Currently, natural and urban ecosystems are affected by different types of atmospheric deposition, which can compromise the balance of the environment. Plastic pollution represents one of the major threats for biota, including lichens. Epiphytic lichens have value as bioindicators of environmental pollution, climate change, and anthropic impacts. In this study, we aim to investigate the lichen bioaccumulation of airborne microplastics along an anthropogenic pollution gradient. We sampled lichens from the Genera and to highlight the effectiveness of lichens as tools for passive biomonitoring of microplastics. We chose three sites, a “natural site” in Altipiani di Arcinazzo, a “protected site” in Castelporziano Presidential estate and an “urban site” in the centre of Rome. Overall, we sampled 90 lichens, observed for external plastic entrapment, melt in oxygen peroxide and analysed for plastic entrapment. To validate the method, we calculated recovery rates of microplastics in lichen. Particularly, 253 MPs particles were detected across the 90 lichen samples: 97 % were fibers, and 3 % were fragments. A gradient in the number of microplastic fibers across the sites emerged, with increasing accumulation of microplastics from the natural site (n = 58) to the urban site (n = 116), with a direct relationship between the length and abundance of airborne microplastic fibers. Moreover, we detected the first evidences of airborne mesoplastics entrapped by lichens. On average, the natural site experienced the shortest fibre length and the centre of Rome the longest. No differences in microplastics accumulation emerged from the two genera. Our results indicated that lichens can effectively be used for passive biomonitoring of microplastic deposition. In this scenario, the role of lichens in entrapping microplastics and protecting pristine areas must be investigated. Furthermore, considering the impact that airborne microplastics can have on human health and the effectiveness of lichens as airborne microplastic bioindicators, their use is encouraged.

中文翻译：

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使用地衣对空气中的微塑料进行被动生物监测：城市、自然和受保护环境之间的比较


目前，自然和城市生态系统受到不同类型的大气沉降的影响，这可能会破坏环境的平衡。塑料污染是包括地衣在内的生物群的主要威胁之一。附生地衣具有作为环境污染、气候变化和人类影响的生物指示剂的价值。在这项研究中，我们的目的是沿着人为污染梯度研究空气中微塑料的地衣生物累积情况。我们对地衣属进行了采样，并强调地衣作为微塑料被动生物监测工具的有效性。我们选择了三个地点：Altipiani di Arcinazzo 的“自然地点”、Castelporziano 总统庄园的“受保护地点”和罗马市中心的“城市地点”。总体而言，我们对 90 种地衣进行了采样，观察外部塑料截留情况，将其融化在过氧化氢中并分析塑料截留情况。为了验证该方法，我们计算了地衣中微塑料的回收率。特别是，在 90 个地衣样本中检测到 253 个 MP 颗粒：97% 是纤维，3% 是碎片。随着从自然地点（n = 58）到城市地点（n = 116）微塑料积累的增加，各个地点的微塑料纤维数量出现了梯度，空气中微塑料纤维的长度和丰度之间存在直接关系。此外，我们首次发现了地衣捕获空气中塑料的证据。平均而言，自然地点的纤维长度最短，罗马中心的纤维长度最长。两个属的微塑料积累没有差异。我们的结果表明，地衣可以有效地用于微塑料沉积的被动生物监测。 在这种情况下，必须研究地衣在捕获微塑料和保护原始区域方面的作用。此外，考虑到空气中的微塑料对人类健康的影响以及地衣作为空气中的微塑料生物指示剂的有效性，鼓励其使用。