Integrating Self-Organizing Maps, Positive Matrix Factorization and Time-Series Decomposition for Urban Air Pollution Source Apportionment: A Comparative Study of Bulgarian Cities.

Molecules · 2026 · PMC13209328 · PMID 42197278

Europe PMC DOI

hedged sentences

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closest p · 0.0× alpha

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boldest claim

The sentences

highly significantp < 2.2 × 10 −16actually significant

Monthly differences were highly significant (Kruskal–Wallis p < 2.2 × 10 −16 ), and this factor exhibited the strongest seasonal component among the three, with a seasonal strength of 33.77%.

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a decreasing trendno p-value reported

In contrast, the traffic-related aerosol factor (F3 in both cities) shows a decreasing trend in both Plovdiv (−5.14% yr −1 ) and Varna (−9.30% yr −1 ), combined with moderate to strong seasonal variability (24.35% and 25.20%, respectively) and significant weekday–weekend differences.

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