Elemental carbon (EC), a ubiquitous component of fine atmospheric aerosol derived from incomplete combustion, is an important player for both climate change and air quality deterioration. Several policy measures have been implemented over the last decades to reduce EC emissions from anthropogenic sources, but still, long-term EC measurements to verify the efficacy of such measurements are limited. In this study, we analyze the concentration of EC suspended in fog water samples, collected over the period 1997–2016 in a rural background site of the southern Po Valley. The comparison between EC in fog water and EC atmospheric aerosol concentration measured since 2012 allowed us to reconstruct EC atmospheric concentration from fog water chemical composition dating back to 1997. The results agree with the EC atmospheric observations performed at the European Monitoring and Evaluation Program (EMEP) station of Ispra in the northern part of the Po Valley since 2002, and confirm that the Po Valley is a pollution hotspot, not only in urban areas, but also in rural locations. The reconstructed trend over the period 1997–2016 indicates that EC concentration during the winter season has decreased on average by 4% per year, in agreement with the emission reduction rate, confirming the effectiveness of air quality measures implemented during the past 20 years.

中文翻译：

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从雾水样品中重建波河谷（意大利）的元素碳长期趋势

元素碳（EC）是不完全燃烧产生的大气细小气溶胶的普遍成分，是导致气候变化和空气质量恶化的重要因素。在过去的几十年中，已经采取了一些政策措施来减少人为来源的EC排放，但是，长期的EC测量以验证此类测量的有效性仍然受到限制。在这项研究中，我们分析了雾水样品中悬浮的EC的浓度，这些样品是在1997年至2016年期间在南部Po Valley的农村背景采集的。自2012年以来测量的雾水中EC和EC大气气溶胶浓度之间的比较使我们能够从1997年的雾水化学成分重建EC大气浓度。结果与2002年以来在Po Valley北部Ispra的欧洲监测与评估计划（EMEP）站进行的EC大气观测结果吻合，并确认Po Valley不仅是城市地区，而且是一个污染热点，而且在农村地区 从1997年至2016年的重构趋势表明，冬季的EC浓度平均每年下降4％，与减排率相符，证实了过去20年实施的空气质量措施的有效性。