We investigate the contributions of natural (geogenic) and anthropogenic sources of lead (Pb) to the Nee Soon Swamp Forest, a relatively undisturbed catchment in Singapore. Using a Bayesian statistical source tracking approach with Pb isotopes preserved in sediment sections, our findings reveal a predominance of geogenic Pb in contemporary sediments, despite the significant presence of anthropogenic Pb in aerosols from local and distant sources. However, the geogenic Pb isotope signatures of the two main soil types in the catchment overlap with those of anthropogenic sources, introducing considerable uncertainty in using Pb isotopes as tracers within this catchment and potentially across larger areas. This uncertainty raises concerns about past interpretations of Pb contamination in both terrestrial and aquatic environments in Singapore and the broader region. To address these challenges, we emphasize the importance of accurately determining the signatures of all natural sources before using Pb isotopes as tracers in future studies. We also suggest that incorporating additional Pb isotope ratios or other stable isotope ratios (e.g., Ba, Cu, Sr, Zn) could enhance our ability to distinguish between natural and anthropogenic Pb sources. Ultimately, our study highlights the complexity of Pb sources in the environment and underscores the need for more comprehensive approaches to assessing their impacts.

中文翻译：

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揭示热带城市沼泽森林中的铅源：见解和挑战


我们调查了铅 （Pb） 的自然（地质）和人为来源对 Nee Soon 沼泽森林的贡献，这是新加坡一个相对未受干扰的集水区。使用贝叶斯统计来源跟踪方法，将 Pb 同位素保留在沉积物部分，我们的研究结果揭示了地质 Pb 在当代沉积物中占主导地位，尽管来自本地和遥远来源的气溶胶中大量存在人为铅。然而，集水区中两种主要土壤类型的地质 Pb 同位素特征与人为来源的地质同位素特征重叠，从而在该集水区内和可能在更大区域内使用 Pb 同位素作为示踪剂带来了相当大的不确定性。这种不确定性引发了人们对过去对新加坡和更广泛地区陆地和水生环境中铅污染的解释的担忧。为了应对这些挑战，我们强调在未来研究中使用 Pb 同位素作为示踪剂之前准确确定所有天然来源的特征的重要性。我们还建议，结合额外的 Pb 同位素比值或其他稳定同位素比值（例如，Ba、Cu、Sr、Zn）可以增强我们区分天然和人为 Pb 来源的能力。最终，我们的研究强调了环境中铅源的复杂性，并强调了需要更全面的方法来评估其影响。