Abstract 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.

中文翻译：

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三个北非尘源区及其地球化学指纹

摘要 北非产生了世界上一半以上的大气粉尘负荷。一旦进入大气，这些粉尘就会对当地的人类健康造成危害。它还在区域范围内调整辐射收支，并提供营养物质，为整个北大西洋和远至亚马逊盆地的初级生产力提供动力。深海和湖泊沉积物中的灰尘积累也为研究古气候变化提供了一种手段，特别是与降雨气候变化相关的那些变化。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理解，但我们对产尘源区域的了解以及我们识别它们对这些出口路线的贡献的能力却出人意料地有限。在这里，我们报告了来自已知产尘基质（干涸的河床和湖床）的沉积物样本的新放射性同位素（Sr 和 Nd）数据，将它们与已发布的同位素数据相结合，并对它们进行加权以进行粉尘源激活。我们定义了三个同位素不同的优先尘埃源区 (PSA)：西部、中部和东部北非 PSA。需要更多数据，尤其是来自西部 PSA 的数据，但我们的结果表明，从西到东，PSA 尘源组成发生了变化，放射成因 Nd 和 Sr 同位素值发生变化，这与下伏基岩的总体年龄下降一致. 我们的数据揭示了中部 PSA 乍得地区的极端同位素异质性，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 Bodele 洼地提供营养。