Although leaded gasoline was banned at the end of the last century, lead (Pb) remains significantly enriched in airborne particles in large cities. The remobilization of historical Pb deposited in soils from atmospheric removal has been suggested as an important source providing evidence for the hypothetical long-term persistency of lead, and possibly other pollutants, in the urban environment. Here, we present data on Pb isotopic composition in airborne particles collected in London (2014 to 2018), which provide strong support that lead deposited via gasoline combustion still contributes significantly to the lead burden in present-day London. Lead concentration and isotopic signature of airborne particles collected at a heavily trafficked site did not vary significantly over the last decade, suggesting that sources remained unchanged. Lead isotopic composition of airborne particles matches that of road dust and topsoils and can only be explained with a significant contribution (estimate of 32 ± 10 to 43 ± 9% based on a binary mixing model) of Pb from leaded gasoline. The lead isotopes furthermore suggest significant contributions from nonexhaust traffic emissions, even though isotopic signatures of anthropogenic sources are increasingly overlapping. Lead isotopic composition of airborne particles collected at building height shows a similar signature to that collected at street level, suggesting effective mixing of lead within the urban street canyon. Our results have important implications on the persistence of Pb in urban environments and suggest that atmospheric Pb reached a baseline in London that is difficult to decrease further with present policy measures.

尽管含铅汽油在上个世纪末被禁止使用，但铅 (Pb) 在大城市的空气颗粒物中仍然显着富集。已建议从大气去除中重新激活历史上沉积在土壤中的 Pb 作为铅和可能的其他污染物在城市环境中的假设长期持久性提供证据的重要来源。在这里，我们展示了在伦敦（2014 年至 2018 年）收集的空气悬浮颗粒中 Pb 同位素组成的数据，这些数据有力地支持了通过汽油燃烧沉积的铅仍然对当今伦敦的铅负担做出了重大贡献。在过去十年中，在一个交通繁忙的地点收集的空气中颗粒物的铅浓度和同位素特征没有显着变化，这表明来源保持不变。空气中的颗粒物的铅同位素组成与道路灰尘和表土的成分相匹配，只能用含铅汽油中铅的显着贡献（根据二元混合模型估计为 32 ± 10 至 43 ± 9%）来解释。铅同位素进一步表明非尾气交通排放的重要贡献，即使人为来源的同位素特征越来越重叠。在建筑物高度收集的空气中颗粒物的铅同位素组成显示出与在街道上收集的相似的特征，表明铅在城市街道峡谷内的有效混合。我们的研究结果对 Pb 在城市环境中的持久性具有重要意义，并表明大气中的 Pb 在伦敦达到了一个基线，目前的政策措施很难进一步降低这一基线。