The Atacama Desert, despite its extreme hostile conditions, still harbours traces of life in its dusty surface. Until now, it remains open whether organic molecules found in topsoils have their origin from in-situ biotic processes in the hyper-arid core, or whether and to which degree they stem from outside the desert and its border regions. In order to trace atmospheric organic matter input, we analyzed the concentration of polycyclic aromatic hydrocarbons (PAHs) which almost exclusively derive from combustion processes and compared this to total organic carbon (TOC) concentrations. We sampled topsoil (0–15 cm depth) in one coastal (Paposo) and one inland aridity transect (Aroma) and compared them to atmospheric dust collected over two months in the hyper-arid core of the desert (Yungay). We found TOC and PAHs in all desert soil and dust samples. The sum of 18 analyzed PAHs ranged from 0.001 to 0.31 ng g in the Paposo transect and from 0.14 to 0.78 ng g in the Aroma transect, with moderate correlation (R = 0.68, < 0.05) between TOC and PAHs. Measured PAH concentration in the dust was up to 5000 times higher and varied between 0.45 and 5.31 ng g. PAHs contributed with up to 0.25% to the TOC in dust and with 0.1% to the TOC in soils. This indicates that not all organic matter found in deserts is a trace for life defying extreme conditions, as it can also stem from sources outside or at the borders of the desert. We hence recommend verifying the origin of organic matter found in regions at the dry limit and highlight the overall presence of atmospheric pollutants on earth.

中文翻译：

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使用多环芳烃作为示踪剂将有机物质进口到阿塔卡马沙漠

阿塔卡马沙漠尽管条件极其恶劣，但其尘土飞扬的表面仍然存在生命的痕迹。到目前为止，表土中发现的有机分子是否起源于超干旱核心的原位生物过程，或者它们是否以及在何种程度上起源于沙漠及其边境地区之外，仍然是一个悬而未决的问题。为了追踪大气有机物输入，我们分析了几乎完全来自燃烧过程的多环芳烃 (PAH) 浓度，并将其与总有机碳 (TOC) 浓度进行比较。我们对一处沿海地区（帕波索）和一处内陆干旱样带（阿罗马）的表土（0-15 厘米深）进行了采样，并将其与两个月来在沙漠超干旱核心地区（永盖）收集的大气尘埃进行了比较。我们在所有沙漠土壤和灰尘样本中都发现了 TOC 和 PAH。 Paposo 横断面中 18 种分析的 PAH 总含量为 0.001 至 0.31 ng g，Aroma 横断面为 0.14 至 0.78 ng g，TOC 和 PAH 之间具有中等相关性（R = 0.68，< 0.05）。测得的灰尘中 PAH 浓度高达 5000 倍，变化范围为 0.45 至 5.31 ng g。 PAH 对灰尘中 TOC 的贡献高达 0.25%，对土壤中 TOC 的贡献高达 0.1%。这表明并非沙漠中发现的所有有机物都是抵抗极端条件的生命痕迹，因为它也可能来自沙漠之外或沙漠边界。因此，我们建议验证干燥极限区域中发现的有机物的来源，并强调地球上大气污染物的整体存在。