson, Paul A.
中科院分区：
文献类型：
--
作者：
Jewell, Amy M.;Drake, Nick;Wilson, Paul A.
北非制造了世界上一半以上的大气沙尘。这种灰尘一旦进入大气，就会在当地对人类健康构成危害。它还修改了区域辐射预算，并提供营养物质，为北大西洋和远至亚马孙盆地的初级生产力提供燃料。深海和湖泊沉积物中的粉尘积累也为研究古气候变化，特别是与降雨气候变化有关的气候变化提供了一种手段。对卫星图像的系统分析极大地提高了我们对远距离北非尘埃羽流轨迹的了解，但我们对产生尘埃的源区的了解以及对它们对这些出口路线的贡献进行指纹识别的能力令人惊讶地有限。在这里，我们报道了来自已知扬尘产生底物(干燥的河床和湖床)的沉积物样品的新的放射性同位素(锶和钕)数据，将它们与已公布的同位素数据相结合，并对它们进行加权，以激活尘源。我们定义了三个同位素不同的优先尘源区域(PSA)：西部、中部和东部北非尘埃源区。还需要更多的数据，特别是来自西部PSA的数据，但我们的结果表明，PSA尘源成分从西到东变化为更具放射性的Nd-和更低的放射性的锶同位素，这与下伏基岩的整体年龄递减相一致。我们的数据揭示了PSA中央乍得地区的极端同位素不均一性，包括一个极其独特的地球化学指纹，为地球上最活跃的尘埃源--博代尔凹陷提供了物质来源。我们的新分析极大地提高了风吹尘埃沉淀物的可靠性，通过这种分析，可以对其遥远的来源区域进行地球化学指纹识别。(C)2020爱思唯尔B.V.保留所有权利。
North Africa produces more than half of the world's atmospheric dust load. Once entrained into the atmosphere, this dust poses a human health hazard locally. It also modifies the radiative budget regionally, and supplies nutrients that fuel primary productivity across the North Atlantic Ocean and as far afield as the Amazonian Basin. Dust accumulation in deep sea and lacustrine sediments also provides a means to study changes in palaeoclimate, particularly those associated with rainfall climate change. Systematic analysis of satellite imagery has greatly improved our understanding of the trajectories of long-range North African dust plumes, but our knowledge of the dust-producing source regions and our ability to fingerprint their contribution to these export routes is surprisingly limited. Here we report new radiogenic isotope (Sr and Nd) data for sediment samples from known dust-producing substrates (dried river and lake beds), integrate them with published isotope data and weight them for dust source activation. We define three isotopically distinct preferential dust source areas (PSAs): a Western, a Central and an Eastern North African PSA. More data are needed, particularly from the Western PSA, but our results show a change in PSA dust source composition to more radiogenic Nd- and less radiogenic Sr-isotope values from west to east, in line with the overall decreasing age of the underlying bedrock. Our data reveal extreme isotopic heterogeneity within the Chadian region of the Central PSA, including an extremely distinctive geochemical fingerprint feeding the Bodele Depression, the most active dust source on Earth. Our new analysis significantly improves the reliability by which windblown dust deposits can be geochemically fingerprinted to their distant source regions. (C) 2020 Elsevier B.V. All rights reserved.